Model 950
Single Channel- Certified Tunable Filter Instruments
Description
Frequency Devices' Model 950 instruments furnish
the user with an 8-pole low-pass or high-pass filter
that is tunable by front panel controls. The controls
allow the user to select a corner frequency between
10 Hz and 50 kHz with 6 steps from each of two
selectable ranges.
The instrument exhibits an input impedance of 1
Meg shunted by 47pF to a single ended signal
source. When configured in the differential mode,
the instrument has a common mode rejection ratio
(CMRR) which exceeds 60dB; in this mode the
instrument presents an input impedance of 2 Meg
shunted by 47pF to a double ended single source.
Front panel gain control also enables the operator
to select a gain factor of 0, 10, or 20dB.
Standard operational features include:
1) Adjustable Frequency Control
Available Low-Pass Models: . . . . . . . . . . . . . Page
2) Differential Input Amplifiers
950L8B 8-pole Butterworth. . . . . . . . . . . . . . . . . . 3
3) Adjustable Gain Control 950L8L 8-pole Bessel . . . . . . . . . . . . . . . . . . . . . 3
4) Off-set Adjustment
Available High-Pass Models: . . . . . . . . . . . . . Page
5) BNC Connectors for Signal I/O 950H8B 8-pole Butterworth. . . . . . . . . . . . . . . . . . 3
Compact size and manual rotary switch front panel General Specifications: . . . . . . . . . . . . . . . . . . . 6
controls make 950 instruments a popular, cost
effective, easy-to-use solution for signal
conditioning applications in the following areas:
Anti-aliasing Filters
Biomedical/Biotechnology Applications
Data Recording/Playback
Data Smoothing
EKG/EEG Signal Filtering
FDM/PCM Signal Filtering
Medical Research
Industrial Process Control
Seismic Analysis
Vibration Analysis
1
CompuMess Elektronik GmbH · Lise-Meitner-Str.1 · 85716 Unterschleissheim
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Model 950
Tunable Filter Instruments
BLOCK DIAGRAM
GAIN (dB)
INPUT
10dB
0dB
A 20dB
A-B + OUT
DIFF 8-POLE TUNABLE OUTPUT
A AMP FILTER AMP
OFFSET
NULLED
B CORNER
FREQUENCY
TUNING TYPICAL
FRONT PANEL
TYPICAL BNC CONNECTOR
OFFSET ADJUSTMENT
FUNCTION
ON
950 20
50 100
200
CORNER
TUNEABLE ACTIVE FILTER FREQUENCY
10 500 IN Hz
INPUT GAIN OFFSET
A B (dB) OUT
A-B 10 R x100
- + A
A 0 N
G
GND 20 E x1
2
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Model 950
Tunable Filter Instruments
Model 950L8B 950L8L Model 950H8B
Product Specifications Low-Pass Low-Pass High-Pass
Transfer Function 8-Pole, Butterworth 8-Pole, Bessel Transfer Function 8-Pole, Butterworth
Range fc 10 Hz to 50.0 kHz 10 Hz to 50.0 kHz Range fc 10 Hz to 50.0 kHz
Theoretical Transfer Appendix A Appendix A Theoretical Transfer Appendix A
Characteristics Page 9 Page 4 Characteristics Page 29
Passband Ripple 0.0 dB 0.0 dB Passband Ripple 0.0 dB
(theoretical) (theoretical)
DC Voltage Gain 0 ± 0.1 dB typ. 0 ± 0.1 dB typ. Voltage Gain 0 ± 0.2 dB to 100 kHz
(non-inverting) 0 ± 0.2 dB max. 0 ± 0.2 dB max. (non-inverting) 0 ± 0.5 dB to 120 kHz
Power Bandwidth 120 kHz
Stopband Stopband
Attenuation Rate 48 dB/Octave 48 dB/Octave Attenuation Rate 48 dB/Octave
Cutoff Frequency fc ± 2% max. fc ± 2% max. Cutoff Frequency fc ± 2% max.
Accuracy ± 0.05% typ. ± 0.05% typ. Accuracy ± 0.05% typ.
± 2% max .± 2% max. ± 2% max.
Stability ± 0.01%/°C typ. ± 0.01%/°C typ. Stability ± 0.01%/°C typ.
± 0.02%/°C max. ± 0.02%/°C max. ± 0.02%/°C max.
Amplitude -3 dB -3 dB Amplitude -3 dB
Phase -360° -182° Phase -360°
Filter Attenuation 0.12 dB 0.80 fc 1.91 dB 0.80 fc Filter Attenuation 80.0 dB 0.31 fc
3.01 dB 1.00 fc 3.01 dB 1.00 fc 60.0 dB 0.42 fc
60.0 dB 2.37 fc 60.0 dB 4.52 fc 3.01 dB 1.00 fc
80.0 dB 3.16 fc 80.0 dB 6.07 fc 0.00 dB 2.00 fc
Total Harmonic Total Harmonic
Distortion @ 1 kHz <-90 dB typ. <-90 dB typ. Distortion @ 1 kHz <-88 dB typ.
Narrow Band Noise 50 mVrms typ. 50 mVrms typ. Narrow Band Noise 100 mVrms typ.
(5 Hz - 100 kHz) (5 Hz - 100 kHz)
3
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Model 950
Location of Front Panel
Terminals and Controls
Location of Front Panel Terminals and Controls
ON
950 20
50 100
200
CORNER
A TUNEABLE ACTIVE FILTER FREQUENCY
10 500 IN Hz
INPUT GAIN OFFSET
G
A B (dB) OUT
C&D
A-B 10 R x100
- + A
A 0 N I
B G
GND 20 E x1 H
E F
Location of Rear Panel Terminals and Controls
K
J APR.01 SN: 00105 950L8L L
corcom
SELECT 115v 230v
FUSE (250V 0.1A) (250V 0.1A)
M
NOM. FREQ. 60 Hz 50 Hz
WARNING: Do not remove covers, no user serviceable parts inside.
Contact: Frequency Devices for service, tech@freqdev.com
MADE IN U.S.A
FRONT PANEL REAR PANEL
A. POWER Status Lamp: This red LED F. OFFSET Adjust: This adjustment is J. IDENTIFICATION LABEL: This label
indicates whether or not the power to the intended to zero the offset that results identifies the date of manufacture, serial
analog filter circuitry of a Model 950 from the instrument's own circuitry and number, filter type and operating power
instrument is on. does not provide for wide range offset to requirements.
remove dc input signals.
B. INPUT Switch: This three position K. POWER CONNECTION: Denotes
toggle configures the instrument for G. CORNER FREQUENCY Selector power plug location.
either differential inputs (A-B), a single- Switch (10-500Hz): This six position
L. POWER ON/OFF Switch: A two-
ended input (A), or input nulling (GND) rotary switch selects the digit value of the
position toggle switch on the back panel
which grounds both the (A) and (B) input corner frequency. The switch selectable
Power Module that interrupts/completes
terminals. values are 10, 20, 50, 100, 200 and 500,
the power circuit.
C. & D. (A) and (B) Input Terminals: H. MULTIPLIER Selector Switch: This
M. Voltage Selector Module:
This pair of shielded, female BNC two-position toggle switch multiplies by a
115V Operation
connectors accept signal inputs (A) and factor of either 1 or 100x, the value set
The power module window shows the
(B). The instrument applies a non- on the CORNER FREQUENCY selector
operating voltage (115V or 230V). At
inverting gain to input (A) and an equal switch.
time of shipment, the voltage window will
but opposite inverting gain to input (B) I. OUT Terminal: This terminal is a be set to the 115V position.
while the GAIN switch sets the magnitude female BNC connector. The shield on 230V Operation
of differential gain to 0, 10, or 20 dB. The the BNC is internally connected to the For 230V operation, use a small flathead
BNC shields have been internally instrument ground. screwdriver to pry open the fuse module
connected to the instrument ground. door. Remove the fuse cartridge, fuse
E. GAIN Switch: This three-position clip and single fuse for 115V operation.
toggle switch selects an overall filter gain Install two 5 X 20 mm 250V, 0.1A fuses
of 0, 10, or 20dB. into the fuse cartridge, rotate and insert
fuse cartridge so 230V is visible in fuse
module door when closed.
4
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Model 950
Operation and
Application Guide Lines
Initial Setup The Differential Input
Select desired operating voltage 115 Vac Set the OFFSET control for a zero-volt The instrument utilizes a differential input
or 230 Vac. See note "N" page four. reading on the scope. amplifier to reject prevalent forms of
electrical interference, while presenting
Set the POWER ON/OFF Switch to ON. Subsequent changes of CORNER
desirable input characteristics to the
A continuously lit POWER lamp indicates FREQUENCY and GAIN control settings
signal source requiring filtering. The
power applied. Allow the instrument a will introduce a small dc output offset,
differential input configuration is ideal for
three-minute warm-up period to achieve which should be zeroed for critical
measuring the difference between two
thermal equilibrium. applications.
values rather than the values
To perform initial adjustment and/or Leaving all other controls unchanged, themselves. Bridge circuits utilizing
operational testing, set the remaining set the Input Switch to (A-B) and apply a strain gages, thermocouples and a
front panel controls as follows: 5Vdc signal simultaneously to input variety of other types of transducers
BNCs (A) and (B). The voltage generate differential full-scale output
a) The CORNER FREQUENCY switch measured at the OUT BNC should be 5- voltages in the order of millivolts that are
and the MULTIPLIER to the desired 5=OVdc. This completes preliminary often superimposed upon volt-level
corner frequency. test and adjustment. reference and noise values.
b) The OFFSET control to approximately
mid-range. Corner Frequency Selection The importance of CMRR
c) The GAIN switch to the desired value. To select a corner frequency, simply set In actual system environments, each
the CORNER FREQUENCY switch and signal and power return conductor can
e) The INPUT switch to ground (GND). the MULTIPLIER switch for the desired generate an interference voltage
Connect a dc-coupled oscilloscope, of numerical value. proportional to the net conductor
vertical sensitivity 10mV/CM or better, or resistance and the electrical current
a digital voltmeter (DVM) to the level. Any such interference voltages
instrument front panel BNC connector appear as common mode signals to the
labeled OUT. amplifier, and are rejected as such.
Circuit model illustrating relationship between filter's differential input
amplifier and external signal and error sources.
0d
B DIFFERENTIAL
INPUT SIGNAL AND 10
NOISE VOLTAGE SOURCES dB INPUT AMPLIFIER
RSA A
* 20
dB
(+)
*
GAIN = K
VA
RCM+ +
*
OUT
VCM
RD DIFF OUTPUT
AMP AMPLIFER
VB -
SIGNAL RCM-
COMMON
(±)
RSB
B Vo = K(VA - VB) + Vcm/CMRR : WHERE
K = 1, 10 AND 10 FOR GAIN SETTINGS
* ±Vs COM +Vs
OF 0, 10 AND 20dB RESPECTIVELY.
SEE TEXT FOR REMAINING TERMS.
COUPLED
POWER LINE
NOISE VOLTAGE (±) (+) * DENOTES FRONT PANEL ACCESS
AC POWER SUPPLY
VP
SIGNAL
COMMON
5
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Model 950
Specifications
(@25°C and rated Power Input)
Input Characteristics Typical Common Mode Rejection Ratio
0
Input Impedance:
Differential 2 M Shunted by 47pF -10
Bessel filter type set to 50 kHz filter
corner frequency, 0 dB gain setting.
Single Ended 1 M Shunted by 47pF -20
Input Voltage: -30
Linear Differential* 20V p-p (Gain Set at 0 dB) -40
dB (RMS)
dB (RMS)
Max Safe Differential Any Continuous Value between ±75V -50
Max Safe Common Mode Any Continuous Value between ±75V -60
Bias Current 4 nA typ.; 20 nA max. -70
Common Mode Rejection ratio with -80
2k source unbalance and 0 dB Gain > 60dB, dc to 50kHz -90
-100
10 100 1000 10000 100000
Frequency(Hz)
Frequency (Hz)
Output Characteristics
Full Power Bandwidth dc to 50kHz
Related Output 10V p-p for RL = 50W Typical Output Noise
0
20V p-p for RL = 2kW
-20 Bessel filter type set to 50 kHz filter corner
Short Circuit Output Current +/-100 mA continuous frequency, 0 dB gain setting, input
grounded.
Output Protection +/-200 mA without damage -40
dB (re:1V RMS)
Short Circuit to Ground Only
dB (re:1VRMS)
-60
Output Impedance 50
Offset Voltage Adjustable to Zero at Front Panel -80
(Range +/-500mV dc) -100
Power Supply -120
AC Line Operation: -140
10 100 1000 10000 100000
Power 6 Watts max. Frequency (Hz)
Frequency (Hz)
Voltage Frequency Range-Rear Panel:
115 V 105 to 125Vac @ 50/60Hz
230 V 210 to 250Vac @ 50Hz
Fuse 0.1 Amp
Temperature
Operating Temperature: 0 °C to +50 °C
Storage Temperature -25 °C to +70 °C
Mechanical
Dimensions 2.375"H x 7.0"W x 8.3"D
6.03cmH x 17.75cmW x 21.08cmD
Weight 1.5 lbs; 0.68 kgs.
Case Material ABS plastic
Color PC Bone
* Signal plus common mode voltage cannot exceed 20V peak for a linear output.
We hope the information given here will be helpful. The information is based on data and our best knowledge, and we consider the information to be true and accurate. Please read all statements,
recommendations or suggestions herein in conjunction with our conditions of sale which apply to all goods supplied by us. We assume no responsibility for the use of these statements,
recommendations or suggestions, nor do we intend them as a recommendation for any use which would infringe any patent or copyright. IN-00950-00
6
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8-Pole
Bessel
Appendix A Low-Pass
Theoretical Transfer Characteristics Frequency Response
1 0
f/fc Amp Phase Delay
(Hz) (dB) (deg) (sec)
-20
0.00 0.00 0.00 .506
Amp (dB)
0.10 -0.029 -18.2 .506 -40
0.20 -0.117 -36.4 .506
0.30 -0.264 -54.7 .506 -60
0.40 -0.470 -72.9 .506
0.50 -0.737 -91.1 .506
-80
0.60 -1.06 -109 .506
0.70 -1.45 -128 .506 -100
0.80 -1.91 -146 .506 2 3 4 5 6 78
0.85 -2.16 -155 .506 0.1 1.0 2 3 4 5 6 7 10.0
0.90 -2.42 -164 .506 Normalized Frequency(f/fc)
0.95 -2.71 -173 .506
1.00 -3.01 -182 .506
1.10 -3.67 -200 .506 Delay (Normalized)
1.20 -4.40 -219 .506
1.30 -5.20 -237 .506 1.0
1.40 -6.10 -255 .505
Delay (sec)
1.50 -7.08 -273 .504
1.60 -8.16 -291 .502
1.70 -9.36 -309 .498
1.80 -10.7 -327 .492 0.5
1.90 -12.1 -345 .482
2.00 -13.7 -362 .468
2.25 -18.1 -402 .417
2.50 -23.1 -436 .352
2.75 -28.3 -465 .291 0.0
0.15 2 3 4 5 6 7 89 1.5
0.1 1.0
3.00 -33.4 -489 .241 Normalized Time (1/f sec)
3.25 -38.3 -509 .201
3.50 -43.1 -526 .170
4.00 -51.8 -552 .126
5.00 -66.8 -587 .077 Step Response
Step Response (V/V)
6.00 -79.2 -610 .052 1.2
7.00 -89.8 -626 .038 1.0
8.00 -99.0 -638 .029
9.00 -107 -647 .023 0.8
10.0 -114 -655 .018
0.6
0.4
0.2
1.Normalized Group Delay:
-0.0
The above delay data is normalized to a corner frequency -0.2
of 1.0Hz.The actual delay is the normalized delay divided 0 1 2 3 4 5
by the actual corner frequency (fc).
Normalized Time (1/f sec)
Normalized Delay
Actual Delay =
Actual Corner Frequency (fc) in Hz
4
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Low-Pass
8-Pole
Appendix A Butterworth
Theoretical Transfer Characteristics Frequency Response
1 0
f/fc Amp Phase Delay
(Hz) (dB) (deg) (sec)
-20
0.00 0.00 0.00 .816
Amp (dB)
0.10 0.00 -29.4 .819 -40
0.20 0.00 -59.0 .828
0.30 0.00 -89.1 .843 -60
0.40 0.00 -120 .867
0.50 0.00 -152 .903
-80
0.60 -0.001 -185 .956
0.70 -0.014 -221 1.04 -100
0.80 -0.121 -261 1.19 2 3 4 5 6 78 1.0 2 3 4 5 67
0.85 -0.311 -283 1.29 0.1 10.0
0.90 -0.738 -307 1.40 Normalized Frequency(f/fc)
0.95 -1.58 -333 1.48
1.00 -3.01 -360 1.46
1.10 -7.48 -408 1.17 Delay (Normalized)
1.20 -12.9 -445 .873 2.0
1.30 -18.2 -472 .672
1.40 -23.4 -494 .540
Delay (sec)
1.50 -28.2 -511 .448
1.60 -32.7 -526 .380
1.70 -36.9 -539 .328 1.0
1.80 -40.8 -550 .287
1.90 -44.6 -560 .253
2.00 -48.2 -568 .226
2.25 -56.3 -586 .174
2.50 -63.7 -600 .139 0.0
2.75 -70.3 -611 .113 0.1 0.15 2 3 4 5 6 7 8 9 1.0 1.5
3.00 -76.3 -621 .094 Normalized Time (1/f sec)
3.25 -81.9 -629 .080
3.50 -87.1 -635 .069
4.00 -96.3 -646 .052
5.00 -112 -661 .033 Step Response
Step Response (V/V)
6.00 -125 -671 .023 1.2
7.00 -135 -678 .017
8.00 -144 -683 .013 1.0
9.00 -153 -687 .010 0.8
10.0 -160 -691 .008
0.6
0.4
0.2
1.Normalized Group Delay: -0.0
The above delay data is normalized to a corner frequency
of 1.0Hz.The actual delay is the normalized delay divided 0 1 2 3 4 5
by the actual corner frequency (fc). Normalized Time (1/f sec)
Normalized Delay
Actual Delay =
Actual Corner Frequency (fc) in Hz
9
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High-Pass
8-Pole
Appendix A Butterworth
Theoretical Transfer Characteristics Frequency Response
1 0
f/fc Amp Phase Delay
(Hz) (dB) (deg) (sec)
-20
0.10 -160 691 0.819
Amp (dB)
0.20 -112 661 0.828 -40
0.30 -83.7 631 0.843
0.40 -63.7 600 0.867 -60
0.50 -48.2 568 0.903
0.60 -35.5 535 .956 -80
0.70 -24.8 499 1.04
0.80 -15.6 459 1.19 -100
0.85 -11.6 437 1.29 2 3 4 5 6 78
0.90 -8.06 413 1.40 0.1 1.0 2 3 4 5 6 7 10.0
Normalized Frequency(f/fc)
0.95 -5.15 386 1.48
1.00 -3.01 360 1.46
1.20 -0.229 275 0.873
1.40 -0.020 226 0.540
1.60 -0.002 194 0.380
1.80 0.00 170 0.287
2.00 0.00 152 0.226
2.50 0.00 120 0.139
3.00 0.00 99.2 0.094
4.00 0.00 74.0 0.052
5.00 0.00 59.0 0.033
6.00 0.00 49.0 0.023
7.00 0.00 42.1 0.017
8.00 0.00 36.8 0.013
9.00 0.00 32.7 0.010
10.0 0.00 29.4 0.008
1.Normalized Group Delay:
The above delay data is normalized to a corner frequency
of 1.0Hz.The actual delay is the normalized delay divided
by the actual corner frequency (fc).
Normalized Delay
Actual Delay =
Actual Corner Frequency (fc) in Hz
29
CompuMess Elektronik GmbH · Lise-Meitner-Str.1 · 85716 Unterschleissheim
Tel 089-321501-0 · Fax 089-321501-11 · www.compumess.de · www.netzteile.de