MODEL 30A SERIES
LOW-PASS ELLIPTICAL
PLUG-IN FILTER MODULES
MODEL 30A-1: 1Hz to 99kHz
MODEL 30A-2: 0.1Hz to 9.9kHz
MODEL 30A-3: 0.01Hz to 990Hz
OPERATING MANUAL
FILTER MODULES
MODEL__________ S/N___________ MODEL___________ S/N__________
MODEL__________ S/N___________ MODEL___________ S/N__________
MODEL__________ S/N___________ MODEL___________ S/N__________
MODEL__________ S/N___________ MODEL___________ S/N__________
MODEL__________ S/N___________ MODEL___________ S/N__________
MODEL__________ S/N___________ MODEL___________ S/N__________
MODEL__________ S/N___________ MODEL___________ S/N__________
MODEL__________ S/N___________ MODEL___________ S/N__________
MAINFRAME MICROPROCESSOR
MODEL__________ S/N___________
MODEL_________ S/N__________
255 Bodwell Street, Avon, MA 02322-1161
Tel: (508) 580-1660; Fax: (508) 583-8989
E-mail: krohnhite@aol.com; Web: www.krohn-hite.com
Model 30A Table of Contents
TABLE OF CONTENTS
1.0 GENERAL DESCRIPTION ...............................................................................1-1
1.1 INTRODUCTION .......................................................................................................1-1
1.2 SPECIFICATIONS.....................................................................................................1-1
2.0 OPERATION....................................................................................................2-1
2.1 INTRODUCTION .......................................................................................................2-1
2.2 TURN-ON PROCEDURE..........................................................................................2-1
2.3 SELF-TEST FEATURE..............................................................................................2-1
2.4 FRONT PANEL CONTROLS and DISPLAY.............................................................2-2
2.5 FILTER CHARACTERISTICS ...................................................................................2-3
2.5.1 Introduction ....................................................................................................2-3
2.5.2 Normalized Ripple Response........................................................................2-3
2.6 VARIABLE BANDPASS and BAND REJECT OPERATION....................................2-3
2.7 TRANSIENT RESPONSE .........................................................................................2-4
2.8 PHASE RESPONSE..................................................................................................2-5
2.9 DELAY TIME..............................................................................................................2-6
2.10 GROUP DELAY .........................................................................................................2-6
3.0 IEEE-488 STD (GPIB) PROGRAMMING ...........................................................3-1
3.1 INTRODUCTION .......................................................................................................3-1
3.2 FILTER TYPE ............................................................................................................3-1
3.3 MODE OF OPERATION............................................................................................3-1
3.4 DEVICE CLEAR .........................................................................................................3-1
4.0 INCOMING ACCEPTANCE ..............................................................................4-1
4.1 INTRODUCTION .......................................................................................................4-1
4.2 TEST EQUIPMENT REQUIRED...............................................................................4-1
4.3 PRE-FILTER, POST-FILTER AND UNITY GAIN ACCURACY................................4-1
4.4 PASSBAND GAIN AND DISTORTION TESTS........................................................4-2
4.4.1 Low Bands Ripple Response ........................................................................4-2
4.4.2 High Band Ripple Response (Model 30A-1) .................................................4-2
4.4.3 High Band Ripple Response (Model 30A-2) .................................................4-3
4.4.4 High Band Ripple Response (Model 30A-3) .................................................4-3
4.5 STOPBAND ATTENUATION ....................................................................................4-3
4.5.1 Band 1............................................................................................................4-3
4.5.2 Band 2............................................................................................................4-3
4.5.3 Band 3............................................................................................................4-3
4.5.4 Band 4............................................................................................................4-4
4.6 CUTOFF FREQUENCY.............................................................................................4-4
4.7 NOISE MEASUREMENTS........................................................................................4-4
i
Model 30A Table of Contents
Model 30A Plug-In Filter Module
ii
Model 30A Section 1 – General Description
SECTION 1
GENERAL DESCRIPTION
1.1 INTRODUCTION
The Model 30A Series are low-pass, 7-pole, 6-zero elliptical plug-in filters providing
115dB/octave roll-off, a minimum stopband attenuation of >80dB, and a typical passband ripple
of 0.22dB peak-to-peak. The Model 30A-1 covers the range from 1Hz to 99kHz. The Model
30A-2 operates from 0.1Hz to 9.9kHz and from 0.01Hz to 990Hz in the Model 30A-3.
With its 115dB/octave rolloff rate, the Model 30A provides a much narrower transition region
than an 8-pole Butterworth, and much less passband attenuation near cutoff. The transition
region from –3dB to –85dB is 64% of fc (cutoff), compared to 242% for the 8-pole Butterworth.
From –0.3dB to –85.6dB, it becomes 70% of fc compared to 404%. This permits lower sampling
rates and wider bandwidths, resulting in lower total system costs.
The Model 30A Series is part of an ever expanding line of plug-in filter cards for use in the
Model 3905C and 3916C Mainframes, which accommodates 5 to 16 filter cards respectively.
1.2 SPECIFICATIONS
FILTER CHARACTERISTICS
Function: Low-pass filter, voltage gain amplifier.
Type: 7-pole, 6-zero elliptical.
Frequency Range fc: Model 30A-1: 1Hz to 99kHz.
Model 30A-2: 0.1Hz to 9.9kHz.
Model 30A-3: 0.01Hz to 990Hz.
Resolution: Model 30A-1
Band
Frequency
Resolution
1 1Hz to 99Hz 1Hz
2 100Hz to 990Hz 10Hz
3 1kHz to 9.9kHz 100Hz
4 10kHz to 99kHz 1000Hz
Model 30A-2
Band
Frequency
Resolution
1 0.1Hz to 9.9Hz 0.1Hz
2 10Hz to 99Hz 1Hz
3 100Hz to 990Hz 10Hz
4 1kHz to 9.9kHz 100Hz
Model 30A-3
Band
Frequency
Resolution
1 0.01Hz to 0.99Hz 0.01Hz
2 1Hz to 99Hz 0.1Hz
3 100Hz to 99Hz 1Hz
4 100Hz to 990Hz 10Hz
1-1
Section 1 – General Description Model 30A
Relative Gain at fc: -0.22dB at 1.01fc nominal.
Cutoff Frequency Accuracy: ±2%.
Stopband Attentuation: >80dB.
Stopband Frequency (fs): 1.7fc.
Insertion Loss: 0dB; ±0.1dB.
Pre-Filter Gain: 0dB, 10dB, 20dB, 30dB, 40dB; ±0.2dB
Post-Filter Gain: 0dB, 20dB; ±0.2dB.
Input Coupling: ac or dc.
Wideband Noise (RFI): min. gain, 1kHz cutoff, <400µV; 99kHz cutoff, <1mV. Max. gain,
<20µV.
Harmonic Distortion: -80dB at 1kHz.
Intermodulation Distortion: -80dB below full scale volts at 70kHz and 90kHz input frequency.
Spurious Components: -80dB below full scale with input source <50 ohms.
DC Stability: Typically ±10µV/°C.
Crosstalk Between Channels: -85dB below full scale with input source <50 ohms.
AMPLIFIER CHARACTERISTICS
Bandwidth: >1MHz min. gain; >400kHz max. gain.
Insertion Loss: 0dB; ±0.05dB.
Gain: 10dB to 60dB in 10dB steps; ±0.1dB.
Input: Differential or single-ended + (in phase), -(inverted).
CMRR: >60dB to 10kHz; >50dB to 99kHz.
Sensitivity: 10mV peak with 60dB total gain for 10V peak output.
Maximum Input: ±10V peak at 0dB gain reduced in proportion to gain setting.
Impedance: 1 megohm in parallel with 100pf.
Coupling: ac or dc.
Maximum dc Component: ±100V in ac coupled mode.
Output:
Maximum Voltage (o.c.): 7Vrms to 200kHz; 3Vrms to 500kHz; 1Vrms to 1MHz.
Impedance: 50 ohms.
DC Offset: Adjustable to zero volts.
Harmonic Distortion (1V output): -80dB (0.01%) to 10kHz; -60dB (0.1%) to 100kHz.
Wideband Noise (referred to input, 2MHz BW detector): 150µV min. gain; 25µV max.
gain.
DC Stability (RFI): Typically ±10µV/°C.
Crosstalk Between Channels: >85dB below full scale with input source <50 ohms.
GENERAL
Switch: For select of Input, +(in phase), Differential or –(inverted).
Input/Output Connectors: BNC.
Power: 15 watts.
Weight: 1.75 lbs. (0.8kg) net.
Specifications apply at 25°C ±5°C.
NOTE: Model 30A Series filter cards must be used with the Model 3905B and 3916B
Mainframes.
1-2
Model 30A Section 2 – Operation
SECTION 2
OPERATION
2.1 INTRODUCTION
The Model 30A Series are low-pass plug-in filter modules covering the frequency range from
1Hz to 99kHz (Model 30A-1); 0.1Hz to 9.9kHz (Model 30A-2); 0.01Hz to 990Hz (Model 30A-3).
It is one of a series of filter modules available for the vide channel Model 3905 or the sixteen
channel 3916 Mainframes. All filter parameters are programmable via the Mainframes front
panel or remotely over the IEEE-488 (GPIB) bus. For detailed information of the front panel
controls and remote programming, refer to Sections 2 and 3 of the Model 3905/3916
Mainframes Operating and Maintenance Manual. Section 2.4 of this manual briefly describes
the operation of the principal front panel controls and data key operation.
2.2 TURN-ON PROCEDURE
a. The line voltage range of the Model 3905/3916 Mainframes has been preset at the
factory for either 115V or 230V operation. This range switch is located internally if a line
voltage change is required. Check to see that a fuse with the correct rating is in the fuse
receptacle.
b. Make certain the POWER switch on the front panel of the unit is in the off position.
c. Plug the line cord into the unit first, then into an ac outlet.
CAUTION
For safety purposes, the line cord must be connected to a grounded 3 terminal
ac outlet. Because of potentially dangerous voltages that exist within the
Mainframe, the covers should be moved by qualified personnel.
d. If the Model 3905/3916 is remotely programmed via the IEEE-488 GPIB, connect the
bus cable to the rear panel outlet of the Model 39/39A microprocessor module at this
time. Programming information is provided in Section 3 of the Model 3905/3916
Operating and Maintenance Manual.
e. The POWER switch is a toggle type, located on the front panel of the 3905//3916. After
familiarizing yourself with the self-test feature described next, turn on the 3905/3916.
2.3 SELF-TEST FEATURE
NOTE
If there is a malfunction in the micro processor, such as a defective RAM or ROM, the
sequence will stop and the word “bAd” will appear in the display followed by a number
from 1 to 3. Refer to Section 7.6, Digital Circuit Maintenance, to find which RAM or
ROM is defective.
2-1
Section 2 - Operation Model 30A
When turned on, the Model 3905/3916 microprocessor performs a Self-Test routine whereby
the entire RAM and ROM operation are verified. During the test the front panel LED’s and
display will light up sequentially.
When the Self-Test program is complete, the Model 3905/3916 will return to the last set-up prior
to turning off the unit.
The Model 3905/3916 is now ready to be programmed for operation.
2.4 FRONT PANEL CONTROLS and DISPLAY
Data Keys:
Data entry keyboard controls, [0]-[9] and [.], and associated 4 digit display set the numeric value
of the parameter selected. If a cutoff frequency of 1.5kHz is required, press the [1][.][5] data
keys and parameter keys [KILO] and [FREQ]. The frequency will be indicated in the 4 digit
display.
[MODE] Key:
Indicates the mode of operation in the channel displayed, alternating between low-pass, “L.P.-1”
and by-pass, “bYP.”, which connects the input to the output. The “-1” indicates suffix of the filer
module Model 30A, i.e. “L.P.-1” is the Model 30A-1.
[Type] Key:
Displays “EL-7”, indicating a 7-pole Elliptical filter.
Channel:
The two channel controls [⇑] [⇓] and associated display increment or decrement the channel
setting. When held, the Model 3905/3916 will cycle through all the channels continuously. The
Model 3905 has a 1 digit display, the Model 3905A has 2 digits. The Model 3916 has a 2 digit
display, the Model 3916A has 3 digits.
Gain Set:
Input and Output gain is controlled by two GAIN SET controls [⇑] [⇓] and associated 2 digit
displays in 10dB steps. Input gain 0dB to 40dB. Output gain 0dB to 20dB.
Input Overload:
With 0dB Input gain, the input overload indicator will turn on with approximately 8Vrms input
signal. At 10dB, approximately 2.5Vrms. AT 20dB, approximately 0.8Vrms. At 30dB,
approximately 0.25Vrms. AT 40dB, approximately 80mVrms.
Output Overload:
With 0dB Input and Output gain, the output overload indicator will turn on with approximately
8Vrms output signal. At 10dB, approximately 2.5Vrms. At 20dB, approximately 0.8Vrms.
[CE] Clear Entry Key:
Display will reset to the previous entry or toggle between present and previous settings.
[ALL CHANNEL] Key:
When on, parameter changes will be made simultaneously to all identical filter channels.
2-2
Model 30A Section 2 - Operation
2.5 FILTER CHARACTERISTICS
2.5.1 INTRODUCTION
The Model 30A is an Elliptical (Cauer) filter used in applications where frequency
response (fast rolloff) is the primary objective and phase distortion, transient and
passband response are secondary requirements. It is an ideal filter for A/D conversion
(anti-aliasing), D/A conversion (smoothing) and many other applications requiring signal
conditioning.
2.5.2 NORMALIZED RIPPLE RESPONSE
The Theoretical 7-pole, 6-zero elliptic low-pass filter response, shown in Figure 2.1, has
0dB gain at low frequencies with three peaks and valleys of 0.22dB p-p amplitude as the
frequency approaches the cutoff frequency of fc. The cutoff frequency occurs where the
filter response is equal to the most negative excursion of the ripple amplitude.
The response of the filter at frequencies greater than the cutoff frequency is attenuated
at an average rate of 115dB/octave, and as shown in Figure 2.1, has three peaks and
nulls of attenuation in the stopband. Minimum attenuation (A min) occurs at frequency fs
(1.7fc) and at three frequencies where the amplitude peaks in the stopband.
Frequency
Figure 2.1 Normalized Ripple Response
2-3
Section 2 - Operation Model 30A
2.6 VARIABLE BANDPASS and BAND REJECT OPERATION
Variable bandpass response can be obtained easily using a Model 30A low-pass filter in series
with a Model 31 high-pass filter and setting the low-pass filter to an equal or high cutoff
frequency than the high-pass filter. Selecting the cutoff frequencies provides the desired
bandpass response.
Variable band reject response is obviously obtained in a manner similar to the variable
bandpass response except that the low-pass cutoff frequency is set at a lower cutoff frequency
than the high-pass filter to provide the desired band reject range.
Null operation is obtained by setting the low cutoff frequency, of the Model 30A (Curve A in
Figure 2.2), a factor of 0.58 below the desired null frequency and the high cutoff frequency, of
the Model 31 (Curve B), a factor of 1.7 above the null frequency.
When maximum selectivity (Curve C of Figure 2.2) at a specified frequency is required to obtain
minimum bandwidth, the Model 30A and Model 31 should be set to the same cutoff frequency.
To prevent the possibility of excessive attenuation due to calibration error, when both cutoffs are
set to the same frequency all Krohn-Hite elliptical filters are offset by 1% from the keyboard
setting. The low-pass filter at 100Hz cutoff freq uency is actually tuned to 101Hz and the highpass filter to 99Hz to provide the correct peak amplitude in narrowband operation.
Frequency
Figure 2.2 Normailzed Band-Pass Response
2-4
Model 30A Section 2 - Operation
2.7 TRANSIENT RESPONSE
The normalized response for a unit step voltage applied to the input of the Model 30A filter is
shown in Figure 2.3. A delay time in seconds for the output of the filter to reach 50% of its input
voltage is determined by the formula 0.869/fc. With a cutoff frequency of fc of 1Hz, the delay
time at point A on the response curve is 0.869 seconds. Since the delay time is inversely
proportional to frequency, the delay time for fc of 0Hz would be 1/10 that of 1Hz or 0.0869
seconds.
The delay time for the output voltage of the filter to increase from 10% to 90% of its input
voltage (point B to point C) is determined by the formula 0.541/fc or 0.541 seconds for a
normalized frequency of 1Hz. The inverse relationship reduces the time delay proportionally at
high cutoff frequencies.
The normalized impulse response of the Model 30A filter is shown in Figure 2.4. An impulse will
produce a damped sinewave whose maximum amplitude over shoot (point D) will be 30% of the
input pulse amplitude and the damped sine wave will approach zero amplitude in approximately
10 cycles.
Figure 2.3 Normalized Unit Step Response
Figure 2.4 Normalized Impulse Response
2-5
Section 2 - Operation Model 30A
2.8 PHASE RESPONSE
Phase characteristics of a 7-pole, 6-zero elliptical filter as shown in Figure 2.5, provides output
phase relative to the input (Curve A) over a 10/1 frequency range. The phase response of
linear phase and Curve C gives the phase distortion, which is the difference in phase response,
between linear phase and elliptical filter.
When the input frequency of the filter is less than 4/10 the cutoff frequency, the phase response
is practically linear and can be calculated by using the formula 0=-293.17xf/fc, which is referred
to as the zero frequency phase response. At a frequency 1/10 the cutoff, the phase shift would
be –29.317 degrees and –2.9317 degrees at 1/100 of the cutoff frequency (not shown on Curve
A).
(C)
(B)
(A)
Figure 2.5 Phase Response
2.9 DELAY TIME
Delay time shown in Figure 2.6 is the time delay before the output voltage of the Model 30A
filter responds to an applied input voltage. With applied input frequency and cutoff frequency of
1Hz, the delay time (point B) is 1.16 seconds. At an applied input frequency of 0.6Hz (point A),
the delay time is 0.86 seconds. If the applied input frequency and cutoff frequency is increased
to 1kHz, the delay time is 1.16 milliseconds. When the input frequency is less, than 1/10th the
cutoff frequency, the delay time can be calculated by using the formula t=0.814/fc, which is
referred to as zero frequency delay time in seconds.
2-6
Model 30A Section 2 - Operation
Figure 2.6 Delay Time
2.10 GROUP DELAY
Group delay1, shown in Figure 2.7, is defined as the derivative of radian phase with respect to
radian frequency, which is the slope of the phase curve. A flat group delay is considered in
linear phase response, which corresponds to a constant slope of the phase curve. With linear
phase response the distortion of complex data signals will be minimized because their various
frequency components, due to a constant time delay, will not shift relative phase.
In numeric terms the phase response shown in Figure 2.5 shows a zero frequency phase of –
293.17°/Hz, when normalized for a cutoff frequency of 1Hz. This will be 2π times greater in °/Hz
for a cutoff of 1 radian/sec or -1842°/Hz. Dividing by 360 converts °/Hz to radians/radians-persec yields a group delay time of 5.12s as shown in Figure 2.7.
Figure 2.7 Normalized Group Delay
[1] IEEE Standard Dictionary of Electrical and Electronic Terms, Institute of Electrical and
Electronic Engineers, IEEE-STD 100-1977, Second Edition, 1977, page 296.
2-7
Section 2 - Operation Model 30A
This Page Intentionally Left Blank
2-8
Model 30A Section 3 – IEEE-488 (GPIB) Programming
SECTION 3
IEEE-488 (GPIB) PROGRAMMING
3.1 INTRODUCTION
Complete information on remote programming is incorporated in Model 3905/3916 Mainframe
operating and instruction manual. Detailed information about the filter type, modes of operation
and device clear command not described in the 3905/3916 manual are specified below.
3.2 FILTER TYPE
1 Elliptical
3.3 MODE OF OPERATION
1 Low-Pass
2 By-Pass
3.4 DEVICE CLEAR
When the device clear command is sent, the following parameters are set as follows:
MODEL 30A-1 30A-2 30A-3
INPUT GAIN 0dB 0dB 0dB
OUTPUT GAIN 0dB 0dB 0dB
CUTOFF FREQUENCY 1kHz 100Hz 10Hz
COUPLING DC DC DC
3-1
Section 3 – IEEE-488 (GPIB) Programming Model 30A
This Page Intentionally Left Blank.
3-2
Model 30A Section 4 – Incoming Acceptance
SECTION 4
INCOMING ACCEPTANCE
4.1 INTRODUCTION
The following procedure should be used to verify that the Model 30A Series filter module,
inserted in a Model 3905/3916 Mainframe is operating within specifications.
These checks may be used for incoming acceptance and periodic performance checks. Test
must be made with all covers in place on the Model 3905/3916, with filter modules inserted,
operating for a minimum time of ½ hour to reach thermal equilibrium. If not operating within
specifications refer to Section 5, Calibration, before attempting any detailed maintenance.
Before testing, follow the initial set-up and operating procedures given in Section 2 of this
manual, or if necessary, in Section 2 of the Model 3905/3916 Operating and Maintenance
Manual.
4.2 TEST EQUIPMENT REQUIRED
The test equipment below is required to perform the following test:
a. RC Oscillator, with a frequency range of .01Hz to 1MHz. Krohn-Hite Model 4100A or
equivalent.
b. RC Oscillator, with a frequency range of 10Hz to 10MHz. Frequency response of
±0.025dB from 10Hz to 500khz. Krohn-Hite Model 4200B/4300B or equivalent.
c. Oscilloscope, bandwidth of DC to 50MHz, vertical input sensitivity of 5mV/cm, Tektronix
465 or equivalent.
d. DC Voltmeter (DVM), capable of measuring 1mV to 20V, Fluke Model 8000A or
equivalent.
e. AC Voltmeter, capable of measuring 100µV to 10Vrms, Fluke Model 8920A or
equivalent.
f. Frequency Counter.
4.3 PRE-FILTER, POST-FILTER AND UNITY GAIN ACCURACY
Set all filters to a cutoff frequency of 900Hz with 0dB Input and Output gain and apply 50mVrms
at 100Hz to INPUT of each filter module. Monitor the OUTPUT with an ac voltmeter. Should be
50mV ±1mV.
Set gain of pre-filter (input) to 10dB, 20dB, 30dB and 40dB. Fluke on the OUTPUT of the filter
should be within ±0.2dB of all four pre-filter gain settings.
Set gain of pre-filter and post-filter to 0dB and apply a 0.7Vrms signal to the INPUT of the filter.
Monitor the OUTPUT of the filter with an ac voltmeter and record the OUTPUT voltage. Set
gain of post-filter (output) to 10dB and 20dB. Fluke on the OUTPUT of the filters should be
within ±0.2dB of both post filter gain settings.
4-1
Section 4 – Incoming Acceptance Model 30A
4.4 PASSBAND GAIN AND DISTORTION TESTS
To verify that the filter is functioning correctly in the passband, set all filter modules to a cutoff
frequency of 900Hz and pre-filter and post-filter amplifier gain to 0dB (unity gain). Apply a
7Vrms signal at 50Hz to the INPUT of each filter module and monitor the OUTPUT of each filter
with a scope, ac voltmeter and a distortion analyzer. The OUTPUT should be within ±0.2dB of
the INPUT and the distortion should be <0.1%.
CAUTION: If the distortion is excessive, verify that the distortion of the oscillator being used is
<0.1%.
4.4.1 LOW BANDS RIPPLE RESPONSE (FIGURE 4.1)
Connect oscillator at 3Vrms at 50Hz to INPUT of filter. Set front panel channel indicator
to the channel of the filter under test. Set filter to 900Hz cutoff frequency with 0dB of
INPUT and OUTPUT gain. Monitor OUTPUT of filter with ac voltmeter. Record
OUTPUT voltage. Set filter to 90Hz cutoff frequency.
Check the response of the three peaks at 42.9Hz, 73.9Hz and 89.1Hz. Check the
response of the three valleys at 22.3Hz, 60.3Hz and 83.4Hz. The adjacent peak-to-
valley ripple should not exceed 0.4dB. If necessary, refer to Section 5, Calibration.
Figure 4.1 Normalized Ripple Response
4.4.2 HIGH BAND RIPPLE RESPONSE (Model 30A-1)
Connect oscillator at 3Vrms at 100Hz to INPUT of filter. Set front panel channel
indicator to the channel of the filter under test. Set the filter to 10kHz cutoff frequency
with 0dB Input and Output gain. Monitor OUTPUT of filter with ac voltmeter. Record
OUTPUT voltage.
Check the response of the three peaks at 4.7kHz, 8.2kHz and 9.9kHz. Check the
response of the three valleys at 2.4kHz, 6.8kHz and 9.2kHz. The adjacent peak-to-
valley ripple should not exceed 0.4dB. If necessary, refer to Section 5, Calibration.
4-2
Model 30A Section 4 – Incoming Acceptance
4.4.3 HIGH BAND RIPPLE RESPONSE (Model 30A-2)
Connect oscillator at 3Vrms at 50Hz to INPUT of filter. Set front panel channel indicator
to the channel of the filter under test. Set the filter to 1kHz cutoff frequency with 0dB
Input and Output gain. Monitor OUTPUT of filter with scope and ac voltmeter. Record
OUTPUT voltage.
Check the response of the three peaks at 470Hz, 820Hz and 985Hz. Check the
response of the three valleys at 240Hz, 680Hz and 920Hz. The adjacent peak-to-valley
ripple should not exceed 0.4dB.
NOTE: Check the accuracy of the ac voltmeter at low frequencies. If necessary, compare the
OUTPUT with the INPUT to eliminate any error.
4.4.4 HIGH BAND RIPPLE RESPONSE (Model 30A-3)
Connect oscillator at 3Vrms at 50Hz to INPUT of filter.
Set front panel channel indicator to the channel of the filter under test. Set the filter to
900Hz cutoff frequency with 0dB Input and Output gain. Monitor OUTPUT of filter with
ac voltmeter. Record OUTPUT voltage and use as reference. Set filter to 100Hz.
Check peaks and valleys of ripple at 47Hz, 82Hz, 99Hz and 24Hz, 68Hz and 92Hz
respectively.
4.5 STOPBAND AT TENUATION
4.5.1 BAND 1
MODEL 30A-1
Set filter to 10Hz with 0dB Input and 20dB Output gain, dc coupling. Set oscillator to
17.5Hz at 7Vrms. Connect scope to OUTPUT. Signal should be less than 20mV p-p.
Set oscillator to 18.7Hz, 25.9Hz and 70Hz. Signal should be less than 20mV p-p.
MODEL 30A-2
Do in same manner as Model 30A-1 setting filter to 1Hz and oscillator to 1.75Hz,
1.87Hz, 2.59Hz and 7.0Hz.
MODEL 30A-3
Do in same manner as Model 30A-1 setting filter to 0.1Hz and oscillator to 0.175Hz,
0.187Hz, 0.259Hz and 0.70Hz.
4.5.2 BAND 2
MODEL 30A-1
Same as Band 1 setting the filter to 100Hz and oscillator to 175Hz, 187Hz, 259Hz and
700Hz.
MODEL 30A-2
Same as Band 1 setting the filter to 10Hz and oscillator to 17.5Hz, 18.7Hz, 25.9Hz and
70.0Hz.
MODEL 30A-3
Same as Band 1 setting the filter to 1Hz and oscillator to 1.75Hz, 1.87Hz, 2.59Hz and
7.0Hz.
4-3
Section 4 – Incoming Acceptance Model 30A
4.5.3 BAND 3
MODEL 30A-1
Same as Band 1 setting the filter to 1kHz and oscillator to 1.75Hz, 1.87kHz, 2.59kHz and
7.0kHz.
MODEL 30A-2
Same as Band 1 setting the filter to 100Hz and oscillator to 175Hz, 187Hz, 259Hz and
700Hz.
MODEL 30A-3
Same as Band 1 setting the filter to 10Hz and oscillator to 17.5Hz, 18.7Hz, 25.9Hz and
70.0Hz.
4.5.4 BAND 4
MODEL 30A-1
Same as Band 1 setting the filter to 10kHz and oscillator to 17.5kHz, 18.7kHz, 25.9kHz
and 70.0kHz.
MODEL 30A-2
Same as Band 1 setting the filter to 1kHz and oscillator to 1.75kHz, 1.87kHz, 2.59kHz
and 7.0kHz.
MODEL 30A-3
Same as Band 1 setting the filter to 100Hz and oscillator to 175Hz, 187Hz, 259Hz and
700Hz.
4.6 CUTOFF FREQUENCY ACCURACY
Connect oscillator a 3Vrms at 42.9Hz to INPUT. Set filter to 90Hz with 0dB Input and Output
gain. Monitor OUTPUT with ac voltmeter. Record voltage at Output. Adjust input frequency
near 90.9Hz to obtain –0.22dB. Frequency should be between 89.12Hz and 92.7Hz.
Set filter and oscillator to 100Hz – adjust oscillator frequency for –0.22dB. Frequency should
read between 99Hz and 103Hz.
MODEL 30A-1 and 30A-2 ONLY
Set filter and oscillator to 1kHz – adjust oscillator frequency for –0.22dB. Frequency should
read between 990Hz and 1.03kHz.
MODEL 30A-1 ONLY
Set filter and oscillator to 10kHz – adjust oscillator frequency for –0.22dB. Frequency should
read between 9.9kHz and 10.3kHz.
4.7 NOISE MEASUREMENTS (use 2MHz limited detector)
MODEL 30A-1 ONLY
Short the INPUT of the filter. Connect ac voltmeter to the OUTPUT of filter. Set filter to 1kHz
with 0dB Input and Output gain. OUTPUT should be less than 0.5mV. Set filter to 99kHz with
0dB Input and Output gain. OUTPUT should be less than 1mV.
Set filter to 99kHz with 0dB Input and 20dB Output gain. OUTPUT should be less than 10mV.
Set filter to 1kHz with 0dB Input and 20dB Output gain. OUTPUT should be less than 5mV.
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Model 30A Section 4 – Incoming Acceptance
Set filter to 1kHz with 40dB Input and 20dB Output gain. OUTPUT should be less than 10mV.
Set filter to 99kHz with 40dB Input and 20dB Output gain. OUTPUT should be less than 60mV.
Set filter to 99kHz with 40dB Input and 0dB Output gain. OUTPUT should be less than 6mV.
Set filter to 1kHz with 40dB Input and 0dB Output gain. OUTPUT should be less than 1mV.
MODEL 30A-2
Same as Model 30A-1 using 1kHz and 9.9kHz.
MODEL 30A-3
Set filter to 990Hz.
Output should be less than 0.5mV with 0dB Input and Output gain.
Output should be less than 5mV with 0dB Input and 20dB Output gain.
Output should be less than 10mV with 40dB Input and 20dB Output gain.
Output should be less than 1mV with 40dB Input and 0dB output gain.
NOTE: The scope presentation should consist of random noise voltage only, with no line
voltage or its harmonic signals.
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Section 4 – Incoming Acceptance Model 30A
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