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2
Preface
The intent of this reference guide is to define low resistance, its measure-
ment methods and the common sources of error inherent in measuring
such a small quantity. This guide provides a general overview of electrical
resistance including mathematical equations, connection methods to the
device under test and methods used by measuring instruments to accu-
rately characterize resistance. Temperature compensation, conductors
and milliohmmeter applications are also discussed.
Low Resistance Measurement Guide
1st Edition, June 2005
Comments: info@quadtech.com
5 Clock Tower Place, 210 East
Maynard, Massachusetts 01754
CompuMess Elektronik GmbH Tel: (800) 253-1230
Lise-Meitner-Str.1, 85716 Unterschleissheim Fax: (978) 461-4295
Tel 089-321501-0 Fax 089-321501-11 Intl: (978) 461-2100
http://www.compumess.de oder http://www.netzteile.de
Web: http://www.quadtech.com
This material is for informational purposes only and is subject to change
without notice. QuadTech assumes no responsibility for any error or for
consequential damages that may result from the misinterpretation of any
procedures in this publication.
3
4
Contents
Terms and Definitions 7 Verification of a Milliohmmeter 26
Standards 26
Resistance 9
Current Shunt 26
Properties 9
Safety 26
Measurement 9
Conductors 10 External Connection to a Milliohmmeter 27
Temperature Dependence 10 Remote I/O 27
Length & Cross-sectional Area 10 RS-232 Interface 27
Conductor Size: AWG 11 IEEE-488 Interface 27
AWG & Resistivity 12 RS-232 and IEEE-488 Control 28
Stranded Wire 12 LR2000 Virtual Front Panel Wizard 28
Summary 12
Applications of Milliohmmeters 29
Milliohmmeter Design Characteristics 13 Surface Resistivity 29
The 2-Wire Measurement 13 Cable Testing 29
The 4-Wire Measurement 14 Component Testing 30
AC vs. DC Resistance Measurements 14
AC Milliohmmeters 15 Examples of High Performance Testers 31
LCR Meters 15 Milliohmmeters 31
Ground Bond Testers 15 LR2000 Milliohmmeter 31
DC Milliohmmeters 15 LR2000 Virtual Front Panel Wizard 31
DC Sources 16 Cable Testers 32
Horizon LV1 Wiring Analyzer 32
Milliohm Measurement Parameters 17 Horizon HV1 Wiring Analyzer 32
Accuracy 17 Horizon SCSI Wiring Analyzer 33
Speed 17 Fusion HV Wire & Cable Analyzers 33
Ranging 17
Dedicated Function Test Instruments 33
Error Sources in Milliohmmeters 18
LCR Meters 33
Noise 18
Megohmmeters 33
The Thermal emf Factor 18
Hipot Testers 33
Current Reversal 19
Electrical Safety Analyzers 33
Offset-Compensated Ohms 19
Dry Circuit Testing 19
Offset Compensation 20 Appendix A 35
Formulas 36
Temperature Compensation 21
Tables 39
Formula 21
Helpful Links 41
Conductor Resistance vs. Temperature 21
Meg/Mil Selection Guide 43
Semiconductors 22
Superconductors 22
Application Note Directory 45
Connection to a Milliohmmeter 23
Test Leads 23 Glossary 49
Kelvin Clip Leads 23
Component Test Fixture 24
Probe Lead Set 24
Connection Techniques to Reduce Error 25
Reliable Connections 25
Zeroing 25
Proper 4-Terminal Positioning 25
5
6
Terms and Definitions
Resistance the opposition to the flow of current characteristic of a medium, substance
or circuit element.
Low Resistance: Electrical resistance typically below 10 ohms, often expressed in terms of
milliohms (10-3) or micro-ohms (10-6).
Bonding Resistance: Electrical resistance across weld joints, crimped connections and bolted joints.
Contact Resistance: Measured resistance of closed contacts, typically that of switches, relays and
connectors.
Dry Contact Resistance: Resistance across closed contacts is usually decreased, with applied voltage,
due to attraction of molecules on the surface of contacts. By limiting the test
voltage and current, electrical changes to the contacts are minimized.
Winding Resistance: Electrical resistance of windings which comprise motors, coils, transformers,
relays and ballasts.
Resistivity: the electrical resistance of a material to the flow of current times the
cross-sectional area of current flow and per unit length of current path. It is
also known as 'specific resistance'.
Conductivity: the ratio of electric current density to the electric field in a material. Conductivity
is also known as 'specific conductance' and is the reciprocal of resistivity.
Current: the flow of electric charge per unit time.
Constant Current: Current that the measuring instrument will output during a resistance test,
independent of device loading.
Current Polarity: Test signal type: positive or negative DC, or positive or negative pulse.
Helps reduce thermal emf effects.
emf: Electromotive force: the difference in electric potential that exists between two
dissimilar electrodes immersed in the same electrolyte or otherwise connected
by ionic conductors.
Thermal emf: the voltage generated by connecting two dissimilar metals, at different
temperatures, together.
Temperature Compensation: Measurements corrected from an ambient temperature back to a reference
temperature (usually 20 degrees C)
Four Wire Kelvin Connection: A four-terminal connection: one pair of terminals to apply current to a device
and another pair to measure voltage across the device.
Zero Offset: A correction for residual resistance resulting for the test leads and connection.
Determined by a SHORT routine with the Kelvin lead test points shorted
together.
Basic Measurement Accuracy: the accuracy of most measurements in %, except the extreme low or
high measurement range values.
7
Terms and Definitions
Table 1: Mathematical Prefixes
Multiple Scientific Prefix Symbol
1000000000000000 1015 Peta P
1000000000000 1012 Tera T
1000000000 10 9 Giga G
1000000 10 6 Mega M
1000 10 3 Kilo k
1 10 0 -- --
.001 10-3 milli m
.000001 10-6 micro µ
.000000001 10-9 nano n
.000000000001 10 -12 pico p
.000000000000001 10 -15 femto f
Table 1 lists mathematical prefixes used in quantifying electrical measurements. For low resist-
ance measurements, the most common units are ohms (), milli-ohms (m) and micro-ohms
(µ).
Note: The symbol for Kilo-ohms (k) is a lower case k. An upper case K is the symbol for
degrees Kelvin.
Refer to the GLOSSARY for a full set of electrical terms and definitions.
8
Resistance
Properties i
Electrical resistance is a property of any mate-
rial that opposes the flow of current.
Resistance has units of ohms, with the Greek DUT V
letter omega ( ) being the standard symbol.
Resistance cannot be directly measured.
Instead, voltage and current are measured and
the resistance calculated using Ohm's Law. Figure 1: Signal Source
Ohm's Law, after German physicist George Most low resistance meters utilize a constant
Simon Ohm, is the algebraic relationship current source and a voltmeter circuit to meas-
between voltage, current and resistance shown ure the voltage across the DUT. The use of a
in Equation 1. constant current source simplifies the circuitry
required to perform the measurement. Rather
V
R= than having a signal generator and two meas-
I urement circuits one for current measurement
and the other for voltage measurement. The
R = Resistance in ohms use of a constant current means the current is
V = Voltage in volts a known and only the voltage has to be meas-
I = Current in amperes ured. This eliminates one entire measurement
circuit. The resistance is then calculated by
Equation 1: Ohm's Law dividing the measured resistance by the con-
stant current value. Refer to Figure 2.
Depending upon the application of the materi-
al, the material is typically defined as a con- i
ductor or insulator. Materials designed to max-
imize opposition to current flow, thus having
high resistance being classified as insulators. 1A DUT V
Materials such as glass, mylar and mica are
examples of insulators. Materials designed to V
Resistance =
have a low resistance and thus minimizing 1A
opposition to current flow being classified as
conductors. Materials such as copper, gold and Figure 2: Constant Current Source
steel are examples of conductors.
Instruments for the measurement of low resist-
ance typically use two different connection
Measurement
methods. The 2-wire and 4-wire connection
The measurement of low resistance is accom- methods are both used for low resistance
plished using a signal source, a voltmeter, a measurements. The resistance value being
current meter and Ohm's Law. The DUT is measured and the required accuracy dictate
placed across the signal source and the volt- which method is used.
age and current are measured. Figure 1 illus-
trates this basic circuit.
9
R = Resistance ohm
= resistivity ohm meter m
l= length meter m
A = cross-sectional area meter 2 m2
l
Length 1meter
Cross A= 1m2 At 20oC:
Copper
Conductor A Sectional RCu = 1.7x10- 8
Area
l RA
Resistance R= =
A l
(1.7x10 -8)1m2
RA =
resistivity = 1m
l
= 1.7x10 -8 m Copper provides a
very low resistance to
= 0.000000017 m the flow of current,
therefore it is a good
conductor.
Figure 3: Copper Characteristics
Conductors Temperature Dependence
Prior to discussing the design characteristics Notice the clarifier 'at room temperature'. For a
and error sources inherent with milliohm meas- conductive material, when the temperature of
urements, a review of conductor resistance the material increases so does its resistivity.
characteristics is beneficial. The material The resistivity of a typical metal increases lin-
under test has unique resistance properties early with a temperature increase. The resis-
that may determine what method is used to tivity of a typical semiconductor (silicon)
measure it. Review for a moment the proper- decreases exponentially with a temperature
ties of a conductor as shown in Figure 3. increase. The resistivity of an insulator (glass,
quartz, sulfur) decreases at an even greater
rate with a temperature increase. All materials
Conductive materials have one or two loosely
do not conduct electricity equally. For more
bound electrons in the outer shell that can
information on temperature refer to the
move easily when a voltage is applied and thus
Temperature Compensation section.
form a current. A material with a bulk resistivi-
ty between 10-6 and 10-4 ohm-cm is consid-
ered a decent conductor. Pure or elemental Length and Cross-sectional Area
metals such as silver, copper, gold and alu- Two other factors affect the resistivity meas-
minum are good conductors. When an impuri- urement: length and cross-sectional area. If
ty is added to a metal it increases the resistivi- one had two copper wires each 1-meter in
ty. Alloys which are combinations of metals length, one with a thickness of 0.45mm and the
have a higher resistivity than the metals they other 0.28mm, which would have the greater
are made from. For example, at room temper- resistivity? The thickness of wire inversely
ature, nickel (Ni) has a resistivity of approxi- affects resistivity which translates the thinner
mately 6.84x10-8 -m. Nichrome, made of wire would have the greater resistivity. The
80% nickel and 20% chromium (Ni 80Cr20), has thicker wire offers less resistance because its
a resistivity of approximately 100x10-8 -m. larger cross-section permits more electrons to
10
Table 2: Resistivity of Common Conductors
Resistivity at room temperature: 20° C, 300K, 68 °F
Material Symbol Resistivity Conductivity Temperature
Coefficient
µ-cm per -m per °C
Element Metal
7
aluminum Al 2.65 3.77 x 10 0.0042
7
copper Cu 1.67 5.95 x 10 0.0040
gold Au 2.21 4.55 x 107 0.0037
7
iron Fe 9.66 1.03 x 10 0.0056
7
lead Pb 20.65 0.43 x 10 0.0042
magnesium Mg 4.3 2.33 x 107
7
manganese Mn 144 0.072 x 10
7
nickel Ni 6.93 1.43 x 10 0.0058
platinum Pt 10.5 0.96 x 107 0.0037
7
silver Ag 1.59 6.29 x 10 0.0038
7
tantalum Ta 13.1 0.76 x 10 Note:
titanium Ti 42 0.24 x 107
7 Tables 2 & 7
tungsten W 5.28 1.89 x 10 0.0044
7 contain data
zinc Zn 5.92 1.69 x 10 0.0038
from different
Alloy Metal
7 sources and
nichrome Ni80Cr20 110 0.095 x 10 0.00017
7 thus have dif-
manganin* CuMnNi 48.21 0.207 x 10 ± 0.000015
steel** FeC 16.62 0.502 x 10
7
0.003 ferent values
Semiconductors for Resistivity
carbon (graphite) C 3500 2.9 x 10
4
-0.0005 and Temp
germanium (pure) Ge 46000 2.2 -0.048 Coefficient.
silicon (pure) Si 64000000 0.0016 -0.075 Refer to
Appendix A
* Manganin composed of 83% copper, 13% manganese and 4% nickel for Tables
** Steel composed of 99.5% iron and 0.5% carbon and Sources.
interact with the electric field. Since there is with increasing gauge number. If the gauge is
more current than voltage, the resistance will increased by 6 AWG, then the diameter
be lower. Translated another way, if the decreases by a factor of 2. Example: 30AWG
area/cross-section of a wire is doubled, its wire has a diameter equal to 10mils. Add 6
resistance is cut in half. gauge and a 36 AWG wire has a diameter
As for the relationship of the length of a wire to equal to 5mils. Table 3 illustrates the general
its resistance: double the length of a wire and rule of thumb for the gauge and diameter rela-
you double its resistance. Again, having two tionship. Equation 2 defines the mathematical
copper wires 1-meter in length each with its relationship between AWG number and wire
own specific resistance. If the two wires of diameter.
equal resistance are put together, two equal Table 3:
resistances in series will add. Relationship of Gauge to Diameter for Solid Wire
When the Then the
Conductor Size: AWG GAUGE DIAMETER
increases by: decreases by factor of:
In the United States, AWG or American Wire 6 2
Gage is the standard designation for conductor 10 3
12 4
size. AWG is based on two reference diame- 14 5
ters: 0.4600 inches (4/0 AWG) and 0.5000 20 10
inches (36 AWG). Wire diameter decreases 40 100
11
39 x log (200D)
AWG: = 36 - Stranded Wire:
log (92)
The size of stranded wire is determined using
36 - AWG
39
the equivalent cross-sectional area of the bun-
D = 0.005 92
dle. Stranded wire is a bundle of small-gauge
wires wrapped in a single layer of insulation.
D = Diameter in inches
Stranded wire has a larger cross section than
Equation 2: Relationship of AWG and D solid wire and less resistance. (Figure 4)
AWG and Resistivity
Turning attention back to the discussion of con-
Summary
ductor resistivity, the information herein is All wires (conductors) are not created equal. A
based on solid copper wire. Solid wire is often wire's resistivity is affected by the material(s)
referred to as single end. Recall the resistivity that it is made of, its thickness (cross-sectional
of copper at 20°C is 1.724x10-8 ohm-meters. area), its length and the temperature in which it
is used. Wires are made of metal for their
Table 4: Solid Wire: AWG & Resistivity
charge carrying capability. Yet heat metal and
AWG Size Diameter Diameter Resistance Resistance
its molecular structure changes causing con-
(Solid Wire) (mm) (inches) /1000feet /1000meters ductivity to decrease and resistivity to increase.
0000 (4/0) 11.684 0.4600 0.049 0.1607
000 (3/0) 10.404 0.4096 0.0618 0.2027 Double the thickness of a wire and cut its
00 (2/0) 9.266 0.3648 0.078 0.2555 resistance in half. Double the length of a wire
0 (1/0) 8.252 0.3249 0.0983 0.3224
1 7.348 0.2893 0.124 0.4063 and its resistance doubles. Choose the con-
5 4.621 0.1819 0.3133 1.0276 ductor material based on its end-use: copper
10 2.588 0.1019 0.9989 3.28
12 2.052 0.0808 1.588 5.21 has a resistivity of 1.72µ-cm which is good for
14 1.6256 0.0640 2.525 8.28
16 1.2903 0.0508 4.016 13.2
low resistance applications; nichrome has a
18 1.0236 0.0403 6.385 20.9 resistivity of 110µ-cm making it a good choice
20 0.8128 0.0320 10.15 33.2
22 0.6451 0.0254 16.14 52.7 for high temperature applications like heat sen-
24 0.5105 0.0201 25.67 84.2 sors.
30 0.2540 0.0100 103.2 338.496
36 0.1270 0.0050 414.8 1360 Note:
40 0.0787 0.0031 1049 3440
Circular Mils is often used to describe conductor size.
Circular Mils = the square of the diameter of the wire
in mils: CM = (d(mil)) 2. 1 mil = .001 inch.
Copper Wire: Single 7 Strand 19 Strand
Figure 4:
#Strands/AWG: 1/30 7/38 19/42
Stranded Wire
AWG: 30 30 30
Nominal Diameter: 0.0100 inches 0.0114 inches 0.0123 inches
0.254 mm 0.290 mm 0.312 mm
Resistance: 347.2 /km 324.8 /km 324.8 /km
* Nominal Diameter (for reference only) and Resistance values from http://www.fiskalloy.com.
12
Milliohmmeter Design Characteristics
The 2-Wire Measurement performed. The measured value is the offset
resistance and is subtracted from all future
Most of today's digital multi-meters (DMM) and
measurements. The use of offset works fine as
some dedicated resistance measurement
long at the offset resistance is a constant.
instruments utilize a 2-wire test method. The 2-
wire method is the simplest and most econom-
ical arrangement. As the name implies two If the offset resistance changes significantly in
wires are used to connect between the meter comparison with the resistance to be meas-
and the DUT. In the 2-wire method, the test ured; due to contact resistance between leads
current (I TEST) is forced through the test leads and DUT, changing of lead length, or use of
and across the resistance (RDUT ) being meas- relays, then the offset cannot be used for accu-
ured. The meter then measures the voltage rate measurements. One way of determining if
across the resistance through the same set of offset can be used, is to perform an offset then
leads and the resistance value is calculated open and short the test leads. A measurement
using Ohm's Law. Figure 5 illustrates the 2- is then performed. Ideally with that previous off-
wire connection to DUT. set performed, the measured value should be
zero. It will never be exactly zero as the con-
tact resistance will have changed. If the
The resistance of the test lead (R LEAD) is the amount of change is small in comparison to the
concern with the 2-wire method when making resistance being measured then a 2-wire
low resistance measurements. The test cur- measurement with offset can be used.
rent (ITEST ) causes a small yet significant volt-
age drop across the lead resistances. The volt-
age drop (V METER ) measured by the meter will One example where the 2-wire method even
not be exactly the same as the voltage (V DUT ) with offset is not ideal for low resistance meas-
urements is when relays are used to switch
directly across the device under test (R DUT) and
between multiple test points. This is due to
considerable errors can result. Typical lead
each relay having a static contact resistance
resistances commonly range from 0.01 - 1
that is different from relay to relay as well as
making accurate 2-wire measurements below
contact resistance stability that is the change of
10 difficult to obtain.
contact resistance over successive closures of
the same relay.
It is possible to zero out leads to improve 2-wire
measurements. During a zero the test leads
are shorted together and a measurement is
DMM VMETER = Voltage measured by meter
R LEAD (HI) ITEST
HI
VDUT = Voltage across DUT (device under test)
VMETER
Measured Resistance = = R DUT + (2 x R LEAD )
VMETER VMETER VDUT R DUT
ITEST
VDUT
Actual Resistance = = R DUT
LO ITEST
R LEAD (LO)
Figure 5: 2-Wire Connection to DUT
13
DMM or Milliohmmeter
R LEAD (Drive) I TEST
Drive HI
VMETER = Voltage measured by meter
Sense HI R LEAD (Sense)
VDUT = Voltage across DUT (device under test)
Because Sense Current is negligible: VMETER = VDUT
V METER VMETER VDUT R DUT
VMETER V DUT
Measured Resistance = =
ITEST ITEST
Sense LO R LEAD (Sense)
Drive LO R LEAD (Drive)
Figure 6: 4-Wire Connection to DUT
The 4-Wire Measurement sible to the DUT. The use of a 4-wire connec-
tion is ideal for use with relays because contact
Due to the limitations of the 2-wire method, the
resistance does not effect the measurement.
4-wire (Kelvin) connection is implemented in
The drawback is that four relays are required
most milliohmmeters. In this connection 4
for each DUT making switching expensive and
wires are connected between the meter and
complicated.
the DUT. One set of leads drives the current
and the second set of leads senses the voltage Figure 7 illustrates a typical milliohmmeter.
across the DUT. Figure 6 illustrates a typical 4- The milliohmmeter has 2 black (Drive-, Sense-
wire connection to DUT. In this configuration, ) and 2 red (Sense+, Drive+) connectors creat-
the test current (I TEST ) is forced through the ing a 4 terminal Kelvin connection.
DUT (R DUT) through one set of leads called
QuadTech LR2000 Milliohmmeter
drive, while the voltage across the DUT (V DUT )
Rx : 2.549 m
is measured by a second set of leads called
sense. 1 0
(-) (+)
Although some small current may flow through
the voltage leads it is usually small enough to DRIVE
(-)
SENSE SENSE
(+)
DRIVE
be ignored. Since the voltage drop across the
+
voltmeter leads is negligible, the voltage across QuadTech LR2000-50 TEST LEADS
DUT
-
the meter can be considered the voltage
across the DUT. In essence the resistance of
the DUT (R DUT) can be measured more accu- Figure 7: 4-Terminal Milliohmmeter
rately with the 4-wire method. The voltage
sensing leads should be connected as close as AC vs. DC Resistance Measurements
possible to the DUT to avoid including the
Resistance can be measured using an AC or a
effects of the voltage drop across the test leads
DC signal. The AC resistance, at low frequen-
in the final measurement
cies, is almost identical to the DC resistance
The 4-wire method minimizes errors due to (DCR). Resistance does increases as fre-
contact resistance of the leads to the DUT, quency increases due to additional losses with-
changing lead lengths and use of relays. The in the material so at higher frequencies the AC
4-wire method is more expensive and compli- resistance will be higher than DC resistance.
cated to implement. Care also has to be taken
to make the Kelvin connection as close as pos-
14
AC Milliohmmeters a measurement range from 1m to 0.5.
Ground bond testers are designed to test the
AC milliohmmeters typically measure resist-
integrity of protective grounding conductor
ance at a frequency of 1kHz and are ideal for
within an electrical product with a 3-prong
applications such as measuring internal battery
resistance. There is not a lot of difference power cord.
between an AC milliohmmeter and an LCR
meter with the exception that AC milliohmme-
ters typically have higher drive currents up to
10mA. The higher drive currents help in mak-
ing more accurate low resistance measure-
ments down to 10µ. Some AC milliohmme-
ters can measure inductance, phase and other
impedance parameters besides resistance.
Figure 9: Ground Bond Tester
LCR Meters
LCR meters are similar to an AC Milliohmmeter
DC Milliohmmeters
except they are not dedicated to measuring just Most milliohmmeters use a DC signal instead
AC resistance. LCR meters are designed to of an AC signal. DC milliohmmeters feature a
measure inductance, capacitance and resist- wide measurement range from 1µ to 2M.
ance. Most LCR meters have a wide meas- Most milliohmmeters have different current lev-
urement range for resistance from a few mil- els depending upon the resistance to be meas-
liohms to several megohms, programmable ured that range from 1uA to 1A with some
test frequency and programmable test signal instruments going as high as 10A.
level. LCR meters are ideal for measurement
of battery impedance and resistance, equiva-
lent series resistance of capacitors, and resist-
ance and impedance characteristics of materi-
als and components.
Figure 10: Example Milliohmmeter
As discussed earlier in this guide a milliohm-
meter must output a constant current, measure
the voltage across the DUT and use Ohm's
Law to calculate the resistance. When design-
Figure 8: Example LCR Meter ing a milliohmmeter the designer wants to have
Ground Bond Testers the measured voltage across the DUT at a rea-
sonable level to reduce errors due to noise,
Another type of an AC resistance-measuring minimize the complexity of the measurement
instrument is the ground bond tester. A ground circuitry and make the instrument as safe as
bond tester is similar to an AC milliohmmeter in possible to use. Typically most milliohmmeters
design, consisting of a constant current source have a maximum measurement voltage of 4.5
and voltmeter circuit. The big difference is the volts and a maximum current level of 1A.
amount of current used during testing and a There are milliohmmeters that do utilize higher
very limited range of resistance measurement. current levels of up to 100A or more.
Test currents are typically from 3A to 45A with
15
DC Sources DUT
There are a number of different types of DC LMEAS
signals used for measurement. Some of the Source Current through DUT
ISOURCE VMETER
different types used in the LR2000 are shown RMEAS
in Figure 11. It is important to select the appro-
priate type of DC signal depending upon the
DUT being measured.
L/R Time Constant is greater than Circuit for testing Resistance of
The PULSE± mode is a positive/negative Pulse Width an INDUCTIVE device
square wave that switches the source signal
from +2V to 0V to -2V to 0V. This mode has the
Figure 12: Inductive DUT
advantage that errors due to thermal emf are
cancelled out due to polarity switching and a
reduced duty cycle can limit heating of the The PULSE+ mode is a positive square wave
DUT. Thermal emf errors are discussed later in that switches the source signal for +2V to 0V.
this guide. The PULSE- mode is a negative square wave
Although pulsing the test current provides the that switches the source signal for -2V to 0V.
benefits of compensating for thermal emf and These modes have the main advantage of a
reduced duty cycle to minimize heating. As the
minimizing device heating, current pulsing may
cause errors in testing inductive devices. The square wave has only one polarity, errors due
inductance of the DUT may prevent the current to thermal emf are not cancelled out.
through the device from reaching its maximum The DC+ and DC- modes provide the source
value before the voltage measurement is signal equal to +2V and -2V respectively.
made. This phenomenon is due to the L/R time These modes are ideal for inductive devices.
constant being larger than the current pulse
width. When this is the case, the current never The STBY mode puts the instrument in stand-
reaches its maximum value resulting in an over by status with no signal being output to the
estimation of the measured resistance. The DUT. This allows connection to the DUT with-
out the worry of transients or dangerously high
solution is to use 'straight', non-pulsed DC test
current when testing an inductive device. Take voltages being produced by cutting off the cur-
into consideration the previous discussion that rent to an inductive device.
such test currents could produce device heat-
ing depending upon the DUT. Figure 11: DC Signal Types
V PULSE +/- : +2V 0V -2V 0V V PULSE +: +2V 0V V PULSE - : -2V 0V
+2V +2V +2V
0V 0V 0V
t t t
-2V -2V -2V
V DC + : +2V V DC - : -2V V STBY : Instrument in Standby Mode
+2V +2V +2V
0V 0V 0V
t t t
-2V -2V -2V
16
Milliohm Measurement Parameters
When considering which milliohmmeter will Slow). The measurement speed can also be
best solve your test requirements, there are referred to as measurement time or integration
three important measurement parameters time. Accuracy is always specified with the
worth examining: accuracy, speed and ranging. slowest measurement speed, generally 1 sec-
Milliohm measurements can be made with ond per measurement.
instruments of all shapes and sizes yet meas-
urement to the milli (10-3) ohm requires accu-
Ranging
racy and resolution below 10-3 .
To maintain a balance between the maximum
voltage and currents limits as well as make an
Accuracy accurate measurement, most milliohmmeters
Most quality milliohmmeters will state accuracy have several measurement ranges. Lower
as having two parts: one being a % of reading resistances ranges use higher currents and
and the second part as either a number of higher resistances ranges use lower current.
counts, least significant digits or a resistance For resistance ranges from 1µ to 2M a mil-
value. The first part covers basic accuracy with liohmmeter like the LR2000 uses currents from
the second part taking into account resolution 1A to 1µA respectively. For example if when
and noise. The LR2000 Milliohmmeter accura- measuring a 2M resistor a current source of
cy is stated separately for each resistance 1µA might be used to keep the measured volt-
range. For example, the 20m range has an age to 2V. As the resistance is reduced the
accuracy of ±[0.05% of reading+0.06m]. This current would be increased at a similar rate so
means that as the measured resistance value at 2k a current source of 1mA would be used.
approaches 0.06m the error approaches At very low resistance values the voltage
100%. across the DUT even at current levels of 1A
becomes very small, usually in the µV range.
This typically results in noisy measurements
The number of digits that are displayed deter- and additional error. Errors in milliohmmeter
mines the resolution of the instrument. A count measurements are discussed in the next sec-
is the least significant digit that can be dis- tion.
played. For example if the accuracy specifica-
tion is given as ±[0.05% of reading + 3counts]
and the display resolution is 0.001m, the Range Resolution Accuracy Test Current
accuracy specification then becomes ±[0.05% (Full-Scale) (Typical)
20m 1µ ±(0.1% of rdg +.006m) 1A
of reading + (3 * 0.001m)] or ±[0.05% of read- 200m 10µ ±(0.05% of rdg +.06m) 100mA
ing + (0.003m)]. 2 100 µ ±(0.05% of rdg +.6m) 10mA
20 1m ±(0.05% of rdg +6m) 1mA
200 10m ±(0.05% of rdg +40m) 1mA
2k 100m ±(0.05% of rdg +.2) 1mA
Speed 20k 1 ±(0.1% of rdg +2) 100µA
200k 10 ±(0.2% of rdg +20) 10µA
Measurement speed is an important considera- 2M 100 ±(0.4% of rdg +200) 1µA
tion when it comes to accuracy. Accuracy and
speed are inversely proportional. That is the Table 5: LR2000 Measurement Ranges
more accurate a measurement the more time it
takes to perform the measurement.
Milliohmmeters meters will generally have 3
measurement speeds (Fast, Moderate or
17
Error Sources in Milliohmmeters
There are a number of different sources of instrument's ability to measure very low voltage
errors in low resistance measurements. levels, thermal emf can significantly contribute
Thermal emf (electro-motive force) and noise to low resistance measurement error.
are common errors. Dry circuit and zero cali-
bration errors also account for inaccuracies in External to the DUT, each connection or con-
low resistance measurements. nector in a test setup is a possible thermal emf
source. These include connections between
Noise the DUT and the input cables; connections
within the input cables and connections
It is important to understand the different types between the input cable and the instruments
of noise sources and techniques for minimize input connector. Even connections internal to
the noise effects. This goes for any type of low the instrument can cause thermal emf.
voltage measurement. Magnetic fields create Thermal emf sources external to the DUT can
noise in cables in two ways. Noise is created be canceled out by the zeroing function.
within test leads when the magnetic field
changes with time or the test leads move with-
in the magnetic field. The best way to prevent Simple instrument zeroing will not compensate
noise issues is to keep test leads short and for the thermal emf sources associated with
eliminate motion in the leads. The leads connections within the DUT or in other connec-
should also be shielded. tions beyond the instrument's input terminals
(the point at which zeroing is performed).
Suggested techniques for minimizing thermal
The Thermal emf Factor emf include using only clean crimped-on simi-
Thermal emfs are small voltages developed at lar metal (copper to copper) connections and
the junctions of dissimilar metals. The magni- keeping all junctions at the same temperature.
tude of thermal emf depends on both the type This is not practical in all test applications so
of metal used and the temperature difference there are two common methods that are used
between the junctions. Since low resistance in many milliohmmeters to circumvent this
measurements are dependent on the test problem. The two methods are Current
Reversal and Offset-Compensated Ohms.
Vemf Vemf
+ -
ISOURCE VMETER ISOURCE VMETER
RMEAS - RMEAS +
VMETER = Meter Voltage VMETER + = Vemf + (ISOURCE) (RMEAS)
Vemf = Thermal emf VMETER - = Vemf - (ISOURCE ) (RMEAS )
ISOURCE = Source Current VMETER = [VMETER + ] - [VMETER - ] [Vemf + (ISOURCE ) (RMEAS )] - [V emf - (ISOURCE ) (RMEAS )]
=
2 2
RMEAS = Measured Resistance VMETER = (ISOURCE ) (RMEAS )
Figure 13: Current Reversal Method
18
1 Measment Cycle
Vemf Vemf
+
VMETER ISOURCE VMETER
- RMEAS
RMEAS Source Current
Voltage Measurement with Voltage Measurement with Thermal Offset
Current Source ON Current Source OFF Measurement
VMETER = Meter Voltage VMETER 1
= Vemf + (ISOURCE ) (RMEAS )
Vemf = Thermal emf
VMETER 2
= Vemf
ISOURCE = Source Current
R MEAS = Measured Resistance
VMETER = [VMETER 1
] - [VMETER 2
]
VMETER = [Vemf + (ISOURCE ) (RMEAS )] - [V emf ] Figure 14:
VMETER = (ISOURCE ) (RMEAS ) Offset-Compensated Ohms
Method
Current Reversal Dry Circuit Testing
Using the Current Reversal method, thermal Low resistance measurements are frequently
emf is canceled by making two measurements made on the contacts of low current devices.
with currents of opposite polarity. The positive Measuring contact resistance in accordance
current (+ISOURCE) is applied and the voltage is with ASTM B539 is common practice with
measured (VMEAS). A negative current (-ISOURCE) switch and relay manufacturers. Contacts on
is applied and the voltage is measured a sec- these devices are made of tin, silver and gold
ond time (VMEAS ). The two measurements are and are not hermetically sealed. Over time,
then combined to cancel any effect of thermal oxide can corrode these metal contacts.
emf. Refer to Figure 13 for equations. The Surface contamination of the contacts can
measured resistance is then computed using result in films (metalic oxides, sulfides and
Ohm's Law as R MEAS=V SOURCE/ISOURCE. Figure 13 halides) building up. These films add series
illustrates the Current Reversal method. resistance on the order of a few milliohms to
the contact resistance.
Using test voltages greater than 20mV can
Offset-Compensated Ohms result in erroneous contact resistance meas-
The Offset-Compensated Ohm method for min- urements. This is due to the voltage beoing
imizing thermal emf applies the source current high enough to breakdown the oxide layer.
(ISOURCE) to the resistance being measured Most milliohmmeters used for contact resist-
(RMEAS ) only during one part of the test cycle. ance measurements feature a dry circuit mode
When the source is ON, the total voltage meas- that limits the voltage to less than 20mV.
ured (VMETER 1) includes the resistor as well as
any thermal emf as illustrated in Figure 14.
The second voltage measurement (VMETER 2) is
made with the Current Source OFF. The two
voltage measurements are then combined to
determine the voltage measurement for the full
test cycle. This voltage is termed the offset-
compensated voltage.
19
Offset/Zero Compensation It is important when performing a zero to have
proper orientation of the Kelvin clips as shown
Most milliohmmeters have an electronic offset
in Figure 16. The drive and sense should be
or zero compensation function. This allows the
oriented in the same direction. This results in
leads to be shorted together and a measure-
the sense connections having a close to zero
ment to be performed. The measured resist-
volts as possible during the zero.
ance value is then subtracted from all future
measurements. Drive +
Correct
Drive -
Q uadTech LR2000 Milliohmmeter
Sense + Sense -
Rx : 2.549 m
1 0 DRIVE (-) SENSE SENSE (+) DRIVE
Incorrect
Drive + Sense -
(-) (+) Voltage Sense: P+, P- Sense + Drive -
DRIVE SENSE SENSE DRIVE
Current Drive: I+, I-
QuadTech LR2000-50 TEST LEADS
Figure 16: Orientation of Test Cables
P- P+
I- I+
SHORT
Figure 15: Offset/Zero Compensation
Even with a Kelvin connection there will still be
a small residual resistance with the leads of the
milliohmmeter shorted together. Offset is very
useful in applications where it is not possible to
maintain a 4 terminal Kelvin connection to the
DUT. This could be due to the use of a switch-
ing matrix or just the fact that it is not practical
to have 4 connections to the DUT.
Table 6: Common Sources of Error When Measuring Resistance
When Measuring: Problem Encountered: Potential Source: Try This Method:
Low Resistance Measured Value too HIGH Lead Resistance 4-Wire Connection to DUT
Measured Value out of spec Thermal emf Current Reversal or Offset Compensation
High Resistance Noise Charge in leads Use Shielded Test Leads
Measured Value too LOW Shunt Use Guarded Test Leads
Measured Value out of spec Offset Current Adjust Offset Current or
Suppress Offset Current using Zero Function
20
Temperature Compensation
Formula Table 7: Temperature Coefficients
When performing low ohm measurements, not Material Resistivity Temperature
only are the connections and zeroing of the (*m) Coefficient
(°C)
-1
meter important, the temperature of the DUT at 20°C
and even the ambient air can change the -8 -3
Silver 1.59x10 3.8x10
resistance reading. The resistivity of a metal Copper 1.7x10
-8
3.9x10
-3
conductor increases linearly with temperature Gold 2.44x10-8 3.4x10-3
-8 -3
as shown in Equation 3. Aluminum 2.82x10 3.9x10
-8 -3
Tungsten 5.6x10 4.5x10
Iron 10x10 -8 5.0x10-3
= o[1 + (T-To)] Platinum 11x10
-8
3.92x10
-3
-8 -3
Lead 22x10 3.9x10
-8 -3
= measured resistance Nichrome 150x10 0.4x10
-8 -3
Nickel 8.7x10 6.8x10
o = resistance at reference temperature (20°C) Carbon 3.5x10
-5
-0.5x10
-3
-3
T = measured temperature Germanium 0.46 -48x10
To = reference temperature
Source: Physics for Scientists & Engineers,
= temperature coefficient of resistivity Raymond A. Serway, 3RD Edition, Volume II, 1990
Note:
Equation 3: Resistivity and Temperature Tables 2 & 7 contain data from different sources
and thus have different values for Resistivity and
Temp Coefficient. Refer to Appendix A.
Conductor Resistance and Temperature
Using the data from Table 7, a plot can be Resistance vs Temperature
made of resistance versus temperature to see
how temperature can effect your milliohm
measurement. Figure 17 shows the resistivity 2.09E-02
of both Copper and Nickel vs temperature. As 2.07E-02
shown in Figure 17 the resistance of Copper
Resistance
2.05E-02
can change more than 3% over 10°C tempera- 2.03E-02
ture change. This change could mean a part 2.01E-02
measured in the morning passes specification,
1.99E-02 Copper
but in the afternoon fails. This change must be
1.97E-02 Nickel
accounted for when performing accurate low
ohm measurements. There are milliohmme- 1.95E-02
15
18
21
24
27
30
ters on the market that have internal tempera-
ture compensation capability. Typically these Temperature °C
meters have one or two material coefficients
and reference 20°C. This is useful if you are
Figure 17: R vs. T for Copper & Nickel
measuring copper, but if your material is
Tungsten then this feature will not give you the The QuadTech LR2000 Wizard will calculate
data, which you may require. Computers have the resistance from its measured reading, the
eased the burden of manual calculations, temperature and the coefficient, which is
reduced human error and allow for flexibility in assigned by the user. The data is stored to a
materials and temperature. file where later the user can create his particu-
lar resistance vs. temperature chart.
21
Resistance vs Temperature of Germanium
6.20E-01
Germanium
5.70E-01
5.20E-01
4.70E-01
Resistance
4.20E-01
3.70E-01
3.20E-01
2.70E-01
2.20E-01
1.70E-01
1.20E-01
15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
Temperature °C
Figure 18: Germanium Resistance vs. Temperature
Semiconductors Material Critical Temperature
It is worth noting that not all materials will Tc (K)
increase in resistance with temperature as Aluminum 1.20
Cadmium 0.56
shown in Figure 18. The resistivity of semicon- Lead 7.2
ductor materials, such as Geranium, exhibit an Mercury 4.16
exponential decrease in resistance as temper- Niobium 8.70
ature increases. This characteristic allows us Thorium 1.37
Tin 3.72
to consider a ceramic semiconductor as a Titanium 0.39
Thermally Sensitive Resistor, more commonly Uranium 1.0
known as a Thermistor. The resistance vs. Zinc 0.91
temperature characteristic of a Thermistor Niobium/Tin 18.1
Cupric Sulphide 1.6
forms a "scale" that allows it to function as a
temperature sensor. Table 8: Critical Temperature
Source: CRC Handbook of Chemistry and Physics,
78th Edition; Superconductivity data: Collier's
Superconductors Encyclopedia (Volume 21, 1968).
Superconductor materials have zero resistance
at a given temperature known as a critical tem- Note:
perature (Tc). The critical temperatures for a When using the Kelvin Temperature scale,
few common substances are shown in Table 8. the symbol is an uppercase K. There is no degree
The resistance versus temperature for a super- symbol used before the K.
conductor resembles that of any typical metal
as shown is Figure 17 for temperatures above
Tc, once the temperature is at or below Tc the
resistance drops to zero.
22
Connection to a Milliohmmeter
Test Leads It is possible to perform 2 terminal connections
Most milliohmmeters are delivered with a set of with a 4 terminal instrument. This would be
leads designed specifically for use with that adequate for measurements above 10 ohms. If
instrument. It is important to use the correct a two terminal connection is to be made care in
leads or leads with similar characteristics to connection should still be made. The drive
those specified by the manufacturer. Longer leads should be on the outside of the sense
leads or leads that have higher resistance can leads. Figure 20 illustrates a two terminal con-
limit the measurement range or output of the nection using banana plugs. The sense
instrument. This is particularly important with banana plugs would then be plugged into the
high current milliohmmeters and ground bond DUT.
testers. Put another way, the maximum drive
current multiplied by the sum of drive lead
resistance and the resistance to be measured
should not exceed the clamping voltage of the Drive + Drive -
instrument.
IDRIVE MAX RDRIVE LEAD + RMEAS VCLAMP Sense + Sense -
Equation 4: Clamp Voltage
+ -
Accurate measurements using a 4 terminal DUT
Kelvin connection requires that the drive and
sense leads come in contact with the DUT and Figure 20: 2-Terminal Connection
not before. If the drive and sense leads come Now that it has been established how important
in contact with each other the voltage at the a 4-wire Kelvin connection is for low resistance
connection will cause an error in the measure- measurements, let's consider connection tech-
ment. Figure 19 illustrates an example of prop- niques in more detail.
er and improper connection to a DUT.
Drive
Kelvin Clip Leads
Sense Drive
Sense
The Kelvin clip is the most common accessory
used for these types of measurements. The 4-
wire Kelvin clips are normally comprised of two
Correct identical clips, each of which has a current
drive connection (one arm of the clip) and the
e
other side the voltage sense connection. This is
ns
Se ideal for attaching to leaded devices or other
Drive
relatively small contacts but in some applica-
tions other techniques must be employed.
Drive + Drive -
Sense + Sense -
Incorrect
Figure 21: Kelvin Clip Lead Set
Figure 19: Drive and Sense Connection to DUT
23
5940 6730
Figure 22: Example Kelvin Clip Leads
Source: Pomona Electronics
http://www.pomonaelectronics.com
There are a number of different types of com- Probe Lead Set
mercially available Kelvin clips. Kelvin clips are For access to surface mount devices, other
available with different types of jaws and jaw small components, or contacts difficult to
widths. Pictured in Figure 22 are Pomona access, a set of Kelvin probe tips may prove to
Kelvin Clips, Model Numbers 5940 and 6730. be the best solution. An example of such a
probe set is the Pomona Model 6303
Component Test Fixtures (www.pomonaelectronics.com). This lead set is
For component sorting of low value resistors of terminated in double banana plugs but could
axial lead construction a slotted test fixture is be modified with other connections for compat-
the most reliable means of connection. A four- ibility with various measuring instruments.
terminal Kelvin fixture normally consists of four
knife blades where one lead of the component
under test is inserted between two blades for
one connection and the other lead between two
blades for the second connection. This type of
fixture is convenient for an operator to install
components, can be used some distance away
from the instrument, while still maintaining the
all important four terminal connection. Figure 24: Example Probe Lead Set
Source: Pomona Electronics
http://www.pomonaelectronics.com
Figure 23: Slotted Test Fixture
24
Connection Techniques for Reducing Errors
Reliable Connections Proper 4-Terminal Positioning
Erratic noisy readings can be the result of When possible the four Kelvin connections
improper connection to the device under test. should be configured to the device for maxi-
An obvious example of this would be the failure mum accuracy of the measurement, as seen in
of one of the connections of the 4-wire connec- Figure 26.
tions to the device under test. Generally the
Q uadTech
occurrence of this would cause unstable read-
LR2000 Milliohmmeter
Rx : 2.549 m
ings. Viewing the displayed value for several
seconds is a method to make sure the meas- 1 0 DRIVE (-) SENSE SENSE (+) DRIVE
urement is stable.
DRIVE
(-)
SENSE SENSE
(+)
DRIVE
Voltage Sense: P+, P-
Zeroing QuadTech LR2000-50 TEST LEADS
Current Drive: I+, I-
For very low resistance measurements, the
zeroing function of test leads of fixture is very
important. During the zeroing function a resid-
ual correction of resistance is determined, I- P- P+ I+
stored, and applied to ongoing measurements.
In the case of Kelvin clip leads (as illustrated in -
DUT
+
Figure 25) or other fixture types, the voltage Figure 26: 4-Terminal Measurement
sense connections (P+, P-) should be posi-
tioned adjacent to each other during the
SHORT configuration. Likewise the current In order to determine the resistance value of a
drive connections (I+, I-) should be positioned device, current is injected to the device through
adjacent to each other. the I+, I- connections. The current that flows is
dependent upon the resistance of the device.
Q uadTech LR2000 Milliohmmeter
This current is measured and used in the
Rx : 2.549 m
resistance calculation. The current through the
resistor will generate a voltage across the
1 0 DRIVE (-) SENSE SENSE (+) DRIVE device. This voltage is measured by the P+, P-
connections, note these connections are closer
DRIVE
(-)
SENSE SENSE
(+)
DRIVE
Voltage Sense: P+, P- to the device than the I+, I-. Since the voltmeter
QuadTech LR2000-50 TEST LEADS
Current Drive: I+, I-
would have a high impedance no current would
flow through the P leads, thus having no influ-
ence on the voltage detected by these connec-
P- P+
tion. A very precise calculation results from this
I- I+
measured current and voltage.
SHORT
Figure 25: Kelvin Leads Zeroing Position
25
Verification of a Milliohmmeter
Standards Safety
There are a number of different low resistance As with any instruments safety precautions
standards and resistors that can be used to should be taken. Most milliohmmeters have a
verify the operation of a milliohmmeter. relatively low clamping voltage however the
Precision Resistor manufactures a PLV-7 instruments do produce high currents.
series of resistors (http://www.precisionresis- Precautions should be taken per manufactur-
tor.com/PLV7.htm). The PLV-7 Series are 4-ter- ers recommendations. It is also important
minal resistors with resistance values from 5m when measuring inductive devices (such as
to 100 , tolerances to 0.005%, excellent tem- coils and inductors) to not disrupt the test by
perature and stability characteristics. disconnecting the leads. This can result in a
dangerously high voltage being produced in
the inductor.
Current Shunt
There are also a wide variety of current shunts
An inductor, a wire wound around a core mate-
such as those from Deltec Company. A shunt
rial, stores energy in a magnetic field. If the cur-
is a very low resistance connection between
rent applied to an inductor is suddenly inter-
two points in an electric circuit that forms an
rupted, a voltage transient occurs across the
alternative path for a portion of the current*.
open circuit. The voltage can increase to a
The voltage drop across the shunt is is used
dangerous level. Proper protection must be
with an ammeter to measure the amperage of
taken when breaking the contact across the
a circuit. Figure 27 illustrates a typical WB cur-
inductor (inductive circuit). Ground the circuit
rent shunt from Deltec. Note that there are two
and ground the individual breaking the contact.
large terminals on the outside for drive connec-
tion and two inner terminals for sense connec-
tion.
Figure 27: Example Current Shunt
*Courtesy Deltec Company
http://www.deltecco.com
Shunts are specified in terms of voltage and
current therefore a 50mV/50A shunt would
have a resistance of 1m. Typically current
shunts are calibrated to an accuracy of 0.25%.
Most calibration laboratories can calibrate cur-
rent shunts to higher accuracy and at the
appropriate current for the milliohmmeter being
tested.
26
External Connection to a Milliohmmeter
Once correct connection to the device under RS-232 Interface
test is established, the automation of milliohm The RS-232 interface is a serial port for trans-
measurements will save time and increase the mission of information in serial bit format. RS-
efficiency of logging data. Remote control of 232 communication requires three lines:
test instrumentation, automation of tests and "receive data", "transmit data" and "signal
collection of the test results are indispensible in ground". Serial port parameters are com-
fast paced production environments. prised of 8 data bits, 1 stop bit and Odd, Even
or No parity. Depending on the instrument,
Remote I/O baud rate is fixed or selectable in multiples of
1200bps (bits per second).
Remote operation decreases the potential for
operator error thus increasing the accuracy DB9 Female
and repeatability of the setup and data. A Received Line
remote I/O interface can be configured as a 9- Signal Detect 1
6 DCE Ready
pin, 24-pin or 25-pin connector or a terminal Transmitted Data 2
strip. The simplest remote I/O interface typi- 7 Clear to Send
Received Data 3
cally accepts the input signals [START] and 8 Request to Send
DTE Ready 4
[STOP] and provides the output signals [PASS] 9 Ring Indicator
and [FAIL]. When making measurements of a Signal Ground 5
small magnitude, precison means leaving the
test leads, DUT and setup alone. Remote oper-
Shield
ation provides that measurement reproducibili-
ty and stability. Figure 29: Typical RS-232 Pin Configuration
Figure 28 illustrates a simple Remote I/O con-
nection to illuminate green/red LEDs on a IEEE-488 Interface
Pass/Fail result. Jumpers are placed between
pins 11 & 10, 8 & 7 and 4 & 3 respectively. The IEEE-488 interface is a parallel port for
START switch is connected between pin 1 and transmission of 8 bits (1 byte) of information at
ground, PASS from pin 21 and FAIL from the a time over 8 separate wires. The information
jumper between pins 4 & 3. travels on 3 buses: handshake, control and
Illuminates START
3k
FAIL Red Switch
Signal LED
jumper
jumper jumper
12 11 10 9 8 7 6 5 4 3 2 1
3k or pin 7
Illuminates
Green PASS
LED Signal 24 23 22 21 20 19 18 17 16 15 14 13
Remote I/O Figure 28:
Note: Connect pins 8 & 7 together for all applications Remote I/O Pass/Fail Connection
27
data. IEEE-488 has a faster transfer rate (up to In response to customer inquiries, QuadTech
1MB/second) than RS-232 but it's connection provides sample software for controlling and
cable is limited to 20 meters. There is no limit collecting data from its instruments. Executable
to the communication cable length with the RS- QuickBasic and VisualBasic programs are
232 interface. available in the Software Resources section of
http://www.quadtech.com.
DIO1
1 13
DIO5
The QuickBasic program for the LR2000 meter
DIO2
2 14
DIO6
verifies communication between a PC and the
DIO3
3 15
DIO7
LR2000. The program prompts the user for
DIO4
4 16
DIO8
com port, queries IDN of the instrument,
EOI
5 17
REN
prompts the user for the number of measure-
DAV
6 18 ments to be take, displays the measurements
NFRD
7 19 on the terminal and saves the data to a file.
NDAC
8 20
IFC
9 21
SRQ
10 22
LR2000 Virtual Front Panel Wizard
ATN
11 23 From any desktop PC, program the source, dry
SHIELD GND
12 24 circuit, range, speed, average and delay func-
tions and click [TRIGGER]. The test results are
saved to an Excel-compatible log file. For tem-
Figure 30: Typical IEEE-488 Pin Configuration perature compensation, enter the temperature
and select your material (or enter your coeffi-
cient) and both resistance values will be dis-
RS-232 & IEEE-488 Control played and logged.
Commands for RS-232 and IEEE-488 commu- Pull up the log file, import it into Excel, select
nication are similar and some are identical the parameters of interest and graph the results
depending upon the instrument. Each com- - a very nice visual and statistical tool for tem-
mand line is terminated with a carriage return perature compensation analysis or resistance
[CR] and a line feed [LF]. Multiple commands characterization.
are separated with a semicolon.
Figure 31: LR2000 Virtual Front Panel
28
Applications of Milliohmmeters
Surface Resistivity - Test Samples Cable Testing
Measurements with a Resistivity Cell Resistance & Capacitance Measurements
The LR2000 instrument can be used for meas- Milliohm measurements are frequently made
uring the resistivity of test samples as on wires and cables since resistivity of the con-
described by ASTM Standard D257, which ducting wire/cable is a primary factor in its final
details the techniques for both surface and vol- application. As detailed in the conductor sec-
ume resistivity measurements. The most com- tion, conductive materials are chosen for their
mon electrode arrangement is illustrated in specific resistivity/conductivity and temperature
Figure 31. characteristics. More than a simple length of
bare copper wire, a cable is comprised of plat-
ed copper (tin, silver, nickel) and bundled in
Guard
Ring strands for electrical as well as physical prop-
Sample
Top
View
erties.
Top
Electrode
Cable strength and flexibility are primary
parameters for cables used in dynamic envi-
ronments where they are pulled, twisted and
Top Electrode Terminal 1
Guard Ring
Guard Side flexed often. Individual strands break causing
Ring View
Sample
Terminal 2 the discontinuity in the cable. Cable made of
Bottom Electrode Terminal 3
strands of alloys (alloy 135) exhibit greater ten-
sile strength than bare copper wire and strand-
Figure 31: ASTM D257 Test Cell ed bare copper wires*. (*Calmont Wire & Cable Inc.,
In this configuration, surface resistivity is meas- `Effect of Flex Life' Technical Bulletin)
ured with terminal 1 tied to the - UNKNOWN Cables are comprised of more than one wire
terminal, terminal 2 tied to the +UNKNOWN and here continuity is an important factor.
terminal and terminal 3 tied to GUARD. Continuity of a cable means that all its intend-
Surface = s =
P
Rs
ed connections are made. The sum of resist-
Resistivity g
ance of each of these connections is defined as
P = effective perimeter of measuring electrode
g = dimension of space between electrodes 2 and 1
the minimum continuity resistance of the cable.
Rs = measured surface resistance in ohms To find the problem in a discontinuous cable,
Equation 5: Surface Resistivity: Test Cell resistance is measured between the end points
of a shorted pair of points to reveal the defec-
Equation 5 is the formual for determining the
tive cable end.
surface resistivity using the test cell in Figure
28. Refer to the ASTM standard for the for- When an open is suspected (an intended con-
mulas required to convert from measured nection in the cable is not made), capacitance
resistance to resistivity. Or visit the American is measured from two end points of the open
Society for Testing and Materials at circuit to all other wires in the cable to reveal
http://www.astm.org for the latest information. the defective cable end. When measuring wire
harnesses, one must consider the shielded
In electrical terms, resistivity is the resistance wires and twisted pair cables that make up the
of a material to the flow of current times the harness. In this instance measuring the capac-
cross-sectional area of current flow per unit itance of the harness can reveal the continuity
length of the current path. of an unterminated shield and/or the miswiring
of twisted pair conductors.
29
Component Testing Therefore the computation of the temperature
rise is:
Determining Temperature Rise of Motors
and Transformers
1.6211 - 1.2367
The determination of the temperature rise in T = = 78.45 oC
1.2367 (0.003931)
motors and transformers due to self-heating is
a very common measurement. Motors, trans-
Equation 7: Temperature Rise
formers, solenoids and coils all exhibit symp-
toms of heat rise during use. The internal
power losses of the device result in heating Ambient temperature changes could have sig-
which increases the operating temperature of nificant impacts on the test results. Some mil-
the unit. In most cases it is impractical to liohmmeters have a temperature sensing func-
measure the temperature with thermocouples tion to measure the ambient temperature or
or other temperature sensors, hence the capability for entering this data. The test
change in resistance method for temperature results and temperature conditions are then
determination. automatically referenced to nominal ambient
The majority of magnetic devices use either temperature (23oC).
copper or aluminum wire in the construction of
their core. These wires have precise tempera-
ture coefficients (TC) that can be used with
resistance measurements to calculate the tem-
perature rise (T) of the device under test
(DUT). The change in temperature is equal to
the resistance of the DUT before use (RCOLD )
minus the resistance of the DUT during use
(RHOT ) divided by the temperature coefficient
times R COLD .
RHOT - RCOLD
T =
RCOLD (TC)
Equation 6: Temperature Rise
Let's look at the calculation of temperature rise
for a motor after 8 hours of operation at a spec-
ified rated load. The field winding of the motor
is constructed of copper wire. This particular
copper wire has a temperature coefficient of
3931ppm/o C (R = 0.3931%/oC). Before run-
ning at a load the ambient winding resistance is
measured as 1.2367. After 8 hours of opera-
tion at full load, the winding resistance is meas-
ured as 1.6211.
30
QuadTech Low Resistance Measurement Instruments
Applications:
o Production Testing of Contact Resistance
of Switches, Relays, Connectors, Cables,
and Other Low Resistance Devices
o Testing of Low Value Resistors, Fuses,
Squibs, and Heating Elements
o Winding Resistance of Motors, Transformers,
Solenoids, and Ballasts
o Conductivity Evaluation in Product Design
LR2000 Milliohmmeter o Incoming Inspection and Quality Assurance
The LR2000 Milliohmmeter has a basic accu- Testing
racy of 0.05% and a wide measurement range LR2000 Virtual Front Panel Wizard
from 1µohm to 2Mohms. For remote operation
and production applications the unit comes
standard with an RS-232 interface, plus IEEE-
488 and handler interfaces are available as
options. For measurement integrity, contact to
the test device is made via a 4-terminal Kelvin
connection that incorporates an automatic
zeroing function to compensate for lead errors.
The LR2000 provides eight measurement
ranges from 20m to 2M with constant cur-
rent between 1A and 1mA. For "dry" contact Written in Visual Basic 6.0, the Virtual Front
measurements (those contacts whose resist- Panel Wizard for the LR2000 will easily config-
ance can be altered by excessive voltage ure the LR2000 Milliohmmeter. From any
potential) the LR2000 can be limited to 20mV desktop PC, program the source, dry circuit,
on selected measurement ranges. range, speed, average and delay functions and
o 1µ - 2M Measurement Range click [TRIGGER]. The test results are saved to
o 1mA - 1A Constant Current an Excel-compatible log file. Pull up the log
o 0.05% Basic Measurement Accuracy file, import it into Excel, select the parameters
o Measurement Speed to 15/second of interest and graph the results - a very nice
o Test Signal: DC+, DC-, Pulse, Pulse+, Pulse- visual and statistical tool for temperature com-
pensation analysis or resistance characteriza-
o Dry Circuit Test Current
tion.
o Graphical LCD Display
Features:
o Four-Terminal Kelvin Connection
o Automatic Zeroing o Log Test Data to Excel-Compatible File
o RS-232 Interface Standard o Remotely Configure Instrument from PC
o Set Room Temperature
o IEEE and Handler Interfaces, Optional
o Set Temperature Coefficient
o Automatic Hi/Lo Comparator Limits
o Pass/Fail Sorting (8 Bins) Requirements:
o Voltage Limiting for Dry Contact Testing o LR2000 Milliohmmeter
o Keypad Lockout o RS-232 Interface with Straight-Through Cable
o Programmable Delay Times o PC with Windows and RS-232 Port
31
Cable Testers Applications:
o Cable Verification
o Relay, Switch & LED Testing
Horizon HV1 High Voltage Wiring Analyzer:
o High Voltage Breakdown to 1500V
o Insulation Resistance to 1.5G
o Programmable 1A Current Source
o 128 Test Points Expandable to 1024 Points
o Self Learn Known Good Products
o Flex Test
QuadTech provides three Horizon Cable
Testers designed for specific cable applica- o Twisted Pair Verification
tions. The Horizon 1500 Series includes the o Resistors, Capacitors, and Diode Testing
LV1 Low Voltage Wiring Analyzer, the HV1 o Built-in Pentium PC
High Voltage Wiring Analyzer and the SCSI o SPC and Data Management
Wiring Analyzer. Resistance measurements o Test 500 Point Net In Less Than 1 Sec.
can be made using two-wire connection for Applications:
simple verification that two points are connect- o Switch-hub Verification
ed and continuous. For more accurate resist-
o Cable Verification
ance measurement a 4 wire Kelvin connection
o Relay, Switch & LED Testing
is available for accuracy of +1m on a 10m
o Circuit Board Assembly Tests
measurement.
Similarly, capacitance measurements can be
made using two-wire connection for verification
that two points are connected and continuous.
All three Horizon Wiring Analyzers (LV1, HV1 &
SCSI) measure capacitance from 50pF to 1mF
with a basic accuracy of 4% and from 50pF to
10,000mF with a basic accuracy of 10%.
Horizon LV1 Low Voltage Wiring Analyzer:
o Low Voltage Switching via Solid State Relays The Horizon SCSI wiring analyzer combines all
o Resistance to 50M the features of the High Voltage Series Horizon
o 128 Test Points Expandable to 1024 Points with SCSI (Small Computer System Interface)
o Self Learn Known Good Products test capability to enable fast, flexible and reli-
o Twisted Pair Verification able SCSI terminator testing. To keep testing
o Resistors, Capacitors, and Diode Testing simple and quick, a comprehensive range of
standard programs is included to fully verify
o Built-in Pentium PC
SCSI terminators in less than 10 seconds. The
o SPC and Data Management
TCL scripting language allows unlimited expan-
o Test 500 Point Net in Less Than 1 sec.
sion of the Horizon SCSI terminator test pro-
o Auto Start Test When Product is Loaded
gram library.
o Flex Test
32
Horizon SCSI Wiring Analyzer Dedicated Function Test Instruments
o Fast SCSI Testing In addition to milliohmmeters and cable testers,
o In Process Testing of Cable and Terminators QuadTech manufactures a full line of passive
o Complete Trace Verification component and electrical safety testing instru-
o Verify Signal Voltages and Quiescent Current mentation, including LCR Meters, Digibridges,
o Verify Isolation of Reserved Pins Megohmeters, Hipot Testers and Electrical
o High Voltage Breakdown to 1500V Safety Analyzers. View complete product spec-
o Insulation Resistance to 1.5G ifications at http://www.quadtech.com.
o Programmable 1A Current Source
o 128 Test Points Expandable to 1024 Points LCR Meters
o Self Learn Known Good Products
o Flex Test & Twisted Pair Verification
o Resistors, Capacitors, and Diode Testing
o Built-in Pentium PC, SPC and Data Management
o Test 500 Point Net in Less Than 1 Sec.
7400 Precision LCR Meter
Applications: Megohmmeters
o SCSI Cables
o SCSI terminators
Fusion Wire & Cable Analyzers
The Fusion Wire & Cable Analyzer is a fully
integrated test system. Hipot, Megohmmeter,
Milliohmmeter & Capacitance Measurements
1868A Megohmmeter
can be performed via a multi-channel scanner
up to 72 points. For low resistance measure- Hipot Testers
ments, a 2-wire and 4-wire configuration is pos-
sible with resolution down to 1m in the 4-wire
mode. Make 2-wire measurements from 1m
to 50M and 4-wire measurements from 1m. to
400k.. The unit is also capable of high resist-
ance measurements to 50M .
Sentry Plus Hipot Tester
Electrical Safety Analyzers
Fusion High Voltage Cable Analyzer Guardian 6000 Electrical Safety Analyzer
33
CompuMess Elektronik GmbH
Lise-Meitner-Str.1, 85716 Unterschleissheim
Tel 089-321501-0 Fax 089-321501-11
http://www.compumess.de oder http://www.netzteile.de
34
Appendix A
35
Formulas
Resistance
i i
V
R=
i
DUT V 1A DUT V
R = Resistance in ohms
V = Voltage in volts
V
Resistance =
I = Current in amperes 1A
2-Wire Resistance Measurement
DMM VMETER = Voltage measured by meter
R LEAD (HI) ITEST
HI
VDUT = Voltage across DUT (device under test)
VMETER
Measured Resistance = = R DUT + (2 x RLEAD
)
VMETER V METER VDUT RDUT
ITEST
VDUT
Actual Resistance = = R DUT
LO I TEST
R LEAD (LO)
4-Wire Resistance Measurement
DMM or Milliohmmeter
R LEAD (Drive) ITEST
Drive HI
VMETER = Voltage measured by meter
Sense HI R LEAD (Sense)
VDUT = Voltage across DUT (device under test)
Because Sense Current is negligible: V METER = V DUT
V METER VMETER VDUT R DUT
V METER VDUT
Measured Resistance = =
ITEST I TEST
Sense LO R LEAD (Sense)
Drive LO R LEAD (Drive)
36
Formulas
Current Reversal
Vemf Vemf
+ -
ISOURCE VMETER ISOURCE VMETER
RMEAS - RMEAS +
VMETER = Meter Voltage VMETER + = Vemf + (ISOURCE) (RMEAS)
Vemf = Thermal emf VMETER - = Vemf - (ISOURCE ) (RMEAS )
ISOURCE = Source Current VMETER = [VMETER + ] - [VMETER - ] [Vemf + (ISOURCE ) (RMEAS )] - [V emf - (ISOURCE ) (RMEAS )]
=
2 2
RMEAS = Measured Resistance VMETER = (ISOURCE ) (RMEAS )
Offset Compensated Ohms
1 Measment Cycle
Vemf Vemf
+
VMETER ISOURCE VMETER
- RMEAS
RMEAS Source Current
Voltage Measurement with Voltage Measurement with Thermal Offset
Current Source ON Current Source OFF Measurement
VMETER = Meter Voltage VMETER 1
= Vemf + (ISOURCE ) (RMEAS )
Vemf = Thermal emf
VMETER 2
= Vemf
ISOURCE = Source Current
R MEAS = Measured Resistance
VMETER = [VMETER 1
] - [VMETER 2
]
VMETER = [Vemf + (ISOURCE ) (RMEAS )] - [V emf ]
VMETER = (ISOURCE ) (RMEAS )
Resistivity
= electrical resistivity ohm-meter
RA R = resistance of conductor ohm
= A = cross-sectional area of conductor meter 2
l
l = length of conductor meter
Resistivity and Temperature
= measured resistivity
0 = resistivity at reference temperature (20oC)
= 0 1 + T - T0 T = measured temperature
T0 = reference temperature
= temperature coefficient of resistivity
37
Formulas
Conductivity
= electrical conductivity
ne 2 l n = density of free electrons
= e, me = charge and mass of an electron
meVrms
Vrms = root-mean-square speed of electrons
l = mean free path length
Temperature Conversion
Celsius Fahrenheit Kelvin
oC oF K
100oC 212oF 373.15 K
Boiling Point H2O
20oC 68oF 293.15 K
Room Temperature
0oC 32oF 273.15 K
Freezing Point H2O
0oF
-273.15oC -459.67oF 0K
Absolute ZERO
Known Temperature Desired Temperature Equation
Fahrenheit °F - °C Celsius °C = (°F 32)/1.8
Fahrenheit °F - K Kelvin K = (°F + 459.67)/1.8
Celsius °C - °F Fahrenheit °F = (1.8 x °C) + 32
Celsius °C - K Kelvin K = °C + 273.15
Kelvin K - °F Fahrenheit °F = (1.8 x K) 459.67
Kelvin K - °C Celsius °C = K 273.15
AWG & Diameter
39 x log (200D)
AWG: = 36 -
log (92)
36 - AWG
39
D = 0.005 92
D = Diameter in inches
38
Tables
Note:
Tables 2 & 7 from the Conductor and Temperature Compensation sections of this guide contain data
from different sources and thus have different values for Resistivity and Temperature Coefficient.
Both tables are repeated here with the sources listed so the reader may verify the content according to
his needs.
Table 2: Resistivity of Common Conductors
Resistivity at room temperature: 20o C = 293K = 68oF
Material Symbol Resistivity Conductivity Temperature
Coefficient
µ-cm per -m per °C
Element Metal
7
aluminum Al 2.65 3.77 x 10 0.0042
7
copper Cu 1.67 5.95 x 10 0.0040
gold Au 2.21 4.55 x 107 0.0037
7
iron Fe 9.66 1.03 x 10 0.0056
7
lead Pb 20.65 0.43 x 10 0.0042
magnesium Mg 4.3 2.33 x 107
7
manganese Mn 144 0.072 x 10
7
nickel Ni 6.93 1.43 x 10 0.0058
platinum Pt 10.5 0.96 x 107 0.0037
7
silver Ag 1.59 6.29 x 10 0.0038
7
tantalum Ta 13.1 0.76 x 10
titanium Ti 42 0.24 x 107
7
tungsten W 5.28 1.89 x 10 0.0044
7
zinc Zn 5.92 1.69 x 10 0.0038
Alloy Metal
7
nichrome Ni80Cr20 110 0.095 x 10 0.00017
7
manganin* CuMnNi 48.21 0.207 x 10 ± 0.000015
7
steel** FeC 16.62 0.502 x 10 0.003
Semiconductors
4
carbon (graphite) C 3500 2.9 x 10 -0.0005
germanium (pure) Ge 46000 2.2 -0.048
silicon (pure) Si 64000000 0.0016 -0.075
* Manganin composed of 83% copper, 13% manganese and 4% nickel
** Steel composed of 99.5% iron and 0.5% carbon
This table was comprised of data from multiple sources including:
All About Circuits: C12 The Physics of Conductors and Insulators
http://www.allaboutcircuits.com/vol_1/chpt_12/1.html
Hyper Physics: Resistivity Table
http://hyperphysics.phy-astr.gsu.edu/hbase/Tables/rstiv.html#c1
MIT course 802: C.6 Current and Resistance
http://web.mit.edu/8.02t/www/802TEAL3D/visualizations/coursenotes/modules/current.pdf
Microwaves 101
http://www.microwaves101.com/encyclopedia/conductivity.cfm#conductor
The Physics HypertextbookTM: Electrical Resistance
http://hypertextbook.com/physics/electricity/resistance/
39
Tables
Table 7: Temperature Coefficients
Material Resistivity Temperature
(*m) Coefficient
(°C)
-1
at 20°C
-8 -3
Silver 1.59x10 3.8x10
-8 -3
Copper 1.7x10 3.9x10
Gold 2.44x10-8 3.4x10-3
-8 -3
Aluminum 2.82x10 3.9x10
-8 -3
Tungsten 5.6x10 4.5x10
Iron 10x10 -8 5.0x10-3
-8 -3
Platinum 11x10 3.92x10
-8 -3
Lead 22x10 3.9x10
-8 -3
Nichrome 150x10 0.4x10
-8 -3
Nickel 8.7x10 6.8x10
-5 -3
Carbon 3.5x10 -0.5x10
-3
Germanium 0.46 -48x10
This table was comprised of data from:
Source: Physics For Scientists & Engineers, Raymond A. Serway, 3RD Edition, Volume II, 1990
Resistivity & AWG
Table 4: Solid Copper Wire: AWG & Resistivity
AWG Size Diameter Diameter Resistance Resistance
(Solid Wire) (mm) (inches) /1000feet /1000meters
0000 (4/0) 11.684 0.4600 0.049 0.1607
000 (3/0) 10.404 0.4096 0.0618 0.2027
00 (2/0) 9.266 0.3648 0.078 0.2555
0 (1/0) 8.252 0.3249 0.0983 0.3224
1 7.348 0.2893 0.124 0.4063
5 4.621 0.1819 0.3133 1.0276
10 2.588 0.1019 0.9989 3.28
12 2.052 0.0808 1.588 5.21
14 1.6256 0.0640 2.525 8.28
16 1.2903 0.0508 4.016 13.2
18 1.0236 0.0403 6.385 20.9
20 0.8128 0.0320 10.15 33.2
22 0.6451 0.0254 16.14 52.7
24 0.5105 0.0201 25.67 84.2
30 0.2540 0.0100 103.2 338.496
36 0.1270 0.0050 414.8 1360
40 0.0787 0.0031 1049 3440
40
Helpful Links
Conductivity
Wikipedia Free Encyclopedia:
http://en.wikipedia.org/wiki/Electrical_conductivity
Microwaves 101
http://www.microwaves101.com/encyclopedia/conductivity.cfm#conductor
Fisk Alloy: Conductor Facts
http://www.fiskalloy.com/c-main-pages/c-welcome.html
All About Circuits: C12 The Physics of Conductors and Insulators
http://www.allaboutcircuits.com/vol_1/chpt_12/1.html
Hyper Physics: Superconductivity
http://hyperphysics.phy-astr.gsu.edu/hbase/solids/scond.html
Resistivity
HyperTextBookTM :
http://hypertextbook.com/facts/index-topics.shtml#resistivity
The Physics Hypertextbook TM : Electrical Resistance
http://hypertextbook.com/physics/electricity/resistance/
Free Dictionary
http://encyclopedia.thefreedictionary.com/electrical%20resistivity
Hyper Physics: Resistivity Table
http://hyperphysics.phy-astr.gsu.edu/hbase/Tables/rstiv.html#c1
MIT course 802: C.6 Current and Resistance
http://web.mit.edu/8.02t/www/802TEAL3D/visualizations/coursenotes/modules/current.pdf
Temperature
Temperature Conversion and Thermocouple Identification Table:
http://www.pmel.org/HandBook/HBpage16.htm
Wire AWG
Wikipedia Free Encyclopedia: American Wire Gauge
http://en.wikipedia.org/wiki/American_wire_gauge
Power Stream: Wire Gauge & Current Limits
http://www.powerstream.com/Wire_Size.htm
Hyper Physics: Wire Gage
http://hyperphysics.phy-astr.gsu.edu/hbase/Tables/wirega.html#c1
epanorama.net: Copper Wire AWG
http://www.epanorama.net/documents/wiring/wire_resistance.html
Tyco Electronics: AWG Chart
http://www.tycoelectronics.com/
Current Rating, Copper Wire Characteristics, AWG
http://allflexinc.com
41
Helpful Links
Cable Characteristics
National Semiconductor Application Note AN-916: Practical Guide to Cable Selection
http://www.national.com/an/AN/AN-916.pdf
Cable Guide
http://www.cvalim.co.il/pdf/electro.pdf
Cable Catalog, Cable AWG Characteristics
http://www.superior-cables.co.il
Current Carrying Capacity, Shielding, Copper Wire AWG
http://www.alphawire.com/pages/383.cfm
http://www.alphawire.com/pages/342.cfm
Current Rating, Copper Wire Characteristics, AWG
http://allflexinc.com
Aerospace Wire & Cable Catalog - Judd Wire
http://www.juddwire.com
Cable Flex Test- Calmont Wire & Cable Inc.
http://www.calmont.com/flex%20test%20summary.pdf
Technical Reference on Wire & Cable - Calmont Wire & Cable Inc.
http://www.calmont.com/tech_11.pdf
Current Shunts
Deltec Inc
http://www.deltecco.com
Resistance Standards
Precision Resistor
http://www.precisionresistor.com
Probe Leads, Kelvin Clips
Pomona Electronics
http://www.pomonaelectronics.com
42
QuadTech MEG/MIL Selection Guide
Milliohmmeters
Tester Accuracy Resistance Voltage Range Test Time Display Output Other
Range & Current Features
LR2000 0.05% 1µ 2M Test Signal: Trigger: LCD RS232 Std. Dry Circuit Mode
Digital Basic 0-2.0V DC+, DC-, 0-1000ms; Full Menu IEEE-488 & Comparator: H/L Limits
Pulse+, Pulse-, Delay Time: Test Setup, Handler Opt. Binning: 8 Bins P/F
Pulse+/-, Stby 0-100s Value, 4-Terminal Kelvin Clips
Test Current: % Value Prog. Delay Time
1A 1uA Value Measurement Average
Bin # Range: Auto/Hold
Trigger: Int, Ext, Man
Megohmmeters
Tester Accuracy Resistance Voltage Range Test Time Display Output Other
Range & Current Features
1863 3.0% Basic 50k 20T 50 500V Manual Analog Analog Portable
Analog <5mA Meter Steel Case
1864 3.0% Basic 50k 200T 10 1090V Manual Analog Analog Portable
Analog <5mA Meter Steel Case
1865 0.5% Basic 1k 100T 1 1000V 0 300s LCD with P/F Indicator Floppy Option
LO limit <2mA Graphics HV Indicator Auto Zero
Digital
RS232 Store & Recall
I/O PORT ENG or SCI display
OPTIONAL: R or I display
IEEE-488 Safety Interlock
OPTIONAL:
Shielded Lead Set
Comp Test Fixture
1867 2.0% Basic 50k 200T 10 1090V: Manual Analog Analog Remote
Analog HI/LO limits 10 500V Meter P/F Indicator (Terminal Strip)
<5mA P/F Alarm IP: Trigger
500 1090V OP: High Fail, Low
<25mA Fail and Pass
1868 2.0% Basic 10k 1P 1868A: Charge LCD with: HV Indicator PCMCIA Interface
Digital Auto Range 10 1000V Measure Text, RS232 Auto Zero
or 4 user 2mA/25mA/80mA Delay Line Graph I/O PORT Store & Recall
selectable 1868D: Discharge: Bar Graph IEEE-488 R or I display
ranges 50-5000V 9999msec Binning Safety Interlock
2mA/10mA/18mA
Capacitor Leakage Current / IR Meter
Tester Accuracy Measurement Voltage Range Test Display Output Other
Range & Current Time Features
1855 Basic: LC:1nA-20mA 1 650V DC Charge, LCD P/F Indicator Withstand Voltage
LC: 0.3% IR: 10 99G Charge Current: Dwell Test Setup P/F Alarm Rise Time
LC & IR
IR: 0.6% WV: 1-650V DC 0.5 -500mA 0-999sec Value RS232 Auto Ranging
Meter Tr: 0.05-120sec Pass/Fail Optional: Averaging 1-8
IEEE & Handler Comparator P/F
43
44
Application Note
Directory
45
QuadTech Application Notes
Contained herein is a list of QuadTech application notes available for download in Adobe PDF for-
mat. To access the application notes visit: http://www.quadtech.com/resources and click on the
Application Note link.
A/N P/N Title/Description Release
035000 Measuring Insulation Resistance of Capacitors 06-03-03
035001 Series & Parallel Impedance Parameters and Equivalent Circuits 07-09-03
035002 Equivalent Series Resistance (ESR) of Capacitors 07-09-03
035003 Increasing Test Voltage on the QuadTech Digibridge 10-10-00
035004 High Voltage DC Bias on the QuadTech Digibridge 10-10-00
035005 Application for Precision Impedance Meters in a Standards Laboratory 09-12-03
035006 Application for Precision Impedanc e Meters in a Standards Laboratory 07-18-00
035007
035008 Application of DSP to Precision LCR Measurements 07-09-03
035009 Measuring Biased Inductors with the 7000 Precision LCR Meters 07-25-03
035010 A Guide to LCR Measurements 07-10-03
035011 A Practical Guide to Dielectric Testing 06-24-03
035012 Measurements of Dielectric Constant and Loss with the LD-3 Cell 08-04-03
035013 Sentry Series Light Ballast Application 10-03-02
035014 Guardian 1030S and Cable Reel Immersion Test 10-03-02
035015 Guardian 1030 used for IR Test on Adhesive Heat Shrink 10-03-02
035016 Sentry Series Panel Meter Application 10-03-02
035017
035018
035019 Helpful Tips on Measuring Capacitors 07-11-03
035020 Testing Capacitors with the QuadTech Model 1865 Megohmmeter/IR Tester 11-08-00
035021 What's Changing in Appliance Hipot Testing and Why 11-08-00
035022 Measuring Biased Inductors with the QuadTech Digibridge 11-08-00
035023 Characteristic Cable Impedance 01-24-03
035024 Calibrating Impedance Meters Using Resistance Standards 08-18-00
035025 Advanced Technique for Dielectric Analysis 06-24-03
035026 Medical Equipment Test Applications using the 7000 Precision LCR Meter 09-28-00
035027 Multi-Terminal Impedance Measurements (Why do these bridges use so...) 07-23-03
035028 Testing Automotive Engine Oxygen Sensors using the 1900 Precision LCR 02-11-02
035029 Hipot Testing of Motors and Safety Standard Compliance 12-19-00
035030 Transformer Turns Ratio using the 7000 Series RLC Meters 12-19-00
035031 The QuadTech 1865 as a Current Meter 12-19-00
035032 Measuring Large Capacitors with the 1865-52 Component Test Fixture 06-03-03
035033 Insulation Resistance of Cables 09-28-00
035034 1865 Remote Pass/Fail Lights 01-08-01
035035 1865 Specified Accuracy 01-08-01
035036 The QuadTech 1865 Average Function 09-19-02
035037 How to Connect a Foot Switch to the 1870 Dielectric Analyzer 01-08-01
035038 The 1880 Specified Accuracy & Constant Current Ranges 01-10-01
035039 External DC Supply for the 1536 Photoelectric Pickoff Cell 01-10-01
035040 Basic Program to Control the Flash on a 1539 Strobe 01-10-01
035041 Characteristic Cable Impedance 01-24-03
035042 Constant Current with the 1693 RLC Digibridge 05-26-00
035043 Charged Capacitor Protection Circuit for the QuadTech Digibridges 02-15-02
035044 Transformer Ratio Measured Directly on the 1689 & 1693 Digibridges 03-25-03
035045 How Much is One Joule 09-11-03
035046 7000 Series Connections to the LD-3 Dielectric Cell 08-05-03
035047 Digibridge Connections to the LD-3 Dielectric Cell 01-15-01
035048 Battery Impedance Measurements 07-18-00
035049 Charged Capacitor Protection for the 7000 02-13-01
035050 What Voltage and Current is Applied to the Unknown? 07-24-03
035051 Power Factor of a Capacitor (1900 Series) 07-28-03
035052 Tutorial on Safety Standard Compliance for Hipot Testing 06-24-03
035053 Benefits and Advantages of Digital Electrical Safety Testers 02-13-01
035054 Measuring Electrical Properties of Copier/Printer Toners 08-06-03
035055 Monitoring the Production Process of Tantalum Powder 08-07-03
035056 Transducers used in Monitoring Nuclear Waste Tanks 07-28-03
035057 Measuring the Dielectric Constant of PVC Compounds 08-08-03
035058 Testing Animal Identification Implants 07-28-03
035059 Testing Telecommunications Transformers 02-28-01
035060 Enhanced Protection When Measuring Charged Capacitors 02-28-01
46
QuadTech Application Notes
A/N P/N Title/Description Release
035061 Guardian 1000 Series Light Ballast Application 10-03-02
035062 Cable Reel IR Testing Application 10-03-02
035063 Adhesive Heat-Shrink IR Testing 10-03-02
035064 Why Perform Electrical Safety Testing? 06-23-03
035065 Ground Bond, Ground Continuity and Earth Continuity 06-23-03
035066 Appliance Testing with the Guardian 6200 Production Safety Analyzer 03-27-01
035067 Determining if a DUT is connected, using the Low Trip Limit (G1000 Series) 02-04-02
035068 UL Standards 03-27-01
035069 Guidelines for External Bias on the 7400 and 7600 04-24-01
035070 Digibridge to 7000 Handler Conversion 04-24-01
035071 Increasing Test Voltage of a 7000 Series RLC Meter 04-24-01
035072 Mutual Inductance Measurements with a 4-Terminal LCR Meter 08-18-00
035073 Connection of the 1865 Megohmmeter to a Resistivity Cell 09-05-03
035074 Guardian 5000 Demo Guide 07-18-00
035075 Guardian 2500 Demo Guide 07-31-00
035076 Sentry 10-35 Demo Guide 07-18-00
035077 Sentry 50 Demo Guide 09-11-03
035078 Glossary of Electrical Safety Terms 06-23-03
035079 Digibridge and Battery Impedance Measurements (1557, 1659, 1689, 1693) 05-16-00
035080 Use of Palm Switches with QuadTech Hipot Testers 05-09-00
035081 Measuring Transformer Turns Ratio using the 1910 Inductance Analyzer
035082 Analyze This Inductor 07-23-03
035083 So You Need To Measure Some Inductors... 07-29-03
035084 LCR Product Accessories 09-19-02
035085 EST Product Accessories 09-19-02
035086 What's Your LCR IQ? 07-23-03
035087 Applying DC Bias to Inductors with the 1910 Inductance Analyzer 05-19-00
035088 Applying DC Bias to Inductors with the 1910 and 1320 07-29-03
035089 LCR & EST Product Interfaces 09-19-02
035090 Electrical Safety Testing of Medical Electronic Equipment 06-16-00
035091 Ensuring RH Sensor Repeatability with Capacitance Testing 07-29-03
035092 Measuring IR with the Guardian 2530 07-05-00
035093 Errors in Low Resistance Measurements 08-20-04
035094 Building the Perfect Component Test Fixture 07-29-03
035095 Custom Design Your Own Shock Therapy 06-13-03
035096 Test Instrumentation: Can't Always Get What You Want? 11-28-00
035097 Guardian 2500 Series Features & Benefits 01-23-01
035098 Sentry Series Features & Benefits 01-23-01
035099 Overview of IEC 60601-1 Medical Electrical Equipment 06-09-03
035100 Why Product Safety Test Your Electrical Medical Products? 06-09-03
035101 Line Leakage Measurement & Human Body Equivalent Circuits 06-09-03
035102 IEC60601-1 and Your Electrical Medical Products 06-09-03
035103 A Bridge to the Future... Capacitance Measurements Through The Ages 07-24-03
035104 What is the Accuracy Anyway? 07-24-03
035105 25 Patents Reference Digibridge 10-15-01
035106 Henry Hall: Father of the Digibridge 10-15-01
035107 1920 Used in Eddy Current Sensor Testing 09-05-03
035108 1689 Digibridge Used In Gas Sensor Materials Testing 07-24-03
035109 Classification per IEC60601-1 06-09-03
035110 EST 101 (IEC60601-1 Electrical Safety Tests) 06-06-03
035111 Ensuring the Safety of Medical Electronics 06-06-03
035112 Low ESR Capacitor Measurements 09-05-03
035113 Measurement of Dielectric Constant and Loss: 1900 LCR Meter & LD-3 Cell 02-11-02
035114 1900 Series Remote I/O Handler 03-11-02
035115 Resistive Load Boxes for Hipot Testers and Megohmmeters 07-29-03
035116 Guardian 6000 Series Scanner Connections 03-29-02
035117 Leakage Current Part 1 06-09-03
035118 Leakage Current Part 2 06-09-03
035119 Calibration of 7000 Series Precision LCR Meters 08-09-02
035120 Testing Power Line Filters using the Guardian 1030S 08-09-02
035121 1864 Megohmmeter used in DC-10 Aircraft Maintenance 09-06-02
035122 1864 Megohmmeter used in Aircraft Fuel Pump Inspection 09-06-02
035123 National Deviations to IEC60601-1 06-09-03
47
QuadTech Application Notes
A/N P/N Title/Description Release
035124 Ground Bond Testing per UL 60950 06-13-03
035125 Connection of Isolation Transformer to Safety Tester 05-15-03
035126 Dielectric Strength Testing of External Cardiac Defibrillators: IEC 60601-2-4 09-05-03
035127 Testing Filter Capacitors on Medical Devices 09-05-03
035128 Hipot Testing Multi-Conductor Feedthroughs used in Implanted Medical Devices 09-05-03
035129 Digibridge Operation and Technique 09-12-03
035130 Open and Short Correction 09-15-03
035131 IR Testing Lithium Batteries for Medical Devices using the 1865 Megohmmeter 09-15-03
035132 Using the 1900 LCR Meter for Medical Industry Capacitance Testing 09-17-03
035133 Automated Quality Testing of Cathode Ray Tubes (CRTs) 01-23-04
035134 A New Reliability Diagnostic for Aged Insulation Systems Based on Cure Monitoring of 04-07-04
Shared "Motorettes" of Catalyzed Mica Tapes Wrapped on Aluminum Bars
Courtesy of Donald R. Speer, W. J. Sarjeant
035135 Determining Cure of a Varnish/Resin After Impregnation of an Electric Motor Stator or Transformer 04-07-04
Shared Courtesy of Donald R. Speer, W.J. Sarjeant, and Roger Ripley
035136 Horizon Marine Application, CableTest Application Note AN-146 04-07-04
Shared Courtesy of CableTest Systems Inc.
035137 Mass HiPot Testing, CableTest Technical Bulletin TB-0110A 04-07-04
Shared Courtesy of CableTest Systems Inc.
035138 High Current Source Compliance Limits, CableTest Technical Bulletin TB-0117 04-07-04
Shared Courtesy of CableTest Systems Inc.
035139 MPT Horizon Capacitance Measurement, CableTest Technical Bulletin TB-0118 04-07-04
Shared Courtesy of CableTest Systems Inc.
035140 DC HiPot Description, CableTest Technical Bulletin TB-0119 04-07-04
Shared Courtesy of CableTest Systems Inc.
035141 F-Type Leakage Measurements with the Guardian 6100 06-14-04
48
Glossary
49
AC Clearance
Alternating current, an electric current that has one Clearance is the shortest distance between two conduc-
polarity during part of the cycle and the opposing polari- tors through air or insulating medium.
ty during the other part of the cycle. Residential electric-
ity is AC. Compare
A procedure for sorting components by comparing the
Accuracy component's measured value against a known standard.
The difference between the measured value or reading
and the true or accepted value. The accuracy of an LCR Conductivity
meter is typically given as a +/- percentage of the meas- The ratio of electric current density to the electric field in
ured value for primary parameters and +/- an absolute a material. Conductivity is also known as `specific con-
value for the secondary parameter. Example: +/-0.05% ductance' and is the reciprocal of resistivity.
for L, C & R and +/-0.0005 for Df.
Creepage
ANSI Creepage is the shortest path along the surface of an
American National Standards Institute, an industry asso- insulator or insulating medium that separates two con-
ciation that defines standards for ductors. The insulator or insulation medium cannot be
data processing and communication. air.
Basic Accuracy CSA
The basic accuracy is specified at optimum test signal, Canadian Standards Association.
frequency, highest accuracy setting or slowest measure-
ment speed and impedance of the DUT. As a general Current
rule this means 1VAC RMS signal level, 1kHz frequency, Constant Current
high accuracy which equates to 1 measurement/second Current the measuring instrument will output during
and a DUT impedance between 10 and 100k. a resistance test, independent of device loading.
Binning Current Polarity
A procedure for sorting components into bins using Test signal type: positive or negative DC or positive
sequential limits or nested limits. or negative pulse. Helps reduce thermal emf effects.
Capacitor DC
Abbreviated as C (as in LCR). A capacitor is a passive Direct current, non-reversing polarity. The movement of
component comprised of two conductors separated by a charge is in one direction. Used to describe both current
dielectric. A capacitor stores charge, blocks DC flow and and voltage. Batteries supply direct current.
allows AC flow based on frequency and capacitor
design. Delay Time
The amount of time an instrument waits before perform-
Capacitance ing a task.
The ratio of charge on either plate of a capacitor to the
potential difference (voltage) across the plates. When a Discharge
voltage is applied, current flows immediately at a high The act of draining off an electrical charge to ground.
rate and then decays exponentially toward zero as the Devices that retain charge should be discharged after a
charge builds up. If an ac voltage is applied, an ac cur- DC hipot or IR test.
rent appears to flow continuously because the polarity of
the voltage is reversed at the frequency of the applied DUT
voltage. The waveform of this current, however, is dis- Device Under Test - the product being tested.
placed in time from the applied voltage by 90°.
Dwell Time
Capacitive Reactance The amount of time the DUT is allowed to stabilize at the
Measurement of the actual AC resistance of a capacitor. test voltage before measurements are performed.
How effective a capacitor is in allowing AC to flows
depends upon its capacitance and frequency.
Xc = 1/2fC.
50
emf IEEE 488
Electromotive force: the difference in electric potential General Purpose Interface Bus (GPIB) - an industry
that exists between two dissimilar electrodes immersed standard definition of a parallel bus connection for the
in the same electrolyte or otherwise connected by ionic purpose of communicating data between devices.
conductors.
Impedance
Electric Current A term used with alternating current circuits to describe
The flow of electrons (or electron "holes") through a con- the "ac resistance" to the flow of current through a circuit
ducting material, which may be a solid, liquid, or gas; the when an ac voltage is applied across the terminals of
rate of flow of charge past a given point in an electric cir- that circuit. Impedance is a complex quantity composed
cuit. The magnitude of current flow through the conduc- of real (in phase with voltage) and reactive (out of phase
tor is proportional to the magnitude of voltage or electri- by 90°) components. Impedance is calculated as voltage
cal potential applied across the conductor and inversely divided by current.
proportional to the resistance (or impedance) of the con-
ductor. Current is expressed in amperes or milliamperes Impedance (Z) is a vector summation of resistance (R)
(amperes/1000). and reactance (X).
Capacitors: Reactance = XC = 1/jC
Equivalent Circuit Inductors: Reactance = XL = jL
The configuration of the device under test. The compo-
Resistors: Resistance = R
nents of the DUT can be represented as a series or par-
allel equivalent circuit. Impedance = Z = square root (X2 + R 2)
Fall Time Inductor
The amount of time it takes to gradually decrease the Abbreviated L (as in LCR). An inductor is a coil of wire. It
voltage to zero potential. is used to create electromagnetic induction in a circuit.
Frequency Inductance
The rate at which a current or voltage reverses polarity The property of a coil to oppose any change in current
and then back again completing a full cycle, measured in through it. If the turns (coils) of the wire are stretched out,
Hertz (Hz) or cycles per second. the field intensity will be less and the inductance will be
less. Unit of measure is the Henry (H).
Ground
The base reference from which voltages are measured, Inductive Reactance
nominally the same potential as the earth. Also the side A measure of how much the counter electro-magnetic
of a circuit that is at the same potential as the base ref- force (emf) of the coil will oppose current variation
erence. through the coil. The amount of reactance is directly pro-
portional to the current variation: XL = 2fL.
Handler
Device for remote control of test instrument in compo- Kelvin Connection
nent handling operations. A circuit configuration that automatically compensates
for measurement errors caused by resistance of leads
Hertz between a tester and the point of measurement on a
The unit of measure of frequency, equivalent to cycles DUT.
per second.
Level
High Limit The test signal level is the programmed RMS voltage of
The upper value for a test to be considered a PASS. If the generator in an LCR meter. The actual test voltage
the measured value is higher than the high limit the test across the DUT is always less than the programmed
is considered a FAIL. level.
IEEE Load
An acronym for Institute of Electrical and Electronic The total resistance or impedance of all circuits and
Engineers, a professional association of engineers. devices connected to a voltage source.
51
Low Limit Permittivity
The lower value for a test to be considered a PASS. If Abbreviated . The dielectric constant multiplied by the
the measured value is lower than the low limit the test is dielectric constant of empty space (o ), where the per-
considered a FAIL. mittivity of empty space (o) is a constant in Coulomb's
law, equal to a value of 1 in centimeter-gram-second
Milliohmmeter
An instrument designed to measure low values of resist- units and to 8.854 x 10-12 farads/meter in rationalized
ance using a dc current or voltage. meter-kilogram-second units.
NIST Phase
National Institute of Standards and Technology, an The time relationships between alternating voltages, cur-
agency of the U.S. Government that sets standards for rents, and impedances. Usually expressed as complex
physical measurements and references, formerly called vectors with "real" (in-phase) and "reactive" (out of
the National Bureau of Standards. phase) components.
NRTL Polarization
Acronym for Nationally Recognized Testing Laboratory, A term used to describe a "one way" limitation on the
such as Underwriters Laboratories (UL), Factory Mutual insertion of a plug into a receptacle for a corded product.
(FM), or Canadian Standards Association (CSA). A polarized plug can be inserted in only one orientation
and cannot be reversed.
Offset
An automatic zeroing function to correct for leakage cur- Potential
rents or additional resistance due to test leads or fix- Electrical potential is a term equivalent to "voltage".
tures. An offset is performed by making a measurement
at the programmed test settings, calculating the differ- Prefixes
ence between the leakage current or resistance meas- The prefixes for Multiple Scientific Engineering Symbols
ured and the ideal current or resistance and then sub- are:
tracting this difference from all future measurements. 1000000000000000 1015 Peta P
1000000000000 1012 Tera T
Ohm's Law
The fundamental law of electrical circuits that describes 1000000000 109 Giga G
the relationship between voltage, current and impedance 1000000 106 Mega M
(or resistance). For DC circuits, Ohm's Law states that 1000 103 Kilo k
Current =Voltage/Resistance. For AC circuits, Current =
0.001 10-3 milli m
Voltage/Impedance. Stated conversely, Voltage =
Current x Resistance (DC) or Current x Impedance (AC). 0.000001 10-6 micro µ
The difference between the dc resistance and ac imped- 0.000000001 10-9 nano n
ance is that ac circuits must deal with phase and time 0.000000000001 10-12 pico p
relationships and dc circuits do not.
0.000000000000001 10-15 femto f
Ohms ()
Protective Earth
The unit of measure of resistance and impedance,
Conductor that connects between any protectively earth-
derived from Ohm's Law.
ed parts of a Class I product and an external protective
earth connection.
OSHA
Occupational Safety and Hazards Administration, an
Microsecond
agency of the U.S. Government that regulates industrial
One millionth of a second.
safety.
Range
Parameter
The resistance ranges the test instrument uses for refer-
Electrical property being tested. The primary parameter
ence in making the measurement.
(L, C, R) is the first property characterized of the device
under test. The secondary parameter (D, Q, ) is the
second property characterized of the device under test.
52
Reactive Dry Contact Resistance
The component of an ac voltage, current, or impedance Resistance across closed contacts is usually
that is 90° out of phase with the "real" or in phase com- decreased, with applied voltage, due to attraction of
ponent. Reactive components are associated with molecules on the surface of contacts. By limiting
capacitive or inductive circuits. the test voltage and current, electrical charges to
the contacts are minimized.
Real
The component of an ac voltage, current, or impedance Low Resistance
that is in phase with the "real" component. Real compo- Electrical resistance typically below 10 ohms, often
nents are associated with purely resistive circuits. expressed in terms of milliohms (10-3) or micro-
ohms (10-6).
Regulation
When applied to electrical circuits, regulation refers to Winding Resistance
the variation in output voltage that occurs when the input Electrical resistance of windings which comprise
voltage changes or when the connected load changes. motors, coils, transformers, relays and ballasts.
When applied to test laboratories and agencies, refers to
the control exercised by these entities over test specs Resistivity
and rules. the electrical resistance of a material to the flow of cur-
rent times the cross-sectional area of current flow and
Repeatability per unit length of current path. It is also known as 'spe-
The difference between successive measurements with cific resistance'.
no changes in the test setup or test conditions.
RS232
Reproducibility An industry standard definition for a serial line communi-
Similar to repeatability but adds the element of what cation link or port.
could be expected under real life conditions.
Reproducibility would take into account the variability in SCC
things like fixturing where the DUT being tested is The Standards Council of Canada, an agency of the
removed from the fixture and then inserted again. Canadian Government analogous to OSHA in the United
States.
Resolution
The smallest value that can be shown on the display in Speed
a digital instrument. LCR meters typically specify a The rate at which the instrument makes a measurement
measurement range that is the largest and smallest in measurements per second. Speed is inversely propor-
value that can be shown on that meter's display. tional to accuarcy.
Resistance Stabilization Time
The electrical characteristic that impedes the flow of cur- The time required for a transient disturbance to decay to
rent through a circuit to which voltage has been applied. a steady state value.
Resistance is calculated by Ohm's Law as voltage divid -
ed by current (for DC circuits). For AC circuits, it is the in- Source Impedance
phase or "real" component of impedance. Units are The impedance of the measuring instrument applied to
expressed in ohms (). the input terminals of the device under test (DUT). If 1V
is the programmed voltage and the source impedance is
Bonding Resistance 25 ohms, DUT is 25 ohms, then the voltage at the DUT
Electrical resistance across weld joints, crimped is 0.5V.
connections and bolted joints.
Temperature Compensation
Contact Resistance Measurements corrected from an ambient temperature
Measured resistance of closed contacts, typically back to a reference temperature (usually 20 degrees C)
that of switches, relays and connectors.
Temperature, Critical
Temperature for superconductors at which the electrical
resistivity of a metal drops to zero.
53
Thermal emf
the voltage generated by connecting two dissimilar met-
als, at different temperatures, together.
Trigger
The device for initiating the test (applying the voltage or
current).
External Trigger
The test is initiated via an external source such as a
computer with an IEEE-488 or Handler interface.
One measurement is made each time the external
trigger is asserted on the handler.
Internal Trigger
The instrument continuously makes measurements.
Manual Trigger
The operator initiates the test by pressing the
[START] button. One measurement is made each
time the trigger is pressed.
UL
Underwriters Laboratories, Inc., an NRTL located in
Illinois.
Voltage
The electrical potential applied to a circuit.
Waveform
The instantaneous value of a variable such as voltage or
current plotted against time.
X (Reactance)
Reactance is the imaginary component of Impedance.
Y (Admittance)
Admittance is the reciprocal of Impedance. Y = 1/Z
Z (Impedance)
Impedance is the sum of alternating current oppositions CompuMess Elektronik GmbH
(capacitive reactance, inductive reactance and resist- Lise-Meitner-Str.1, 85716 Unterschleissheim
ance). Z = R + jX Tel 089-321501-0 Fax 089-321501-11
http://www.compumess.de oder http://www.netzteile.de
Zero Offset
A correction for residual resistance resulting for the test
leads and connection. Determined by a SHORT routine
QuadTech is a trademark of QuadTech, Inc.
with the Kelvin lead test points shorted together.
Digibridge is a registered trademark of QuadTech, Inc.
Copyright 2005 by QuadTech, Inc.
1ST Edition, June 2005, P/N 030144/A1
All rights reserved.
Printed in the U.S.A.
54