Krohn-Hite 38 User manual

Model 38
Plug-In Filter Card
0.03Hz to 1MHz Low-Pass
0.03Hz to 300kHz High-Pass
Operating Manual

Service and Warranty
Krohn-Hite Instruments are designed and manufactured in accordance with sound engineering
practices and should give long trouble-free service under normal operating conditions. If your in-
strument fails to provide satisfactory service and you are unable to locate the source of trouble, con-
tact our Service Department at [phone], giving all the information available concerning the
failure.
DO NOT return the instrument without our written or verbal authorization to do so. After contacting
us, we will issue a Return Authorization Number which should be referenced on the packing slip and
purchase order. In most cases, we will be able to supply you with the information necessary to repair
the instrument, avoiding any transportation problems and costs. When it becomes necessary to re-
turn the instrument to the factory, kindly pack it carefully and ship it to us prepaid.
All Krohn-Hite products are warranted against defective materials and workmanship. This war-
ranty applies for a period of one year from the date of delivery to the Original Purchaser. Any instru-
ment that is found within the one year warranty period not to meet these standards, will be repaired
or replaced. This warranty does not apply to electron tubes, fuses or batteries. No other warranty is
expressed or implied.
Krohn-Hite Corporation reserves the right to make design changes at any time without incurring
any obligation to incorporate these changes in instruments previously purchased.
Modifications to this instrument must not be made without the written consent of an authorized em-
ployee of Krohn-Hite Corporation.

MODEL 38
Plug-In Filter Card
0.03Hz to 1MHz Low-Pass
0.03Hz to 300kHz High-Pass
Serial No. __________
Operating Manual
Copyright©. 2005 Krohn-Hite Corporation. All rights reserved.
Contents of this publication may not be reproduced in any form
without the written permission of Krohn-Hite Corporation.
Printed in U.S.A. - 042505.
15 Jonathan Drive, Unit 4, Brockton, MA 02301-5566 U.S.A.
Tel: [phone]; Fax: [phone]
[email protected]; www.krohn-hite.com

TABLE OF CONTENTS
SECTION 1 - GENERAL DESCRIPTION
1.1 INTRODUCTION ················································1-1
1.2 FUNCTION ···················································1-1
1.3 FILTER MODE ·················································1-1
1.4 AMPLIFIER MODE ···············································1-1
1.5 GENERAL ····················································1-2
1.6 OPTIONS·····················································1-2
SECTION 2 - OPERATION
2.1 INTRODUCTION ················································2-1
2.2 OPERATING PROCEDURE ··········································2-1
2.2.1 Channel Selection ············································2-1
2.2.2 All Channel Key Procedure ·······································2-1
2.2.3 Cutoff Frequency ············································2-1
2.2.4 Input Gain (Pre-Filter) ·········································2-1
2.2.5 Output Gain (Post-Filter) ········································2-1
2.2.6 Mode of Operation ···········································2-1
2.2.7 Filter Type ···············································2-1
2.2.8 Clear Entry Operation ··········································2-2
2.2.9 Storing Set-Ups ·············································2-2
2.2.10 Recalling Set-Ups ············································2-2
2.2.11 Second Function Keys Operation ······························2-2
2.2.12 Input Connectors ······································2-2
2.2.13 DC Level Adjust (rear panel) ································2-3
2.3 FILTER OPERATION ··············································2-3
2.3.1 Introduction ···············································2-3
2.3.2 Variable Band-Pass ···········································2-3
2.3.3 Amplitude Response ··········································2-3
2.3.4 Phase Response ·············································2-3
2.3.5 Group Delay···············································2-4
2.3.6 Transient Response ···········································2-4
i
Model 38 Table of Contents

TABLE OF CONTENTS
(CONTINUED)
SECTION 3 - IEEE-488 STD (GPIB) PROGRAMMING
3.1 INTRODUCTION ················································3-1
3.2 PRELIMINARY PROGRAMMING INFORMATION ·····························3-1
3.2.1 GPIB Primary Bus Address ·······································3-1
3.2.2 IEEE-488 Bus Interface Programming Connector · · · · · · ·····················3-1
3.3 ASCII DATA COMMANDS···········································3-2
3.3.1 Format··················································3-2
3.3.2 Types of Data Commands········································3-2
3.3.3 Table of ASCII Commands ·······································3-2
3.3.4 Examples ················································3-2
3.3.4.1 Example 1 ··········································3-2
3.3.4.2 Example 2 ··········································3-3
3.3.4.3 Example 3 ··········································3-3
4.3 IEEE-488 STANDARD COMMANDS ·····································3-3
3.4.1 Multiline Messages ···········································3-3
3.4.2 Polling Commands ···········································3-4
3.4.2.1 Parallel Polling ·······································3-4
3.4.2.2 Service Request and Serial Polling ·····························3-4
3.4.2.3 Serial Responses ······································3-4
3.4.3 Uniline Messages ············································3-5
3.5 TALKER FORMAT ···············································3-5
3.5.1 Parameter Information Format ·····································3-5
3.5.2 Model Number and Software Version Format ·····························3-5
3.6 PROGRAMMING EXAMPLE··········································3-6
3.6.1 Example 1 - Microsoft Quick Basic···································3-6
SECTION 4 - INCOMING ACCEPTANCE
4.1 INTRODUCTION ················································4-1
4.2 TEST EQUIPMENT REQUIRED ········································4-1
4.3 CUTOFF FREQUENCY ACCURACY CHECK ································4-1
4.4 STOPBAND ATTENUATION CHECK ·····································4-1
4.5 PRE-FILTER GAIN CHECK ··········································4-2
4.6 NOISE CHECK ·················································4-2
4.7 COMMON MODE REJECTION CHECK ····································4-2
ii
Table of Contents Model 38

TABLE OF CONTENTS
(CONTINUED)
SECTION 4 - INCOMING ACCEPTANCE (continued)
4.8 DISTORTION CHECK ·············································4-2
4.9 AC/DC COUPLING CHECK ··········································4-2
iii
Model 38 Table of Contents

SECTION 1
GENERAL DESCRIPTION
1.1 INTRODUCTION
The Krohn-Hite Model 38 Butterworth/Bessel plug-in filter
card is one of a family of filters which plug into the Model
3905B and 3916B Filter Mainframes, providing a tunable
frequency range from 0.03Hz to 1MHz in the low-pass
mode and 0.03Hz to 300kHz in the high-pass mode. Both
modes can be extended down to 0.003Hz with the 002 op-
tion. The frequency response characteristic is either maxi-
mally flat (Butterworth) for clean filtering in the frequency
domain, or linear phase (Bessel) to provide superior pulse or
complex filtering is operator selectable.
Each Model 38 card is an 8-pole, wide range, low-
pass/high-pass filter or an amplifier providing gains to 70dB
in 0.1dB steps. The 38 will accept input signals of ±10V
peak at 0dB gain and has selectable ac or dc coupling. Over-
load detectors are standard and assist the user in detecting
input signals or incorrect gain settings. Band-pass operation
is achieved by simply connecting the two channels in series.
Applications of the Model 38 are ultra-sound measurements,
random noise testing, sound recording, suppressing interfer-
ence in audio communications and related fields of medical,
geological, geophysical, oceanographic, military and many
more.
1.2 FUNCTION
Low-pass filter, high-pass filter; voltage gain amplifier.
1.3 FILTER MODE
Type: 8-pole, Butterworth, Bessel.
Attenuation: 48dB/octave.
Tunable Frequency Range fc:Low-pass, 0.03Hz to 1MHz;
high-pass, 0.03Hz to 300kHz; (option 002, 0.003Hz).
Frequency Resolution: 3 digits, 0.5Hz to max fc; 2 digits,
0.03Hz to 0.5Hz; (option 002, 3 digits, 0.05Hz to 0.5Hz; 2
digits, 0.003Hz to 0.05Hz).
Cutoff Frequency Accuracy: ±1%, 0.5Hz to 50kHz; ±2%,
50.1kHz to max fc; ±5%, 0.03Hz to 0.5Hz (option 002,
±5%, 0.003Hz to 0.5Hz).
Relative Gain at fc:–3dB, Butterworth; –12.6dB, Bessel.
High-Pass Bandwidth (0dB gain): >4MHz.
Stopband Attenuation: >80dB.
Maximum Input: ±10V peak at 0dB gain reduced in pro-
portion to gain setting; ±7 peak for LP, fc>500kHz, fsig
>500kHz.
Pre-Filter Gain: 0dB, 10dB, 20dB, 30dB, 40dB, 50dB,
±0.2dB.
Post-Filter Gain: 0dB to 20dB in 0.1dB steps, ±0.2dB.
Wideband Noise (2MHz bandwidth detector): 0dB gain,
<300µVrms for fc≤5kHz, <500µVrms for fc≤50kHz,
1mVrms for fc>50kHz. Max. gain, <25µVrms RTI.
Harmonic Distortion: –80dB at 1kHz.
DC Stability (RTI): Typically ±2mV/°C.
1.4 AMPLIFIER MODE
Bandwidth: >7MHz min. gain; >700kHz max. gain.
Response: ±0.1dB typical, ±0.5dB max.
Gain: 0dB to 70dB in 0.1dB steps, ±0.2dB.
Input: Differential or single-ended +(in phase), –(inverted).
CMRR: >60dB to 10kHz; >50dB to 100kHz.
Sensitivity: 3mV peak with 70dB 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 (0.16Hz) or dc.
Maximum DC Component: ±100V in ac coupled
mode.
Output:
Maximum Voltage (open circuit): ±10V peak.
Maximum Current: ±80mA peak.
Impedance: 50 ohms.
DC Offset: Adjustable to zero volts.
Harmonic Distortion (1V output): –80dB (0.01%) to
10kHz; –60dB (0.1%) to 100kHz..
1-1
Model 38 Section 1 - General Description

Wideband Noise (RTI, 2MHz BW detector): 200µVrms
min. gain; 25µVrms max. gain.
DC Stability (RTI): Typically ±10mV/°C.
1.5 GENERAL
Crosstalk Between Channels: –85dB below full scale with
input source <50 ohms.
Low-Pass Phase Match Between Channels: ±2° to
500kHz, ±5° to 1MHz. Only for cards purchased at the same
time.
High-Pass Phase Match Between Channels: For fc
≤100kHz, ±2° for fsig ≤500kHz, 2° times fsig/500kHz for
fsig to 2MHz; for fc>100kHz, ±5° for fsig ≤500kHz, 5°
times fsig/500kHz for fsig to 2MHz. Only cards purchased at
the same time.
Gain Match Between Channels: ±0.2dB max. to 100kHz.
Switch: For selection of Input, +(in phase), Differential or
–(inverted).
Input/Output Connectors: BNC.
Power: 15 watts.
Weights: 1.75 lbs (.79kg).
1.6 OPTIONS
002: extends low end cutoff to 0.003Hz.
Ew38: Extended one year warranty.
Specifications apply at 25°C, ±5°C.
1-2
Section 1 - General Description Model 38

SECTION 2
OPERATION
2.1 INTRODUCTION
The Model 3988 is a plug-in filter card covering the fre-
quency range from 0.03Hz (0.003Hz with option 002) to
1MHz in low-pass mode and 300kHz in high-pass mode.
The filter has three modes of operation: high-pass, low-pass
and gain only.
2.2 OPERATING PROCEDURE
2.2.1 Channel Selection
Up and down controls [↑] and [↓] increase or decrease
channel setting shown on the DISPLAY. When held, chan-
nels will cycle through all active channels continuously.
Channel selection can also be accomplished by entering the
desired channel number in the keyboard and momentarily
pressing either up [↑] or down [↓] channel controls.
2.2.2 All Channel Key Procedure
When frequency, input/output gain, type, mode or coupling
are entered or changed, and the LED in the [ALL CHAN]
key is on, the new setting will also be entered in all other fil-
ters of the same card type.
2.2.3 Cutoff Frequency
Data entry keyboard controls [0] to [9] and [.] set the nu-
meric value of the cutoff frequency desired. To program
1.5kHz press the [1][.][5] data keys and parameter keys
[KILO]and [FREQ]. The cutoff frequency will be entered
only in the channel displayed and indicated in Hertz in the
four digit DISPLAY.
2.2.4 Input Gain (Pre-Filter)
Up and down GAIN SET controls [↑] and [↓] increase or
decrease the input amplifier by 10dB up to 50dB. The two
digit DISPLAY will indicate the selected gain setting.
2.2.5 Output Gain (Post Filter)
Up and down GAIN SET controls [↑] and [↓] increase or
decrease the output amplifier by dB. The two digit DIS-
PLAY will indicate either 00 or 20dB.
2.2.6 Mode of Operation
When the [MODE] key is pressed, the DISPLAY indicates
the mode of operation in the channel displayed, alternating
as the [MODE] key is pressed between low-pass “L.P.”,
high-pass “h.P.”, band-pass “b.P.” and gain “gAIn” which
connects input to output.
2.2.7 Filter Type
The DISPLAY will indicate the filter type in the channel
displayed when the [TYPE] key is pressed, alternating be-
tween Butterworth “bu.” and Bessel “bES.” response.
NOTE: For gains >10dB, the decimal point is off for whole
dB’s (10, 11, 12, Etc.), but ON for fractional (10.1 – 10.9,
11.1 – 11.9, Etc.).
2.2.8 Clear Entry Key Operation
When entering a numeric value in the keyboard, but not
specifying a parameter, pressing the clear entry key will
function as an error correction procedure and restore DIS-
PLAY to its previous set-up.
When a numeric value and its parameter has been entered
and the numeric value is then changed, pressing the [CE]
key will restore DISPLAY to the previous value of that pa-
rameter.
When either the [SECOND FUNCTION][STORE] or [RE-
CALL] key is pressed, the next memory location will be in-
dicated on the DISPLAY. Pressing the [CE] key will re-
store DISPLAY to its previous setting.
When the DISPLAY contains information other than the
frequency, pressing the [CE] key will restore the DISPLAY
to the current frequency.
If the Model 3905B or 3916B is operating via the IEEE-488
bus (the front panel REMOTE LED is `on’), pressing the
[CE] key will return unit to LOCAL operation.
2-1
Model 38 Section 2 - Operation