Tektronix ADA400A Differential Preamplifier Instruction Manual

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Form 080/01

Instruction Manual

ADA400A

Differential Preamplifier

070-9164-01

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.

Table of Contents

General Safety Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Getting Started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Product Description

Accessories

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Functional Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Operating Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Determining the Effective Volts/Division . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Connecting the Inputs

Setting the Controls

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Tips for Reducing Signal Interference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Nominal Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Warranted Characteristics

Typical Characteristics

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Performance Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Requirements for Performance

Equipment Required

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Adjustment Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Requirements for Performance

Equipment Required

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Warranty Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Preparation

Cleaning

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Replacement Procedures

Replacement Parts

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Theory of Operation

Troubleshooting

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Repackaging Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Replaceable Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Parts Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Using the Replaceable Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

29

29

29

30

37

37

37

38

21

21

22

24

iii

1

1

1

2

4

7

10

11

11

15

19

55

55

56

61

47

47

47

48

48

52

52

54

54

63

ADA400A Differential Preamplifier

i

Contents

ii

List of Figures

Figure 1: Configuration Jumper for Scale Factor Coding

Figure 2: Front Panel Controls

. . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Figure 3: Input Connectors and Fuses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Figure 4: Output Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Figure 5: Selecting the Input Impedance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Figure 6: Differential Rejection of Common-Mode Signal

Figure 7: Eliminating Ground Loops in a Differential Setup

. . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . .

Figure 8: Input and Offset Range for X 0.1 Gain

Figure 9: Input and Offset Range for X 1 Gain

. . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . .

Figure 10: Input and Offset Range for X 10 Gain . . . . . . . . . . . . . . . . . . . . . . . .

Figure 11: Input and Offset Range for X 100 Gain . . . . . . . . . . . . . . . . . . . . . . .

Figure 12: Typical DC and AC Coupled CMRR in X0.1 Gain . . . . . . . . . . . . . .

Figure 13: Typical AC and DC Coupled CMRR in X1 Gain

Figure 14: Typical and Warranted CMRR in X10 Gain

. . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . .

Figure 15: Typical and Warranted CMRR in X100 Gain . . . . . . . . . . . . . . . . . . .

Figure 16: Location of Adjustments Underneath Inner Shield . . . . . . . . . . . . . .

Figure 17: Replacing TEKPROBE Interface Pins . . . . . . . . . . . . . . . . . . . . . . . .

Figure 18: Replacing the TEKPROBE collar

Figure 19: Input Connectors and Fuses

. . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Figure 20: Potentiometer Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Figure 21: Diagram of the ADA400A Differential Preamplifier . . . . . . . . . . . . .

Figure 22: ADA400A Differential Preamplifier — Exploded View . . . . . . . . . .

17

17

17

18

26

27

27

8

13

14

15

3

7

8

28

39

49

49

50

51

52

59

List of Tables

Table 1: Gain settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Table 2: Controls, Connectors, and Indicators . . . . . . . . . . . . . . . . . . . . . . . . . .

Table 3: Effective Volts Per Division Settings . . . . . . . . . . . . . . . . . . . . . . . . . .

Table 4: Nominal Characteristics — Signal Acquisition System

Table 5: Warranted Characteristics — Signal Acquisition System

. . . . . . . . . . . .

. . . . . . . . . . .

Table 6: Warranted Characteristics — Environmental . . . . . . . . . . . . . . . . . . . .

Table 7: Typical Characteristics — Signal Acquisition System . . . . . . . . . . . . .

Table 8: Typical Characteristics — Mechanical Characteristics

Table 9: Test Equipment

. . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Table 10: Equipment Settings for Gain Checks . . . . . . . . . . . . . . . . . . . . . . . . .

Table 11: Equipment Settings for X100, 100 kHz CMRR Checks

Table 12: Equipment Settings for X100, 10 kHz CMRR Checks

. . . . . . . . . . .

. . . . . . . . . . . .

Table 13: Equipment Settings for X100, 100 Hz CMRR Checks . . . . . . . . . . . .

Table 14: Equipment Settings for X10, 100 kHz CMRR Checks

Table 15: Equipment Settings for X10, 10 kHz CMRR Checks

. . . . . . . . . . . .

. . . . . . . . . . . . .

Table 16: Equipment Settings for X10, 100 Hz CMRR Checks

Table 17: Equipment Settings for Gain Adjustments

. . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .

Table 18: Equipment Settings for Offset Adjustments . . . . . . . . . . . . . . . . . . . .

Table 19: Equipment Settings for Attenuator Balance Adjustments . . . . . . . . .

Table 20: Equipment Settings for CMRR Adjustments . . . . . . . . . . . . . . . . . . .

Table 21: Equipment Settings for LF Adjustments . . . . . . . . . . . . . . . . . . . . . . .

Table 22: Second Equipment Settings for LF Adjustments . . . . . . . . . . . . . . . .

Table 23: Electrical Faults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ADA400A Differential Preamplifier

35

36

36

40

41

42

43

45

45

54

26

29

31

33

34

35

5

9

10

21

22

23

24

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

Avoid Electric Overload

To avoid electric shock or fire hazard, do not apply a voltage to a terminal that is outside the range specified for that terminal.

Ground the Product

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.

Do Not Operate Without

Covers

To avoid electric shock or fire hazard, do not operate this product with covers or panels removed.

Do Not Operate in

Wet/Damp Conditions

Do Not Operate in

Explosive Atmosphere

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

Do Not Operate With

Suspected Failures

If you suspect there is damage to this product, have it inspected by qualified service personnel.

Do Not Immerse in Liquids

Clean the instrument using only a damp cloth. Refer to cleaning instructions.

ADA400A Differential Preamplifier

iii

General Safety Summary

Safety Terms and Symbols

Terms in This Manual

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.

Terms on the Product

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.

Symbols on the Product

The following symbols may appear on the product:

DANGER

High Voltage

Protective Ground

(Earth) Terminal

ATTENTION

Refer to

Manual

Double

Insulated

ADA400A Differential Preamplifier

iv

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.

H 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.

H Operating Basics contains a graphical overview and a brief description of each control and connector of the ADA400A Differential Preamplifier.

H The Reference section describes how to connect the ADA400A Differential

Preamplifier to small signals and make the proper settings.

H Specifications lists the electrical and mechanical characteristics of the

ADA400A Differential Preamplifier.

H Performance Verification contains procedures for verifying the warranted characteristics of the ADA400A Differential Preamplifier.

H The sections behind the warning page contain service information for the

ADA400A Differential Preamplifier: Adjustment Procedures, Maintenance and Replaceable Parts.

ADA400A Differential Preamplifier

v

Preface

Contacting Tektronix

Phone

Address

1-800-833-9200*

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

1-800-833-9200, select option 1*

Sales support

Service support

1-800-833-9200, select option 2*

Technical support

Email: [email protected]

1-800-833-9200, select option 3*

1-503-627-2400

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

vi

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 measurements 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:

H Selectable gains of X100, X10, X1, and X0.1 provide wide range of sensitivity.

H Common-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.

H Bandwidth 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.

H Input impedance of 1 MW in all settings and selectable impedance of infinite

W (u10

12

W) in X100 and X10 gain settings. The high input impedance prevents loading down signals with high source impedance.

H Adjustable differential offset allows the user to null out transducer bridge bias, galvanic potentials from the test setup, or other DC voltages.

H Special circuitry greatly reduces the annoying DC drift commonly found in older types of differential preamplifiers.

H TEKPROBE



Interface provides power input and signal output connections.

Accessories

Standard accessories for the ADA400A Differential Preamplifier include the following items:

H This instruction manual

H Two spare input fuses

ADA400A Differential Preamplifier

1

2

Getting Started

Recommended accessories for the ADA400A Differential Preamplifier include the following items:

H P6101B 1X Passive Probe

H 1103 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.

Oscilloscopes with the

TEKPROBE Interface

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 Preamplifier. 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 50.

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.

ADA400A Differential Preamplifier

Getting Started

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.

Oscilloscopes without the

TEKPROBE Interface

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.

ADA400A Differential Preamplifier

3

4

Getting Started

Check the Oscilloscope

Input Impedance and

Coupling

Always set the input impedance of the oscilloscope to 1 M

W and the input coupling of the oscilloscope to DC. Setting the impedance to 50

W loads

(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

Time/Division

Input Coupling

Input Impedance

100 mV

100 ms

DC

1 M

W

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

GAIN

OFFSET

UPPER BANDWIDTH

GND (both inputs)

0.1

OFF

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.

ADA400A Differential Preamplifier

Getting Started

Table 1: Gain settings

Gain setting

0.1

1

10

100

Oscilloscope reading

1.00 V

100 mV

10.0 mV

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.

ADA400A Differential Preamplifier

5

Getting Started

6

ADA400A Differential Preamplifier

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.

1

W

W

Input Coupling

Vertical Gain Control

Overrange Indicator

Upper Bandwidth

Selector

}

}

Vertical Offset

Controls

Figure 2: Front Panel Controls

ADA400A Differential Preamplifier

7

Operating Basics

+ Input Fuse + Input BNC

Connector

Figure 3: Input Connectors and Fuses

– Input BNC

Connector

– Input Fuse

8

Signal Output

BNC

TEKPROBE Interface Pins

Figure 4: Output Connector

ADA400A Differential Preamplifier

Operating Basics

Table 2: Controls, Connectors, and Indicators

Feature

+ Input BNC

Connector

– Input BNC

Connector

Description

Input BNCs. The BNC connectors provide the differential input connections to the preamplifier. These connectors accept coaxial cables, 1X probes, adapters, or other input leads that terminate with male BNC connectors. Before connecting the inputs, see page 11.

NOTE. Avoid using attenuating probes. The slightest difference in attenuation match greatly lowers the common-mode rejection ratio.

Input Fuses. The input fuses and internal circuitry protect the input circuits from excessive surge currents. To replace the fuses, see page 50.

+ Input

Fuse

1

W

W

– Input

Fuse

}

}

Selectable Impedance. Internal jumpers select infinite impedance for measuring signals with high source impedance. To select the input impedance, see page 12.

Input Coupling Switches. Use the input coupling switches to select the proper mode for coupling the input signals to the internal inputs of the preamplifier.

The AC position couples the input signal through a capacitor and blocks any DC and AC components of the signal from 0 to 2 Hz.

GND decouples the signal from the input and couples the internal input of the preamplifier to ground. This position also precharges the coupling capacitor to the DC level of the input signal (see page 16).

The DC position couples both AC and DC components of the input signal.

Overrange Indicator. The OVERRANGE indicator lights red when the signal input exceeds the selected range of the amplifier. If the indicator is on, the output signal is not a true representation of the input signal(s). See page 16.

Gain Selector. The gain selectors set the gain of the preamplifier to X0.1, X1, X10, or

X100. If the oscilloscope does not display the correct volts per division for each gain setting, refer to Table 3 on page 10.

Offset Controls. The ON/OFF switch activates the offset controls. The COARSE and

FINE controls provide a maximum of 40 volts offset in the X0.1 and X1 gain settings and a maximum of 1 volt offset in X10 and X100 gain settings. See page 16.

ADA400A Differential Preamplifier

9

Operating Basics

Table 2: Controls, Connectors, and Indicators (Cont.)

Feature Description

Upper Bandwidth Selector. The Upper Bandwidth Selector reduces electrical interference by limiting the frequency response of the amplifier to FULL (1 MHz),

100 kHz, 3 kHz, or 100 Hz.

Output Connector. The output connector contains connections for the TEKPROBE interface and signal output.

Determining the Effective Volts/Division

If your oscilloscope cannot read the scale factor information, see Table 3 to determine the effective volts/division setting. The effective volts per division is the volts per division setting of the oscilloscope divided by the gain setting of the ADA400A Differential Preamplifier. For example, if the volts/division setting on the oscilloscope is 500 mV/division and the gain setting is 10, the effective volts/division is 500 divided by 10 or 50 mV.

Table 3: Effective Volts Per Division Settings

Scope Volts/Div Gain = .1

1 10

500 m 5

200 m 2

100 m

50 m

20 m

10 m

5 m

2 m

1 m

1

500 m

200 m

100 m

50 m

20 m

10 m

100 m

50 m

20 m

10 m

5 m

2 m

1 m

Effective Volts Per Division

Gain = 1

1

500 m

200 m

Gain = 10

100 m

50 m

20 m

10 m

5 m

2 m

1 m

500 m

200 m

100 m

Gain = 100

10 m

5 m

2 m

1 m

500 m

200 m

100 m

50 m

20 m

10 m

ADA400A Differential Preamplifier

10

Reference

The Reference section describes how to connect the inputs of the ADA400A

Differential Preamplifier and make the proper control settings. To achieve the best performance it is important to make the proper signal and ground connections, set the controls to optimize the performance of the preamplifier, and reduce unwanted electrical interference.

Connecting the Inputs

Making the proper input connections is crucial to maintaining the fidelity of the signal as well as eliminating unwanted noise. The characteristics of the signal source and the type of measurement you wish to make, determine the type of input leads you should use and the way you should connect the inputs.

WARNING. Do not attach the ADA400A Differential Preamplifier to human subjects for any testing or bio-monitoring. The ADA400A Differential Preamplifier is not safety certified for direct connection to humans.

Input Devices

The ADA400A Differential Preamplifier is able to amplify extremely small signals that may or may not have a ground reference. Often the signals originate from low-level, low-frequency transducers, and other similar sources of small differential or floating voltages.

The inputs of the ADA400A Differential Preamplifier connect easily to devices or leads that terminate with male BNC connectors. There are numerous adapters readily available that can adapt other types of wire, cables, or plugs to a BNC connector.

NOTE. Avoid using attenuating probes. The slightest difference in attenuation match greatly lowers the common-mode rejection ratio.

ADA400A Differential Preamplifier

11

Reference

Using the Proper Input

Leads

To reduce unwanted electrical interference on the input leads, use shielded coaxial cable or the recommended 1X probes to connect signals to the preamplifier inputs. The shielding in these types of leads intercepts and shunts electrical noise to ground.

When you must use any length of unshielded wire, twist the wires together and connect the wires differentially. Twisting the wires together helps to introduce any electrical interference as common-mode noise that the differential preamplifier cancels out with a differential setup on the inputs.

For other tips on reducing signal interference, refer to page 19.

Input Voltages

Because the ADA400A Differential Preamplifier is designed to amplify small

DC and AC voltages, do not connect voltages that exceed the input rating.

CAUTION. To avoid damaging the inputs of the ADA400A Differential Preamplifier, do not apply more than 40 volts (DC + peak AC) between any one input and ground or 80 volts (DC + peak AC) differential between the inputs.

12

Input Protection

To prevent damage to the input circuitry from the misapplication of large voltages, a fuse on each input opens if the input current exceeds 62 mA (

1

/

16

A).

To replace or check these fuses, refer to the procedure on page 50.

Input Impedance

Each input connector of the ADA400A Differential Preamplifier has a characteristic input impedance of 1 M

W to ground in parallel with approximately 55 pF.

For low source impedances, this 1 M

W is more than adequate to prevent the inputs from loading the signal source.

If impedance of the signal source approaches 1 M

W, the impedance of the inputs begin to load the signal source and reduce the amplitude. In effect, the extremely low current of the signal source is not able to develop a voltage across the 1 M

W resistance and there is no signal to amplify. In this case you may want to select the infinite

W position.

Infinite

W. To measure signals from high impedance sources, you can internally disconnect the 1 M

W resistance of the ADA400A Differential Preamplifier. and select the infinite

W position. This position prevents the preamplifier from loading a high impedance signal source.

Observe the following operating limitations when you select the infinite

W position:

H Select either the X100 or the X10 gain position. Operation in the 0.1X and

1X gain results in gain errors.

ADA400A Differential Preamplifier

Reference

H Ensure that the source has some impedance to ground. The internal input amplifier requires some input bias current to operate. Typically this amount of input bias current is less than 25 pA.

H Select the DC coupling position when operating the preamplifier. The AC coupling position blocks the bias current that the preamplifier input requires to operate.

H Take steps to reduce interference from other sources (see page 19). Because the input impedance is essentially infinite you may notice an increased susceptibility to noise and DC drift.

Selecting the Infinite

W Position. To select the infinite impedance, remove the knobs and top housing of the preamplifier. Do not remove the inner shield. With a pair of needle-nose pliers or tweezers, move the jumpers from the 1 M

W to the infinite

W position as Figure 5 illustrates.

–

Input

+

Input

Infinite

W

1 M

W

Figure 5: Selecting the Input Impedance

Input Configurations

There are two basic types of input configurations on the ADA400A Differential

Preamplifier: single-ended or differential. Whether one or the other of these configurations is appropriate depends on the type of signal and the electrical environment of the test setup.

Single-Ended. To monitor a ground-referenced signal you only need to make a single input connection. All the controls on the preamplifier still operate. The only difference is that the preamplifier cannot cancel out common mode noise without using the other input connection. When making single-ended measurements, set the coupling for the unused input to GND.

ADA400A Differential Preamplifier

13

Reference

Single-ended measurements, however, often yield unsatisfactory information because of interference resulting from ground-loop currents between the oscilloscope and the device under test. In other cases, it is desirable to eliminate a common-mode DC voltage without using a DC blocking capacitor or the AC coupling capacitor of the preamplifier. These capacitors limit low-frequency response. Connecting the signals differentially virtually eliminates these effects.

Differential. Figure 6 shows two signals connected to the ADA400A Differential

Preamplifier. One signal is connected to the + input and the other is connected to the – input. Because the preamplifier inverts the signal at the – input, the preamplifier amplifies only differential voltages between the inputs and rejects

(cancels) voltages that are common to both inputs. The oscilloscope displays the waveform of the differential signal only.

NOTE. To avoid creating a fictitious differential offset, set both AC GND DC coupling switches to the same AC or DC switch position.

+

Differential

Amplifier

–

Figure 6: Differential Rejection of Common-Mode Signal

To avoid ground loops in a differential setup it is important to leave the grounds of the shielded coax disconnected and to route the chassis ground to the oscilloscope ground using a separate ground lead. Figure 7 on page 15 illustrates this type of connection.

ADA400A Differential Preamplifier

14

Reference

Circuit

Under Test

+

Differential

Amplifier

–

Common Ground

Oscilloscope

Input

Figure 7: Eliminating Ground Loops in a Differential Setup

Oscilloscope Input

Impedance and Coupling

Always set the input impedance of the oscilloscope to 1 M

W and the input coupling of the oscilloscope to DC. Setting the impedance to 50

W loads

(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.

Setting the Controls

The controls of the ADA400A Differential Preamplifier determine signal coupling, amplification, DC offset, and the bandwidth limit.

Input Coupling

The type of input coupling you select depends on whether or not you want to pass or block the DC component of the input signal.

AC Coupling. Setting the coupling switch to AC places a capacitor in the signal path and blocks DC to about 2 Hz signals. Select the AC position to block DC components on the signal input and couple AC signals higher than approximately 2 Hz. This setup is useful when the test setup has a DC bias which drifts.

NOTE. To prevent the circuit under test from receiving the effects of charging and

discharging the AC coupling capacitor, refer to the procedure for Precharging the Signal Input in the section that follows.

ADA400A Differential Preamplifier

15

Reference

GND Coupling. The GND position decouples the signal from the input and couples the internal input of the preamplifier to ground. This position also precharges the AC coupling capacitor to the DC level of the signal. (See the following section, Precharging the Signal Input.)

DC Coupling. The DC position couples all signal components, AC and DC, to the preamplifier. (You can adjust the offset controls to null out DC biases.)

Precharging the Signal

Input

Follow the procedure below when coupling AC signals that have a high DC voltage level or when probing between signals that differ greatly in DC levels.

This procedure becomes especially useful when you disable the 1 M

W input resistance and it takes a long time to charge the input capacitors back to the bias voltage.

1. Set the input coupling switch to GND before connecting the input to a signal source.

2. Connect the preamplifier input to the signal source.

3. Wait two seconds for the input coupling capacitor to charge to the DC level of the signal source.

4. Set the input coupling switch to AC. Position the AC signal within the graticule area on the oscilloscope display.

Gain, Input Range, and

Offset Range

The gain selector sets amplification factor of the preamplifier to X0.1, X1, X10, or X100. Each gain setting has a characteristic differential or single-ended range, a common-mode (dynamic) range, and variable offset range. To prevent the signal from distorting or “clipping” (see Figure 10) you must use the appropriate gain setting and offset.

The amount of differential, common-mode, and offset range depends on the gain setting. Figures 8 through 11 beginning on page 17 show the common-mode, differential, and offset range for each gain setting of the preamplifier.

The OVERRANGE indicator lights when the input signal is outside the differential input range for a particular gain setting. This light indicates that the output signal is distorted or “clipped” and the oscilloscope display may not be accurate. Try a lower gain setting or check the position of the offset controls if the OVERRANGE indicator is on.

ADA400A Differential Preamplifier

16

Reference

80

40

30

20

10

–10

–20

–30

–40

–80

Maximum

Single-Ended

Input

Common-Mode and Offset

Range

Maximum

Differential Input

Figure 8: Input and Offset Range for X 0.1 Gain

40

30

20

10

–10

–20

–30

–40

Maximum

Differential or

Single Ended Input

Common-Mode

Range and Offset

Range

Figure 9: Input and Offset Range for X 1 Gain

(“Clipped”

Waveform)

+10 V

+1 V

–1 V

Maximum

Differential and

Single-Ended Input

Offset Range

Common-Mode

Range

–10 V

Figure 10: Input and Offset Range for X 10 Gain

ADA400A Differential Preamplifier

17

Reference

18

+10V

+1V

+100mV

–100mV

Maximum

Differential and

Single-Ended Input

Offset Range

Common Mode

Range

–1V

–10V

Figure 11: Input and Offset Range for X 100 Gain

Adjusting the Offset

Controls

Setups that have a large DC offset, but must measure small changes in DC voltage or signal voltage below 2 Hz, require that you to adjust the offset controls of the preamplifier. Typical setups include those with transducers or setups that measure galvanic potentials.

To compensate for a DC offset, perform the following procedure:

1. Set the input coupling to GND on both inputs of the preamplifier and switch offset controls to OFF.

2. Preset the GAIN switch of the preamplifier and the volts/division switch of the oscilloscope to the appropriate settings based on the amount of offset you expect to measure. See Figures 8 through 11. (Select a lower gain setting if you are unsure of the amount of the offset.)

3. Center the oscilloscope display using the vertical position control on the oscilloscope.

4. Set the offset controls ON and center the display with the COARSE and

FINE offset controls.

5. Set the input coupling to DC on the signal input(s) and, if necessary, measure the amount of DC offset.

6. Center the display using the COARSE and FINE controls and change the volts/division setting on the oscilloscope to better display the signal.

Limiting Bandwidth

The ADA400A Differential Preamplifier has a selector for limiting the upper bandwidth. Limiting the bandwidth is desirable in setups where electrical interference from higher frequency sources is a problem. The ADA400A

ADA400A Differential Preamplifier

Reference

Differential Preamplifier allows you to select upper bandwidth limits of FULL

(1 MHz), 100 kHz, 3 kHz and 100 Hz.

Tips for Reducing Signal Interference

Disruptive electrical interference or “noise” from sources near the test setup can affect measurements. The effects become even more apparent when measuring low-amplitude voltages.

The electric-power system, for example, generates a line frequency of 50 or

60 Hz and can couple electrical noise from other devices. Power switches or switching devices generate power line spikes. Unshielded or poorly grounded electric motors can generate disruptive transients. Power lines and transformers create magnetic fields that can induce a disruptive voltage in wires or input leads that are not properly twisted together.

Devices such as digital or microprocessor based systems can radiate signals that sensitive electronic detectors or amplifiers can receive and amplify. Switch-mode power supplies generate interference in the range of 20 to 100 kHz. Sources of interference can include florescent lights, laser printers, monitors, CRTs, even radio transmissions.

Proper setup of the ADA400A Differential Preamplifier minimizes or eliminates signal interference in most cases. There are three important strategies to reducing signal interference:

1. Use the proper signal and ground connections for the particular application.

2. Limit the bandwidth of the test setup.

3. Isolate or eliminate sources of signal interference.

Signal and Ground

Connections

The techniques for proper signal and ground connections involve limiting noise to the input:

H Minimize length of input leads.

H Select input leads that have the same length and type of construction.

H Use shielded coaxial cable or “twisted-pair” leads on the inputs.

H Connect shield or ground leads close to signal source.

H Restrict movement of input leads.

H Eliminate ground loops.

H Reject common-mode noise by operating in differential mode.

ADA400A Differential Preamplifier

19

Reference

Bandwidth Limiting

Limiting the bandwidth is a useful technique for keeping unwanted high frequency noise from interfering with the display of lower frequency signals. The

ADA400A Differential Preamplifier allows you to limit the upper bandwidth to

100 Hz, 3 kHz, 100 MHz, and FULL (1 MHz).

Isolating or Eliminating

Sources of Interference

Some pieces of electronic or electrical equipment can generate enormous amounts of electrical noise. One solution is to isolate or eliminate the noise that these devices emit:

H Move sources of noise away from test setup or isolate test setup.

H Shield test setup.

H Make sure all electronic equipment that is connected to the AC power line is properly grounded through the power cord.

20

ADA400A Differential Preamplifier

Specifications

This section describes three classes of characteristics for the ADA400A

Differential Preamplifier: nominal, warranted, and typical.

Nominal Characteristics

Nominal traits are described using simple statements of fact such as “Differential, ‘+’ and ‘–’” for the characteristic “Input Configuration,” rather than in terms of limits that are performance requirements.

Table 4: Nominal Characteristics — Signal Acquisition System

Name

Input Configuration

Input Coupling

Gain Settings

Analog Bandwidth Selections

Offset Ranges

Description

Differential, ‘+’ and ‘–’

DC, AC, or GND

Ground coupling connects a ground reference to the input of the attenuator or differential amplifier and allows the AC coupling capacitor to charge up to the input voltage through a large resistance.

0.1, 1, 10, 100

100 Hz, 3 kHz, 100 kHz, and FULL (1 MHz)

Gain Setting

0.1

1

10

100

Offset Range

±

40 V

±

40 V

±

1 V

±

1 V

ADA400A Differential Preamplifier

21

Specifications

Warranted Characteristics

Warranted characteristics are described in terms of quantifiable performance limits which are warranted.

NOTE. In these tables, those warranted characteristics that are checked in the

procedure Performance Verification appear in boldface type under the column

Name.

The performance limits in this specification are valid with these conditions:

H This instrument must have been calibrated/adjusted at an ambient temperature of 22

±

5

_ C.

H The instrument must be in an environment with temperature, altitude, humidity, and vibration within the operating limits described in these specifications.

H The instrument must have had a warm-up period of at least 20 minutes.

H The instrument must be used with an oscilloscope that is compatible with the scale factor coding of the ADA400A Differential Preamplifier. See page 2.

Table 5: Warranted Characteristics — Signal Acquisition System

Name

Input Resistance, DC Coupled

DC Gain Accuracy

Maximum Input Voltage

Differential Signal Range (DC OFFSET not used)

Common Mode Signal Range

Description

1 M

W

±

2%

±

2%

30 VAC

RMS

, 42 V (DC + peak AC), between signal and common of the same input; derate at 20 dB/decade above 1 MHz.

Gain Setting

0.1

1

10

100

Gain Setting

0.1

1

10

100

Differential Input Signal Range

±

80 V

±

10 V

±

1 V

±

100 mV

Common Mode Input Signal Range

±

40 V

±

40 V

±

10 V

±

10 V

ADA400A Differential Preamplifier

22

Specifications

Table 5: Warranted Characteristics — Signal Acquisition System (Cont.)

Name Description

1

Common Mode Rejection Ratio

(See Figures 14 to 15 on page 27.)

Frequency

100 Hz

10 kHz

100 kHz

100 Hz

10 kHz

100 kHz

The limits given are for the ambient temperature of 22

±

5

_ C

Gain Setting

10

100

CMRR

1

(DC coupled)

85 dB

85 dB

60 dB

90 dB

90 dB

60 dB

Table 6: Warranted Characteristics — Environmental

Name

Atmospherics

Dynamics

Description

Temperature

Operating: 0

_ C to +50_ C

Non-operating: –55

_ C to +75_ C

Relative Humidity (tested to the following limits)

Operating: 90–95% RH, +30

_ C to +50_ C

Non-operating: 90–95% RH, +30

_ C to +60_ C

Random Vibration

Operating: 2.66 g rms overall, 3 axis, 20 min/axis (60 min total)

Non-operating: 3.48 g rms overall, 3 axis, 20 min/axis (60 min total)

Mechanical Shock

Half Sine, 500 g’s

3 axis, 3 drops each axis, 1 ms duration, 18 drops total

ADA400A Differential Preamplifier

23

Specifications

Table 6: Warranted Characteristics — Environmental (Cont.)

Name

Electromagnetic Compatibility (EMC)

Description

Emissions:

Meets or exceeds the requirements of the following standards:

EN 55022 Class B limits for radiated emissions when operated as a system with a TDS460 series oscilloscope (FCC 47 CFR, Part 15,

Subpart B for Class A equipment.)

ADA400A Settings: Gain=100; Offset=off; DC coupled; Filter=1 MHz

TDS 460 Settings: 500 ns/div; 5 mV/div; DC coupled

Immunity:

Radio Frequency Electromagnetic Field less than

±

2 divisions of leakage signal when the instrument is subjected to a 3 V/M electromagnetic field over the frequency range of 27 MHz to

500 MHz.

Electrostatic Discharge (ESD)

Up to 8 kV with no change to control settings of impairment of normal operation, and up to 15 kV with no loss of stored data or damage that prevents recovery of normal operation by the user.

Typical Characteristics

Typical characteristics are described in terms of typical or average performance.

Typical characteristics are not warranted.

Table 7: Typical Characteristics — Signal Acquisition System

Name

Input Capacitance

Analog Bandwidth Selection Accuracy

Linearity

Lower Frequency Limit, AC Coupled

Harmonic Distortion

Recovery Time

Description

55 pF

±

20%

±

12% for 100 Hz, 3 kHz, 100 kHz selections

≥

1 MHz for the FULL (1 MHz) selection

±

0.01% of linear dynamic range

≤

2 Hz (lower –3 dB frequency)

≤

0.002% measured using 3 V

RMS

output at 100 Hz and 1 kHz

≤

1.5 ms to recover to within 0.5% of zero level after over driving the amplifier by

±

150%

ADA400A Differential Preamplifier

24

Specifications

Table 7: Typical Characteristics — Signal Acquisition System (Cont.)

Name

Zero Offset

(Offset control off)

DC Offset Drift with Temperature

Input Current

Random Noise

Bandwidth Selection

1 MHz

100 kHz

3 kHz

100 Hz

Common Mode Rejection Ratio

(See Figures 12 to 15 on pages 26 to 28)

Frequency

100 Hz

10 kHz

100 kHz

100 Hz

10 kHz

100 kHz

100 Hz

10 kHz

100 kHz

100 Hz

10 kHz

100 kHz

Description

Gain Setting

0.1

1

10

100

Gain Setting Offset On Offset Off

0.1

1

0.750 mV/

_ C

0.300 mV/

_ C

0.250 mV/

_ C

0.200 mV/

_ C

10

100

10 mV/_ C

5 mV/_ C

5

3 mV/_ C mV/_ C

Less than 25 pA at an ambient temperature of 22

±

5

_ C

RMS Noise

Zero Offset Referred to the Input of the Amplifier

±

50 mV

±

5 mV

±

500 mV

±

50 mV

Gain of 0.1

≤

5 mV

≤

4 mV

≤

4 mV

≤

4 mV

Gain of 1

≤

3 mV

≤

1 mV

≤

1 mV

≤

1 mV

Gain Setting

0.1

1

10

100

100 dB

100 dB

90 dB

100 dB

100 dB

90 dB

Gain of 10

≤

50 mV

≤

40 mV

≤

40 mV

≤

40 mV

CMRR

(DC coupled)

60 dB

52 dB

50 dB

75 dB

60 dB

52 dB

75 dB

95 dB

90 dB

80 dB

100 dB

90 dB

Gain of 100

≤

30 mV

≤

10 mV

≤

10 mV

≤

10 mV

CMRR

(AC coupled)

45 dB

50 dB

50 dB

50 dB

55 dB

52 dB

ADA400A Differential Preamplifier

25

Specifications

Table 8: Typical Characteristics — Mechanical Characteristics

Name

Weight

Overall Dimensions

Cable Length

Description

Shipping: 1.78 kg (3.92 lbs) including accessories

Net Weight: 1.14 kg (2.51 lbs)

Height: 36 mm (1.42 in)

Width: 112 mm (4.41 in)

Depth: 203 mm (8.00 in)

2 m (78.7 in)

Gain – 0.1

dB

80

70

60

110

100

90

DC Typical

50

40

30

20

10

0

10

AC Typical

100 1 k

Frequency (Hz)

10 k

Figure 12: Typical DC and AC Coupled CMRR in X0.1 Gain

100 k 1 M

ADA400A Differential Preamplifier

26

Gain – 1.0

dB

60

50

40

30

20

110

100

90

80

70

10

0

10

DC Typical

AC Typical

100 1 k

Frequency (Hz)

10 k

Figure 13: Typical AC and DC Coupled CMRR in X1 Gain

Gain – 10.0

dB

60

50

40

30

20

110

100

90

80

70

10

0

10

DC Typical

DC Warranted

AC Typical

100 1 k

Frequency (Hz)

10 k

Figure 14: Typical and Warranted CMRR in X10 Gain

ADA400A Differential Preamplifier

100 k

100 k

1 M

1 M

Specifications

27

Specifications

Gain – 100.0

dB

60

50

40

30

20

110

100

90

80

70

10

0

10

DC Typical

DC Warranted

AC Typical

100 1 k

Frequency (Hz)

10 k

Figure 15: Typical and Warranted CMRR in X100 Gain

100 k 1 M

28

ADA400A Differential Preamplifier

Performance Verification

This section contains procedures for checking that the ADA400A Differential

Preamplifier meets warranted specifications.

Requirements for Performance

The performance limits of this procedure are valid with the following conditions:

H The ADA400A Differential Preamplifier is in an environment that is within the operating limits of temperature, altitude, humidity, and vibration described in Specifications.

H The data line jumper located inside the ADA400A Differential Preamplifier.

is properly configured depending on the type of oscilloscope you connect to the output. See the Installation section on page 2.

H The ADA400A Differential Preamplifier has a period of at least a 20 minutes to warm up prior to verification.

Equipment Required

Table 9 lists the equipment required to verify and adjust the ADA400A

Differential Preamplifier. The Adjustment Procedures section begins on page 37.

Table 9: Test Equipment

Item Number and

Description

1.

Digitizing Oscilloscope

2.

Sine Wave Generator

3.

Digital Multimeter

Minimum Requirements

Bandwidth: > 5 MHz

Sensitivity: 1 mV/div

Auto Measurement: Frequency,

Amplitude

Input Impedance: 1 M

W

Must have TekProbe Level 2

Meet functional check with scale factor coding (see page

2).

Frequency Range: 1 Hz to

5 MHz

Resolution:

≥

3.5 digits

Accuracy:

≤

0.5%

Resistance Range: 200

W to

10 M

W

Example

––

SG5030

DM2510

ADA400A Differential Preamplifier

Purpose

Supply power to and display output of ADA400A

CMRR checks and adjustments

Input resistance check

29

Performance Verification

Table 9: Test Equipment (Cont.)

Item Number and

Description

4.

Calibration Generator

5.

BNC Adapters

Minimum Requirements

Calibrated Amplitude:

Period: 1 ms

Amplitude: 50 mVp-p to

20 V p-p into 1 M

W

Aberrations:

≤

2% p-p

Accuracy:

≤

0.5%

Fastrise:

≤

500 ns

1 Vp-p into 50

W

BNC Female to Dual Banana

6.

Dual Input Connector

7.

50

W

Terminators (2)

8.

10X Attenuators (2)

9.

Coaxial Cables (2)

10. Adjustment Tool, Probe

Example

CG5011

Dual Input Cable BNC

50

W, 2W, BNC

10:1 Attenuator, 50

W

,

BNC

50

W, 36 in. L, BNC male both ends

Plastic Insulated

Tektronix part number

103–0090–00

Tektronix part number

067–0525–02

Tektronix part number

011–0049–01

Tektronix part number

011–0059–02

Tektronix part number

012–1341–00

Tektronix part number

003–0675–01

Procedures

Purpose

Gain check and adjustment.

LF Compensation adjustments

Signal connection

Signal connection

Signal connection

Signal attenuation

Signal connection

Adjustments (Adjustment

Procedure only)

Before beginning the procedures in this section, connect the output of the

ADA400A Differential Preamplifier to the oscilloscope, turn the oscilloscope on, and let the ADA400A warm up for 20 minutes.

NOTE. Before performing these procedures, make sure your oscilloscope can display the proper scale factor. If you are using an oscilloscope that is not compatible with the scale factor coding of the ADA400A Differential Preamplifier to perform these procedures, see page 2 to properly configure the scale factor coding.

To convert the volts/division settings for oscilloscopes that cannot read the scale factor from the ADA400A, multiply the volts/div setting in the procedure by the gain setting of the ADA400A.

ADA400A Differential Preamplifier

30

Performance Verification

Input Resistance

Equipment

Required

One digitizing oscilloscope (item 1) to supply power to the ADA400A

One digital multimeter (item 3)

One BNC female to dual banana connector (item 5)

One coaxial cable (item 9)

1. Set digital multimeter to measure resistance.

2. Connect banana-to-BNC adapter to digital multimeter.

NOTE. To avoid an erroneous resistance measurement, make sure the 1 M

W input

resistance jumpers are installed.

3. Set ADA400A ‘+’ input to DC.

4. Connect coaxial cable from ‘+’ input of ADA400A to the BNC-to-banana adapter on the multimeter.

5. Check input resistance = 1 M

W

±

2% (980 k

W to

1.02

M

W

).

6. Remove coaxial cable from ADA400A ‘+’ input and connect it to the

‘–’ input.

7. Set the ADA400A ‘–’ input to DC.

8. Check input resistance = 1 M

W

±

2% (980 k

W to

1.02

M

W

).

Gain

Equipment

Required

One digitizing oscilloscope (item 1)

One dual input coupler (item 6)

One calibration generator (item 4)

One coaxial cable (item 9)

1. Connect the ADA400A to Ch1 of the oscilloscope and make the equipment settings according to Table 10.

Table 10: Equipment Settings for Gain Checks

ADA400A Control

+ Input

– Input

Gain

Upper Bandwidth

Setting

DC

Gnd

100

100 kHz

ADA400A Differential Preamplifier

31

Performance Verification

Table 10: Equipment Settings for Gain Checks (Cont.)

ADA400A Control

Offset

Oscilloscope Control

Channel Selection

Vertical input impedance

Vertical gain

Time base

Vertical Coupling

Vertical Position

Trigger

Trigger position

Trigger source

Acquisition mode

Auto Measurement

Bandwidth

Calibration Generator Control

Output

Setting

Off

Setting

Ch1

1

M

W

10 mV/div

200 ms/div

DC

0 V (mid-scale)

Edge

50%

Ch4

Hi Res

Amplitude

Full

Setting

50 mV, 1 kHz

2. Connect a dual input connector to inputs of ADA400A.

3. Connect a coaxial cable from calibration generator output to dual input connector.

4. Adjust vertical position knob on the oscilloscope to center square wave on screen.

5. Check DC gain accuracy is

±

2% (49 to 51 mV). (Use amplitude measurement function.)

6. Set ADA400A gain setting to 10.

7. Set calibration generator to 0.5 V amplitude.

8. Adjust vertical position knob on oscilloscope to center square wave on screen.

9. Check DC gain accuracy is

±

2% (490 mV to 510 mV).

10. Set ADA400A gain setting to 1.

11. Set calibration generator to 5 V amplitude.

ADA400A Differential Preamplifier

32

Performance Verification

12. Adjust vertical position knob on oscilloscope to center square wave on screen.

13. Check DC gain accuracy is

±

2% (4.9 V to 5.1 V).

14. Set ADA400A gain setting to 0.1.

15. Set calibration generator to 20 V amplitude.

16. Adjust vertical position knob on oscilloscope to center square wave on screen.

17. Check DC gain accuracy is

±

2% (19.6 V to 20.4 V).

18. Disconnect setup from the inputs of the ADA400A.

CMRR

Equipment

Required

One digitizing oscilloscope (item 1)

One sine wave generator (item 2)

One dual input coupler (item 6)

One 50

W terminator (item 7)

Two 10X attenuators (item 8)

Two coaxial cables (item 9)

1. Connect the ADA400A to Ch1 of the oscilloscope and make the equipment settings according to Table 11.

Table 11: Equipment Settings for X100, 100 kHz CMRR Checks

ADA400A

+ Input

– Input

Gain

Upper Bandwidth

Offset

Oscilloscope

Vertical gain

Time base

Acquisition mode

Number of waveforms to average

Trigger source

Setting

DC

Gnd

100

FULL (1 MHz)

Off

Setting

2 mV/div

5 ms/div

Average

20

Ch4

ADA400A Differential Preamplifier

33

Performance Verification

Table 11: Equipment Settings for X100, 100 kHz CMRR Checks (Cont.)

Sine Wave Generator

Output

Setting

100 kHz, 1 Vp-p into 50

W

2. Connect a coaxial cable from sine wave generator trigger output to Ch4 of the oscilloscope.

3. Connect dual input connector to inputs of ADA400A.

4. Connect 50

W terminator to dual input connector.

5. Connect two 10X attenuators to 50

W terminator.

6. Connect a coaxial cable from sine wave generator output to 10X attenuators.

7. Adjust trigger level for a steady display.

8. Adjust the amplitude of the sine wave generator for 5 divisions on screen.

9. Remove the two 10X attenuators and connect the cable directly to the 50

W terminator.

10. Set ADA400A ‘–’ input to DC.

11. Set oscilloscope to 1 mV/div.

12. Measure signal is

≤

1 division (1 mV, 60 dB).

13. Modify the equipment settings according to Table 12.

Table 12: Equipment Settings for X100, 10 kHz CMRR Checks

ADA400A

Upper Bandwidth

Oscilloscope

Vertical gain

Time base

Sine Wave Generator

Output

Setting

100 kHz

Setting

2 mV/div

50 ms/div

Setting

10 kHz

14. Set ‘–’ input to GND.

15. Do steps 5 to 10.

16. Set oscilloscope to 10 mV/div. Measure trace is t 3.2 divisions wide (32 mV,

90 dB).

ADA400A Differential Preamplifier

34

Performance Verification

17. Modify the equipment settings according to Table 13.

Table 13: Equipment Settings for X100, 100 Hz CMRR Checks

ADA400A

Upper Bandwidth

Oscilloscope

Vertical gain

Time base

Sine Wave Generator

Output

Setting

3 kHz

Setting

2 mV/div

5 ms/div

Setting

100 Hz

18. Set ‘–’ input to GND.

19. Do steps 5 to 10.

20. Set oscilloscope to 10 mV/div. Measure trace is t 3.2 divisions wide (32 mV,

90 dB).

21. Modify the equipment settings according to Table 14.

Table 14: Equipment Settings for X10, 100 kHz CMRR Checks

ADA400A

Gain

Upper Bandwidth

Oscilloscope

Vertical gain

Time base

Sine Wave Generator

Output

Setting

10

1 MHz

Setting

20 mV/div

5 ms/div

Setting

100 kHz

22. Set ‘–’ input to GND.

23. Do steps 5 to 10 but with only one 10X attenuator.

24. Set oscilloscope to 1 mV/div. Measure trace is t 1 division wide (1 mV,

60 dB).

25. Modify the equipment settings according to Table 15.

ADA400A Differential Preamplifier

35

Performance Verification

Table 15: Equipment Settings for X10, 10 kHz CMRR Checks

ADA400A

Upper Bandwidth

Oscilloscope

Vertical gain

Time base

Sine Wave Generator

Output

Setting

100 kHz

Setting

20 mV/div

50 ms/div

Setting

10 kHz

26. Set ‘–’ input to GND.

27. Do steps 5 to 10 but with only one 10X attenuator.

28. Set oscilloscope to 100 mV/div. Measure trace is t 0.56 division wide

(56 mV, 85 dB).

29. Modify the equipment settings according to Table 16.

Table 16: Equipment Settings for X10, 100 Hz CMRR Checks

ADA400A

Upper Bandwidth

Oscilloscope

Vertical gain

Time base

Sine Wave Generator

Output

Setting

3 kHz

Setting

20 mV/div

5 ms/div

Setting

100 Hz

30. Set ‘–’ input to GND.

31. Do steps 5 to 10 but with only one 10X attenuator.

32. Set oscilloscope to 100 mV/div. Measure trace is t 0.56 division wide

(56 mV, 85 dB).

33. Disconnect setup.

This completes the performance verification procedure.

ADA400A Differential Preamplifier

36

WARNING

The following servicing instructions are for use only by qualified personnel. To avoid injury, do not perform any servicing other than that stated in the operating instructions unless you are qualified to do so. Refer to all safety summaries before performing any service.

Adjustment Procedures

Use the procedures in this section to return the ADA400A Differential Preamplifier to conformance with the Warranted Characteristics listed in the Specifica-

tions section on page 21.

Before performing any procedures in this section, please read the sections entitled Requirements for Performance and Equipment Required.

Requirements for Performance

Before performing these procedures, please address the following requirements:

H You must be a trained service technician to perform this procedure.

H You must adjust the ADA400A Differential Preamplifier in an environment in which temperature, altitude, humidity, and vibration are within the operating limits described in Specifications.

H You must calibrate the ADA400A Differential Preamplifier at the center temperature range of 22

±

5

_ C.

H You must warm up the ADA400A Differential Preamplifier for at least 20 minutes prior to adjustment.

Equipment Required

For a complete list of equipment required to perform the procedures in this section, see the Equipment Required section under Performance Verification on page 29.

ADA400A Differential Preamplifier

37

Adjustment Procedures

Procedure

Before you begin these procedures, remove the top housing using the procedure on page 50. Leave the inner shield in place. See Figure 16 for a diagram of the adjustment locations.

NOTE. To avoid contaminating the sensitive areas of the circuit board, do not remove inner shield or touch the circuit board. Access all adjustments through holes of inner shield

Connect the output of theADA400A Differential Preamplifier to the oscilloscope, turn the oscilloscope on, and let the ADA400A warm up for 20 minutes.

NOTE. Before performing these procedures, make sure your oscilloscope can display the proper scale factor. If you are using an oscilloscope that is not compatible with the scale factor coding of the ADA400A Differential Preamplifier to perform these procedures, see page 2 to properly configure the scale factor coding.

To convert the volts/division settings for oscilloscopes that cannot read the scale factor from the ADA400A, multiply the volts/div setting in the procedure by the gain setting of the ADA400A.

ADA400A Differential Preamplifier

38

Adjustment Procedures

CV14

(LF Compensation)

*CV13

R18

(HF CMRR)

*CV17

RV106

(10X Gain)

RV32

(Offset Zero)

CV6

(LF Compensation)

*CV12

*CV18

RV17

(LF CMRR)

CV4 (HF)

RV62

(100X Gain)

RV33

(Offset Balance)

*Factory adjust only

Figure 16: Location of Adjustments Underneath Inner Shield

ADA400A Differential Preamplifier

39

Adjustment Procedures

40

Gain Adjustments

Equipment

Required

One digitizing oscilloscope (item 1)

One dual input coupler (item 6)

One calibration generator (item 4)

One coaxial cable (item 9)

One adjustment tool (item 10)

1. Connect the ADA400A to Channel 1 and make the equipment settings according to Table 17.

Table 17: Equipment Settings for Gain Adjustments

ADA400A

+ Input

– Input

Gain

Upper Bandwidth

Offset

Oscilloscope

Channel Selection

Vertical input impedance

Vertical gain

Time base

Coupling

Vertical Position

Trigger

Trigger position

Trigger source

Acquisition mode

Auto Measurement

Bandwidth

Calibration Generator

Output

Setting

DC

Gnd

100

100 kHz

Off

Setting

Ch1

1

M

W

10 mV/div

200 ms/div

DC

0 V (mid-scale)

Edge

50%

Ch4

Hi Res

Amplitude

Full

Setting

50 mV calibrated, 1 kHz

2. Connect a dual input connector to inputs of ADA400A.

3. Connect a coaxial cable from the output of the calibration generator to the dual input connector.

ADA400A Differential Preamplifier

Adjustment Procedures

Zero Offset Adjustments

4. Adjust vertical position knob on the oscilloscope to center square wave on screen.

5. Adjust RV62 for 5.0 divisions on screen (50 mV).

6. Set ADA400A gain setting to 10.

7. Set calibration generator to 0.5 V amplitude.

8. Adjust the vertical position knob on the oscilloscope to center square wave on screen.

9. Adjust RV106 to 5.0 divisions.

Equipment

Required

One digitizing oscilloscope (item 1)

1. Connect the ADA400A to Channel 1 and make the equipment settings according to Table 18.

Table 18: Equipment Settings for Offset Adjustments

ADA400A

+ Input

– Input

Gain

Upper Bandwidth

Offset

Oscilloscope Control

Channel Selection

Vertical input impedance

Vertical gain

Time base

Vertical Coupling

Vertical Position

Trigger mode

Acquisition mode

Bandwidth

Setting

Gnd

Gnd

10

100 Hz

Off (remains off through out the test)

Setting

Ch1

1

M

W

500 mV/div

5 ms/div

DC

0 V (mid-scale)

Auto

Hi Res

Full

2. Check to make sure oscilloscope is at position 0 and vertical offset 0.

ADA400A Differential Preamplifier

41

Adjustment Procedures

42

3. Switch the gain setting between 10 and 100 while adjusting RV33 for minimum shift in the oscilloscope trace.

a. Make note of trace position at gain setting of 10.

b. Switch gain setting to 100.

c.

Adjust trace to where it was at the gain setting of 10.

d. Repeat steps a to c until there is a minimum amount of shift.

4. Adjust RV32 to center trace on screen.

5. Switch the gain setting from 0.1, 1, 10 and 100 and verify that trace does not shift more than one division from center.

6. Disconnect setup.

LF CMRR Adjustments

Equipment

Required

One digitizing oscilloscope (item 1)

One sine wave generator (item 2)

One dual input coupler (item 6)

One 50

W terminator (item 7)

Two coaxial cables (item 9)

One adjustment tool (item 10)

1. Connect the ADA400A to Channel 1 and make the equipment settings according to Table 19.

Table 19: Equipment Settings for Attenuator Balance Adjustments

ADA400A

+ Input

– Input

Gain

Upper Bandwidth

Oscilloscope

Vertical gain

Time base

Trigger Source

Sine Wave Generator

Output

Setting

DC

Gnd

1

100 Hz

Setting

1 V/div

20 ms/div

Ch4

Setting

10 Hz

ADA400A Differential Preamplifier

Adjustment Procedures

2. Connect dual input connector to inputs of ADA400A.

3. Connect 50

W terminator to dual input connector.

4. Connect a coaxial cable from sine wave generator output to 50

W terminator.

5. Connect another coaxial cable from trigger output of sine wave generator to

Ch4 of oscilloscope.

6. Adjust sine wave generator attenuator variable knob for 5 divisions (5 V) on screen.

7. Set ADA400A ‘–’ input to DC.

8. Set oscilloscope volts/div to 1 mV.

9. Adjust RV17 for minimum signal amplitude.

10. Disconnect setup.

CMRR Adjustments

Equipment

Required

One digitizing oscilloscope (item 1)

One sine wave generator (item 2)

One dual input coupler (item 6)

One 50

W terminator (item 7)

Two 10X attenuators (item 8)

Two coaxial cables (item 9)

One adjustment tool (item 10)

1. Connect the ADA400A to Channel 1 and make the equipment settings according to Table 20.

Table 20: Equipment Settings for CMRR Adjustments

ADA400A

+ Input

– Input

Gain

Upper Bandwidth

Oscilloscope

Vertical gain, Ch 1

Time base

Acquisition mode

Setting

DC

Gnd

100

FULL (1 MHz)

Setting

2 mV/div

5.0 ms/div

Average

ADA400A Differential Preamplifier

43

Adjustment Procedures

Table 20: Equipment Settings for CMRR Adjustments (Cont.)

Oscilloscope

Number of waveforms to average

Trigger source

Sine Wave Generator

Output

Setting

20

Ch4

Setting

100 kHz, 1 Vp-p into 50

W

2. Connect a coaxial cable from trigger output of sine wave generator to Ch4 of oscilloscope.

3. Connect dual input connector to inputs of ADA400A.

4. Connect 50

W terminator to dual input connector.

5. Connect two 10X attenuators to 50

W terminator.

6. Connect a coaxial cable from sine wave generator output to 10X attenuators.

7. Adjust trigger level for a steady display.

8. Adjust amplitude for 5 divisions (10 mV) on screen.

9. Remove the two 10X attenuators and connect the cable directly to the 50

W terminator.

10. Set ADA400A ‘–’ input to DC.

11. Set oscilloscope to 2 mV/div.

12. Adjust CV4 and R18 for minimum signal amplitude (

≤

1 mV).

13. Disconnect setup.

LF Compensation

Adjustments

Equipment

Required

One digitizing oscilloscope (item 1)

One calibration generator (item 4)

One dual input coupler (item 6)

One 50

W terminator (item 7)

Two coaxial cables (item 9)

One adjustment tool (item 10)

1. Connect the ADA400A to Channel 1 and make the equipment settings according to Table 21.

ADA400A Differential Preamplifier

44

Adjustment Procedures

Table 21: Equipment Settings for LF Adjustments

ADA400A

+ Input

– Input

Gain

Upper Bandwidth

Oscilloscope

Vertical gain, Ch1

Time base

Calibration Generator

Output Mode

Setting

DC

Gnd

1

Full (1 MHz)

Setting

200 mV/div

20 ms/div

Setting

Fast Rise, 10 kHz

2. Connect dual input connector to ADA400A input.

3. Connect 50

W terminator to dual input connector.

4. Connect a coaxial cable to calibration generator fast rise output to 50

W terminator.

5. Connect a coaxial cable from trigger out of calibration generator to Ch4 of oscilloscope.

6. Adjust amplitude for 5 divisions on screen.

7. Adjust CV6 for flat response.

8. Make the second equipment settings according to Table 22.

Table 22: Second Equipment Settings for LF Adjustments

ADA400A

+ Input

– Input

Oscilloscope

Vertical gain

Time base

Setting

DC

DC

Setting

5 mV/div

20 ms/div

9. Adjust CV14 for minimum trace.

10. Disconnect setup.

This completes the ADA400A adjustment procedures.

ADA400A Differential Preamplifier

45

Adjustment Procedures

46

ADA400A Differential Preamplifier

Maintenance

This section details the maintenance and replacement procedures for the

ADA400A Differential Preamplifier.

Warranty Service

Tektronix warrants this product for three years from date of purchase. (A complete warranty statement appears at the front of this manual.) Tektronix provides warranty service at most Tektronix service locations worldwide. The

Tektronix product catalog lists all service locations worldwide.

Should the ADA400A Differential Preamplifier require replacement under terms of the warranty, return the preamplifier to a Tektronix service center. Include the following information: name of purchaser, return address, name and phone number of a person that Tektronix may contact, date of purchase, and a description of the defect.

In the U.S., call 1-800-TEK WIDE (1-800-835-9433) for further assistance.

Preparation

This manual provides information for limited servicing of the ADA400A

Differential Preamplifier

NOTE. Only qualified service personnel should attempt any internal repair or maintenance of the ADA400A Differential Preamplifier.

Before Servicing

Before servicing the ADA400A Differential Preamplifier, please read the

General Safety Summary starting on page iii.

Preventing ESD

The ADA400A Differential Preamplifier contains internal components that are susceptible to damage from electrostatic discharge (ESD).

ADA400A Differential Preamplifier

47

Maintenance

CAUTION. To prevent damaging internal components by means of electrostatic discharge (ESD), perform all service at a static-free work station and wear a grounded anti-static wrist strap.

Do not slide the internal module over any surface. Place internal module in static-free bag for transportation away from work station.

Cleaning

To prevent damage to the ADA400A Differential Preamplifier, avoid using chemicals that contain benzine, benzene, toluene, xylene, acetone, or similar solvents.

Do not immerse the ADA400A Differential Preamplifier or use abrasive cleaners.

Dirt on external surfaces may be removed with a soft cloth dampened with a mild detergent and water solution, or isopropyl alcohol.

NOTE. Certain areas of the circuit board are sensitive to surface contamination.

Avoid touching the surfaces of the circuit board. Handle the circuit board by the edges. If the circuit board is contaminated, wash the board with Isopropyl

Alcohol and rinse with warm deionized water.

Replacement Procedures

Refer to the procedures in this section before replacing any part on the

ADA400A Differential Preamplifier. For a list of all customer replaceable parts, see the Replaceable Parts section that begins on page 55 and the exploded view on page 59.

48

Replacing TEKPROBE

Interface Pins

Periodically check to see that each of the interface pins move freely and fully extends out of the interface. If any pin fails to move freely and fully extend, it should be replaced.

To remove a TEKPROBE interface pin, firmly grasp the pointed tip with pliers and pull the pin out of the connector. See Figure 17.

No tools are required to install a replacement pin. Insert a new pin into the connector socket as far as possible using finger pressure. If necessary, seat the pin into the connector by pressing the tip gently but firmly against a hard surface, such as a wood block or table top.

ADA400A Differential Preamplifier

Maintenance

Figure 17: Replacing TEKPROBE Interface Pins

Replacing the TEKPROBE

Interface Collar

To remove the TEKPROBE interface collar, firmly grasp the body of the output head with one hand, and the TEKPROBE interface collar with the other hand.

Firmly pull the interface collar off.

To replace the collar, first note the pin configuration in the interface collar. The group of three pins fit through the smaller of the two holes in the interface collar.

Align the tab to the slot and gently press the two pieces together. See Figure 18.

Once installed, the TEKPROBE collar should rotate freely to lock and unlock.

Tab

Slot

Figure 18: Replacing the TEKPROBE collar

ADA400A Differential Preamplifier

49

Maintenance

Replacing the Input Fuses

To remove and replace an input fuse, insert a flat-blade screwdriver into the slot on the fuse cap, press in and turn counter clockwise to remove the fuse.

CAUTION. To properly protect the inputs of the ADA400A Differential Preamplifi-

er, replace fuses with the type specified in the Replaceable Parts section.

Insert the replacement fuse into the cap on the fuse holder, insert, and use the flat-blade screwdriver to press in and lock the fuse cap counterclockwise.

50

+ Input Fuse

Figure 19: Input Connectors and Fuses

– Input Fuse

Accessing Internal

Components

To access internal components of the ADA400A Differential Preamplifier, refer to the exploded view, Figure 22, on page 59 and perform the following procedure:

1. Using a 1/16-inch Allen wrench, loosen the set screws on the COARSE and

FINE controls and remove the knobs.

2. Remove the four screws that hold the top housing, separate the top housing from the bottom housing and set the top housing to one side.

STOP. If you intend to electrically adjust the ADA400A or move a jumper, do not proceed further. The adjustments and jumpers are accessible through holes in the circuit board shield. Proceed further only if you intend to replace parts under the shield.

3. Following the static precautions presented at the beginning of this section, remove the screws on the top of the shield and carefully lay the shield over to the side without straining the wires of the potentiometers.

Replacing the

Potentiometers

After performing the procedure to access the internal components of the

ADA400A Differential Preamplifier, replace one of the potentiometers as follows:

ADA400A Differential Preamplifier

Maintenance

1. Unsolder the wires from the potentiometer.

2. Remove the nut on the shaft of the potentiometer and replace the potentiometer with the new part. Replace and tighten the nut and washer on the shaft.

3. Resolder the wires as Figure 20 illustrates.

(Fine)

311–2533–00

(Coarse)

311–2158–02

Brown

Orange

Red

Orange

Red

Brown

Figure 20: Potentiometer Connections

Replacing the Cable

Assembly

After performing the procedure to access the internal components of the

ADA400A Differential Preamplifier, replace the cable assembly as follows:

1. Remove the remaining two screws that hold the circuit board to the bottom housing.

NOTE. To prevent contaminating sensitive areas of the circuit board, handle the circuit board by the edges only.

2. Unsolder the four colored wires from the top of the circuit board and the three ground prongs from the bottom of the circuit board.

3. Note the color-code information on the circuit board. Replace the cable assembly and solder the new wires.

4. Place the circuit board and cable strain relief in the bottom housing and reinstall hardware.

ADA400A Differential Preamplifier

51

Maintenance

Replacement Parts

Refer to the Replaceable Parts section beginning on page 55 for a list of customer replacement parts.

Theory of Operation

Input

+

Figure 21 illustrates the functional blocks of circuitry from left to right in the order of input to output. The darker boxes in the illustration designate front panel controls and lines with arrows indicate the functional blocks that the controls affect.

ADA400A Differential Preamplifier

TEKPROBE

Interface

Oscilloscope

AC-GND-DC

Input Coupling/

Input Protection

DC

Offset

1 M /

1 W

Select

High-Z

Attenuator

(1/1, 1/100)

High-Impedance

Amplifier

+

+

–

Gain = X10

On/Off,

Coarse, Fine

Low-Z

Attenuator

(1/1, 1/10)

Low-Pass

Filter

Overrange

Detect

Output

Amplifier

50

W

Gain = X10

Signal Out

Upper Bandwidth Select

100 Hz, 3 kHz, 100 kHz 1 MHz

–

Input Coupling/

Input Protection

Output

Cable

AC-GND-DC Gain .1, 1, 10, 100

Scale Factor

Coding

+15V

–15V

+5V

Data

Ground

Figure 21: Diagram of the ADA400A Differential Preamplifier

ADA400A Differential Preamplifier

52

Maintenance

Input Protection and

Coupling

Any signals on the inputs of the ADA400A Differential Preamplifier must pass through the input protection and coupling circuits.

Input Protection. The input protection circuit shunts excessively high-voltage signals to ground and blows the protective fuse if the current exceeds 1/16 ampere for any length of time.

Input Coupling. The coupling switch for a particular input selects one of the following connections to the input of the preamplifier: AC, GND (ground), or

DC. For more information on these switch positions, see page 15.

Input Impedance

Internal jumpers connect an input impedance of 1 M

W in parallel with 55 pF.

With the jumpers disconnected the input impedance is virtually infinite (10

12

W).

For more information about these jumpers, see page 12.

Attenuation and

Amplification

The gain switch sets the gain of the preamplifier by selecting the amount of attenuation at two different points in the circuitry: 1/1 or 1/100 attenuation in the high-impedance attenuator and 1/1 or 1/10 attenuation in the low-impedance attenuator. The lowest gain setting, for example, selects the highest total amount of attenuation.

DC Offset

The offset controls adjust the DC component of the input signal. To keep the signal from distorting, the signal must be within the dynamic range of the amplifier. For more information on the dynamic range characteristic, refer to the notes on page 16.

Low-Pass Filter

The Upper Bandwidth Control selects different RC networks in the low-pass filter. The bandwidth settings are 100 Hz, 3 kHz, 100 kHz, and 1 MHz.

Overrange Detect

Should the input signal exceed the dynamic range of the output amplifier, the overrange detection circuit activates the indicator on the front panel.

Scale-Factor Coding

The gain switch also selects a resistance that appears on the data pin. If the host oscilloscope is properly equipped (see Installation on page 2), this resistance determines the vertical scale factor on the oscilloscope display.

TEKPROBE



Interface

The TEKPROBE interface provides power, signal, and data connections between the ADA400A Differential Preamplifier and the oscilloscope.

ADA400A Differential Preamplifier

53

Maintenance

Troubleshooting

Table 23 lists symptoms of electrical faults, possible causes, and corrective actions.

Table 23: Electrical Faults

Symptom

No power

No output signal on connector end of cable assembly or output too high or low

Intermittent or difficult positioning

No signal output to cable assembly — interface power is present and fuses are not blown

Possible Cause

Damage to TEKPROBE interface connections. Check interface pins and cable assembly wires for damage.

Blown input fuse

Damage to output cable

Defective position controls

Faulty module

Corrective Action(s)

Replace interface pin(s)

Replace or repair cable assembly

Check and replace fuse(s)

Repair or replace cable assembly

Replace position control(s)

Send unit to service center for exchange or replacement.

Repackaging Instructions

If the original packaging is unfit for use or not available, use the following packaging guidelines:

1. Use a corrugated cardboard shipping carton having inside dimensions at least one inch greater than the probe dimensions. The box should have a carton test strength of at least 200 pounds.

2. Put the probe into a plastic bag or wrap to protect it from dampness.

3. Place the probe into the box and stabilize it with light packing material.

4. Seal the carton with shipping tape.

ADA400A Differential Preamplifier

54

Replaceable Parts

This section contains a list of the replaceable modules for the ADA400A

Differential Preamplifier. Use this list to identify and order replacement parts.

Parts Ordering Information

Replacement parts are available through your local Tektronix field office or representative.

Changes to Tektronix instruments are sometimes made to accommodate improved components as they become available and to give you the benefit of the latest circuit improvements. Therefore, when ordering parts, it is important to include the following information in your order.

H Part number

H Instrument type or model number

H Instrument serial number

H Instrument modification number, if applicable

If you order a part that has been replaced with a different or improved part, your local Tektronix field office or representative will contact you concerning any change in part number.

Change information, if any, is located at the rear of this manual.

Module Servicing

Modules can be serviced by selecting one of the following options. Contact your local Tektronix service center or representative for repair assistance.

Module Exchange. In some cases you may exchange your module for a remanufactured module. These modules cost significantly less than new modules and meet the same factory specifications. For more information about the module exchange program, call 1-800-TEK-WIDE, extension 6630.

New Modules. You may purchase replacement modules in the same way as other replacement parts.

ADA400A Differential Preamplifier

55

Replaceable Parts

Using the Replaceable Parts List

This section contains a list of the mechanical and/or electrical components that are replaceable for the ADA400A Differential Preamplifier. Use this list to identify and order replacement parts. The following table describes each column in the parts list.

Parts List Column Descriptions

7

8

Column Column Name

1 Figure & Index Number

Description

Items in this section are referenced by figure and index numbers to the exploded view illustrations that follow.

2

3 and 4 Serial Number

5

Tektronix Part Number Use this part number when ordering replacement parts from Tektronix.

Qty

Column three indicates the serial number at which the part was first effective. Column four indicates the serial number at which the part was discontinued. No entries indicates the part is good for all serial numbers.

This indicates the quantity of parts used.

6 Name & Description

Mfr. Code

Mfr. Part Number

An item name is separated from the description by a colon (:). Because of space limitations, an item name may sometimes appear as incomplete. Use the U.S. Federal Catalog handbook

H6-1 for further item name identification.

This indicates the code of the actual manufacturer of the part.

This indicates the actual manufacturer’s or vendor’s part number.

Abbreviations

Abbreviations conform to American National Standard ANSI Y1.1–1972.

Mfr. Code to Manufacturer

Cross Index

The table titled Manufacturers Cross Index shows codes, names, and addresses of manufacturers or vendors of components listed in the parts list.

ADA400A Differential Preamplifier

56

Replaceable Parts

Manufacturers Cross Index

Mfr.

Code Manufacturer

0JR05

0KB01

18359

22526

32997

61935

71400

73743

78189

80009

TRIQUEST CORP

STAUFFER SUPPLY

PYLON CO INC

BERG ELECTRONICS INC (DUPONT)

BOURNS INC

TRIMPOT DIV

SCHURTER INC

BUSSMANN

DIV OF COOPER INDUSTRIES INC

FISCHER SPECIAL MFG CO

ILLINOIS TOOL WORKS INC

SHAKEPROOF DIV

TEKTRONIX INC

93907 TEXTRON INC

CAMCAR DIV

Address

3000 LEWIS AND CLARK HWY

810 SE SHERMAN

51 NEWCOMB ST

857 OLD TRAIL RD

1200 COLUMBIA AVE

1016 CLEGG COURT

114 OLD STATE RD

PO BOX 14460

111 INDUSTRIAL RD

ST CHARLES ROAD

14150 SW KARL BRAUN DR

PO BOX 500

600 18TH AVE

City, State, Zip Code

VANCOUVER WA 98661–2999

PORTLAND OR 97214

ATTLEBORO MA 02703–1403

ETTERS PA 17319

RIVERSIDE CA 92507–2114

PETALUMA CA 94952–1152

ST LOUIS MO 63178

COLD SPRING KY 41076–9749

ELGIN IL 60120

BEAVERTON OR 97077–0001

ROCKFORD IL 61108–5181

ADA400A Differential Preamplifier

57

Replaceable Parts

Replaceable Parts List

Fig. &

Index

Number

Tektronix Part

Number

22–1

–2

–3

380–1098–00

334–8900–00

366–1861–03

–4

–5

–6

–7

–8

–9

–10

–11

–12

–13

–14

–15

–16

–17

–18

–19

–20

–21

–22

–23

–24

211–0541–00

220–0495–00

210–0012–00

337–4037–00

311–2158–02

––––––––––

159–0024–00

200–2264–00

131–0993–00

220–0497–00

210–0986–00

211–0711–00

210–1039–00

348–0187–00

211–0408–00

131–3627–01

205–0191–00

174–3462–01

311–2533–00

210–0004–00

211–0394–00

Serial No.

Effective

Serial No.

Discont’d Qty Name & Description

1

1

1

2

2

2

2

3

2

4

1

2

2

4

5

5

1

1

1

1

2

4

7

1

HOUSING:TOP & BOTTOM,STEEL–ZINC PLATE

MARKER,IDENT:INSTRUMENT LABEL

KNOB:GREY,0.252 ID X 0.706 OD X0.612 H,

W/SET SCREWS

SCREW,MACHINE:6–32 X 0.25,FLH,100 DEG,STL,CD PL,

POZ

NUT,PLAIN,HEX:0.375–32 X 0.438 HEX,BRS,CD PL

WASHER,LOCK:0.384 ID,INTL,0.022 THK,STL

SHIELD:0.040 STEEL,ZINC PLATE,7.5X 5.0

RES,VAR,WW:PNL,5K OHM,5%,1W

CIRCUIT BD ASSY:MAIN

(EXCHANGE ONLY)

FUSE,CARTRIDGE:3AG,0.062A,250V,0.3 SEC

CAP,FUSEHOLDER:3AG FUSES

CONN,BOX:SHUNT,;FEMALE,STR,1 X 2,0.1 CTR,

0.385 H,30 GOLD,BLACK,JUMPER

(SUBPART OF 22–9)

NUT,PLAIN,HEX:0.5–28 X 0.562 HEX,BRS CD PL

WASHER,FLAT:0.5 ID X 0.672 OD X 0.035,STL CD PL

SCR,ASSEM WSHR:6–32 X 0.250,PNH,STL,CDPL,

T–15 TORX DR,MACHINE

WASHER,LOCK:0.521 ID,INT,0.025 THK,SST

FOOT,CABINET:BLACK POLYURETHANE

SCR,ASSEM WSHR:4–40 X 0.250,PNH,STL,CDPL,

T–10 TORX DR

CONTACT,ELEC:GOLD PLATED TIP

(SUBPART OF 22–21)

SHELL,ELEC CONN:BNC,ABS,DOVE GRAY

(SUBPART OF 22–21)

CABLE ASSY:CABLE W/COMP BOX

RES,VAR,PANEL:CERMET;50K OHM,10%,1.0W,LINEAR

TAPER,12.5 MM SQ,0.375DIA X 0.375 L BUSHING,

SOLDER LUGS

WASHER,LOCK:#4 INTL,0.015 THK,STL

SCREW,MACHINE:4–40 X 0.875,PNH,STL CD PL TORX,

T10

STANDARD ACCESSORIES

159–0024–00

070–9164–xx

P6101B

2

1

1

FUSE,CARTRIDGE:3AG,0.062A,250V,0.3SEC

MANUAL,TECH:INSTRUCTION,ADA400A,DP

OPTIONAL ACCESSORIES

PROBE,PASSIVE:15MHZ 1X 2.0M

Mfr.

Code Mfr. Part Number

80009 380109800

80009 334890000

80009 366186103

80009 211054100

73743 ORDER BY DESC

78189 1220–02–00–0541

80009 337403700

32997 84A1C–B24–J13

71400 AGC 1/16

61935 FEK 031 1666

22526 65474–006

73743 ORDER BY DESC

80009 210098600

0KB01 ORDER BY DESC

0KB01 1224–02–00–541

80009 348018700

0KB01 211–0408–00

18359 P–6158–1

80009 205019100

80009 174346201

32997 53AAA–B24–A18R7

78189 1204–00–00–0541

93907 B20–69595–003

71400

80009

AGC 1/16

0709164xx

80009 P6101B

ADA400A Differential Preamplifier

58

Replaceable Parts

21

19

20

1

2

3

24

23

5

6

7

5

6

22

8

9

10

11

12

4

18

15

14

13

17

1

16

Figure 22: ADA400A Differential Preamplifier — Exploded View

ADA400A Differential Preamplifier

59

Replaceable Parts

60

ADA400A Differential Preamplifier

Glossary

Alternating Current (AC)

An electric current whose instantaneous value and direction change periodically.

Amplitude

The difference between a high and a low point on a waveform. Signal amplitude can be measured in terms of “peak-to-peak” or “peak” for example.

Attenuation

The degree the amplitude of a signal is reduced when it passes through an attenuating device such as a probe or attenuator. That is, the ratio of the input measure to the output measure. For example, a 10X attenuator will attenuate, or reduce, the input voltage of a signal by a factor of 10.

Bandwidth

Bandwidth is the specified frequency range of the vertical system wherein the vertical response is greater than or equal to 0.707 (–3dB) of the specified frequency down to DC or 0 Hz.

Common mode

Signals on both preamplifier inputs that are identical in voltage and phase.

Common-Mode Rejection Ratio (CMRR)

The extent to which a differential amplifier rejects a common-mode voltage presented on the inputs. CMRR is the ratio of the differential gain to the common-mode gain and is usually expressed in decibels (dB).

Coupling

The method of connecting the input circuit to the signal source. A coupling circuit, for example, may pass only AC signals above a certain frequency.

Differential

Signals that are not identical in amplitude or phase and thereby present a difference on the inputs of the preamplifier.

Direct Current

An electric current that flows in only one direction with essentially constant value.

Frequency

A timing measurement that is the reciprocal of the period. Frequency is measured in Hertz (Hz) where 1 Hz = 1 cycle per second.

Floating

A signal or voltage that does not have a reference to ground.

ADA400A Differential Preamplifier

61

Glossary

62

Gain

Increase in signal strength.

Ground

A connection or reference to the zero voltage potential of earth ground.

Ground loop

Two or more paths between grounded points in a circuit in which a current circulates. This current may induce a voltage potential which corrupts sensitive measurements.

Hertz

The unit of frequency, one cycle per second.

Megahertz (MHz)

A frequency of one million Hz (cycles per second), or 10

6

Hz.

Noise

An unwanted voltage or current in an electrical signal.

Normal mode

The signal of interest without the common-mode element.

Peak

The difference in amplitude between the maximum value and the average or mean value of a waveform.

Peak-to-Peak

Amplitude measurement of the absolute difference between the maximum and minimum amplitude.

Period

A timing measurement of the time covered by one complete signal cycle. It is the reciprocal of frequency and is measured in seconds.

Phase

A timing measurement between two waveforms of the amount one leads or lags the other. Phase is expressed in degrees where 360

_ comprises one complete cycle of one of the waveforms.

RMS

Amplitude (voltage) measurement of the true Root-Mean-Square voltage.

Single ended

A connection to one input of the preamplifier only. The coupling of the other side must be set to ground (GND).

Waveform

The shape or form (visible representation) of a signal expressed as amplitude versus time (Y-T).

ADA400A Differential Preamplifier

Index

A

accessories recommended, 2 standard, 1 adjustment procedures, 37

CMRR, 43 equipment required, 29 gain, 40

LF CMRR, 42

LF compensation, 44 zero offset, 41

B

bandwidth limit, 18, 53 block diagram, 52

C

cable housing, procedure for replacing, 51 checks, functional, 4 cleaning, 48 clipping, 16 common-mode rejection, 14 connections differential, 14 input, 11–15 single-ended, 13 connectors, illustrated, 8 controls offset, 18, 53 overview, 7–10 cover, procedure for removing, 50

D

diagnostic procedures, 54

E

effective volts/division, 10 electrostatic discharge, preventing, 47

ADA400A Differential Preamplifier

F

fuses, 50 location of, 8

G

gain, 16, 53 ground loops, 15

H

housing, procedure for removing, 50

I

input common-mode range, 16 differential range, 16 input coupling, 15, 53 oscilloscope, 4, 15 precharging, 16 input impedance oscilloscope, 4, 15 preamplifier, 12, 53 input protection, 53 input range, 16 installation, 2 interference, 19

J

jumper input impedance, 12 scale-factor coding, 2

M

maintenance, 47–54

O

offset range, 16 overrange detection circuit, 53 overrange indicator, 9, 16

63

Index

P

parts list of replaceable, 55–60 replacement of. See Maintenance performance verification, 29

CMRR, 33 equipment required, 29 gain, 31 input resistance, 31 potentiometers, procedure for replacing, 50 procedures, performance verification, 29

R

repackaging, 54 replacement procedures, 48

S

safety, general summary, iii scale-factor coding, 53 shield, procedure for removing, 50 signal distortion, 16

T

TEKPROBE interface, 53 installation, 2 replacing interface collar, 49 replacing pins, 48 troubleshooting, 54

W

warranty service, 47

64

ADA400A Differential Preamplifier