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Decade Series 1491 Inductor
USES: All-Purpose Inductor for
· For Calibrating Working Standards
· Verification & Calibration of LCR
Design and Measurement
Meters
· Working Standard Introduction
· Inductance Measurement The 1491 Decade Inductor is an assembly of several Decade-Inductor Units in a
single metal cabinet. The units have no electrical connection to the panel, but a
Functions
separate ground terminal is provided, which can be connected to the adjacent low
· Verification of Calibration of terminal, leading to the smallest decade.
Multimeters
· For Calibrating Instrumentation
Description
· For Substitution Inductance These inductance decades are convenient elements for use in wave filters, equaliz-
Measurements ers, and tuned circuits throughout the range of audio and low radio frequencies.
As components in oscillators, analyzers, and similar equipment, they are especially
useful during the preliminary design period, when you need to vary circuit ele-
FEATURES: ments over relatively wide ranges to determine optimum operating values. As
· Shielded toroidal cores for small moderately precise standards of inductance they have values of low-frequency
mutual inductance and minimal storage factor, Q, that are much larger than those of air-core coils.
effect from external fields
Figure 1: Percentage change in
· Sealed against moisture for long- normal and incremental induc-
tance with AC and bias current.
term stability Incremental curve is limited to
an AC excitation less than I1.
· Excellent as a moderately precise
standard of inductance .
· High-Q, 200 and above
Figure 2: Variation of induc-
tance with frequency for the
1491 Decade Inductors.
Figure 3: Variation of Q for the
maximum inductance at low
excitation levels. Dashed
curvescorrespond to use with
chassis floating.
HIPOT · LCR METERS · MEGOHMMETERS · MILLIOHMMETERS · DECADES · STANDARDS
For more information about special
purchase, rent & lease options, call
IET LABS, INC.
CompuMess Elektronik GmbH · Lise-Meitner-Str.1 · 85716 Unterschleissheim
Tel 089-321501-0 · Fax 089-321501-11 · www.compumess.de · www.netzteile.de
Series 1491 Decade Inductor
Frequency Characteristics:
Percentage increase in effective series inductance (above the zero-frequency value, Lo) may be obtained by
interpolation in accompanying graph (see Figure 2) for any setting of the highest-value decade used, when
LOW terminal is grounded to cabinet.
Zero Inductance: Approximately 1µH.
Maximum Voltage: 500V rms. Switch will break circuit at 500V if turned rapidly, but voltages above 150V may cause destructive
arcing with switch between detent positions.
Accuracy (Low Frequency, Low Signal Level):
Inductance Per Step
Model 100,µH 1mH 10mH 100mH 1H
1491-9704 N/A +/-2% +/-1.6% +/-0.8% +/-0.8%
1491-9707 +/-2% +/-2% +/-1.6% +/-0.8% +/-0.8%
Change in Inductance with Current:
Fractional change in initial inductance with AC current for each type of toroid is shown in the normal curves,
Figure 1, in terms of the ratio of the operating current, I , to I 1 the current for 0.25% change, solid line (0.1%,
broken line). For ratios below unity, inductance change is directly proportional to current. Values of I 1, listed
below, are approximate and are based on the largest inductor in the circuit for each setting.
Incremental Inductance:
DC bias current I B will reduce the initial inductance as shown in the incremental curves, Figure 1.
RMS I1 (mA)
0.1% Increase 0.25% Increase
Inductance per Step
Switch Setting 100µH 1mH 10mH 100mH 1H
1 141 17 5.4 1.7 .54
2,3,4 100 12 3.8 1.2 .38
5,6,7,8,9,10 63 8 2.4 0.8 0.24
Maximum I 4A 1.5A 500mA 150mA 50mA
Storage Factor Q: See Figure 3.
DC Resistance: Approximately 45V per Henry.
Temperature Coefficient:
Approximately -25ppm per degree C between 16º and 32ºC.
Terminals: Binding posts on ¾-in centers; separate ground terminal provided.
Mechanical: Lab-bench cabinet.
Dimensions: (w x h x d): 17 x 8.75 x 6.5in (432 x 223 x 166mm).
Weight: · 1491-D, bench model, 23 lbs. (11kg) net, 30 lbs (14kg) shipping
· 1491-G, bench model, 27 lbs (12kg) net, 34 lbs (16kg) shipping
Ordering Information
1491 Decade Inductor
Catalog Number Item Total Steps
1491-9704 1491-D Decade Inductor 11.11H 0.001H Includes:
Calibration Certificate Traceable to NIST
1491-9707 1482-G Decade Inductor 11.111H
0.0001H
Optional Accessories:
Calibration Data
IET LABS, INC.
CompuMess Elektronik GmbH · Lise-Meitner-Str.1 · 85716 Unterschleissheim
Tel 089-321501-0 · Fax 089-321501-11 · www.compumess.de · www.netzteile.de