Data Translation DT9838 User Manual

UM-24789-G

DT9838
User’s Manual

Title Page

Copyright Page

Seventh Edition
December, 2015

Data Translation, Inc.
100 Locke Drive
Marlboro, MA 01752-1192
[phone]
www.datatranslation.com
Fax: [phone]
E-mail: [e-mail]

Copyright © 2015 by Data Translation, Inc.

All rights reserved.

Information furnished by Data Translation, Inc. is believed to be
accurate and reliable; however, no responsibility is assumed by
Data Translation, Inc. for its use; nor for any infringements of
patents or other rights of third parties which may result from its
use. No license is granted by implication or otherwise under any
patent rights of Data Translation, Inc.

Use, duplication, or disclosure by the United States Government
is subject to restrictions as set forth in subparagraph (c)(1)(ii) of
the Rights in Technical Data and Computer software clause at 48
C.F.R, 252.227-7013, or in subparagraph (c)(2) of the Commercial
Computer Software - Registered Rights clause at 48 C.F.R.,
52-227-19 as applicable. Data Translation, Inc., 100 Locke Drive,
Marlboro, MA 01752.

Data Translation® is a registered trademark of Data Translation,
Inc. QuickDAQ™, DT-Open Layers
Class Library

TM

, DataAcq SDKTM, and LV-LinkTM are trademarks

TM

, DT-Open Layers for .NET

of Data Translation, Inc.

All other brand and product names are trademarks or registered
trademarks of their respective companies.

Radio and Television Interference

This equipment has been tested and found to comply with CISPR EN55022 Class A and
EN61000-6-1 requirements and also with the limits for a Class A digital device, pursuant to
Part 15 of the FCC Rules. These limits are designed to provide reasonable protection against
harmful interference when the equipment is operated in a commercial environment. This
equipment generates, uses, and can radiate radio frequency energy and, if not installed and
used in accordance with the instruction manual, may cause harmful interference to radio
communications. Operation of this equipment in a residential area is likely to cause harmful
interference, in which case the user will be required to correct the interference at his own
expense.

Changes or modifications to this equipment not expressly approved by Data Translation could
void your authority to operate the equipment under Part 15 of the FCC Rules.

Note: This product was verified to meet FCC requirements under test conditions that
included use of shielded cables and connectors between system components. It is important
that you use shielded cables and connectors to reduce the possibility of causing interference
to radio, television, and other electronic devices.

FCC Page

Canadian Department of Communications Statement

This digital apparatus does not exceed the Class A limits for radio noise emissions from
digital apparatus set out in the Radio Interference Regulations of the Canadian Department of
Communications.

Le présent appareil numérique n’émet pas de bruits radioélectriques dépassant les limites
applicables aux appareils numériques de la class A prescrites dans le Règlement sur le
brouillage radioélectrique édicté par le Ministère des Communications du Canada.

Table of Contents

Table of Contents

About this Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Intended Audience. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

How this Manual is Organized . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Conventions Used in this Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Related Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Where To Get Help. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Chapter 1: Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

DT9838 Hardware Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Supported Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Supported Accessories. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Getting Started Procedure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Chapter 2: Setting Up and Installing the Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Unpacking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

System Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

(Optional) Applying Power to the Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Attaching Modules to the Computer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Connecting Directly to the USB Ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Connecting to an Expansion Hub . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Configuring the DT9838 Device Driver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Chapter 3: Wiring Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Preparing to Wire Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

General Wiring Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Analog Input Connector Pin Assignments (RJ50 Connector) . . . . . . . . . . . . . . . . . . . . 41

Connecting a General-Purpose or Bridge-Completion Accessory . . . . . . . . . . . . . . . . . . . . 42

Connecting Quarter-Bridge Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Wiring a Quarter-Bridge (Axial and Bending) Circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Remote Sensing In Quarter-Bridge Configurations . . . . . . . . . . . . . . . . . . . . . . . . . 47

Shunt Calibration in Quarter-Bridge Configurations . . . . . . . . . . . . . . . . . . . . . . . 48

Wiring a Quarter-Bridge Temp Comp Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Remote Sensing In Quarter-Bridge Temp Comp Configurations . . . . . . . . . . . . . 50

Shunt Calibration in Quarter-Bridge Temp Comp Configurations . . . . . . . . . . . . 51

Connecting Half-Bridge Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

Wiring a Half-Bridge Poisson Circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

Remote Sensing In Half-Bridge Poisson Configurations . . . . . . . . . . . . . . . . . . . . 54

Shunt Calibration in Half-Bridge Poisson Configurations . . . . . . . . . . . . . . . . . . . 55

5

Contents

Wiring a Half-Bridge Bending Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

Remote Sensing In Half-Bridge Bending Configurations . . . . . . . . . . . . . . . . . . . . 57

Shunt Calibration in Half-Bridge Bending Configurations . . . . . . . . . . . . . . . . . . 58

Connecting Full-Bridge Circuits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

Wiring a Full-Bridge Bending Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

Remote Sensing in Full-Bridge Bending Configurations . . . . . . . . . . . . . . . . . . . . 61

Shunt Calibration in Full-Bridge Bending Configurations . . . . . . . . . . . . . . . . . . . 61

Wiring a Full-Bridge Bending Poisson Configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . 62

Remote Sensing in Full-Bridge Bending Poisson Configurations . . . . . . . . . . . . . 63

Shunt Calibration in Full-Bridge Bending Poisson Configurations . . . . . . . . . . . 64

Wiring a Full-Bridge Axial Poisson Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

Remote Sensing in Full-Bridge Axial Poisson Configurations . . . . . . . . . . . . . . . . 66

Shunt Calibration in Full-Bridge Axial Poisson Configurations . . . . . . . . . . . . . . 67

Connecting Load Cells and Other Transducers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

Connecting Voltage Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

Connecting a Tachometer Input Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

Connecting an External Trigger Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

Chapter 4: Verifying the Operation of a Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

Select the Device. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

Measure Strain Gage Data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

Configure the Channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

Configure the Recording Settings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

Configure the Acquisition Settings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

Start the Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

Chapter 5: Principles of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

Analog Input Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

Analog Input Channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

Specifying a Single Analog Input Channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

Specifying One or More Analog Input Channels . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

Bridge Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94

Quarter-Bridge Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

Quarter-Bridge Temp Comp Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

Half-Bridge Poisson Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

Half-Bridge Bending Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

Full-Bridge Bending Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

Full-Bridge Bending Poisson Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

Full-Bridge Axial Poisson Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

Transducer Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

Bridge Excitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

Remote Sensing and Lead Wire Correction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

6

Shunt Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

Shunt Calibration Equation for the Quarter-Bridge and Quarter-Bridge Temp

Comp Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

Shunt Calibration Equation for the Half-Bridge Poisson Configuration . . . . . . 104

Shunt Calibration Equation for the Half-Bridge Bending Configuration . . . . . . 104

Shunt Calibration Equation for the Full-Bridge Bending Configuration . . . . . . 105

Shunt Calibration Equation for the Full-Bridge Bending Poisson

Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

Shunt Calibration Equation for the Full-Bridge Axial Poisson Configuration . 105

Offset Nulling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

TEDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

Input Resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

Input Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

A/D Sample Clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

Analog Input Conversion Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

Single-Value Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

Continuous Scan Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

Input Triggers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

Start Trigger Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

Reference Trigger Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

Error Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

Tachometer Input Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

Synchronizing Acquisition on Multiple Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

Triggering DT9838 and DT9837 Series Modules Using the Sync Bus . . . . . . . . . . . . . 116

Contents

Chapter 6: Supported Device Driver Capabilities. . . . . . . . . . . . . . . . . . . . . . . . . . . 119

Data Flow and Operation Options. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

Buffering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122

Triggered Scan Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122

Data Encoding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122

Channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

Ranges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124

Resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124

Current and Resistance Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124

Thermocouple, RTD, and Thermistor Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

IEPE Support. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126

Bridge and Strain Gage Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126

Start Triggers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127

Reference Triggers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127

Clocks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

7

Contents

Counter/Timers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

Tachometers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130

Chapter 7: Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131

General Checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132

Technical Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134

If Your Module Needs Factory Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135

Chapter 8: Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137

Using the Calibration Utility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138

Calibrating the Analog Input Subsystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

Connecting a Precision Voltage Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

Using the Auto-Calibration Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

Using the Manual Calibration Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140

Calibrating the Internal Analog Output Circuity (Excitation Voltage) . . . . . . . . . . . . . . . 141

Connecting a Digital Voltmeter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

Calibrating the Analog Output Circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

Appendix A: Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143

Analog Input Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144

Bridge Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145

Tachometer Input Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146

Trigger Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147

Power, Physical, and Environmental Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148

Regulatory Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149

Connector Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150

External Power Supply Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151

Appendix B: Connector Pin Assignments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153

Analog Input Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154

Sync Bus Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155

External Trigger and Tachometer Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156

External USB Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157

External Power Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158

Screw Terminals on the STP STRAIN, STP STRAIN 120, and STP STRAIN 350 . . . . . . . 159

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161

8

The first part of this manual describes how to install and set up your DT9838 module and
device driver, and verify that your module is working properly.

The second part of this manual describes the features of the DT9838 module, the capabilities of
the DT9838 Device Driver, and how to program the DT9838 module using DT-Open Layers for
.NET Class Library™ software. Troubleshooting information is also provided.

Notes: For more information on the class library, refer to the DT-Open Layers for .NET Class
Library User’s Manual. If you are using the DataAcq SDK or a software application to program

your device, refer to the documentation for that software for more information.

Intended Audience

This document is intended for engineers, scientists, technicians, or others responsible for
installing, setting up, using, and/or programming DT9838 modules for data acquisition
operations.

About this Manual

It is assumed that you are familiar with the requirements of your application. It is also
assumed that you have some familiarity with data acquisition principles, that you understand
your application, and that you are familiar with the Microsoft
or Windows 8 operating system.

How this Manual is Organized

This manual is organized as follows:

• Chapter 1, “Overview,” describes the major features of the DT9838 module, as well as the
supported software and accessories for the modules.

• Chapter 2, “Setting Up and Installing the Module,” describes how to apply power to the
module, how to attach the module to your computer, and how to configure the device
driver.

• Chapter 3, “Wiring Signals,” describes how to wire signals to the DT9838 module.

• Chapter 4, “Verifying the Operation of a Module,” describes how to verify the operation
of the module with the QuickDAQ application.

• Chapter 5, “Principles of Operation,” describes all of the features of the module and how
to use them in your application.

• Chapter 6, “Supported Device Driver Capabilities,” lists the data acquisition subsystems
and the associated features accessible using the DT9838 Device Driver.

®

Windows Vista®, Windows 7,

• Chapter 7, “Troubleshooting,” provides information that you can use to resolve problems
with the module and device driver, should they occur.

11

About this Manual

Conventions Used in this Manual

• Chapter 8, “Calibration,” describes how to calibrate the analog I/O circuitry of the
module.

• Appendix A, “Specifications,” lists the specifications of the DT9838 module.

• Appendix B, “Connector Pin Assignments,” shows the pin assignments of the connectors
on the DT9838 module.

• An index completes this manual.

The following conventions are used in this manual:

• Notes provide useful information that requires special emphasis, cautions provide
information to help you avoid losing data or damaging your equipment, and warnings
provide information to help you avoid catastrophic damage to yourself or your
equipment.

• Items that you select or type are shown in bold.

• Courier font is used to represent source code.

Related Information

Refer to the following documents for more information on using the DT9838 module:

• Benefits of the Universal Serial Bus for Data Acquisition. This white paper describes why USB
is an attractive alternative for data acquisition. It is available on the Data Translation®
web site (www.datatranslation.com).

• QuickDAQ User’s Manual (UM-24774). This manual describes how to create a QuickDAQ
application to acquire and analyze data from DT-Open Layers data acquisition devices.

• DT-Open Layers for .NET User’s Manual (UM-22161). For programmers who are developing
their own application programs using Visual C# or Visual Basic .NET, this manual
describes how to use the DT-Open Layers for .NET Class Library to access the capabilities
of Data Translation data acquisition devices.

• DataAcq SDK User’s Manual (UM-18326). For programmers who are developing their own
application programs using the Microsoft C compiler, this manual describes how to use
the DT-Open Layers
acquisition devices. This manual is included on the Data Acquisition OMNI CD.

• LV-Link Online Help. This help file describes how to use LV-Link™ with the LabVIEW™
graphical programming language to access the capabilities of Data Translation data
acquisition devices.

• DAQ Adaptor for MATLAB (UM-22024). This document describes how to use Data
Translation’s DAQ Adaptor to provide an interface between the MATLAB Data
Acquisition subsystem from The MathWorks and Data Translation’s DT-Open Layers
architecture.

TM

DataAcq SDKTM to access the capabilities of Data Translation data

12

• Microsoft Windows Vista, Windows 7, or Windows 8 documentation.

• USB web site (http://www.usb.org).

Where To Get Help

Should you run into problems installing or using a DT9838 module, our Technical Support
Department is available to provide technical assistance. Refer to Chapter 7 starting on page

131 for information on how to contact the Technical Support Department. If you are outside

the U.S. or Canada, call your local distributor, whose number is listed on Data Translation’s
web site (www.datatranslation.com).

About this Manual

13

About this Manual

14

1

Overview

DT9838 Hardware Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Supported Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Supported Accessories. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Getting Started Procedure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

15

Chapter 1

DT9838 Hardware Features

The DT9838 module, shown in Figure 1, is a USB strain gage measurement device intended for
full-, half, and quarter-bridge strain gage elements and bridge-based sensor assemblies such
as load cells, torque sensors, and pressure sensors, as well as general-purpose voltage
measurements. It is compatible with USB 2.0 and USB 1.1 ports.

Figure 1: DT9838 Module

The key hardware features of the DT9838 are as follows:

• Simultaneous measurement of four 24-bit analog input channels and one tachometer in
the analog input stream

• Direct full-bridge and half-bridge support with half-bridge completion

• Quarter-bridge support with external bridge-completion resistor

• Load cell support

• Non-bridged voltage input configuration

• Programmable input and bridge configuration

• Internal bridge excitation of 0 to 10 V in 167 μV steps

• Programmable 100 kΩ ±0.1% shunt resistor per channel

• TEDS (IEEE 1451.4) sensor compatible

• Software calibration of the bridge offset and gain

• Sampling frequency from 195.3125 Hz to 52.734 kHz

16

• Input range of ±250 mV

• Continuously paced analog input operations

• Software-programmable trigger type (software, external digital trigger, or variable digital
threshold trigger) to start analog input operations

• Sync Bus (RJ45) connector for synchronizing acquisition on up to four DT9838 modules

• LEDs for monitoring the arm/trigger state and USB status

Note: A board-level version of this module (without the enclosure) is also available for OEM
applications.

Overview

17

Chapter 1

Supported Software

The following software is available for use with the DT9838 module and is included on the
Data Acquisition OMNI CD:

• DT9838 Device Driver – The DT9838 Device Driver allows you to use a DT9838 module
with any of the supported software packages or utilities.

• QuickDAQ Base Version – The base version of QuickDAQ is free-of-charge and allows
you to acquire and analyze data from all Data Translation USB and Ethernet devices,
except the DT9841 Series, DT9817, DT9835, and DT9853/54. Using the base version of
QuickDAQ, you can perform the following functions:

− Discover and select your devices.

− Configure all input channel settings for the attached sensors.

− Load/save multiple hardware configurations.

− Generate output stimuli (fixed waveforms, swept sine waves, or noise signals).

− On each supported data acquisition device, acquire data from all channels supported

in the input channel list.

− Choose to acquire data continuously or for a specified duration.

− Choose software or triggered acquisition.

− Log acquired data to disk in an .hpf file.

− Display acquired data during acquisition in either a digital display using the Channel

Display window or as a waveform in the Channel Plot window.

− Choose linear or logarithmic scaling for the horizontal and vertical axes.

− View statistics about the acquired data, including the minimum, maximum, and mean

values and the standard deviation in the Statistics window.

− Export time data to a .csv or .txt file; you can open the recorded data in Microsoft

Excel® for further analysis.

− Read a previously recorded .hpf data file.

− Customize many aspects of the acquisition, display, and recording functions to suit

your needs, including the acquisition duration, sampling frequency, trigger settings,
filter type, and temperature units to use.

• QuickDAQ FFT Analysis Option – When enabled with a purchased license key, the
QuickDAQ FFT Analysis option includes all the features of the QuickDAQ Base version
plus basic FFT analysis features, including the following:

− The ability to switch between the Data Logger time-based interface and the FFT

Analyzer block/average-based interface.

18

− Supports software, freerun, or triggered acquisition with accept and reject controls for

impact testing applications.

− Allows you to perform single-channel FFT (Fast Fourier Transform) operations,

including AutoSpectrum, Spectrum, and Power Spectral Density, on the acquired
analog input data. You can configure a number of parameters for the FFT, including
the FFT size, windowing type, averaging type, integration type, and so on.

− Allows you to display frequency-domain data as amplitude or phase.

− Supports dB or linear scaling with RMS (root mean squared), peak, and peak-to-peak

scaling options

− Supports linear or exponential averaging with RMS, vector, and peak hold averaging

options.

− Supports windowed time channels.

− Supports the following response window types: Hanning, Hamming, Bartlett,

Blackman, Blackman Harris, and Flat top.

− Supports the ability to lock the waveform output to the analysis frame time.

− Allows you to configure and view dynamic performance statistics, including the input

below full-scale (IBF), total harmonic distortion (THD), spurious free dynamic range
(SFDR), signal-to-noise and distortion ratio (SINAD), signal-to-noise ratio (SNR), and
the effective number of bits (ENOB), for selected time-domain channels in the Statistics
window.

− Supports digital IIR (infinite impulse response) filters.

• QuickDAQ Advanced FFT Analysis Option – When enabled with a purchased software
license, the QuickDAQ Advanced FFT Analysis option includes all the features of the
QuickDAQ Base version with the FFT Analysis option plus advanced FFT analysis
features, including the following:

Overview

− Allows you to designate a channel as a Reference or Response channel.

− Allows you to perform two-channel FFT analysis functions, including Frequency

Response Functions (Inertance, Mobility, Compliance, Apparent Mass, Impedance,
Dynamic Stiffness, or custom FRF) with H1, H2, or H3 estimator types,
Cross-Spectrum, Cross Power Spectral Density, Coherence, and Coherent Output
Power.

− Supports the Exponential response window type.

− Supports the following reference window types: Hanning, Hamming, Bartlett,

Blackman, Blackman Harris, FlatTop, Exponential, Force, and Cosine Taper windows.

− Supports real, imaginary, and Nyquist display functions.

− Allows you to save data in the .uff file format.

• DT-Open Layers for .NET Class Library – Use this class library if you want to use Visual
C# or Visual Basic for .NET to develop your own application software for a DT9838
module using Visual Studio 2003 to 2012; the class library complies with the DT-Open
Layers standard.

• DataAcq SDK – Use the Data Acq SDK if you want to use Visual Studio 6.0 and Microsoft
C or C++ to develop your own application software for a DT9838 module using Windows
Vista, Windows 7, or Windows 8; the DataAcq SDK complies with the DT-Open Layers
standard.

• DAQ Adaptor for MATLAB – Data Translation’s DAQ Adaptor provides an interface
between the MATLAB Data Acquisition (DAQ) subsystem from The MathWorks and Data
Translation’s DT-Open Layers architecture.

19

Chapter 1

• LV-Link – A link to LV-Link is included on the Data Acquisition OMNI CD. Use LV-Link if
you want to use the LabVIEW graphical programming language to access the capabilities
of the DT9838 module.

Refer to the Data Translation web site (www.datatranslation.com) for information about
selecting the right software package for your needs.

20

Supported Accessories

The following accessories are available for the DT9838 module:

• STP STRAIN General-Purpose Accessory – This accessory contains four
general-purpose screw terminal panels. Use one screw terminal panel for each channel.

Overview

Figure 2: STP STRAIN General-Purpose Accessory

• STP STRAIN 120 Quarter-Bridge Completion Accessory – This accessory contains four
screw terminal panels with a 120 Ω quarter-bridge completion resistor installed on each
screw terminal panel. Use one screw terminal panel for each channel.

Figure 3: STP STRAIN 120 Quarter-Bridge Completion Accessory

21

Chapter 1

• STP STRAIN 350 Quarter-Bridge Completion Accessory – This accessory contains four
screw terminal panels with a 350 Ω quarter-bridge completion resistor installed on each
screw terminal panel. Use one screw terminal panel for each channel.

Figure 4: STP STRAIN 350 Quarter-Bridge Completion Accessory

• EP398 RJ50 cables – The EP398 accessory contains four RJ50 cables that are used to
connect four STP STRAIN, STP STRAIN 120, or STP STRAIN 350 screw terminal panels to
the DT9838 module. Figure 5 shows an RJ50 cable.

Figure 5: RJ50 Cable

22

• EP394 +5 V external power supply – Use this optional power supply, shown in Figure 6, if
you want to use an external +5 V power supply to power the DT9838 module. Refer to

page 31 for information on using internal USB power or external +5 V power to power the

DT9838 module.

Figure 6: EP394 External +5 V Power Supply

Overview

• EP386 panel – The EP386 panel, shown in Figure 7, contains four RJ45 connectors that are
wired in parallel, making it useful when attaching up to four DT9838 modules together
using the Sync Bus. Refer to page 114 for more information on using this panel.

Figure 7: EP386 Panel

23

Chapter 1

Set Up and Install the Module

(see Chapter 2 starting on page 27)

Wire Signals

(see Chapter 3 starting on page 37)

Verify the Operation of the Module

(see Chapter 4 starting on page 73)

Getting Started Procedure

The flow diagram shown in Figure 8 illustrates the steps needed to get started using the
DT9838 module. This diagram is repeated in each Getting Started chapter; the shaded area in
the diagram shows you where you are in the procedure.

Figure 8: Getting Started Flow Diagram

24

Part 1: Getting Started

2

Setting Up and Installing the Module

Unpacking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

System Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

(Optional) Applying Power to the Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Attaching Modules to the Computer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Configuring the DT9838 Device Driver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

27

Chapter 2

Set Up and Install the Module

(this chapter)

Wire Signals

(see Chapter 3 starting on page 37)

Verify the Operation of the Module

(see Chapter 4 starting on page 73)

Note: The DT9838 module is factory-calibrated. If you decide that you want to recalibrate
the analog input circuitry, refer to the instructions on Chapter 8.

28

Unpacking

Open the shipping box and verify that the following items are present:

• DT9838 module

• Data Acquisition OMNI CD

If an item is missing or damaged, contact Data Translation. If you are in the United States, call
the Customer Service Department at [phone], ext. 1323. An application engineer will
guide you through the appropriate steps for replacing missing or damaged items. If you are
located outside the United States, call your local distributor, listed on Data Translation’s web
site (www.datatranslation.com).

Setting Up and Installing the Module

29

Chapter 2

System Requirements

For reliable operation, ensure that your computer meets the following system requirements:

• Processor: Pentium 4/M or equivalent

•RAM: 1 GB

• Screen Resolution: 1024 x 768 pixels

• Operating System: Windows 8, Windows 7, or Windows Vista (32- and 64-bit)

• Disk Space: 4 GB

30

Setting Up and Installing the Module

(Optional) Applying Power to the Module

The DT9838 is designed to operate from USB power alone. However, the number of channels
that it can power is limited by the USB port power capability, the programmed excitation
voltage, and the bridge resistance. To enhance the bridge drive capability, you can purchase
the optional +5 V power supply (model number EP394) available from Data Translation or use
an external +5 to +24 VDC power supply to power the DT9838 module.

Tabl e 1 shows the number of channels that are supported when the module is powered with

USB power or external power, given different bridge configurations and excitation voltages.

Table 1: Number of Channels Supported when Module is Powered with USB Power or External Power

USB Power Supplied 5 V to 24 V External Power Supplied

Bridge Resistance Bridge Resistance

Bridge

Configuration

Full Bridge 2.5 V 3 channels 4 channels 4 channels 4 channels 4 channels 4 channels

Excitation

Voltag e

3.3 V 2 channels 4 channels 4 channels 4 channels 4 channels 4 channels

120 Ω 350 Ω 1 kΩ 120 Ω 350 Ω 1 kΩ

Quarter Bridge
and

Half Bridge

5 V – 4 channels 4 channels – 4 channels 4 channels

10 V – 1 channel 3 channels – 4 channels 4 channels

2.5 V 4 channels 4 channels 4 channels 4 channels 4 channels 4 channels

3.3 V 4 channels 4 channels 4 channels 4 channels 4 channels 4 channels

5 V 3 channels 4 channels 4 channels 4 channels 4 channels 4 channels

10 V – 2 channel 4 channels – 4 channels 4 channels

To attach an external power supply to the module, do the following:

1. Connect the +5 V power supply (EP394) to the auxiliary power connector on the DT9838

module, as shown in Figure 9.

2. Plug the power supply into a wall outlet.

31

Chapter 2

To wall outlet

EP394 +5 V

Powe r S up ply

DT9838 Module

Auxiliary Power

Connector

Figure 9: Attaching an External +5 V Power Supply to the DT9838 Module

32

Attaching Modules to the Computer

DT9838 Module

USB
Port

Connect the USB cable to the DT9838

module and to your computer.

Tri g g e r LED

USB LED

This section describes how to attach DT9838 modules to the host computer.

Note: Most computers have several USB ports that allow direct connection to USB devices.
If your application requires more DT9838 modules than you have USB ports for, you can
expand the number of USB devices attached to a single USB port by using expansion hubs.
For more information, refer to page 34.

You can unplug a module, then plug it in again, if you wish, without causing damage. This
process is called hot-swapping. Your application may take a few seconds to recognize a
module once it is plugged back in.

You must install the device driver before connecting your DT9838 module(s) to the host
computer. Run the installation program on your Data Acquisition OMNI CD to install the
device driver and other software for the module.

Setting Up and Installing the Module

Connecting Directly to the USB Ports

To connect a DT9838 module directly to a USB port on your computer, do the following:

1. Attach one end of the USB cable to the USB port on the module.

2. Attach the other end of the USB cable to one of the USB ports on the host computer, as

shown in Figure 10.

The operating system automatically detects the USB module and starts the Found New Hardware
wizard.

Figure 10: Attaching the DT9838 Module to the Host Computer

33

Chapter 2

3. For Windows Vista:

a. Click Locate and install driver software (recommended).

The popup message "Windows needs your permission to continue" appears.

b. Click Continue.

The Windows Security dialog box appears.

c. Click Install this driver software anyway.

The USB LED on the module turns green.

Note: Windows 7 and Windows 8 find the device automatically.

4. Repeat these steps to attach another DT9838 module to the host computer, if desired.

Connecting to an Expansion Hub

Expansion hubs are powered by their own external power supply. The practical number of
DT9838 modules that you can connect to a single USB port depends on the throughput you
want to achieve.

To connect multiple DT9838 modules to an expansion hub, do the following:

1. Attach one end of the USB cable to the module and the other end of the USB cable to an

expansion hub.

2. Connect the power supply for the expansion hub to an external power supply.

3. Connect the expansion hub to the USB port on the host computer using another USB

cable.

The operating system automatically detects the USB module and starts the Found New Hardware
wizard.

4. For Windows Vista

a. Click Locate and install driver software (recommended).

The popup message "Windows needs your permission to continue" appears.

b. Click Continue.

The Windows Security dialog box appears.

c. Click Install this driver software anyway.

The USB LED on the module turns green.

Note: Windows 7 and Windows 8 find the device automatically.

:

34

5. Repeat these steps until you have attached the number of expansion hubs and modules

that you require. Refer to Figure 11.

The operating system automatically detects the USB devices as they are installed.

Setting Up and Installing the Module

USB Cable

Expansion Hubs

Host Computer

DT9838
Module

Power Supply

for Hub

DT9838
Module

DT9838
Module

USB Cables

USB Cables

USB Cable

DT9838
Module

Power Supply

for Hub

Figure 11: Attaching Multiple Modules Using Expansion Hubs

35

Chapter 2

Configuring the DT9838 Device Driver

Note: In Windows 7, Windows 8, and Vista, you must have administrator privileges to run
the Open Layers Control Panel. When you double-click the Open Layers Control Panel icon,
you may see the Program Compatibility Assistant. If you do, select Open the control panel
using recommended settings. You may also see a Windows message asking you if you want
to run the Open Layers Control Panel as a "legacy CPL elevated." If you get this message,
click Yes.

If you do not get this message and have trouble making changes in the Open Layers Control
Panel, right click the DTOLCPL.CPL file and select Run as administrator. By default, this file
is installed in the following location:

Windows 7, Windows 8, and Vista (32-bit)
C:\Windows\System32\Dtolcpl.cpl

Windows 7, Windows 8, and Vista (64-bit)
C:\Windows\SysWOW64\Dtolcpl.cpl

To configure the device driver for the DT9838 module, do the following:

1. If you have not already done so, power up the host computer and all peripherals.

2. From the Windows Start menu, select Settings|Control Panel.

3. From the Control Panel, double-click Open Layers Control Panel.

The Data Acquisition Control Panel dialog box appears.

4. If you want to rename the module, click the name of the module that you want to rename,

click Edit Name, enter a new name for the module, and then click OK. The name is used
to identify the module in all subsequent applications.

5. Repeat step 4 for the other modules that you want to configure.

6. When you are finished configuring the modules, click Close to close the Control Panel.

36

3

Wiring Signals

Preparing to Wire Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Connecting a General-Purpose or Bridge-Completion Accessory . . . . . . . . . . . . . . . . . . . . 42

Connecting Quarter-Bridge Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Connecting Half-Bridge Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

Connecting Full-Bridge Circuits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

Connecting Load Cells and Other Transducers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

Connecting Voltage Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

Connecting a Tachometer Input Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

Connecting an External Trigger Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

37

Chapter 3

Set Up and Install the Module

(see Chapter 2 starting on page 27)

Wire Signals

(this chapter)

Verify the Operation of the Module

(see Chapter 4 starting on page 73)

38

Preparing to Wire Signals

A/D

Chan 0

A/D

Chan 1

A/D

Chan 2

A/D

Chan 3

Ext Trigger

and

Tachometer

USB
Port

Sync BusAuxiliary Power

Connector

Trigg er L E D

USB LED

Figure 12 shows the connectors of the DT9838 module. The left side of the DT9838 module

contains four analog input (RJ50) connectors for connecting strain gages, load cells and other
sensors, and/or voltage input signal. The right side of the DT9838 module provides the
following connectors:

• Auxiliary power connector – Allows you to attach the optional EP394 external power
supply.

• External trigger and tachometer connector – Provides screw terminals for connecting an
external trigger and/or tachometer input signal.

• Sync Bus connector – Allows you to attach multiple modules together.

• USB connector – Allows you to attach the DT9838 module to your computer.

Wiring Signals

Figure 12: Connectors on the DT9838 Module (Side Views)

39

Chapter 3

General Wiring Recommendations

Keep the following recommendations in mind when wiring signals to the DT9838 module:

• Follow standard ESD procedures when wiring signals to the module.

• Separate power and signal lines by using physically different wiring paths or conduits.

• To avoid noise, do not locate the DT9838 module and cabling next to sources that produce
high electromagnetic fields, such as large electric motors, power lines, solenoids, and
electric arcs, unless the signals are enclosed in a mumetal shield.

• Prevent electrostatic discharge to the I/O while the DT9838 module is operational.

• Use an overall shielded cable for connections between the strain gages and the DT9838,
with the shield connected to the chassis ground connection of the DT9838. A shield
connection point is provided on pin 11 of the STP STRAIN, STP STRAIN 120, and STP
STRAIN 350 accessories.

• Use individually shielded twisted-pair wire (size 14 to 26 AWG) when wiring voltage
input signals to the DT9838 module.

Definitions

The following terms are used in this chapter:

• ε is the measured strain (+ε is the tensile strain and –ε is the compressive strain)

• ν is the Poisson’s ratio, defined as the negative ratio of transverse strain to axial
(longitudinal) strain

•R

is the lead resistance

L

•R

is the nominal gage resistance, which is specified by the gage manufacturer

g

40

Analog Input Connector Pin Assignments (RJ50 Connector)

12345678 109

For analog input channels 0 to 3, the DT9838 module provides RJ50 connectors, shown in

Figure 13, for connecting strain gages, load-cell sensors, and/or voltage inputs. Tab l e 2 lists

the pin assignments for the RJ50 connectors.

Figure 13: Analog Input (RJ50) Connector

Wiring Signals

Table 2: Pin Assignments for the RJ50 Connectors

Pin Signal Description

1 RSHUNT+

2AIN+

3AIN–

4 SENSE+

5 SENSE–

6 EXC+

7 EXC–

8 TEDS DATA

9 TEDS RETURN

10 RSHUNT –

41

Chapter 3

Connect the

RJ50 cable to

the DT9838

Connect bridge signals to the

screw terminals

External bridge completion
resistors are provided on the
STP STRAIN 120 and STP
STRAIN 350 accessories.

Screw Terminal 1

Connecting a General-Purpose or Bridge-Completion Accessory

To make wiring bridges easier, you may want to purchase one of the following optional
accessories:

• STP STRAIN General-Purpose Accessory – This accessory contains four
general-purpose screw terminal panels. Use one screw terminal panel for each channel.

• STP STRAIN 120 Quarter-Bridge Completion Accessory – This accessory contains four
screw terminal panels with a 120 Ω quarter-bridge completion resistor installed on each
screw terminal panel. Use one screw terminal panel for each channel.

• STP STRAIN 350 Quarter-Bridge Completion Accessory – This accessory contains four
screw terminal panels with a 350 Ω quarter-bridge completion resistor installed on each
screw terminal panel. Use one screw terminal panel for each channel.

Figure 14 shows the layout of the STP STRAIN, STP STRAIN 120, and STP STRAIN 350

accessories.

42

Figure 14: Layout of the STP STRAIN, STP STRAIN 120, and STP STRAIN 350 Accessories

The screw terminal assignments of the STP STRAIN, STP STRAIN 120, and STP STRAIN 350
screw terminal panels, listed in Tab le 3, match the pin designations of the RJ50 analog input
connectors on the DT9838.

Table 3: Pin Assignments for the STP STRAIN, STP STRAIN 120,

and STP STRAIN 350 Screw Terminal Panels

Pin Signal Description

1 Shunt Cal+

2 Input+

3 Input–

4 Sense+

5 Sense–

6 Excitation+

7 Excitation–

8 TEDS+ (Data)

9 TEDS– (Return)

10 Shunt Cal–

11 Shield

Wiring Signals

The optional EP398 contains four RJ50 cables. Use an RJ50 cable to connect the RJ50 connector
on the STP STRAIN, STP STRAIN 120, or STP STRAIN 350 screw terminal panel to the RJ50
connector on the DT9838 module, as shown in Figure 15.

Figure 15: Connecting the STP STRAIN, STP STRAIN 120, or STP STRAIN 350 Accessory to the

DT9838 Module

43

Chapter 3

Axial

Bending

R

4

(+ε)

R

4

(+ε)

Strain
Gage

Strain
Gage

Connecting Quarter-Bridge Circuits

The DT9838 module supports the following quarter-bridge configurations:

• Quarter-Bridge (Axial and Bending)

• Quarter-Bridge Temp Comp

This section describes how to wire the Quarter-Bridge and Quarter-Bridge Temp Comp
circuits to the DT9838 module. For more information about these bridge configuration types,
refer to page 96.

Wiring a Quarter-Bridge (Axial and Bending) Circuit

The Quarter-Bridge configuration, shown in Figure 16, measures axial or bending strain.

44

Figure 16: Quarter-Bridge Configuration

The Quarter-Bridge configuration has the following characteristics:

• A single active strain gage element is mounted in the direction of axial or bending strain.

• You must supply a resistor (R

) that matches the nominal resistance of the bridge to

3

complete the bridge externally. This is supplied for you when you use the STP STRAIN
120 or STP STRAIN 350 quarter-bridge completion accessory.

Wiring Signals

Note: In some cases, you may wish to use a rosette, which is arrangement of two or three
closely positioned strain gage grids that are oriented to measure the normal strains along
different directions in the underlying surface of a test material. The DT9838 supports
rectangular and delta rosettes; tee rosettes are not supported.

A rectangular rosette is an arrangement of three strain gage grids where the second grid is
angularly displaced from the first grid by 45 degrees and the third grid is angularly displaced
from the first grid by 90 degrees. A delta rosette is an arrangement of three strain gage grids
where the second grid is angularly displaced from the first grid by 60 degrees and the third
grid is angularly displaced from the first grid by 120 degrees.

To use a rectangular or delta rosette, use the Quarter-Bridge configuration with the proper
bridge completion. You can then read the strain value from each analog input channel
individually, and if desired, use software to calculate the minimum and maximum principal
strain values and their associated angles (in degrees).

Figure 17 shows how to connect a 3-wire Quarter-Bridge circuit to the STP STRAIN 120 or STP

STRAIN 350 quarter-bridge completion accessory. Remote sense lines (SENSE+ and SENSE–)
are not used in the 3-wire connection scheme using the STP STRAIN 120 or STP STRAIN 350
quarter-bridge completion accessories; therefore, the remote sense lines are connected to the
excitation lines (SENSE+ is connected to EXC+ and SENSE– is connected to EXC–) to ensure
proper bridge voltage regulation. If the lead wire resistance is known, you can enter the lead
wire correction coefficient in software. Refer to page 102 for more information.

45

Chapter 3

*With the STP STRAIN 120 quarter-bridge completion accessory, the
value of resistor R

3

is 120 Ω to match the value of resistor R4.

With the STP STRAIN 350 quarter-bridge completion accessory, the
value of resistor R

3

is 350 Ω to match the value of resistor R4.

10 kO

10 kO

R

1

+

-

EXC+

AIN+

Bridge

Excitation

Precision

Instrumentation Amp

ADC

24-bit

100 kO

QTR

TEDS

SER

RJ50

6

4

2
3

5

1

8
9

7

10

R

4

R

2

DT9838

R

L

R

L

R3*

RJ50

Quarter-Bridge

Completion

Accessory

EXC+

SENSE+

AIN+

AIN-

EXC-

SENSE-

RSHUNT-

RSHUNT+

6

2

1

+e

10 kΩ

10 kΩ

100 kΩ

Figure 17: Connecting a Quarter-Bridge Circuit to the DT9838 When Using the STP STRAIN 120 or

STP STRAIN 350 Quarter-Bridge Completion Accessory

Figure 18 shows how to connect a Quarter Bridge circuit to the DT9838 when using the

general-purpose STP STRAIN accessory. In this example, the user-supplied resistor is
mounted at the strain gage and the remote sense lines (SENSE+ and SENSE–) are not used;
therefore, the remote sense lines are connected to the excitation lines (SENSE+ is connected to
EXC+ and SENSE– is connected to EXC–) to ensure proper bridge voltage regulation. If the
lead wire resistance is known, you can enter the lead wire correction coefficient in software.
Refer to page 102 for more information.

46

Wiring Signals

10 kΩ

10 kΩ

R

1

+

-

(User Supplied )

EXC+

SENSE+

AIN+

AIN-

Bridge

Excitation

Precision

Instrumentation Amp

ADC

24-bit

100 kΩ

EXC-

SENSE-

RSHUNT-

RSHUNT+

TEDS

SER

RJ50

6

4

2
3

5

1

8
9

7

10

R

4

R

3

R

2

General-Purpose STP STRAIN

Accessory Connected to DT9838

R

L

R

L

R

L

R

L

100 kΩ

10 kΩ

10 kΩ

+ε

Figure 18: Connecting a Quarter-Bridge Circuit to the DT9838 and General-Purpose STP STRAIN

Accessory when the Completion Resistor is Mounted at the Strain Gage

Remote Sensing In Quarter-Bridge Configurations

Remote sensing is not used in the 3-wire Quarter-Bridge configurations that use the STP
STRAIN 120 and STP STRAIN 350 quarter-bridge completion accessories, as shown in Figure

17. However, you may want to use the remote sense lines (SENSE+ and SENSE–) in some

applications that use Quarter-Bridge configurations, particularly where long wires and/or
small gauge wires are used, to minimize voltage drops caused by the lead wire resistance of
the EXC+ and EXC– lines.

Figure 19 shows how to connect a Quarter Bridge circuit to the DT9838 using remote sense

lines. In this example, the general-purpose STP STRAIN accessory is used and the
user-supplied resistor is mounted at the strain gage.

Note: When remote sensing is used, enter 0 Ω for the lead wire correction coefficient in
software. Refer to page 102 for more information.

47

Chapter 3

10 kO

10 kO

R

1

+

-

(User
Supplied)

EXC+

SENSE+

AIN+

AIN-

Bridge

Excitation

Precision

Instrumentation Amp

ADC

24-bit

100 kO

EXC-

SENSE-

RSHUNT-

RSHUNT+

TEDS

SER

6

4

2
3

5

1

8
9

7

10

R

4

R

L

R

2

R

L

R

3

R

L

R

L

General-Purpose STP STRAIN

Accessory Connected to DT9838

100 kΩ

10 kΩ

10 kΩ

+ε

48

Figure 19: Connecting a Quarter-Bridge Circuit to the DT9838 and General-Purpose STP STRAIN

Accessory when the Completion Resistor is Mounted at the Strain Gage and the

Remote Sense Lines are Used

Shunt Calibration in Quarter-Bridge Configurations

When setting up your strain gage, you can use shunt calibration to correct for errors due to
lead wire resistance (R
shunt calibration in Quarter-Bridge configurations.

To perform shunt calibration in a Quarter-Bridge configuration, the RSHUNT+ and
RSHUNT– lines for the internal 100 kΩ shunt resistor are connected either across R
the connected bridge. However, when using the STP STRAIN 120 or STP STRAIN 350 bridge
completion accessory, as shown in Figure 17, the shunt resistor can only be connected across
R

. Figure 18 and Figure 19 show how to connect the RSHUNT+ and RSHUNT– lines when

3

using the general-purpose STP STRAIN accessory.

In either case, while the bridge is in the unstrained condition, you can use software to switch
in the shunt calibration resistor to simulate a known amount of strain. The measured output
value with the shunt resistor in place is then compared to the expected value of strain with the
shunt resistor in place. The gain of the bridge transfer function is then modified by the ratio of
the expected strain to the measured strain, calibrating the system. Refer to your software
documentation for more information about shunt calibration

Once you have verified your setup, you can disconnect the RSHUNT+ and RSHUNT– lines, if
desired.

) in the excitation wiring. Refer to page 104 for the equations used for

L

or R4 of

3

Wiring a Quarter-Bridge Temp Comp Circuit

R3

Axial

Bending

R4 (+ε)

R4 (+ε)

Active
Strain
Gage

Dummy
Strain
Gage

R

3

Active
Strain
Gage

Dummy
Strain
Gage

The Quarter-Bridge Temp Comp configuration, shown in Figure 20, measures axial and
bending strain and compensates for temperature.

Note: This configuration is often confused with the more commonly used Half-Bridge
Poisson configuration, described on page 52. In the Half-Bridge Poisson configuration, the R
element is active and is bonded to the strain specimen to measure the effect of the Poisson
ratio. In the Quarter-Bridge Temp Comp configuration, R
is used) and is not bonded to the specimen.

Wiring Signals

is not active (a dummy strain gage

3

3

Figure 20: Quarter-Bridge Temp Comp Configuration

The Quarter-Bridge Temp Comp configuration has the following characteristics:

• Uses active strain gage element and one passive (dummy) strain gage element.

• The active strain gage element is mounted in the direction of axial or bending strain.

• The passive (dummy) strain gage element, R

is mounted in close thermal contact with

3,

the strain specimen to compensate for temperature, but is not bonded to the specimen; it
does not respond to the axial or bending strain of the specimen.

Although it is not necessary, the dummy strain gage element is usually mounted
perpendicular to the axis of strain.

49

Chapter 3

10 kΩ

10 kΩ

R

1

+

-

(Dummy)

EXC+

SENSE+

AIN+

AIN-

Bridge

Excitation

Precision

Instrumentation Amp

ADC

24-bit

100 kΩ

EXC-

SENSE-

RSHUNT-

RSHUNT+

TEDS

SER

RJ50

6
4

2

3

5

1

8
9

7

10

R

4

R

3

R

2

General-Purpose STP STRAIN

Accessory Connected to DT9838

R

L

R

L

100 kΩ

10 kΩ

10 kΩ

+ε

Figure 22 shows how to connect a Quarter-Bridge Temp Comp circuit to the DT9838 when

using the general-purpose STP STRAIN accessory and remote sensing.

Note: When remote sensing is used, enter 0 Ω for the lead wire correction coefficient in
software. Refer to page 102 for more information.

50

Figure 21: Connecting a Quarter Bridge Temp Comp Circuit to the DT9838 When Using the

General-Purpose STP STRAIN Accessory and Remote Sensing

Remote Sensing In Quarter-Bridge Temp Comp Configurations

Although not required for operation in Quarter-Bridge Temp Comp configurations, it is
recommended that you connect the bridge SENSE+ and SENSE– lines, as shown in Figure 21
to minimize voltage drops caused by the lead wire resistance of the EXC+ and EXC– lines.
This is most important in applications where long wires and/or small gauge wires, which
have greater resistance, are used.

If you do not use remote sense leads, you must connect the sense leads to the excitation leads
(connect SENSE+ to EXC+ and SENSE– to EXC–), as shown in Figure 22, to ensure proper
bridge voltage regulation. If the lead wire resistance is known, you can enter the lead wire
correction coefficient in software. Refer to page 102 for more information.

Wiring Signals

R

1

+

-

(Dummy)

EXC+

SENSE+

AIN+

AIN-

Bridge

Excitation

Precision

Instrumentation Amp

ADC

24-bit

EXC-

SENSE-

RSHUNT-

RSHUNT+

TEDS

SER

RJ50

6

4

2
3

5

1

8
9

7

10

R

4

R

3

R

2

General-Purpose STP STRAIN

Accessory Connected to DT9838

R

L

R

L

R

L

R

L

100 kΩ

10 kΩ

10 kΩ

+ε

Figure 22: Connecting a Quarter Bridge Temp Comp Circuit to the DT9838 When Using the

General-Purpose STP STRAIN Accessory Without Remote Sensing

Shunt Calibration in Quarter-Bridge Temp Comp Configurations

When setting up your strain gage, you can use shunt calibration to correct for errors due to
lead wire resistance (R
shunt calibration in Quarter-Bridge Temp Comp configurations.

To perform shunt calibration in a quarter-bridge configuration using the internal 100 kΩ
resistor, connect the internal RSHUNT+ and RSHUNT– lines across gage R

Figure 21 and Figure 22. You can then use software to switch in 100 kΩ across gage R

when no strain is applied to the specimen, creating a known change in the bridge output. You
can then use software to measure the output of the bridge, compare it to the expected bridge
output value, and adjust the gain of the DT9838 to compensate for these errors.

Once you have verified your setup, you can disconnect the RSHUNT+ and RSHUNT– lines, if
desired.

Refer to your software documentation for more information about shunt calibration.

) in the excitation wiring. Refer to page 104 for the equations used for

L

3 or R4

, as shown in

3 or R4

51

Chapter 3

R4 (+ε)

R

3

(–νε)

R3 (–νε)

R4 (+ε)

Axial

Bending

Strain
Gage

Strain
Gage

Strain
Gage

Strain
Gage

Connecting Half-Bridge Circuits

The DT9838 module supports the following half-bridge configurations:

• Half-Bridge Poisson (Bending or Axial)

• Half-Bridge Bending

This section describes how to wire the Half-Bridge Poisson and Half-Bridge Bending circuits
to the DT9838 module. The wiring diagram is the same for all half-bridge configurations;
however, the meaning of R
more information about these bridge configuration types, refer to page 97.

Wiring a Half-Bridge Poisson Circuit

The Half-Bridge Poisson configuration, shown in Figure 23, measures either axial or bending
strain, compensates for temperature, and compensates for the aggregate effect on the principle
strain measurement due to the Poisson ratio of the specimen material.

and R4 differs depending on the configuration you choose. For

3

52

Figure 23: Half-Bridge Poisson Configuration

The Half-Bridge Poisson configuration has the following characteristics:

10 kΩ

10 kΩ

R

1

+

-

EXC+

SENSE+

AIN+

AIN-

SENSE-

EXC-

RSHUNT-

RSHUNT+

RJ50

ADC

24- bit

Bridge

Excitation

Precision

Instrumentation Amp

TEDS

SER

100kΩ

6
4

2
3

5

1

8
9

7

10

General-Purpose STP STRAIN

Accessory Connected to DT9838

R

2

R

4

R

3

R

L

R

L

10 kΩ

100 kΩ

10 kΩ

+ε

−νε

• Uses two active strain gage elements.

Wiring Signals

• One strain gage element, R

The other strain gage element, R

(+ε), is mounted in the direction of axial strain.

4

(–νε), is mounted transversely (perpendicular) to the

3

axis of strain to measure the Poisson effect.

• The DT9838 provides two internal 10 kΩ resistors R

and R2, to complete the sensor side of

1

the bridge circuit.

Figure 24 shows how to connect a Half-Bridge Poisson circuit to the DT9838 when using the

general-purpose STP STRAIN accessory and remote sensing.

Note: When remote sensing is used, enter 0 Ω for the lead wire correction coefficient in
software. Refer to page 102 for more information.

Figure 24: Connecting a Half-Bridge Poisson Circuit to the DT9838 When Using the

General-Purpose STP STRAIN Accessory and Remote Sensing

53

Chapter 3

10 kO

10 kO

R

1

+

-

EXC+

SENSE+

AIN+

AIN-

SENSE-

EXC-

RSHUNT-

RSHUNT+

RJ50

ADC

24-bit

Bridge

Excitation

Precision

Instrumentation Amp

TEDS

SER

100kO

6

4

2
3

5

1

8
9

7

10

General-Purpose STP STRAIN

Accessory Connected to DT9838

R

2

R

4

R

3

R

L

R

L

R

L

R

L

10 kΩ

100 kΩ

10 kΩ

+ε

−νε

Remote Sensing In Half-Bridge Poisson Configurations

Although not required for operation in Half-Bridge Poisson configuration, it is recommended
that you connect the bridge SENSE+ and SENSE– lines, as shown in Figure 24 to minimize
voltage drops caused by the lead wire resistance of the EXC+ and EXC– lines. This is most
important in applications where long wires and/or small gauge wires, which have greater
resistance, are used.

If you do not use remote sense lines, you must connect the sense leads to the excitation leads
(connect SENSE+ to EXC+ and SENSE– to EXC–), as shown in Figure 25, to ensure proper
bridge voltage regulation. If the lead wire resistance is known, you can enter the lead wire
correction coefficient in software. Refer to page 102 for more information.

54

Figure 25: Connecting a Half-Bridge Poisson Circuit to the DT9838 When Using the

General-Purpose STP STRAIN Accessory Without Remote Sensing

Shunt Calibration in Half-Bridge Poisson Configurations

When setting up your strain gage, you can use shunt calibration to correct for errors due to
lead wire resistance (R
shunt calibration in a Half-Bridge Poisson configuration.

To perform shunt calibration in a Half-Bridge Poisson configuration using the internal 100 kΩ
resistor, connect the internal RSHUNT+ and RSHUNT– lines across gage R

Figure 24 and Figure 25. You can then use software to switch in 100 kΩ across the selected

gage when no strain is applied to the specimen, creating a known change in the bridge output.
Using software, you can then measure the output of the bridge, compare it to the expected
bridge output value, and adjust the gain of the DT9838 to compensate for these errors.

Once you have performed the shunt calibration procedure, you can disconnect the RSHUNT+
and RSHUNT– lines, if desired.

Refer to your software documentation for more information about shunt calibration.

) in the excitation wiring. Refer to page 104 for the equation used for

L

3 or R4,

as shown in

Wiring Signals

55

Chapter 3

R4 (+ε)

Bending

R

3

(–ε)

Strain
Gage

Wiring a Half-Bridge Bending Circuit

The Half-Bridge Bending configuration, shown in Figure 26, measures bending strain, rejects
axial strain, and compensates for temperature.

Figure 26: Half-Bridge Bending Configuration

The Half-Bridge Bending configuration has the following characteristics:

• Uses two active strain gage elements.

• One strain gage element, R

(+ε ), is mounted in the direction of bending strain on the top

4

of the specimen.

The other strain gage element, R

(–ε), is mounted in the direction of bending strain on the

3

bottom of the specimen.

• The DT9838 provides two internal 10 kΩ resistors (R

and R2) to complete the sensor side

1

of the bridge circuit.

Figure 27 shows how to connect a Half-Bridge Bending circuit to the DT9838 when using the

general-purpose STP STRAIN accessory and remote sensing.

Note: When remote sensing is used, enter 0 Ω for the lead wire correction coefficient in
software. Refer to page 102 for more information.

56

Wiring Signals

10 kΩ

10 kΩ

R

1

+

-

EXC+

SENSE+

AIN+

AIN-

SENSE-

EXC-

RSHUNT-

RSHUNT+

RJ50

ADC

24- bit

Bridge

Excitation

Precision

Instrumentation Amp

TEDS

SER

100 kΩ

6

4

2
3

5

1

8
9

7

10

General-Purpose STP STRAIN

Accessory Connected to DT9838

R

2

R

4

R

3

R

L

R

L

10 kΩ

100 kΩ

10 kΩ

+ε

−ε

Figure 27: Connecting a Half-Bridge Bending Circuit to the DT9838 When Using the

General-Purpose STP STRAIN Accessory and Remote Sensing

Remote Sensing In Half-Bridge Bending Configurations

Although not required for operation in Half-Bridge Bending configurations, it is
recommended that you connect the bridge SENSE+ and SENSE– lines, as shown in Figure 27
to minimize voltage drops caused by the lead wire resistance of the EXC+ and EXC– lines.
This is most important in applications where long wires and/or small gauge wires, which
have greater resistance, are used.

If you do not use remote sense lines, you must connect the sense leads to the excitation leads
(connect SENSE+ to EXC+ and SENSE– to EXC–), as shown in Figure 28, to ensure proper
bridge voltage regulation. If the lead wire resistance is known, you can enter the lead wire
correction coefficient in software. Refer to page 102 for more information.

57

Chapter 3

10 kΩ

10 kΩ

R

1

+

-

EXC+

SENSE+

AIN+

AIN-

SENSE-

EXC-

RSHUNT-

RSHUNT+

RJ50

ADC

24-bit

Bridge

Excitation

Precision

Instrumentation Amp

TEDS

SER

100 kΩ

6
4

2
3

5

1

8
9

7

10

General-Purpose STP STRAIN

Accessory Connected to DT9838

R

2

R

4

R

3

R

L

R

L

R

L

R

L

10 kΩ

100 kΩ

10 kΩ

+ε

−ε

Figure 28: Connecting a Half-Bridge Bending Circuit to the DT9838 When Using the

General-Purpose STP STRAIN Accessory Without Remote Sensing

Shunt Calibration in Half-Bridge Bending Configurations

When setting up your strain gage, you can use shunt calibration to correct for errors due to
lead wire resistance (R
shunt calibration in a Half-Bridge Bending configuration.

To perform shunt calibration in a Half-Bridge Bending configuration using the internal 100 kΩ
resistor, connect the internal RSHUNT+ and RSHUNT– lines across gage R

Figure 27 and Figure 28. You can then use software to switch in 100 kΩ across the selected

gage when no strain is applied to the specimen, creating a known change in the bridge output.
Using software, you can then measure the output of the bridge, compare it to the expected
bridge output value, and adjust the gain of the DT9838 to compensate for these errors.

Once you have performed the shunt calibration procedure, you can disconnect the RSHUNT+
and RSHUNT– lines, if desired.

Refer to your software documentation for more information about shunt calibration.

) in the excitation wiring. Refer to page 104 for the equation used for

L

3 or R4,

as shown in

58

Connecting Full-Bridge Circuits

R2 (+ε)

R

3

(–ε)

R

1

(–ε)

R

4

(+ε)

Bending

Strain
Gage

Strain
Gage

The DT9838 module supports the following full-bridge configurations:

• Full-Bridge Bending

• Full-Bridge Bending Poisson

• Full-Bridge Axial Poisson

This section describes how to wire the Full-Bridge Bending, Full-Bridge Bending Poisson, and
Full-Bridge Bending configurations to the DT9838 module. The wiring diagram is the same for
all full-bridge configurations; however, the meaning of R
the configuration you choose. For more information about these bridge configuration types,
refer to page 100.

Wiring a Full-Bridge Bending Circuit

The Full-Bridge Bending configuration, shown in Figure 29, measures bending strain. It also
rejects axial strain, compensates for temperature, and compensates for lead resistance if
remote sense lines are used.

Wiring Signals

, R2, R3, and R4 differs depending on

1

Figure 29: Full-Bridge Bending Configuration

59

Chapter 3

TEDS

SER

Bridge

Excitation

100 kΩ

EXC +

SENSE+

SENSE -

EXC -

RSHUNT+

RSHUNT-

10 kΩ

10 kΩ

RJ50

R

L

R

L

R

2

R

1

R

3

R

4

ADC

24-bit

Precision

Instrumentation Amp

AIN-

AIN+

+

-

R

3

-

+

V

O

6
4

2
3

5
7

10

1

8
9

General-Purpose STP STRAIN

Accessory Connected to DT9838

10 kΩ

100 kΩ

10 kΩ

−ε

+ε

−ε

+ε

The Full-Bridge Bending configuration has the following characteristics:

• Uses four active strain gages.

• Two strain gages, R

(+ε) and R2 (+ε), are mounted in the direction of bending strain on

4

the top of the specimen.

The other two strain gages, R

(–ε) and R1 (–ε), are mounted in the direction of bending

3

strain on the bottom of the specimen.

Figure 30 shows how to connect a Full-Bridge Bending circuit to the DT9838 when using the

general-purpose STP STRAIN accessory and remote sensing.

Note: When remote sensing is used, enter 0 Ω for the lead wire correction coefficient in
software. Refer to page 102 for more information.

Figure 30: Connecting a Full-Bridge Bending Circuit to the DT9838 When Using the

General-Purpose STP STRAIN Accessory and Remote Sensing

60

Remote Sensing in Full-Bridge Bending Configurations

ADC

24-bit

TEDS

SER

Bridge

Excitation

100kΩ

Precision

Instrumentation Amp

EXC +

SENSE+

SENSE -

EXC -

RSHUNT+

RSHUNT-

AIN-

AIN+

10 kΩ

10 kΩ

+

-

RJ50

R

L

R

L

R

L

R

2

R

1

R

3

R

4

R

L

-

+

V

O

6

4

2
3

5

7

10

1

8
9

General-Purpose STP STRAIN

Accessory Connected to DT9838

10 kΩ

100 kΩ

10 kΩ

−ε

+ε

−ε

+ε

Although not required for operation, it is recommended that you connect the bridge SENSE+
and SENSE– leads, as shown in Figure 30 to minimize voltage drops caused by the lead wire
resistance (R
wires and/or small gauge wires, which have greater resistance, are used.

If you do not use remote sense leads, you must connect the sense leads to the excitation leads
(connect SENSE+ to EXC+ and SENSE– to EXC–), as shown in Figure 31, to ensure proper
bridge voltage regulation. If the lead wire resistance is known, you can enter the lead wire
correction coefficient in software. Refer to page 102 for more information.

) of the EXC+ and EXC– lines. This is most important in applications where long

L

Wiring Signals

Figure 31: Connecting a Full-Bridge Bending Circuit to the DT9838 When Using the

General-Purpose STP STRAIN Accessory Without Remote Sensing

Shunt Calibration in Full-Bridge Bending Configurations

When setting up your strain gage, you can use shunt calibration to correct for errors due to
lead wire resistance (R
shunt calibration in a Full-Bridge Bending configuration.

To perform shunt calibration in a full-bridge configuration using the internal 100 kΩ resistor,
connect the RSHUNT+ and RSHUNT– lines across any active gage (R
in Figure 30 and Figure 31. You can then use software to switch 100 kΩ across the selected
gage when no strain is applied to the specimen, creating a known change in the bridge output.

) in the excitation wiring. Refer to page 105 for the equation used for

L

, R2, R3, or R4), as shown

1

61

Chapter 3

Bending

R

4

(+ε)

R

1

(–νε)

R

2

(+νε)

R

3

(–ε)

Strain
Gage

Strain
Gage

Using software, you can then measure the output of the bridge, compare it to the expected
bridge output value, and adjust the gain of the DT9838 to compensate for these errors.

Once you have performed the shunt calibration procedure, you can disconnect the RSHUNT+
and RSHUNT– lines, if desired.

Refer to your software documentation for more information about shunt calibration.

Wiring a Full-Bridge Bending Poisson Configuration

The Full-Bridge Bending Poisson configuration, shown in Figure 32, measures bending strain.
It also rejects axial strain, compensates for temperature, compensates for lead resistance, and
compensates for the aggregate effect on the principle strain measurement due to the Poisson’s
ratio of the specimen material.

62

Figure 32: Full-Bridge Bending Poisson Configuration

The Full-Bridge Bending Poisson configuration has the following characteristics:

• Uses four active strain gages.

• Two strain gages, R

(+ε) and R3 (–ε), are mounted in the direction of bending strain, with

4

one mounted on the top and the other on the bottom of the specimen.

The other two strain gages, R
mounted transversely (perpendicular) to the axis of bending strain, with one mounted on

(+νε) and R1 (–νε), measure the Poisson effect and are

2

the top and the other on the bottom of the specimen.

Figure 30 shows how to connect a Full-Bridge Bending Poisson circuit to the DT9838 when

using the general-purpose STP STRAIN accessory and remote sensing.

Note: When remote sensing is used, enter 0 Ω for the lead wire correction coefficient in

TEDS

SER

Bridge

Excitation

100 kΩ

EXC +

SENSE+

SENSE -

EXC -

RSHUNT+

RSHUNT-

10 kΩ

10 kΩ

RJ50

R

L

R

L

R

2

R

1

R

3

R

4

ADC

24-bit

Precision

Instrumentation Amp

AIN-

AIN+

+

-

R

3

-

+

V

O

6
4

2
3

5
7

10

1

8
9

General-Purpose STP STRAIN

Accessory Connected to DT9838

10 kΩ

100 kΩ

10 kΩ

−νε

+νε

−ε

+ε

software. Refer to page 102 for more information.

Wiring Signals

Figure 33: Connecting a Full-Bridge Bending Poisson Circuit to the DT9838 When Using the

General-Purpose STP STRAIN Accessory and Remote Sensing

Remote Sensing in Full-Bridge Bending Poisson Configurations

Although not required for operation, it is recommended that you connect the bridge SENSE+
and SENSE– leads, as shown in Figure 33, to minimize voltage drops caused by the lead wire
resistance (R
wires and/or small gauge wires, which have greater resistance, are used.

) of the EXC+ and EXC– lines. This is most important in applications where long

L

If you do not use remote sense leads, you must connect the sense leads to the excitation leads
(connect SENSE+ to EXC+ and SENSE– to EXC–), as shown in Figure 34, to ensure proper
bridge voltage regulation. If the lead wire resistance is known, you can enter the lead wire
correction coefficient in software. Refer to page 102 for more information.

63

Chapter 3

ADC

24-bit

TEDS

SER

Bridge

Excitation

100kΩ

Precision

Instrumentation Amp

EXC +

SENSE+

SENSE -

EXC -

RSHUNT+

RSHUNT-

AIN-

AIN+

10 kΩ

10 kΩ

+

-

RJ50

R

L

R

L

R

L

R

2

R

1

R

3

R

4

R

L

-

+

V

O

6

4

2
3

5

7

10

1

8
9

General-Purpose STP STRAIN

Accessory Connected to DT9838

10 kΩ

100 kΩ

10 kΩ

−νε

+νε

−ε

+ε

Figure 34: Connecting a Full-Bridge Bending Poisson Circuit to the DT9838 When Using the

General-Purpose STP STRAIN Accessory Without Remote Sensing

Shunt Calibration in Full-Bridge Bending Poisson Configurations

When setting up your strain gage, you can use shunt calibration to correct for errors due to
lead wire resistance (R
shunt calibration in a Full-Bridge Bending Poisson configuration.

To perform shunt calibration in a full-bridge configuration using the internal 100 kΩ resistor,
connect the RSHUNT+ and RSHUNT– lines across any active gage (R
shown in Figure 33 and Figure 34. You can then use software to switch 100 kΩ across the
selected gage when no strain is applied to the specimen, creating a known change in the
bridge output. Using software, you can then measure the output of the bridge, compare it to
the expected bridge output value, and adjust the gain of the DT9838 to compensate for these
errors.

Once you have performed the shunt calibration procedure, you can disconnect the RSHUNT+
and RSHUNT– lines, if desired.

Refer to your software documentation for more information about shunt calibration.

64

) in the excitation wiring. Refer to page 105 for the equation used for

L

, R2, R3, or R4), as

1

Wiring a Full-Bridge Axial Poisson Circuit

R4 (+ε)

R

3

(–νε)

R2 (+ε)

R1 (–νε)

Strain
Gage

Strain
Gage

Axial

The Full-Bridge Axial Poisson configuration, shown in Figure 35, measures axial strain. It also
compensates for temperature, rejects bending strain, compensates for lead resistance if remote
sense lines are used, and compensates for the aggregate effect on the principle strain
measurement due to the Poisson ratio of the specimen material.

Wiring Signals

Figure 35: Full-Bridge Type Axial Poisson Configuration

The Full-Bridge Axial Poisson configuration has the following characteristics:

• Uses four active strain gages.

• Two strain gages, R

(+ε) and R2 (+ε), are mounted in the direction of axial strain, with one

4

mounted on the top and the other on the bottom of the specimen.

The other two strain gages, R

(–νε) and R1 (–νε), measure the Poisson effect and are

3

mounted transversely (perpendicular) to the axis of axial strain, with one mounted on the
top and the other on the bottom of the specimen.

Figure 36 shows how to connect a Full-Bridge Axial Poisson circuit to the DT9838 when using

the general-purpose STP STRAIN accessory and remote sensing.

Note: When remote sensing is used, enter 0 Ω for the lead wire correction coefficient in
software. Refer to page 102 for more information.

65

Chapter 3

TEDS

SER

Bridge

Excitation

100 kΩ

EXC +

SENSE+

SENSE -

EXC -

RSHUNT+

RSHUNT-

10 kΩ

10 kΩ

RJ50

R

L

R

L

R

2

R

1

R

3

R

4

ADC

24-bit

Precision

Instrumentation Amp

AIN-

AIN+

+

-

R

3

-

+

V

O

6
4

2
3

5
7

10

1

8
9

General-Purpose STP STRAIN

Accessory Connected to DT9838

10 kΩ

100 kΩ

10 kΩ

−νε

+ε

−νε

+ε

Figure 36: Connecting a Full-Bridge Axial Poisson Circuit to the DT9838 When Using the

General-Purpose STP STRAIN Accessory and Remote Sensing

Remote Sensing in Full-Bridge Axial Poisson Configurations

Although not required for operation, it is recommended that you connect the bridge SENSE+
and SENSE– leads, as shown in Figure 36, to minimize voltage drops caused by the lead wire
resistance (R
wires and/or small gauge wires, which have greater resistance, are used.

If you do not use remote sense leads, you must connect the sense leads to the excitation leads
(connect SENSE+ to EXC+ and SENSE– to EXC–), as shown in Figure 37, to ensure proper
bridge voltage regulation. If the lead wire resistance is known, you can enter the lead wire
correction coefficient in software. Refer to page 102 for more information.

66

) of the EXC+ and EXC– lines. This is most important in applications where long

L

Wiring Signals

ADC

24-bit

TEDS

SER

Bridge

Excitation

100kΩ

Precision

Instrumentation Amp

EXC +

SENSE+

SENSE -

EXC -

RSHUNT+

RSHUNT-

AIN-

AIN+

10 kΩ

10 kΩ

+

-

RJ50

R

L

R

L

R

L

R

2

R

1

R

3

R

4

R

L

-

+

V

O

6

4

2
3

5

7

10

1

8
9

General-Purpose STP STRAIN

Accessory Connected to DT9838

10 kΩ

100 kΩ

10 kΩ

−νε

+ε

−νε

+ε

Figure 37: Connecting a Full-Bridge Axial Poisson Circuit to the DT9838 When Using the

General-Purpose STP STRAIN Accessory Without Remote Sensing

Shunt Calibration in Full-Bridge Axial Poisson Configurations

When setting up your strain gage, you can use shunt calibration to correct for errors due to
lead wire resistance (R
shunt calibration in a Full-Bridge Axial Poisson configuration.

To perform shunt calibration in a Full-Bridge Axial Poisson configuration using the internal
100 kΩ resistor, connect the RSHUNT+ and RSHUNT– lines across any active gage (R
or R4), as shown in Figure 36 and Figure 37. You can then use software to switch 100 kΩ across
the selected gage when no strain is applied to the specimen, creating a known change in the
bridge output. Using software, you can then measure the output of the bridge, compare it to
the expected bridge output value, and adjust the gain of the DT9838 to compensate for these
errors.

Once you have performed the shunt calibration procedure, you can disconnect the RSHUNT+
and RSHUNT– lines, if desired.

Refer to your software documentation for more information about shunt calibration.

) in the excitation wiring. Refer to page 105 for the equation used for

L

, R2, R3,

1

67

Chapter 3

TEDS

SER

Bridge

Excitation

100kΩ

DATA

TEDS

EXC +

SENSE+

SENSE -

EXC -

RSHUNT+

RSHUNT-

RTN

10 kΩ

10 kΩ

RJ50

R

2

R

1

R

3

R

4

ADC

24-bit

Precision

Instrumentation Amp

AIN-

AIN+

+

-

R

3

-

+

V

O

6
4

2
3

5
7

10

1

8
9

Load C ell Sensor

General-Purpose STP STRAIN

Accessory Connected to DT9838

10 kΩ

10 kΩ

100 kΩ

Connecting Load Cells and Other Transducers

The DT9838 supports load cells (force sensors) as well as pressure transducers, and/or torque
sensors that are based on the Wheatstone bridge.

These transducers typically use a full-bridge configuration with a 350 Ω nominal bridge
resistance.

Many large load cells use the remote sense wires, as they are located farther away from the
DT9838. Smaller load cells, which are located closer to the DT9838 typically, do not use remote
sense lines; instead, the excitation (EXC+ and EXC–) and remote sense (SENSE+ and SENSE–)
lines are connected at the DT9838.

Figure 38 shows how to connect load cells and other sensors that use remote sensing to the

DT9838 when connected to the general-purpose STP STRAIN accessory. Figure 39 shows how
to connect load cells and other sensors that do not use remote sensing to the DT9838 when
connected to the general-purpose STP STRAIN accessory.

Notes: In load-cell configurations, the RSHUNT– and RSHUNT+ lines are not used, but
optionally can be connected at the DT9838. TEDS connections are also optional.

Refer to the sensor manufacturer for information on wiring to your sensor type.

Figure 38: Connecting a Load Cell or Other Transducer to the DT9838 When Using the

General-Purpose STP STRAIN Accessory and Remote Sensing

68

Wiring Signals

TEDS

SER

Bridge

Excitation

100 kΩ

DATA

TEDS

EXC +

SENSE+

SENSE -

EXC -

RSHUNT+

RSHUNT-

RTN

10 kΩ

10 kΩ

RJ50

R

L

R

2

R

1

R

3

R

4

R

L

ADC

24-bit

Precision

Instrumentation Amp

AIN-

AIN+

+

-

R

3

-

+

V

O

6

4

2

3

5

7

10

1

8
9

Load Cell Sensor

General-Purpose STP STRAIN

Accessory Connected to DT9838

10 kΩ

10 kΩ

100 kΩ

Figure 39: Connecting a Load Cell or Other Transducer to the DT9838

Without Using Remote Sensing

69

Chapter 3

ADC

24-bit

TEDS

SER

Bridge

Excitation

100 kO

Precision

Instrumentation Amp

AIN-

AIN+

10 kO

10 kO

+

-

Voltage Source

(+/- 250 mV
Full-Scale)

3

2

5

1

8
9

7

10

4

6

Device Under Test

General-Purpose STP STRAIN

Accessory Connected to DT9838

+

-

R*

*To minimize noise pickup,
reference pin 3 to analog
ground with a resistor
between 100

O

and 10 kO.

10 kΩ

100 kΩ

10 kΩ

Ω.

Ω

Connecting Voltage Inputs

Figure 40 shows how to connect a voltage input source to a channel of the DT9838 when it is

connected to a general-purpose STP STRAIN accessory. Note that the voltage source must be
in the ±250 mV full-scale range.

Figure 40: Connecting Voltage Inputs to the DT9838 When Using the General-Purpose

70

STP STRAIN Accessory

Note: For best accuracy when connecting voltage inputs, use twisted-pair wires.

Connecting a Tachometer Input Signal

Signal

Source

Tachometer In - Pin 1

Tachometer Return - Pin 2

Ext Trigger and

Tachometer

Connector

You can connect a ±30 V tachometer input signal to External Trigger and Tachometer
connector (J6) on the DT9838 module, as shown in Figure 41.

Note: In software, you can read tachometer measurements as part of the analog input
channel list. Refer to page 112 for more information on tachometer measurements.

Wiring Signals

Figure 41: Connecting a Tachometer Input Signal to the DT9838 Module

71

Chapter 3

External Trigger - Pin 3

Ext Trigger and

Tachometer

Connector

External Trigger Return - Pin 4

Tri gger
Source

Connecting an External Trigger Signal

You can connect an external digital trigger signal to the External Trigger and Tachometer
connector (J6) on the DT9838 module, as shown in Figure 42. Refer to page 112 for more
information on the external digital trigger.

Figure 42: Connecting an External Trigger Input Signal to the DT9838 Module

72

4

Verifying the Operation of a Module

Select the Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

Measure Strain Gage Data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

73

Chapter 4

Set Up and Install the Module

(see Chapter 2 starting on page 27)

Wire Signals

(see Chapter 3 starting on page 37)

Verify the Operation of the Module

(this chapter)

You can verify the operation of a DT9838 module using the QuickDAQ application.

QuickDAQ allows you to acquire and analyze data from all Data Translation USB and
Ethernet devices, except the DT9841 Series, DT9817, DT9835, and DT9853/54. This chapter
describes how to verify the operation of a DT9838 module using the QuickDAQ base version.

74

Select the Device

To get started with your DT9838 module and QuickDAQ, follow these steps:

1. Connect the DT9838 module to the USB port of your computer, and connect your strain

gage sensors to the module.

2. Start the QuickDAQ application.

The Device Selection window appears.

Verifying the Operation of a Module

3. For the Device Family selection, select OpenLayersDevices.

By default, the application "discovers" all devices that are available for the specified
device family and displays the module name for the USB devices in the drop-down list. If
you want to refresh this list to determine if other devices are available, click Refresh.

4. Select the module name for the DT9838 module that you want to use from the list of

Available Devices, and click Add.

Information about the device, including the model number, serial number, firmware version, driver
version, and scanning status is displayed.

75

Chapter 4

5. If you want to rename your device, do the following:

a. Click the Row Selector button for the device.

b. Click the IP address or module name in the Name column to highlight it and enter a

meaningful name to represent each available device.

6. If you are using multiple devices, you must configure one device as the clock and trigger

master, as follows:

a. Click the Row Selector button for the device that you want to be the clock and trigger

master.

b. For the clock and trigger master device, check the box under the Master column.

Note: Only one device can be the clock and trigger master. If you are using a single

device, the application automatically configures the device as the master.

The DT9838 devices support that capability of synchronizing up to four devices. If you are
using more than one of these devices, ensure that you connect the devices together using
network cables and the Synchronization (RJ45) connector on each device. Then, configure
one device as the master and the other devices as slaves. The software automatically
drives out the appropriate clock and trigger signals. Refer to page 114 for more
information on syncrhonizing devices.

76

7. (Optional) If you want to remove a device from list of selected devices, click the Row

Selector button for the device, and then click Remove.

8. Once you have added all the devices that you want to use with the application, click OK.

The latest state is saved and used when the application is next run, and the interface of the
QuickDAQ is displayed.

Verifying the Operation of a Module

77

Chapter 4

Measure Strain Gage Data

The following steps describe how to use the QuickDAQ application to configure a strain gage
measurement.

This example uses a full-bridge strain gage (full-bridge bending configuration) connected to a
DT9838 module to measure strain.

Configure the Channels

Configure the channels as follows:

1. Ensure that the strain gage is connected to your data acquisition device.

In this example, the strain gage is connected to analog input channel 0 of the DT9838. Refer to

Figure 30 on page 60 for the wiring diagram used for a full-bridge bending configuration.

2. Configure each analog input channel by clicking the Input Channel Configuration

toolbar button ( ) or by clicking the Configuration menu and clicking Input

Channel Configuration.

3. Enable analog input channel 0 by clicking the Enable checkbox for analog input channel

0.

78

4. In the Channel Name column, enter Full Bridge Bending for the name of analog input

channel 0.

5. In the Enable Shunt Resistor column, leave the checkbox unchecked; this disables the

shunt resistor.

6. Click the Configure and Calibrate button.

The following wizard appears:

Verifying the Operation of a Module

7. Select Strain Gage, and click Next. (Note that TEDS is not supported for this sensor;

therefore, you do not need to click the Open TEDS data file... button.)

A screen similar to the following appears:

79

Chapter 4

8. For the Bridge Type field, select the bridge configuration of your strain gage.

In this example, the Full Bridge Bending bridge configuration is used.

9. For the Excitation Voltage field, enter the excitation voltage value for your strain gage.

In this example, 5 V is used as the excitation voltage value.

10. For the Nominal Gage field, enter the nominal gage resistance, in ohms, for your strain

gage as determined by the manufacturer.

In this example, 350 is used as the nominal gage resistance.

11. For the Gage Factor field, enter the gage factor for your strain gage as determined by the

manufacturer.

In this example, 2 is used as the gage factor.

12. For the Using Sense Lines field, select Yes if you are using remote sense lines in your

wiring, or No if you are not using remote sensing in your wiring.

In this example, remote sensing is not used.

13. For the Lead Wire Resistance field, enter the lead wire resistance, in ohms, for your strain

gage.

In this example, 0.1 is used as the lead wire resistance.

14. For the Min Range field, enter the minimum value of the range for your strain gage.

In this example, –1000 is used as the minimum strain value.

80

Verifying the Operation of a Module

15. For the Max Range field, enter the maximum value of the range for your strain gage.

In this example, 1000 is used as the maximum strain value.

16. For the Units field, select the engineering units for the strain gage.

In this example, μStrain is used.

17. In the Poisson Ratio column, enter the Poisson ratio for your strain gage.

In this example, the Poisson ratio is not used.

18. Click Next.

A screen similar to the following appears:

19. Select the calibration steps to perform.

In this example, Offset Nulling and Shunt Calibration are selected.

20. Click Next.

A screen similar to the following appears:

81

Chapter 4

21. Ensure that the bride is in the unstrained state, and the click the Calibrate button to

perform offset nulling procedure.

The expected voltage is shown along with the calibrated offset voltage.

82

Verifying the Operation of a Module

22. Click Next.

A screen similar to the following appears:

83

Chapter 4

23. For the Select Resistor Source field, select Internal if you are using the internal shunt

resistor provided on the DT9838 module to perform shunt calibration, or External if you
are using your own external resistor to perform shunt calibration.

In this example, Internal is used.

24. For the Select Node to Shunt field, select the resistive node or element to which to apply

the shunt resistor.

In this example, R2 is used.

25. Click Calibrate to perform the shunt calibration procedure.

The calculated value is displayed along with the measured value and correction coefficient.

84

Verifying the Operation of a Module

26. Click Finish.

27. If desired, enter a test point number under the Point # column.

In this example, 1 is used.

28. Click Close to close the Configure Devices dialog box.

85

Chapter 4

Configure the Recording Settings

For this example, configure the recording settings as follows:

1. Click the Recording tab of the Acquisition Config window.

86

2. For Filename generation, use the default Filename option.

3. For Filename, use the default name for the data file.

4. Leave the Enable Continuous Acquisition checkbox unchecked.

5. For Acquisition Duration, enter 5 seconds.

The number of seconds for the total run and the amount of available disk space are shown.

6. For X Span Axis, enter 5 seconds.

Configure the Acquisition Settings

For this example, configure the acquisition settings as follows:

1. Click the Acquisition tab of the Acquisition Config window.

Verifying the Operation of a Module

87

Chapter 4

2. For the Per Channel Sampling Frequency text box, enter 1000.

The sampling rate, sample interval, and number of scans are displayed.

3. For the Trigger Source check box, select Software to ensure that the measurement starts

as soon as the Record button is clicked.

Start the Operation

Once you have configured the channels, start acquisition and log data to disk by clicking the
Record toolbar button ( ).

Results similar to the following are displayed in the Channel Plot window.

88

Note: Many additional options are provided in QuickDAQ for measuring and analyzing the
data. Refer to the QuickDAQ User’s Manual for detailed information.

Part 2: Using Your Module

5

Principles of Operation

Analog Input Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

Tachometer Input Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

Synchronizing Acquisition on Multiple Modules. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

91

Chapter 5

Acquisit ion Ctrl

Input
FIFO

8 ksamples

Trigger

4 pos
Screw

Terminal

ADC

24-bit

Bus I nte rfac e

&

Control Registers

Tach

Clocks

&

Trigge rs

ADC
PCG

Tach

PLL_REF_CLK

32-bit

LVDS

LVDS

LVDS

Sync
Sync

In/Out

Tach

SyncBus

Sync

Ref
Clock
In/Out

Trigger

In/Out

ID/CAL

EEPROM

SRAM
128KB

USB

USB 2.0

High-Speed

Interfac e

RJ45

Trigger

DAC

16-bit

TEDS

SER

ADC

24 bit

Bridge

Input 3

ADC

24 bit

Bridge

Input 2

ADC

24 bit

Bridge

Input 1

Bridge

Excitation

100kO

Prec ision

Instrum entation

Amp

DATA

TEDS

EXC +

SENSE+

SENSE -

EXC -

RSHUNT+

RSHUNT-

RTN

AIN-

AIN+

10kO

10kO

+

-

RJ50

Bridge

Input 0

Figure 43 shows a block diagram of the DT9838 module.

92

Figure 43: Block Diagram of the DT9838 Module

Analog Input Features

This section describes the following features of the analog input (A/D) subsystem on the
DT9838 module:

• Analog input channels, described on this page

• Bridge configurations, described on page 94

• Transducer support, described on page 101

• Bridge excitation, described on page 102

• Remote sensing and lead wire correction, described on page 102

• Shunt calibration, described on page 103

• TEDS, described on page 105

• Input resolution, described on page 106

• Input ranges and gains, described on page 106

• Sample clock sources, described on page 106

• Conversion modes, described on page 107

Principles of Operation

• Triggers, described on page 109

• Data format, described on page 111

• Error conditions, described on page 111

Analog Input Channels

The DT9838 module supports four, simultaneous, analog input channels that accept bridge
sensors through RJ50 connectors on the module.

You can acquire data from a single analog input channel or from a group of analog input
channels on the module. Analog input channels are numbered 0 to 3.

The following subsections describe how to specify the channels.

Specifying a Single Analog Input Channel

The simplest way to acquire data from a single analog input channel is to specify the channel
for a single-value analog input operation using software; refer to page 107 for more
information about single-value operations.

Specifying One or More Analog Input Channels

You can read data from one or more analog input channels by specifying the channel (0 to 3) in
the analog input channel list.

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Chapter 5

R

3

R

2

R

1

V

EX+

R

4

V

O

–

+

The DT9838 module also allows you to read the value of the tachometer input in the analog
input data stream. This feature is particularly useful when you want to correlate the analog
input measurements with tachometer data. Refer to page 112 for more information about the
tachometer input channel.

Using software, specify the channels that you want to sample. For the DT9838, you can enter
up to five entries in the analog channel list, including the analog input channels (0 to 3) and
the tachometer input (channel 4).

Because this module features simultaneous sampling, the order of the channels in the channel
list does not matter. You cannot specify the same channel more than once in the list.

Bridge Configurations

All strain gage configurations are based on the concept of a Wheatstone bridge. A Wheatstone
bridge is a network of four resistive legs, or nodes. One or more of these nodes can be active
sensing element. Figure 44 shows a basic circuit diagram of a Wheatstone bridge.

Figure 44: Wheatstone Bridge Circuit Diagram

The Wheatstone bridge is the electrical equivalent of two parallel voltage divider circuits. R

comprise one voltage divider circuit, and R

and R

2

divider circuit. The output of a Wheatstone bridge is measured between the middle nodes of
the two voltage dividers (V

).

O

Physical phenomena, such as a change in strain applied to a specimen or a temperature shift,
changes the resistance of the active sensing elements in the Wheatstone bridge. The

and R3 comprise the second voltage

4

1

Wheatstone bridge configuration is used to help measure the small variations in resistance
that the sensing elements produce corresponding to a physical change in the specimen.

94

Principles of Operation

A strain gage is a collection of all the active elements of a Wheatstone bridge. You use different
bridge configurations for different tasks. For each analog input channel, the DT9838 module
supports the following bridge configurations to measure axial and/or bending strain:

•Quarter-Bridge

• Quarter-Bridge Temp Comp

• Half-Bridge Poisson

• Half-Bridge Bending

• Full-Bridge Bending

• Full-Bridge Bending Poisson

• Full-Bridge Axial Poisson

Note: If you do not wish to use a bridge, you can also configure the channel for a voltage
measurement.

You specify the bridge configuration in software. The bridge configuration that you select
determines the way you wire the sensor elements to the channel. Refer to Chapter 3 starting
on page 37 for more information on how to wire these bridge configurations to the DT9838
module.

Measured strain is determined by referencing the acquired data when the bridge is in the
strained condition to the acquired data when the bridge in an unstrained condition. The
difference in measurements is then applied to the appropriate strain transfer function for the
particular bridge configuration, which yields a value of strain in units of strain or microstrain.
This transfer function can be modified by including corrections for lead wire resistance
and/or shunt calibration.

The following sections provide the circuit diagram for each of the supported bridge
configurations as well as the bridge transfer function that the DT9838 uses to convert voltage
to strain for each configuration. The following terms are used in this section:

• ε is the measured strain (+e is the tensile strain and –ε is the compressive strain).

• GF is the gage factor, which is specified by the gage manufacturer. You specify this value
in software for each bridge (analog input channel).

•R

is the nominal gage resistance, which is specified by the gage manufacturer. You

g

specify this value in software for each bridge (analog input channel).

•R

is the lead wire resistance. You specify this value in software for each bridge (analog

L

input channel).

• ν is the Poisson ratio, defined as the negative ratio of transverse strain to axial
(longitudinal) strain. You specify this value in software for each bridge (analog input
channel).

•V

is the excitation voltage. You specify this value in software. Refer to page 102 for more

EX

information on the excitation voltage.

•V

is the initial, unstrained voltage output.

u

95

Chapter 5

Vr

Vs Vu–

VEX

-------------------=

R

1

R

2

R

3

User-supplied

R

4 (Rg

= ε)

R

L

R

L

R

L

In this diagram:

R

1

and R2 are half-bridge completion resistors

that are provided by the DT9838.

R

3

is the quarter-bridge completion resistor

that you must supply.

R

4

is the active strain-gage element that

measures the tensile strain (R

g

= +ε).

V

EX

V

O

+
–

+

–

Strain ε()

4Vr–

GF 12Vr+()

-------------------------------=

•Vs is the measured voltage output when strained.

•V

is the voltage ratio that is used in the voltage-to-strain conversion equations and is

r

defined by the following equation:

Quarter-Bridge Configuration

Figure 45 shows the circuit diagram that the DT9838 uses for a 3-wire Quarter-Bridge

configuration.

Note: This configuration is used with rectangular and delta rosettes. Tee rosettes are not
supported. Refer to page 44 for more information on rosettes.

Figure 45: Quarter-Bridge Circuit Diagram

For a 3-wire Quarter-Bridge configuration, the following bridge transfer function is used to
convert voltage to strain when lead wire correction and shunt calibration are not used:

Refer to page 102 for more information on lead wire resistance; refer to page 103 for more
information on shunt calibration.

Refer to page 44 for information on wiring a Quarter-Bridge configuration to the DT9838.

96

Principles of Operation

In this diagram:

R

1

and R2 are half-bridge completion resistors

that are provided by the DT9838.

R

4

is an active strain-gage element that
measures axial or bending strain in the
principal direction of strain (R

g

= +ε).

R

3

is a dummy strain gage element (Rg =
dummy gage) that has the same nominal
resistance and temperature coefficient as R

4

.

R

1

R

2

R3 (Rg = dummy)

R

L

R

L

R

L

V

EX

V

O

+
–

+

–

R

4 (Rg

= ε)

Strain ε()

4Vr–

GF 12Vr+()

-------------------------------=

Quarter-Bridge Temp Comp Configuration

Figure 46 shows the circuit diagram that the DT9838 uses for the Quarter-Bridge Temp Comp

configuration. This circuit diagram (and bridge transfer function) is also used for a
Quarter-Bridge configuration where the user places a resistor at the strain gage.

Figure 46: Quarter-Bridge Temp Comp Circuit Diagram

For the Quarter-Bridge Temp Comp configuration, the following bridge transfer function is
used to convert voltage to strain when lead wire correction and shunt calibration are not used:

Refer to page 102 for more information on lead wire resistance; refer to page 103 for more
information on shunt calibration.

Refer to page 49 for information on wiring a Quarter-Bridge Temp Comp configuration to the
DT9838.

Half-Bridge Poisson Configuration

Figure 47 shows the circuit diagram that the DT9838 uses for the Half-Bridge Poisson

configuration.

97

Chapter 5

In this diagram:

R

1

and R2 are half-bridge completion resistors that

are provided by the DT9838.

R

4

is the active strain-gage element that measures
strain in the direction of axial or bending strain
(R

g

= +ε).

R

3

is the active strain gage that measures strain in the
direction perpendicular to the principal axis of strain
(R

g

= –νε).

R

1

R

2

R3 (Rg= –νε

R

L

R

L

R

L

V

EX

V

O

+
–

+

–

R

4 (Rg

= ε)

Strain ε()

4Vr–

GF 1 ν+()2V r ν 1–()–[]

------------------------------------------------------------=

In this diagram:

R

1

and R2 are half-bridge completion resistors

that are provided by the DT9838.

R

3

(Rg = –ε) and R4 (Rg = +ε) are both active
strain gages mounted in the direction of
bending strain but on opposite sides of the
specimen.

R

1

R

2

R3 (Rg = –ε

R

L

R

L

R

L

V

EX

V

O

+
–

+

–

R

4 (Rg

= ε)

Figure 47: Half-Bridge Poisson Circuit Diagram

For the Half-Bridge Poisson configuration, the following bridge transfer function is used to
convert voltage to strain when lead wire correction and shunt calibration are not used:

Refer to page 102 for more information on lead wire resistance; refer to page 103 for more
information on shunt calibration.

Refer to page 52 for information on wiring a Half-Bridge Poisson configuration to the DT9838.

Half-Bridge Bending Configuration

Figure 48 shows the circuit diagram that the DT9838 uses for the Half-Bridge Bending

configuration.

Figure 48: Half-Bridge Bending Circuit Diagram

98

For the Half-Bridge Bending configuration, the following bridge transfer function is used to

Strain ε()

2Vr–

GF

------------=

In this diagram:

Four active strain gage elements are used.

R

1

(–ε) and R3 ( –ε) are mounted in the direction of

bending strain on the bottom of the specimen.

R

2

(+ε) and R4 (+ε) are mounted in the direction of

bending strain on the top of the specimen.

R

1

(–ε)

V

EX

V

O

+
–

+

–

R

2

(+ε)

R

3

(–ε)

R

4

(+ε)

R

L

R

L

Strain ε()

Vr–

GF

--------=

convert voltage to strain when lead wire correction and shunt calibration are not used:

Refer to page 102 for more information on lead wire resistance; refer to page 103 for more
information on shunt calibration.

Refer to page 56 for information on wiring a Half-Bridge Bending configuration to the
DT9838.

Full-Bridge Bending Circuit

Figure 49 shows the circuit diagram that the DT9838 uses for the Full-Bridge Bending

configuration.

Principles of Operation

Figure 49: Full-Bridge Bending Circuit Diagram

For the Full-Bridge Bending configuration, the following bridge transfer function is used to
convert voltage to strain when lead wire correction and shunt calibration are not used:

Refer to page 102 for more information on lead wire resistance; refer to page 103 for more
information on shunt calibration.

Refer to page 59 for information on wiring a Full-Bridge Bending configuration to the DT9838.

99

Chapter 5

In this diagram:

Four active strain gage elements are used.

R

3

(–ε) and R4 (+ε) are mounted in the direction of

bending strain with R

4

mounted on the top of the

specimen and R

3

mounted on the bottom of the

specimen.

R

1

(–νε) and R2 (+νε) act together as a Poisson

gage and are mounted perpendicular to the
principal axis of strain with R

1

mounted on the

top of the specimen and R

2

mounted on the

bottom of the specimen.

R

1

(–νε)

V

EX

V

O

+
–

+

–

R

2

(+νε)

R

3

(–ε)

R

4

(+ε)

R

L

R

L

Strain ε()

2Vr–

GF 1 ν+()

--------------------------=

Full-Bridge Bending Poisson Configuration

Figure 50 shows the circuit diagram that the DT9838 uses for the Full-Bridge Bending Poisson

configuration.

Figure 50: Full-Bridge Bending Poisson Circuit Diagram

For the Full-Bridge Bending Poisson configuration, the following bridge transfer function is
used to convert voltage to strain when lead wire correction and shunt calibration are not used:

Refer to page 102 for more information on lead wire resistance; refer to page 103 for more
information on shunt calibration.

Refer to page 62 for information on wiring a Full-Bridge Bending Poisson configuration to the
DT9838.

100

Full-Bridge Axial Poisson Configuration

In this diagram:

Four active strain gage elements are used.

R

2

(+ε) and R4 (+ε) are mounted in the direction of axial

strain with R

2

mounted on the top of the specimen and

R

4

mounted on the bottom of the specimen.

R

1

(–νε) and R3 (–νε) act together as a Poisson gage

and are mounted perpendicular to the principal axis of
strain with R

1

mounted on the top of the specimen and

R

3

mounted on the bottom of the specimen.

R

1

(–νε)

V

EX

V

O

+
–

+

–

R

2

(+ε)

R

3

(–νε)

R

4

(+ε)

R

L

R

L

Strain ε()

2Vr–

GF ν 1+()Vr ν 1–()–[]

---------------------------------------------------------=

Figure 51 shows the circuit diagram that the DT9838 uses for the Full-Bridge Axial Poisson

configuration.

Principles of Operation

Figure 51: Full-Bridge Axial Poisson Circuit Diagram

For the Full-Bridge Axial Poisson configuration, the following bridge transfer function is used
to convert voltage to strain when lead wire correction and shunt calibration are not used:

Refer to page 102 for more information on lead wire resistance; refer to page 103 for more
information on shunt calibration.

Refer to page 65 for information on wiring a Full-Bridge Axial Poisson configuration to the
DT9838.

Transducer Support

In addition to strain gages, the DT9838 supports a variety of transducer types, including load
cells, pressure transducers, and torque sensors that are based on the Wheatstone bridge.

A load cell, which consists of a number of strain gages, measures load and force by
determining the deformation of a structural member as a load or force is applied. Pressure
transducers, which consist of strain gages mounted on a diaphragm, measure the deformation
of the diaphragm that is proportional to the pressure that is applied. Torque sensors, which
consist of strain gages mounted on a torsion bar, measure the shear stress as the torsion bar
turns that is proportional to the torque.

101

Chapter 5

To use these transducers, configure the analog input channel for a full-bridge configuration.
These transducers typically use 350 Ω nominal bridge resistance. Refer to page 68 for wiring
information.

Instead of supplying a gage factor, use software to enter the sensitivity of the unit provided by
the manufacturer of the transducer. For example, a load cell rated for 100 pounds with a
2 mV/V output has a full-scale output of 20 mV when using 10 V of excitation.

Some transducers also support TEDS or virtual TEDS. The DT9838 provides TEDS support to
interface to these transducers directly. Refer to page 105 for more information on TEDS.

Bridge Excitation

Using software, you can program the analog input subsystem on the DT9838 to accept an
internal bridge excitation source between 0 VDC and 10 VDC, with better than 1 mV of
resolution. The internal bridge excitation circuitry consists of a 16-bit DAC that programs the
bridge excitation for all four channels, and a separate bridge drive and sense amplifier for
each channel for individual channel regulation. Each channel is also individually current
limited to 50 mA.

The DT9838 can be operated on USB power alone; however, you may not be able to use all the
channels depending on the bridge resistance and excitation voltage. Alternatively, you can
powered the DT9838 using an external 5 VDC to 24 VDC power supply. Refer to is shown in

Table 1 on page 31 for detailed information on the number of channels supported with USB

power or external power using various bridge and excitation voltage configurations.

Remote Sensing and Lead Wire Correction

All bridge types, with the exception of the 3-wire Quarter-Bridge configuration, support the
use of remote sense lines (SENSE+ and SENSE–). Refer to Chapter 3 starting on page 37 for
connection information. The remote sense lines continuously monitor the voltage that is
applied across the bridge at the bridge connection points and null the effects of lead wire
resistance by regulating the excitation voltage across a remotely located bridge or half bridge.

If you do not use the remote sense lines to regulate the bridge, the sense lines must still be
connected to the excitation lines either at the screw terminal panel or as the lines exit the RJ50
connector (connect SENSE+ to EXC+ and SENSE– to EXC–). You then have the option to
correct for lead wire effects in software by entering the value of the lead wire resistance from
the DT9838 module to the strain gage. Use the same gage wire for the EXC+ and EXC– lines to
ensure that the resistances are matched. Using software, enter the resistance of one line, not
the sum of the two lines. The software applies the correction coefficient to the bridge transfer
function for the particular channel.

102

Note: If the remote sense leads are used, enter a lead wire resistance correction value of 0 Ω.
The module cannot detect whether the remote sense lines have been connected or not, so you
must be aware of how the strain gage was wired and determine the appropriate lead wire
correction value.