Tektronix TEKFAX ADA400A User manual

Instruction Manual
ADA400A
Differential Preamplifier
070-9164-02
Warning
The servicing instructions are for use by qualified
personnel only. To avoid personal injury, do not
perform any servicing unless you are qualified to
do so. Refer to the Safety Summary prior to
performing service.

Copyright ©Tektronix, Inc. All rights reserved.
Tektronix products are covered by U.S. and foreign patents, issued and pending. Information in this publication supercedes
that in all previously published material. Specifications and price change privileges reserved.
Tektronix, Inc., P.O. Box 500, Beaverton, OR 97077
TEKTRONIX and TEK are registered trademarks of Tektronix, Inc.

WARRANTY
Tektronix warrants that this product will be free from defects in materials and workmanship for a period of three (3) years
from the date of shipment. If any such product proves defective during this warranty period, Tektronix, at its option, either
will repair the defective product without charge for parts and labor, or will provide a replacement in exchange for the
defective product.
In order to obtain service under this warranty, Customer must notify Tektronix of the defect before the expiration of the
warranty period and make suitable arrangements for the performance of service. Customer shall be responsible for
packaging and shipping the defective product to the service center designated by Tektronix, with shipping charges prepaid.
Tektronix shall pay for the return of the product to Customer if the shipment is to a location within the country in which the
Tektronix service center is located. Customer shall be responsible for paying all shipping charges, duties, taxes, and any
other charges for products returned to any other locations.
This warranty shall not apply to any defect, failure or damage caused by improper use or improper or inadequate
maintenance and care. Tektronix shall not be obligated to furnish service under this warranty a) to repair damage resulting
from attempts by personnel other than Tektronix representatives to install, repair or service the product; b) to repair
damage resulting from improper use or connection to incompatible equipment; or c) to service a product that has been
modified or integrated with other products when the effect of such modification or integration increases the time or
difficulty of servicing the product.
THIS WARRANTY IS GIVEN BY TEKTRONIX WITH RESPECT TO THIS PRODUCT IN LIEU OF ANY
OTHER WARRANTIES, EXPRESSED OR IMPLIED. TEKTRONIX AND ITS VENDORS DISCLAIM ANY
IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
TEKTRONIX’ RESPONSIBILITY TO REPAIR OR REPLACE DEFECTIVE PRODUCTS IS THE SOLE AND
EXCLUSIVE REMEDY PROVIDED TO THE CUSTOMER FOR BREACH OF THIS WARRANTY. TEKTRONIX
AND ITS VENDORS WILL NOT BE LIABLE FOR ANY INDIRECT, SPECIAL, INCIDENTAL, OR
CONSEQUENTIAL DAMAGES IRRESPECTIVE OF WHETHER TEKTRONIX OR THE VENDOR HAS
ADVANCE NOTICE OF THE POSSIBILITY OF SUCH DAMAGES.

ADA400A Differential Preamplifier
i
Table of Contents
General Safety Summary v...................................
Preface vii...................................................
Contacting Tektronix viii.............................................
Getting Started 1............................................
Product Description 1..............................................
Accessories 1.....................................................
Installation 2.....................................................
Functional Check 4................................................
Operating Basics 7..........................................
Determining the Effective Volts/Division 10.............................
Reference 11.................................................
Connecting the Inputs 11.............................................
Setting the Controls 15..............................................
Tips for Reducing Signal Interference 19................................
Specifications 21.............................................
Nominal Characteristics 21...........................................
Warranted Characteristics 22..........................................
Typical Characteristics 24............................................
Performance Verification 29...................................
Requirements for Performance 29......................................
Equipment Required 29..............................................
Procedures 30......................................................
Adjustment Procedures 41.....................................
Requirements for Performance 41......................................
Equipment Required 41..............................................
Procedure 42......................................................
Maintenance 51..............................................
Warranty Service 51................................................
Preparation 51.....................................................
Cleaning 52.......................................................
Replacement Procedures 52..........................................
Replacement Parts 56...............................................
Theory of Operation 56..............................................
Troubleshooting 58.................................................
Repackaging Instructions 58..........................................
Replaceable Parts 59..........................................
Parts Ordering Information 59.........................................
Using the Replaceable Parts List 60....................................
Glossary 65.................................................
Index 67....................................................

Table of Contents
ii
ADA400A Differential Preamplifier
List of Figures
Figure 1: Configuration Jumper for Scale Factor Coding 3........
Figure 2: Front Panel Controls 7...............................
Figure 3: Input Connectors and Fuses 8........................
Figure 4: Output Connector 8.................................
Figure 5: Selecting the Input Impedance 13......................
Figure 6: Differential Rejection of Common-Mode Signal 14........
Figure 7: Eliminating Ground Loops in a Differential Setup 15......
Figure 8: Input and Offset Range for X 0.1 Gain 17................
Figure 9: Input and Offset Range for X 1 Gain 17.................
Figure 10: Input and Offset Range for X 10 Gain 17...............
Figure 11: Input and Offset Range for X 100 Gain 18..............
Figure 12: Typical DC and AC Coupled CMRR in X0.1 Gain 26.....
Figure 13: Typical AC and DC Coupled CMRR in X1 Gain 27......
Figure 14: Typical and Warranted CMRR in X10 Gain 27..........
Figure 15: Typical and Warranted CMRR in X100 Gain 28.........
Figure 16: Location of Adjustments Underneath Inner Shield 43.....
Figure 17: Replacing TEKPROBE Interface Pins 53...............
Figure 18: Replacing the TEKPROBE collar 53...................
Figure 19: Input Connectors and Fuses 54.......................
Figure 20: Potentiometer Connections 55.........................
Figure 21: Diagram of the ADA400A Differential Preamplifier 56....
Figure 22: ADA400A Differential Preamplifier — Exploded View 63.
List of Tables
Table 1: Gain settings 5......................................
Table 2: Controls, Connectors, and Indicators 9.................
Table 3: Effective Volts Per Division Settings 10..................
Table 4: Nominal Characteristics — Signal Acquisition System 21...
Table 5: Warranted Characteristics — Signal Acquisition System 22.
Table 6: Warranted Characteristics — Environmental 23..........
Table 7: Typical Characteristics — Signal Acquisition System 24....
Table 8: Typical Characteristics — Mechanical Characteristics 26...
Table 9: Test Equipment 29...................................
Table 10: Equipment Settings for Gain Checks 31................
Table 11: Equipment Settings for Offset Adjust 33................

Table of Contents
ADA400A Differential Preamplifier
iii
Table 12: Equipment Settings for X100, 100 kHz CMRR Checks 34.
Table 13: Equipment Settings for X100, 10 kHz CMRR Checks 35..
Table 14: Equipment Settings for X100, 100 Hz CMRR Checks 36...
Table 15: Equipment Settings for X10, 100 kHz CMRR Checks 36..
Table 16: Equipment Settings for X10, 10 kHz CMRR Checks 37...
Table 17: Equipment Settings for X10, 100 Hz CMRR Checks 37....
Table 18: Equipment Settings for Gain Adjustments 44............
Table 19: Equipment Settings for Offset Adjustments 45...........
Table 20: Equipment Settings for Attenuator Balance Adjustments 46
Table 21: Equipment Settings for CMRR Adjustments 47..........
Table 22: Equipment Settings for LF Adjustments 49..............
Table 23: Second Equipment Settings for LF Adjustments 49.......
Table 24: Electrical Faults 58..................................

Table of Contents
iv
ADA400A Differential Preamplifier

ADA400A Differential Preamplifier
v
General Safety Summary
Review the following safety precautions to avoid injury and prevent damage to
this product or any products connected to it.
Only qualified personnel should perform service procedures.
Injury Precautions
To avoid electric shock or fire hazard, do not apply a voltage to a terminal that is
outside the range specified for that terminal.
This product is grounded through the grounding conductor of the oscilloscope
power cord. To avoid electric shock, the grounding conductor must be connected
to earth ground. Before making connections to the input or output terminals of
the product, ensure that the product is properly grounded.
To avoid electric shock or fire hazard, do not operate this product with covers or
panels removed.
To avoid electric shock, do not operate this product in wet or damp conditions.
To avoid injury or fire hazard, do not operate this product in an explosive
atmosphere.
Product Damage Precautions
If you suspect there is damage to this product, have it inspected by qualified
service personnel.
Clean the instrument using only a damp cloth. Refer to cleaning instructions.
Avoid Electric Overload
Ground the Product
Do Not Operate Without
Covers
Do Not Operate in
Wet/Damp Conditions
Do Not Operate in
Explosive Atmosphere
Do Not Operate With
Suspected Failures
Do Not Immerse in Liquids

General Safety Summary
vi
ADA400A Differential Preamplifier
Safety Terms and Symbols
These terms may appear in this manual:
WARNING. Warning statements identify conditions or practices that could result
in injury or loss of life.
CAUTION. Caution statements identify conditions or practices that could result in
damage to this product or other property.
These terms may appear on the product:
DANGER indicates an injury hazard immediately accessible as you read the
marking.
WARNING indicates an injury hazard not immediately accessible as you read the
marking.
CAUTION indicates a hazard to property including the product.
The following symbols may appear on the product:
DANGER
High Voltage
Protective Ground
(Earth) Terminal
ATTENTION
Refer to
Manual
Double
Insulated
Terms in This Manual
Terms on the Product
Symbols on the Product

ADA400A Differential Preamplifier
vii
Preface
This manual contains both user and service information for the ADA400A
Differential Preamplifier. The following is a brief overview of what each section
of the manual contains.
HGetting Started includes a description of the product features and a list of
standard and optional accessories. This section also describes how to supply
power to the preamplifier and how to connect the preamplifier to an
oscilloscope.
HOperating Basics contains a graphical overview and a brief description of
each control and connector of the ADA400A Differential Preamplifier.
HThe Reference section describes how to connect the ADA400A Differential
Preamplifier to small signals and make the proper settings.
HSpecifications lists the electrical and mechanical characteristics of the
ADA400A Differential Preamplifier.
HPerformance Verification contains procedures for verifying the warranted
characteristics of the ADA400A Differential Preamplifier.
HThe sections behind the warning page contain service information for the
ADA400A Differential Preamplifier: Adjustment Procedures,Maintenance
and Replaceable Parts.

Preface
viii
ADA400A Differential Preamplifier
Contacting Tektronix
Phone [phone]*
Address Tektronix, Inc.
Department or name (if known)
14200 SW Karl Braun Drive
P.O. Box 500
Beaverton, OR 97077
USA
Web site www.tektronix.com
Sales support 1-800-833-9200, select option 1*
Service support 1-800-833-9200, select option 2*
Technical support Email: [e-mail]
1-800-833-9200, select option 3*
6:00 a.m. -- 5:00 p.m. Pacific time
*This phone number is toll free in North America. After office hours, please leave a
voice mail message.
Outside North America, contact a Tektronix sales office or distributor; see the
Tektronix web site for a list of offices.

ADA400A Differential Preamplifier
1
Getting Started
Getting Started includes a description of the product features and a list of
standard and optional accessories. This section also describes how to supply
power to the preamplifier and how to connect the preamplifier to an oscilloscope.
Product Description
The ADA400A Differential Preamplifier allows direct oscilloscope measure-
ments of very low amplitude voltages and signals that do not have a ground
reference. These measurements are typical in setups that depend on transducers
or other sensitive devices to supply the electrical signal.
Highlights of the ADA400A Differential Preamplifier are as follows:
HSelectable gains of X100, X10, X1, and X0.1 provide wide range of
sensitivity.
HCommon-mode rejection of greater than or equal to 100,000 to 1 in the
frequency range of DC to 10 kHz removes unwanted common mode
electrical noise from sensitive pickups.
HBandwidth of greater than or equal to 1 MHz amplifies signals with fast
transients. Selectable bandwidth limits of 100 Hz, 3 kHz, 100 kHz reject
normal-mode noise.
HInput impedance of 1 MΩin all settings and selectable impedance of
infinite Ω(>1012 Ω) in X100 and X10 gain settings. The high input
impedance prevents loading down signals with high source impedance.
HAdjustable differential offset allows the user to null out transducer bridge
bias, galvanic potentials from the test setup, or other DC voltages.
HSpecial circuitry greatly reduces the annoying DC drift commonly found in
older types of differential preamplifiers.
HTEKPROBEInterface provides power input and signal output connections.
Accessories
Standard accessories for the ADA400A Differential Preamplifier include the
following items:
HThis instruction manual
HTwo spare input fuses

Getting Started
2
ADA400A Differential Preamplifier
Recommended accessories for the ADA400A Differential Preamplifier include
the following items:
HP6101B 1X Passive Probe
H1103 Probe Power Supply for oscilloscopes that do not have the TEK-
PROBE Interface.
Installation
Before you connect the output of the ADA400A Differential Preamplifier,
determine whether or not your oscilloscope has the TEKPROBE interface. The
interface provides connections for power, signal, and scale factor coding for
compatible probes and accessories.
The polarized output connector of ADA400A Differential Preamplifier connects
to any oscilloscope with the TEKPROBE interface.
NOTE. To avoid misleading scale factor readouts of the ADA400A Differential
Preamplifier, the oscilloscope must be compatible with the scale factor coding;
otherwise, you must remove the preamplifier housing and disconnect the internal
line that carries the scale factor coding.
Compatible Oscilloscopes. Most oscilloscopes with the TEKPROBE interface,
except the 11000 Series models, are compatible with the scale factor coding of
the ADA400A Differential Preamplifier. The factory configures the internal
jumper to connect the scale factor coding. See Figure 1.
Perform the Functional Check on page 4, steps 1--6, and verify that the
oscilloscope volt/division readings match the manual for all gain settings in step
6. If the readings are not correct for any scale setting, the oscilloscope is not
compatible with the scale factor coding of the ADA400A Differential Preamplifi-
er. In this case, use the procedure that follows to disable the scale factor coding.
1. Remove the top housing of the preamplifier by following the procedures on
page 54.
2. Identify the jumper on the data line (See Figure 1) and position the jumper to
disable the scale factor coding.
3. Replace the top housing on the preamplifier box.
Oscilloscopes with the
TEKPROBE Interface

Getting Started
ADA400A Differential Preamplifier
3
Enabled Disabled
Figure 1: Configuration Jumper for Scale Factor Coding
Because the line that carries the scale factor coding is disabled, see the chart on
page 10 to correctly interpret the volts/division setting of the oscilloscope.
Connecting the TEKPROBE Output. To engage the TEKPROBE output, align the
fin on the output head counterclockwise with the clearance on the oscilloscope
connector. Push the connector in and and lock the fin clockwise.
Use the 1103 TEKPROBE Power Supply to connect the ADA400A Differential
Preamplifier to any oscilloscope that does not provide TEKPROBE power. The
1103 TEKPROBE Power Supply has connections for two probe channels.
NOTE. Use the offset controls of the ADA400A Differential Preamplifier to adjust
the offset level. The offset controls on the 1103 TEKPROBE Power Supply do not
operate with the ADA400A Differential Preamplifier.
Because the 1103 TEKPROBE Power Supply does not connect the line that
carries the scale factor coding, see the chart on page 10 to correctly interpret the
volts/division setting of the oscilloscope.
For more information about using the 1103 TEKPROBE Power Supply, refer to
the instruction manual that comes with the power supply.
Oscilloscopes without the
TEKPROBE Interface

Getting Started
4
ADA400A Differential Preamplifier
Always set the input impedance of the oscilloscope to 1 MΩand the input
coupling of the oscilloscope to DC. Setting the impedance to 50 Ωloads
(reduces) the amplitude of the output signal from the ADA400A Differential
Preamplifier. AC coupling on the oscilloscope interferes with the signal output.
Use the input coupling switch on the preamplifier to select other types of signal
coupling.
Functional Check
The following procedure checks the output level of the ADA400A Differential
Preamplifier and the functionality of the offset controls with no signal applied.
1. Without any connection on the input of the oscilloscope, power on the
oscilloscope and make the following control settings:
Volts/Division 100 mV
Time/Division 100 s
Input Coupling DC
Input Impedance 1 MΩ
2. Adjust the oscilloscope to display a flat signal trace at center screen.
3. Connect the output of the ADA400A Differential Preamplifier (or 1103
TEKPROBE Power Supply) to the input connector of the oscilloscope.
4. With no input signal or voltage connected, make the following control
settings on the ADA400A Differential Preamplifier:
AC GND DC GND (both inputs)
GAIN 0.1
OFFSET OFF
UPPER BANDWIDTH FULL (1 MHz)
5. Check that the trace on the oscilloscope centers around zero volts and the
OVERRANGE indicator does not light.
6. Set the GAIN switch to each of the higher gain settings and check that the
trace on the oscilloscope is adjustable to center screen. Make sure the
volts/division reading on the scope matches the readings below in table 1. If
the readings do not match, the oscilloscope is not compatible with the scale
factor coding of the ADA400A Differential Preamplifier. See page 2. If the
scale factor coding is disabled, see table 3 on page 10 for proper readings.
Check the Oscilloscope
Input Impedance and
Coupling

Getting Started
ADA400A Differential Preamplifier
5
Table 1: Gain settings
Gain setting Oscilloscope reading
0.1 1.00 V
1100 mV
10 10.0 mV
100 1.00 mV
7. With the GAIN switch on the highest setting, set the ON OFF switch for the
OFFSET controls to ON.
8. Adjust the COARSE and FINE controls to bring the trace to center screen.
9. Set each input separately to AC,DC, and back to GND and check that the
offset controls still bring the trace to center screen for each setting.
10. Return the GAIN setting to .1 and the input coupling switches to GND.
The ADA400A Differential Preamplifier is now ready to use. For a complete
performance verification procedure, refer to page 29.

Getting Started
6
ADA400A Differential Preamplifier

ADA400A Differential Preamplifier
7
Operating Basics
Operating Basics contains a graphical overview and a brief description of each
control and connector of the ADA400A Differential Preamplifier. See Figures 2
through 4 and Table 2.
Ω1
Ω
}
}
Input Coupling
Vertical Offset
Controls
Upper Bandwidth
Selector
Vertical Gain Control
Overrange Indicator
Figure 2: Front Panel Controls

Operating Basics
8
ADA400A Differential Preamplifier
+ Input Fuse -- Input Fuse-- Input BNC
Connector
+ Input BNC
Connector
Figure 3: Input Connectors and Fuses
TEKPROBE Interface Pins
Signal Output
BNC
Figure 4: Output Connector