Tektronix Keithley DAS-16 Series User's Manual 62045A User manual

DAS-16 Series

User’s Manual

A GREATER MEASURE OF CONFIDENCE

WARRANTY

Hardware

Keithley Instruments, Inc. warrants that, for a period of one (1) year from the date of shipment (3 years for Models 2000,
2001, 2002, 2010 and 2700), the Keithley Hardware product will be free from defects in materials or workmanship. This
warranty will be honored provided the defect has not been caused by use of the Keithley Hardware not in accordance with
the instructions for the product. This warranty shall be null and void upon: (1) any modification of Keithle y Hardw are that
is made by other than Keithley and not approved in writing by Keithley or (2) operation of the Keithley Hardware outside
of the environmental specifications therefore.

Upon receiving notification of a defect in the Keithley Hardware during the warranty period, Keithley will, at its option,
either repair or replace such Keithley Hardware. During the first ninety days of the warranty period, Keithley will, at its
option, supply the necessary on site labor to return the product to the condition prior to the notification of a defect. Failure
to notify Keithley of a defect during the warranty shall relieve Keithley of its obligations and liabilities under this
warranty.

Other Hardware

The portion of the product that is not manufactured by Keithley (Other Hardware) shall not be covered by this warranty,
and Keithley shall have no duty of obligation to enforce an y manufacturers' warranties on behalf of the customer. On those
other manufacturers’ products that Keithley purchases for resale, Keithley shall have no duty of obligation to enforce any
manufacturers’ warranties on behalf of the customer.

Software

Keithley warrants that for a period of one (1) year from date of shipment, the Keithle y produced portion of the software or
firmware (Keithley Software) will conform in all material respects with the published specifications provided such K eithley
Software is used on the product for which it is intended and otherwise in accordance with the instructions therefore.
Keithley does not warrant that operation of the Keithle y Software will be uninterrupted or error -free and/or that the Keithley
Software will be adequate for the customer's intended application and/or use. This warranty shall be null and void upon any
modification of the Keithley Software that is made by other than Keithle y and not approved in writing by Keithley.

If Keithley receiv es notification of a Keithle y Software nonconformity that is cov ered by this warranty during the warranty
period, Keithley will revie w the conditions described in such notice. Such notice must state the published specification(s)
to which the Keithley Software fails to conform and the manner in which the Keithley Software fails to conform to such
published specification(s) with sufficient specificity to permit Keithley to correct such nonconformity. If Keithley deter­mines that the Keithley Software does not conform with the published specifications, Keithley will, at its option, provide
either the programming services necessary to correct such nonconformity or develop a program change to bypass such
nonconformity in the Keithley Software. Failure to notify Keithley of a nonconformity during the warranty shall relieve
Keithley of its obligations and liabilities under this warranty.

Other Software

OEM software that is not produced by Keithley (Other Software) shall not be covered by this w arranty, and Keithley shall
have no duty or obligation to enforce any OEM's warranties on behalf of the customer.

Other Items

Keithley warrants the following items for 90 days from the date of shipment: probes, cables, rechar geable batteries, diskettes,
and documentation.

Items not Covered under Warranty

This warranty does not apply to fuses, non-rechargeable batteries, damage from battery leakage, or problems arising from
normal wear or failure to follow instructions.

Limitation of Warranty

This warranty does not apply to defects resulting from product modification made by Purchaser without Keithley's express
written consent, or by misuse of any product or part.

Disclaimer of Warranties

EXCEPT FOR THE EXPRESS WARRANTIES ABOVE KEITHLEY DISCLAIMS ALL OTHER WARRANTIES,
EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION, ALL IMPLIED WARRANTIES OF MERCHANT­ABILITY AND FITNESS FOR A PARTICULAR PURPOSE. KEITHLEY DISCLAIMS ALL WARRANTIES WITH
RESPECT TO THE OTHER HARDWARE AND OTHER SOFTWARE.

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KEITHLEY INSTRUMENTS SHALL IN NO EVENT, REGARDLESS OF CAUSE, ASSUME RESPONSIBILITY FOR
OR BE LIABLE FOR: (1) ECONOMICAL, INCIDENTAL, CONSEQUENTIAL, INDIRECT, SPECIAL, PUNITIVE OR
EXEMPLARY DAMAGES, WHETHER CLAIMED UNDER CONTRACT, TORT OR ANY OTHER LEGAL THEORY,
(2) LOSS OF OR DAMAGE TO THE CUSTOMER'S DATA OR PROGRAMMING, OR (3) PENALTIES OR PENALTY
CLAUSES OF ANY DESCRIPTION OR INDEMNIFICATION OF THE CUSTOMER OR OTHERS FOR COSTS, DAM­AGES, OR EXPENSES RELATED TO THE GOODS OR SERVICES PROVIDED UNDER THIS WARRANTY.

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BELGIUM: Keithley Instruments B.V. Bergensesteenweg 709 • B-1600 Sint-Pieters-Leeuw • 02/363 00 40 • Fax: [phone]
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09/00

DAS-16 Series

User’s Guide

©1999, Keithley Instruments, Inc.

All rights reserved.

Cleveland, Ohio, U.S.A.

First Printing, October 2000

Document Number: 62045 Rev. A

New Contact Information

Keithley Instruments, Inc.

28775 Aurora Road

Cleveland, OH 44139

Technical Support: 1-888-KEITHLEY

Monday – Friday 8:00 a.m. to 5:00 p.m (EST)

Fax: [phone]

Visit our website at http://www.keithley.com

The information contained in this manual is believed to be accurate and reliable. However, the
manufacturer assumes no responsibility for its use; nor for any infringements of patents or other rights
of third parties that may result from its use. No license is granted by implication or otherwise under any
patent rights of the manufacturer.

THE MANUFACTURER SHALL NOT BE LIABLE FOR ANY SPECIAL, INCIDENTAL, OR
CONSEQUENTIAL DAMAGES RELATED TO THE USE OF THIS PRODUCT. THIS PRODUCT IS
NOT DESIGNED WITH COMPONENTS OF A LEVEL OF RELIABILITY THAT IS SUITED FOR
USE IN LIFE SUPPORT OR CRITICAL APPLICATIONS.

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

Part Number 24840
Revision H, September 1999

©Copyright Keithley Instruments, Inc., 1999, 1997, 1993.

All rights reserved. Reproduction or adaptation of any part of this documentation beyond that permitted
by Section 117 of the 1979 United States Copyright Act without permission of the Copyright owner
is unlawful.

Keithley Instruments, Inc.

28775 Aurora Road, Cleveland, OH 44139

Telephone: [phone] • FAX: [phone]

http://www.keithley.com

Preface

This guide describes how to set up, install, and operate the following
Keithley products:

The DAS-16, and DAS-16F boards, which are referred to collectively

●

as DAS-16/16F Series boards.

●

The DAS-16G1 and DAS-16G2 boards, which are referred to
collectively as DAS-16G1/G2 Series boards.

Unless this manual refers specifically to a particular board, it refers to all
models collectively as the DAS-16 Series boards.

To follow the information and instructions contained in this manual, you
must be familiar with the operation of an IBM
computer in the Windows (95/98, or NT) environment. You must also be
familiar with data acquisition principles and the requirements of your
applications.

PC AT, or equivalent

vii

Manual Organization

The following table lists the topics this guide focuses on and indicates
where you can find information about a topic.

To learn more about See

The capabilities of DAS-16 Series boards
What software is available for the boards Section 1
What accessories are available for the boards Section 1
Functionality of DAS-16 Series boards Section 2
Installing the DAS-16 Series DriverLINX and associated software Section 3
Setting up switch-selectable options Section 3
Installing your boards Section 3
Attaching accessories Section 4
Precautions to observe when connecting signals Section 4
Using the DriverLINX Analog I/O Panel software for test

and data acquisition
Calibrating the board Section 6
Troubleshooting and obtaining technical support Section 7
DAS-16 Series specifications Appendix A
I/O connector pin assignments Appendix B

Section 1

Section 5

The register level I/O map Appendix C
IBM DMA Structure Appendix D

viii

Related Documents

You can find more information on DAS-16 Series software and
accessories in the related documents listed in the following table.

EXP-16 & EXP-16/A Expansion Multiplexer/Amplifier System User’s Guide
EXP-GP Signal Conditioning Multiplexer User’s Guide
MB Series User’s Guide
ISO-4 User’s Guide

DriverLINX User’s Guides:

DriverLINX Installation and Configuration Guide

DriverLINX Appendix F: Configuration and Implementation Notes for
Keithley DAS-16/1600
DriverLINX Analog I/O Programming Guide
DriverLINX Digital I/O Programming Guide
DriverLINX Counter/Timer Programming Guide

Document

ix

x

Table of Contents

Manual Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .viii

Related Documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ix

Overview

1

System requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-2

Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-3

Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-4

Accessories. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5

2

Functional Description

Analog Input Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-4

Differential/Single-Ended Selection . . . . . . . . . . . . . . . . . . . .2-4

Unipolar/Bipolar Selection . . . . . . . . . . . . . . . . . . . . . . . . . . .2-4

Channel Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-5

Channel Selection in Expanded Configurations. . . . . . . . .2-6

Selecting Input Channel Range and Gain . . . . . . . . . . . . .2-7

Clock Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-8

Triggers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-10

Hardware Gates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-12

Data Transfer Modes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-14

Analog Output Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-15

Used with an AC Reference (Digital Attenuator). . . . . . .2-16

Arbitrary Waveform Output . . . . . . . . . . . . . . . . . . . . . . .2-17

Digital I/O Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-18

Counter/Timer Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-19

Using the Timer-Counter Enable with the Counter. . . . . . . .2-27

Generating Square Waves of Programmed Frequency . . . . .2-27

Measuring Frequency and Period . . . . . . . . . . . . . . . . . . . . .2-28

Frequency Measurement . . . . . . . . . . . . . . . . . . . . . . . . .2-29

Triggering the A/D Periodically . . . . . . . . . . . . . . . . . . . . . .2-31

Generating Interrupts with the Counter/Timer . . . . . . . . . . .2-32

Wait State Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-33

Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-33

xi

3

Setup and Installation

Unwrapping and Inspecting Your Board . . . . . . . . . . . . . . . . . . .3-1

Standard Software for DAS-16 Series Boards. . . . . . . . . . . . . . .3-2

Installing the Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-4

Software Options. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-4

DriverLINX driver software for Windows 95/98/NT. . . . .3-4

TestPoint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-5

LabVIEW. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-6

Installing DriverLINX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-7

Installing Application Software and Drivers. . . . . . . . . . . . . .3-7

Installing the TestPoint software and driver. . . . . . . . . . . .3-7

Installing the LabVIEW software and driver. . . . . . . . . . .3-7

Setting Switch-Configurable Options . . . . . . . . . . . . . . . . . . . . .3-8

Base Address Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-10

Channel (System) Configuration Switch . . . . . . . . . . . . .3-12

DMA Level Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-12

A/D Switch. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-13

GAIN Switch (DAS-16/16F Only). . . . . . . . . . . . . . . . . .3-13

Jumpers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-14

The TIMER Jumper . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-14

The WAIT STATE Jumper . . . . . . . . . . . . . . . . . . . . . . . .3-14

Main I/O Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-15

Setting up the Computer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-16

Selecting an Expansion Slot. . . . . . . . . . . . . . . . . . . . . . . . . . . .3-16

Installing the Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-17

Configuring DriverLINX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-18

xii

Cabling and Wiring

4

Attaching Screw Terminal Accessories . . . . . . . . . . . . . . . . . . . .4-2

Attaching an STC-37. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-2

Attaching an STP-37. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-4

Attaching an STA-16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-5

Attaching Expansion Accessories . . . . . . . . . . . . . . . . . . . . . . . .4-7

Attaching an EXP-16 or EXP-16/A Expansion Accessory. . .4-7

Attaching an EXP-GP Expansion Accessory . . . . . . . . . . . . .4-8

Attaching Multiple Expansion Accessories . . . . . . . . . . . . . .4-9

Attaching an MB Series Backplane . . . . . . . . . . . . . . . . . . . . . .4-11

Attaching an MB01/05 Backplane . . . . . . . . . . . . . . . . . . . .4-12

Attaching an MB02 Backplane. . . . . . . . . . . . . . . . . . . . . . .4-13

Attaching an STA-MB . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-15

Connecting Analog Input Signals . . . . . . . . . . . . . . . . . . . . . . .4-16

Connecting a Signal to a Single-Ended Analog Input. . . . . .4-16

Connecting a Signal to a Differential Analog Input . . . . . . .4-17

Avoiding a Ground Loop Problem. . . . . . . . . . . . . . . . . . . . . . .4-19

Connecting Analog Output Signals . . . . . . . . . . . . . . . . . . . . . .4-21

Measuring Current and 4–20mA Current Loops . . . . . . . . .4-22

The D/A Voltage Reference. . . . . . . . . . . . . . . . . . . . . . . . . .4-22

Interface to Transducers, Thermocouples, etc.. . . . . . . . . . . . . .4-23

Precautions for Operating at High Gains. . . . . . . . . . . . . . . . . .4-24

Additional Precautions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-25

DriverLINX Analog I/O Panel

5

Test Panel Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-2

6

Calibration

Equipment Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-1

Potentiometers and Test Points . . . . . . . . . . . . . . . . . . . . . . . . . .6-1

Calibration Utility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-3

Calibrating the A/D. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-4

Calibrating the D/As . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-5

Programmable Timer and Digital I/O . . . . . . . . . . . . . . . . . . .6-6

Troubleshooting

7

Problem Isolation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-1

Using the DriverLINX Event Viewer . . . . . . . . . . . . . . . . . . .7-1

Device Initialization Error Messages . . . . . . . . . . . . . . . . . . .7-2

Identifying Symptoms and Possible Causes . . . . . . . . . . . . . .7-2

Testing the Board and Host Computer . . . . . . . . . . . . . . . . . .7-5

Testing the Accessory Slot and I/O Connections . . . . . . . . . .7-6

Technical Support. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-7

xiii

A

Specifications

DAS-16 Series Specifications . . . . . . . . . . . . . . . . . . . . . . . . A-1

Power Consumption. . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1

Analog Inputs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1

A/D Specification. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-3

Sample Hold Amplifier. . . . . . . . . . . . . . . . . . . . . . . . . . . A-3

Reference Voltage Output. . . . . . . . . . . . . . . . . . . . . . . . . A-3

D/A Converters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-4

Digital I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-4

Interrupt Inputs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-5

Direct Memory Access Channel. . . . . . . . . . . . . . . . . . . . A-5

Programmable Timer . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-6

Power Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-6

General Environmental. . . . . . . . . . . . . . . . . . . . . . . . . . . A-6

Connector Pin Assignments

B

Main I/O Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1

Register-Level Address Map

C

Register Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-1

ADC Registers (Base Address +0h and +1h). . . . . . . . . . . . . . . C-3

MUX Scan Register (Base Address +2h). . . . . . . . . . . . . . . . . . C-4

Unidirectional Digital I/O Registers

(Base Address +3h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-5

DAC Output Registers (Base Address +4h to +7h) . . . . . . . . . . C-6

DAC0. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-7

DAC1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-7

Status Register (Base Address +8h). . . . . . . . . . . . . . . . . . . . . . C-8

Control Register (Base Address +9h). . . . . . . . . . . . . . . . . . . . . C-9

Counter Enable Register (Base Address +Ah). . . . . . . . . . . . . C-11

Programmable Gain (Base Address +Bh) . . . . . . . . . . . . . . . . C-13

Programmable Interval Counter/Timer

(Base Addresses +Ch, +Dh, +Eh, +Fh) . . . . . . . . . . . . . . . . . . C-14

Counter/Timer Control Register (Base Address +Fh). . . . . C-14

Readback Command Byte . . . . . . . . . . . . . . . . . . . . . . . C-18

Status Byte Format (Returned if STA =0) . . . . . . . . . . . C-19

xiv

The IBM PC DMA Structure

D

Page Register and DMA Controller Functions . . . . . . . . . . . D-3

1

Overview

The Model DAS-16, DAS-16F, and DAS-16G (hereinafter referred to as
DAS-16) are multi-function, high-speed, programmable, A/D (and D/A)
I/O expansion boards for the IBM Personal Computer. They are full
length boards that install internally in an expansion slot of an IBM PC and
compatibles to turn the computer into a fast, high-precision data
acquisition and signal analysis instrument. DAS-16 boards are of
multilayer construction with integral ground plane to minimize noise and
crosstalk at high frequencies. The DAS-16G includes an additional
register at an I/O address location for setting the gain.

Table 1-1. DAS-16 Series Models

Model Description

DAS-16 Includes the DAS-16, a 16-channel, high speed A/D interface

with DMA, (70,000 samples/sec. max.) as well as software and
appropriate documentation.

DAS-16F Includes the DAS-16F, a 16-channel, high speed A/D interface

with DMA, (100,000 samples/sec. max.) as well as software
and appropriate documentation.

DAS-16G1 Includes the DAS-16G1, a 16-channel, high speed A/D

interface with software selectable input gains (1, 10, 100, and

500), software, and appropriate documentation.

DAS-16G2 Includes the DAS-16G2, a 16-channel, high speed A/D

interface with software selectable input gains (1, 2, 4, and 8),
software, and appropriate documentation.

1-1

System requirements

The system capabilities required to run the DAS-16 Series board, and to
use the DriverLINX software supplied with the board, are listed in
Table 1-2.

Table 1-2. System requirements

CPU Type

Operating system

Memory

Hard disk space

Other

Pentium or higher processor on motherboard with
PCI bus version 2.1.

Windows 95 or 98.
Windows NT version 4.0 or higher.
16 MB or greater RAM when running Windows 95

or 98.
32 MB or greater RAM when running Windows NT.
4 MB for minimum installation.
50 MB for maximum installation.
A CD-ROM drive.*
A free PCI-bus expansion slot capable of bus

mastering.
Enough reserve computer power supply capacity to

power the KPCI-3101–4 Series board, which draws

0.9A at 5VDC and 48mA at +12VDC.
A VGA, or compatible, display (640 x 480 or

higher, 256 colors recommended).

*Any CD-ROM drive that came installed with the required computer should be satisfactory.

However, if you have post-installed an older CD-ROM drive or arrived at your present system by
updating the microprocessor or replacing the motherboard, some early CD-ROM drives may not
support the long file names often used in 32 bit Windows files.

1-2 Overview

Software

DriverLINX — the high-performance real-time data-acquisition device
drivers for Windows application development including:

●

DriverLINX API DLLs and drivers supporting the DAS-16 Series
hardware.

Analog I/O Panel — A DriverLINX program that verifies the

●

installation and configuration of DriverLINX to your DAS-16 Series
board and demonstrates several virtual bench-top instruments.

●

Learn DriverLINX — an interactive learning and demonstration
program for DriverLINX that includes a Digital Storage
Oscilloscope.

●

Source Code — for the sample programs.
DriverLINX Application Programming Interface files — for the

●

DAS-16 Series compiler.

● DriverLINX On-line Help System — provides immediate help as you

operate DriverLINX.
Supplemental Documentation — on DriverLINX installation and

●

configuration; analog and digital I/O programming; counter/timer
programming; technical reference; and information specific to the
DAS-16 Series hardware.

●

DAS-16 Series utilities — The following DriverLINX utilities are
provided as part of the DAS-16 Series standard software package:

– Calibration Utility
– Test Panel Utility

The user can select a fully integrated data acquisition software package
such as TestPoint or LabVIEW or write a custom program supported by
DriverLINX.

DriverLINX is the basic Application Programming Interface (API) for the
DAS-16 Series boards:

It supports programmers who wish to create custom applications

●

using Visual C/C++, Visual Basic, or Delphi.
It accomplishes foreground and background tasks to perform data

●

acquisition.

Software 1-3

Features

It is the needed interface between TestPoint and LabVIEW and a

●

DAS-16 Series board.

DriverLINX software and user’s documentation on a CD-ROM are
included with your board.

TestPoint is an optional, fully featured, integrated application package
with a graphical drag-and-drop interface which can be used to create data
acquisition applications without programming.

LabVIEW is an optional, fully featured graphical programming language
used to create virtual instrumentation.

Features shared by the DAS-16 Series boards are as follows:

Boards are switch-configurable for 16 single-ended or eight

●

differential analog input channels.
Analog inputs are switch-configurable for either unipolar (0 to

●

10V) or bipolar (±10V) signals.
Analog input gain may be set for the DAS-16/G1 boards to 1, 10, 100,

●

or 500. The DAS-16/G2 boards have gain selection of 1, 2, 4, or 8.

●

Analog input sampling is a maximum of 70ksamples/s for DAS-16
and 100ksamples/s for DAS-16F; with 12-bit resolution.

The base I/O address and Direct Memory Address (DMA) channel

●

are switch-configurable; interrupt levels are software-configurable.
The boards perform 8-bit data transfers on the ISA bus.

●

●

Switch selectable Channel Input Configuration, High Impedance
Ranges, Base I/O Address, and DMA Level.

●

A/D conversions can be triggered by any of the following: software
command, internal programmable-interval timer, or direct external
trigger to the A/D. Once the A/D conversion has been completed, data
transfers are accomplished via program transfer, interrupt, or DMA.

1-4 Overview

A 3-channel programmable interval timer (Intel 8254) provides

●

trigger pulses for the A/D at any rate from 250KHz down to 8
pulses/hr. Two channels are operated in fixed divider configuration
from an internal crystal clock. The third channel is uncommitted and
provides a gated 16-bit binary counter that can be used for event or
pulse counting, delayed triggering, and in conjunction with the other
channels for frequency and period measurement.

●

The boards have four unidirectional digital inputs and four
unidirectional digital outputs.

●

Digital I/O consists of four bits of TTL/DTL-compatible digital
output and four bits of digital input. Apart from being addressed as
individual I/O ports, some of the digital inputs do double duty in
some modes as A/D trigger and counter gate control inputs.

●

One feature of the DAS-16 is the availability of two channels of
multiplying 12-bit D/A output. The DACs may use a fixed -5V
reference available from on-board for a 0 to +5V output range.
Alternatively, an external AC or DC reference may be used to give
different output ranges or programmable attenuator action on an AC
signal. D/A’s are double-buffered to provide instantaneous single-step
updates.

Accessories

●

A -5V (± 0.05V) precision reference voltage output is derived from
the ADC reference. Typical applications are providing a DC reference
input for the DACs and providing offsets and bridge excitation to
user-supplied input circuits.

For more information on these features, refer to the functional description
in Section 2.

The following accessories are available for use with the DAS-16 Series
boards.

●

STA-16 — Screw-terminal adapter accessory that connects to the
main I/O connector of a DAS-160 Series board through a C-1800
cable.

STA-U — Universal screw-terminal accessory that connects to the

●

DAS-16 Series board through a C-1800 cable.

Accessories 1-5

STC-37 — Direct DAS-16 Series board to screw terminal interface.

●

●

STP-37 — Screw-terminal panel that connects to the main I/O
connector of a DAS-16 Series board through a C-1800 cable.

●

MB Series modules and backplanes — Plug-in, isolated,
signal-conditioning modules and the backplanes that hold them.
Supported backplanes include the MB01, MB02, and MB05.

●

STA-MB — Screw terminal accessory for MB Series modules. The
STA-MB connects to a DAS-16 Series board through a C-1800 cable
and contains mounting holes for up to four MB Series modules. The
STA-MB brings all signal lines from the DAS-16 Series board and all
inputs and outputs from the MB Series modules out to external screw
terminals.

STA-SCM16 — Screw terminal accessory that attaches to the main

●

I/O of a DAS-16 Series board through a C-1800 cable and attaches up
to four MB02 backplanes through C-2600 cables.

EXP-16 and EXP-16/A — 16-channel expansion multiplexer and

●

signal conditioning boards; requires the S-1600 cable and the
PG-408A option.

●

C-1800 — Cable for attaching the main I/O connector of a DAS-16
Series board to an STA-16, STA-MB, STA-SCM-16, or STP-37
accessory. This cable can also be used to connect a DAS-16 Series
board to an STA-U accessory; or to cascade additional EXP-GP or
EXP-16 accessories.

S-1800 — Shielded version of the C-1800 cable.

●

●

S-1600 — Cable for attaching an STA-16 or STA-MB to an EXP-16,
EXP-GP, or ISO-4 accessory.

●

C-16MB1 — Cable for attaching the main I/O connector of a
DAS-16 Series board to an MB01/05 backplane.

●

C-2600 — Cable for attaching an STA-SCM16 to an MB02
backplane.

1-6 Overview

2

Functional Description

This section describes the following features of DAS-16 Series boards:

● Analog input

●

Analog output
Digital I/O

●

● 82C54 counter/timer

● Wait state selection

●

Power

These descriptions are offered to familiarize you with the operating
options and to enable you to make the best use of your board. The block
diagrams in Figure 2-1 and Figure 2-2 represent the DAS-16 Series
boards.

2-1

Figure 2-1. DAS-16/16F Functional Block Diagram

2-2 Functional Description

Figure 2-2. DAS-16G1/G2 Functional Block Diagram

2-3

Analog Input Features

The analog input section of a DAS-16 Series board multiplexes all the
active input channels (up to 16 single-ended or eight differential) into a
single, 12-bit, sampling, analog-to-digital converter (ADC).

Other features of this section include input configurations, gain selection,
conversion modes, triggers, clock sources, and data transfer modes. These
features are described in the following subsections.

Differential/Single-Ended Selection

Using configuration switches, you can select either eight differential or 16
single-ended inputs. Differential inputs measure the difference between
two signals. Single-ended inputs are referred to a common ground.

Generally, you want to use differential inputs for low-level signals whose
noise component is a significant part of the signal or for signals that have
nonground common mode. You want to use single-ended inputs for high­level signals whose noise component is not significant.

The specific level at which input configurations work best depends on the
application. However, you generally use differential inputs for voltage
ranges of 100mV and less.

Unipolar/Bipolar Selection

Using configuration switches, you can set the DAS-16 Series boards to
operate in either unipolar or bipolar input mode. A unipolar signal is
always positive (0 to 10V, for example), while a bipolar signal can swing
up and down between negative and positive peak values (
for example).

The DAS-16 Series boards use left-justified, offset binary to represent
signals. In a given input range with the same peak-voltage capacity for
both modes, unipolar mode doubles the converter’s resolution.

10V to +10V,

−

2-4 Functional Description

Channel Selection

You can use DAS-16 Series boards to acquire data from a single analog
input channel or from a range of contiguous, on-board analog input
channels using automatic channel scanning. These two methods of
channel selection are described as follows:

●

Single channel — You use software to specify a single channel and
initiate a conversion.

●

Automatic channel scanning — You use software to specify the first
and last channels in a range of contiguous, on-board channels (0 to 7).
The channels are sampled in order from first to last; the hardware
automatically increments the analog input multiplexer address shortly
after the start of each conversion. When the last address is reached,
the multiplexer returns to the start address and the channels are
sampled again. For example, assume that the start channel is 4, the
stop channel is 7, and you want to acquire five samples. Your program
reads data first from channel 4, then from channels 5, 6, and 7, and
finally from channel 4 again.

Note:

An error results if the start channel number is higher than the stop

channel number.

When using automatic channel scanning, all contiguous, on-board
channels must have the same gain (analog input range).

DriverLINX allows you to acquire data from a range of multiple channels
that includes channels on expansion boards or MB Series backplanes.
DriverLINX provides for expansion board configuration in its Special
selection of the Device Subsystem page, which allows you to record the
settings of your analog input multiplexers and enable the expansion
channels. Refer to Appendix F: Configuration and Implementation Notes,
Keithley DAS-16/1600 Series manual that accompanies DriverLINX.

Analog Input Features 2-5

Channel Selection in Expanded Configurations

The DAS-16 Series supports 16 single-ended or eight differential analog
input channels. If you require additional analog input channels or signal
conditioning for transducer inputs, you can attach EXP-16, EXP-16/A, or
EXP-GP expansion accessories. Attaching any combination of up to eight
16-channel EXP-16 or EXP-16/A accessories, and/or eight 8-channel
EXP-GP accessories can increase the number of available channels to

128. Attaching up to sixteen 16-channel EXP-16 accessories can increase
the number of available channels to 256.

When you daisy-chain expansion boards from the analog inputs, you are
advised to make the first expansion board multiplex onboard channel 0,
the next expansion board multiplex channel 1, and so on. You select an
onboard channel using jumper settings on the expansion board.

You can access any unused onboard channels by placing an STA-16 screw
terminal accessory first in the daisy-chain configuration. Figure 2-3
illustrates how expansion boards and accessories interface with the analog
channels of DAS-16 Series boards.

DAS-16 Series
Boards

ch 0
ch 1

ch 2

Transducer

16 multiplexed input

channels

8 multiplexed input

channels

.

.

ch 7

digital output

port

Expansion Channel
Select Lines (OP0 to 3)

Figure 2-3. Expanding the Analog Inputs of DAS-16 Series Boards

EXP-16,
EXP-16/A

You can also use up to four MB02 backplanes to increase the number of
available channels to 64 isolated or 12 nonisolated. For more information
about connecting channel expansion boards, refer to Section 4.

EXP-GPSTA-16

2-6 Functional Description

Notes: You must specify a single-ended input configuration for all

onboard channels associated with channels on MB02 backplanes.

If you are using EXP-16, EXP-16/A, or EXP-GP expansion accessories
or MB Series backplanes, the digital output lines of the DAS-16 Series
board select a particular channel on the expansion board or backplane to
read.

Selecting Input Channel Range and Gain

The DIP switch labeled GAIN controls the full-scale range common to all
the channels. The slide switch marked A/D has two positions: UNI
(Unipolar) and BIP (Bipolar). These two switches determine the input
scaling and whether the range is unipolar (zero to some positive full
scale) or bipolar (from a negative to a positive full scale).

DriverLINX detects the position of the UNI/BIP switch through the DAS­16 status register, and it adjusts the data for unipolar and bipolar ranges
accordingly. Unipolar scalings correspond to 0 to 4095 bits of output
from the A/D, whereas bipolar scalings correspond to -2048 to +2047
bits. In this way 0 bits always corresponds to 0 volts, so the only
operation usually required is a simple multiplication to scale the reading
to real units; for example, on the ±5V or 0–10V range, multiply the
integer data returned by DriverLINX by the actual bit weight (2.44
millivolts/bit) to obtain volts. Refer to Appendix F: Configuration and
Implementation Notes, Keithley DAS-16/1600 Series manual that
accompanies DriverLINX.

The DAS-16/16F has a 5-position DIP switch (marked A, B, C, D, USER)
which is set according to the instructions given in Section 3. You can have
a non-standard input scale by soldering a precision resistor into the USER
location and selecting the USER position on the GAIN switch. Scale span
(the difference between full-scale limits) is related to resistor value as
follows:

Span (in volts) = 10 / (1 + 20,000/Ruser).
For example, Ruser = 1053 ohms gives 0.5V span.

Signals below 0.5 volt are subject to system noise and should therefore be
pre-amplified using an EXP-16 (or equivalent) before applying them to
DAS-16 inputs).

Analog Input Features 2-7

The available gains, their corresponding input ranges, and throughput
rates are listed in Table 2-1 for the DAS-16G1 and Table 2-2 for the DAS­16G2.

Table 2-1. DAS-16G1 Gains, Ranges, and Throughput Rates for

Unipolar and Bipolar Selections

Maximum

Gain Unipolar Range Bipolar Range

1 0.0 to +10.0V −10.0 to +10.0V 70ksamples/s

010 0.0 to +1.0V −1.0 to +1.0V 60ksamples/s

100 0.0 to +100mV −100 to +100mV 50ksamples/s
500 0.0 to +20mV −20 to +20mV 30ksamples/s

Table 2-2. DAS-16G2 Gains, Ranges, and Throughput Rates for

Unipolar and Bipolar Selections

Gain Unipolar Range Bipolar Range

1 0.0 to +10.0V −10 to +10V 70ksamples/s

Throughput Rate

Maximum

Throughput Rate

Clock Sources

2 0.0 to +5.0V −5.0 to +5.0V 60ksamples/s
4 0.0 to 2.5V −2.5 to + 2.5V 60ksamples/s
8 0.0 to 1.25V −1.25 to +1.25V 60ksamples/s

DAS-16 Series boards support the paced conversion mode. Paced mode is
best-suited for continuous scanning of multiple channels at a constant
rate. In paced mode, the conversion rate equals the pacer clock rate. The
sample rate, which is the rate at which a single channel is sampled, is the
pacer clock rate divided by the number of channels sampled.

The following clock sources are available for conversions on DAS-16
Series boards:

● Software — DAS-16 Series boards allow you to acquire single or

multiple samples under program control.

● Hardware (internal clock source) — The internal pacer clock is

derived from the onboard 82C54 counter/timer and a switch­configurable, crystal-controlled 1MHz or 10MHz timebase. The

2-8 Functional Description

pacer clock uses two cascaded counters of the 82C54. The maximum
allowable rate is 100ksamples/s, and the minimum conversions per
hour is determined as follows:

10MHz

------------------ 2.328 103–× 8.38==

32

2

1MHz

--------------- 2.328 104–× 0.838==

32

2

When not used to pace the analog input, the internal clock source can
pace other events, such as digital I/O and analog outputs (on the
DAS-16 Series boards), through the use of interrupts.

● Hardware (external clock source) — The external pacer clock

source must be an externally applied, TTL-compatible, rising-edge
signal attached to the IP0/TRIG 0 pin (25) of the main I/O connector.

An external clock source is useful if you want to pace at rates not
available with the 82C54 counter/timer, if you want to pace at uneven
intervals, or if you want to pace on the basis of an external event. An
external clock also allows you to synchronize multiple boards with a
common timing source.

Figure 2-4 illustrates how conversions are initiated when using an internal
and an external clock source. (Note that Figure 2-4 assumes that you are
not using a hardware trigger; refer to Figure 2-5 for an illustration of
conversions when using a hardware trigger.)

Operation is started

External Clock
Source

Internal Clock
Source

Conversions begin
when using an
internal clock source

(idle state)

count

count

Conversions begin
when using an
external clock source

count

count

Figure 2-4. Initiating Conversions

Analog Input Features 2-9

Triggers

Note: The ADC acquires samples at a maximum of 100ksamples/s (one

sample every 10.0µs). If you are using an external clock, make sure it
does not initiate conversions at a faster rate than the ADC can handle.

If you are acquiring samples from multiple channels, the maximum
sampling rate for each channel is equal to 100ksamples/s divided by the
number of channels.

A trigger starts an analog input operation. The polarity of external triggers
in the DAS-16 Series boards is software-configurable. You can use one of
the following trigger sources to start an analog input operation:

● Internal — When you enable the analog input operation, conversions

begin immediately.

● External Analog — While an analog trigger is not a hardware feature

of the DAS-16 Series boards, you can program an analog trigger
using one of the analog input channels as the trigger channel.
DriverLINX provides functions for an analog trigger; refer to the

DriverLINX Installation and Configuration Guide and Appendix F:
Configuration and Implementation Notes—for Keithley DAS-16/1600

manuals for more information.

● External Digital — While a digital trigger is not a hardware feature

of the DAS-16 Series boards, you can apply a digital trigger to the
digital input IP1 pin (6) of the main I/O connector. Refer to the

DriverLINX Installation and Configuration Guide and Appendix F:
Configuration and Implementation Notes—For Keithley DAS-16/1600

manuals.

2-10 Functional Description

Hardware Trigger

Trigger types are as follows:
– Positive-edge trigger — Conversions begin on the rising edge of

the trigger signal.

– Negative-edge trigger — Conversions begin on the falling edge

of the trigger signal.

– Positive-level trigger — Conversions begin when the signal is

above a positive level. See Appendix A for logic levels.

– Negative-level trigger — Conversions begin when the signal is

below a negative level. See Appendix A for logic levels.

Figure 2-5 illustrates how conversions are started when using a
hardware trigger.

Trigger event occurs

Conversions begin
when using an
external clock source

External Clock
Source

Internal Clock
Source

(idle state)

count

count

Conversions begin
when using an
internal clock source

count

count

Figure 2-5. Initiating Conversions with a Hardware Trigger

Analog Input Features 2-11

Hardware Gates

A hardware gate is an externally applied digital signal that determines
whether conversions occur. You connect the gate signal to the IP0/TRIG 0
pin (pin 25) on the main I/O connector. DAS-16 Series boards support a
positive gate only. Therefore, if the hardware gate is enabled and the
signal to IP0/TRIG 0 is high, conversions occur; if the signal to
IP0/TRIG 0 is low, conversions are inhibited.

Note: You cannot use the hardware gate with a hardware trigger.

However, the gate signal itself can act as a trigger. If the gate signal is low
when the software starts the analog input operation, the board waits until
the gate signal goes high before conversions begin.

When using the hardware gate, the way conversions are synchronized
depends on whether you are using a hardware external clock or a
hardware internal clock, as follows:

● External clock — The signal from the external clock continues

uninterrupted while the gate signal is low; therefore, conversions are
synchronized to the external clock.

● Internal clock — The 82C54 does not count while the gate signal is

low. Whenever the gate signal goes high, the 82C54 is loaded with its
initial count value and starts counting; therefore, conversions are
synchronized to the gate signal.

2-12 Functional Description

Gate Signal

Software starts
the operation

External Clock
Source

Figure 2-6 illustrates how to use the hardware gate with both an external
clock and an internal clock.

Gate is high;
conversions occur

1st conversion
(external clock)

Gate is low;
conversions inhibited

3rd conversion
(external clock)

2nd conversion
(external clock)

Internal Clock
Source

1st conversion
(internal clock)

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

2nd conversion
(internal clock)

3rd conversion
(internal clock)

Figure 2-6. Hardware Gate

Note: Although DAS-16 Series boards do not provide a hardware-based

analog trigger, you can program an analog trigger through software, using
one of the analog input channels as the trigger channel. DriverLINX
provides functions for both an analog trigger and a digital trigger. Refer to
the DriverLINX Appendix F: Configuration and Implementation Notes:
Keithley DAS-16/1600 manual for more information.

4th conversion
(internal clock)

Analog Input Features 2-13

Data Transfer Modes

You can transfer data from the DAS-16 Series boards to the computer
using the following data transfer modes:

● Single mode — In a single-mode operation, a data acquisition board

acquires a single sample from a single channel; you cannot perform
any other operation until the single-mode operation is complete.

● Synchronous — In a synchronous-mode operation, a data acquisition

board acquires one or more samples from one or more channels; you
cannot perform any other operation until the synchronous-mode
operation is complete.

● Interrupt — You can program the board to acquire data, then

generate an interrupt when data is available for transfer. When
interrupt mode is used, data is transferred by an interrupt service
routine; you can perform other operations while an interrupt mode
operation is in progress. The interrupt level is software-configurable.

Unpredictable interrupt latencies in the Windows environment tend to
make maximum board speeds unachievable in the interrupt mode.
When in the Windows environment, you are advised to use DMA
mode instead of interrupt mode.

● DMA — DMA is a method of bypassing the CPU to transfer data

directly between an I/O device and computer memory. In the IBM PC
family, DMA is directed by the DMA controller and executes
independently while the CPU is executing other instructions.
Therefore, you can perform other operations while a DMA mode
operation is in progress. The ability to run independently of the CPU
and at high-transfer rates makes DMA an attractive method for
transferring data in data acquisition systems.

DAS-16 Series boards can use either DMA channel 1 or 3 to perform
single-cycle DMA transfers of A/D data from the board to memory.

2-14 Functional Description

Analog Output Features

The D/A channels consist of two separate double–buffered, 12–bit
multiplying D/A converters. Each D/A may be used with the fixed -5V
DC reference as a conventional 0 to +5V output D/A. Alternatively, the
D/As may be operated with a variable, or AC, reference signal as
multiplying D/As, the output is the product of reference and digital
inputs. Accuracy remains at 12–bits up to 1KHz. The maximum output
swing of the D/As is ±10V. A simplified diagram of each D/A channel is
shown in the following diagram.

Functional Description

2

Figure 2-7. D/A Configuration and connections

Since data is 12 bits, it must be written to each D/A in two consecutive
bytes. The first byte is the least significant and contains the four least
significant bits of data. The second byte is the most significant and
contains the most significant eight bits of data. The least significant byte
should be written first and is stored in an intermediate register in the D/A,
having no effect on the output. When the most significant byte is written,
its data is added to the stored least significant data and presented
“broadside” to the D/A converter thus assuring a single step update. This
process is known as double buffering. See Appendix C.

Analog Output Features 2-15

You can write single values to the DACs using synchronous mode or
single mode. You can write multiple values to the DACs using
synchronous mode.

The DAS-16 Series provides a

−5V (±0.05V) precision reference voltage

that is derived from the DAC reference voltage. Typical applications for
precision voltages are providing a DC reference input for the DACs and
providing offsets and bridge excitation to user-supplied input circuits.

Used with an AC Reference (Digital Attenuator)

Apart from its use as a standard DC output D/A, the D/As can be used
with variable bipolar, AC, or DC reference signals. In this mode, they
behave as a digitally programmed gain control or attenuator. The voltage
output V

V

= −(Digital input) * V

out

Two additional parameters are of interest in AC operation. The first is
feedthrough, the amount of residual signal at digital zero. The second
parameter is the accuracy/frequency characteristic––it is a limit at a lower
frequency. Feedthrough which is mainly a function of stray capacitance,
rises with frequency; at 10KHz, it is typically 5mV peak–peak with a
±5V reference. Due to distributed capacitance in the R–2R ladder
network of the D/A, the full 12 bit performance falls off as the frequency
rises. Above about 1KHz the dynamic performance of the D/A will have
less than 12-bit accuracy.

is as follows:

out

/ 4096

ref

The D/As will perform well in synchro-digital and resolver applications
for sine/cosine generation with 400 Hz reference.

2-16 Functional Description

Arbitrary Waveform Output

One common requirement is to output a waveform from a D/A converter.
At slow speeds this can be done with a timing loop in your program, but it
is usually difficult to control the timing with any degree of precision
especially when operating at more than a few points per second.

The lower the frequency the more steps or points we can put in the
waveform. Using a clock frequency of 10MHz, we can set Counters 1 and
2 to output a frequency of 3000.3Hz with a division C ratio of 3333. In
turn with 50 points per cycle, this would give us an output of 60.006Hz,
fairly close to the desired 60Hz.

Analog Output Features 2-17

Digital I/O Features

DAS-16 Series boards contain four digital inputs (IP0 to IP3) and four
digital outputs (OP0 to OP3) that are accessible through the main I/O
connector.

Logic 1 on an I/O line indicates that the input/output is high; logic 0 on an
I/O line indicates that the input/output is low (see Appendix A for logic
levels). The digital inputs are compatible with TTL-level signals. These
inputs are provided with 10k
inputs appear high (logic 1) with no signal connected.

You can use the digital inputs and outputs for any general-purpose tasks
except the following:

● If you are using an external digital trigger or gate, you must use

digital input line IP0/TRIG 0 to attach the trigger and digital input
line IP2/CTR 0 GATE to attach the counter 0 gate signal. In either of
these cases, you cannot use the corresponding bit for general-purpose
digital input.

Ω pull-up resistors to +5V; therefore, the

● If you are using an external pacer clock, you must use digital input

line IP0/TRIG 0 to attach the external pacer clock signal; in this case,
you cannot use IP0/TRIG 0 for general-purpose digital input.

When the analog inputs are disabled, you can pace the digital I/O with
interrupts generated by the onboard pacer clock.

You can read or write a single value from or to a DAS-16 Series board
using synchronous mode or single mode. You can read or write multiple
values from or to a DAS-16 Series board using synchronous mode or
interrupt mode.

2-18 Functional Description

Counter/Timer Features

The Intel 82C54 programmable interval timer is used in the DAS–16.
This is a flexible but complex device consisting of three independent
16–bit pre-settable down counters. Each counter can be programmed to
divide by any integer in the range 2 – 65,536. In the DAS-16, Counters 1
and 2 are cascaded with the input of Counter 1 connected to a precision 1
or 10MHz crystal oscillator. The output of Counter 1 is connected to the
input of Counter 2, and Counter 2 output may be selected internally as
well as being available to the user at the COUNTER 2 OUT (Pin 20). The
other counter, Counter 0, is uncommitted and its input, output, and gate
control are available to the user on COUNTER 0 IN (Pin 21), COUNTER
0 OUT (Pin 2), and IP2 (Pin 24). A block diagram of the DAS-16 counter
arrangement is shown in Figure 2-8.

Figure 2-8. Programmable Timer Configuration

Counter/Timer Features 2-19

Programmable timer configuration principal uses of the 82C54 are as
follows:

1. A programmable timer for generating interrupts and triggering
periodic A/D conversions.

2. A variable-frequency square wave generator for testing and for
frequency synthesis.

3. An event counter for external pulse inputs.

4. A time–delay generator.

Each counter has a clock input, a gate input that controls counting and
triggering, and an output. The maximum clock input frequency on any
counter is 10MHz with minimum clock duty cycles of 30ns high and 50ns
low (note that this specification applies only to the -2 version of the
82C54). On later models of the DAS-16, it is also possible to drive
Counters 1 and 2 from a 10MHz clock. This selection is made via a
jumper block on the board marked TIMER, the 1 position corresponding
to a 1MHz clock and the 10 position to 10MHz. The usual function of
these two counters is to provide programmable pulse rates to trigger the
A/D. Counter 0 is uncommitted and can be used as a secondary pulse-rate
generator, a square-wave generator, a programmable monostable delay or
an event counter. Counters 1 and 2 are initialized by the DAS-16 driver to
operate in the Rate Generator Configuration (#2) and output 1KHz
(10KHz with 10MHz clock) after running initializing MODE 0; but there
are actually six possible operating configurations for each counter, as
described in the next section.

You can program the 82C54 counter/timer circuitry to operate in one of
the following counter/timer modes:

2-20 Functional Description

Clock pulse

Pulse on terminal count (Mode 0) — This mode is useful for event
counting or for programming a time delay. The software forces the output
low. On the next clock pulse after the software writes the initial count
value, the counter is loaded. When the counter reaches zero, the output
goes high and remains high until the software writes a new count value.
Note that the output does not go high until n + 1 clock pulses after the
initial count is written, where n indicates the loaded count.

A high gate input enables counting; a low gate input disables counting.
The gate input has no effect on the output. Note that an initial count value
written while the gate input is low is still loaded on the next clock pulse.

Figure 2-9 illustrates pulse on terminal count mode.

Software forces
output low

Output

Software writes initial
count value of 3

3 2 1

Figure 2-9. Pulse on Terminal Count Mode

Counter/Timer Features 2-21

Clock pulse

• Programmable one-shot (Mode 1) — This mode is useful for
providing a hardware-triggered delay or one-shot pulse. The output is
initially high. A trigger loads the initial count value into the counter.
At the next clock pulse after the trigger, the output goes low and
remains low until the counter reaches zero. (The one-shot pulse is n
clock cycles in duration, where n indicates the loaded count.) After
the counter reaches zero, the output goes high and remains high until
the clock pulse after the next trigger; this makes the one-shot
pulse retriggerable.

You do not have to reload the count into the counter. The gate input
has no effect on the output. Writing a new count to the counter during
a one-shot pulse does not affect the current one-shot pulse.

Figure 2-10 illustrates programmable one-shot mode.

Output

Trigger loads initial
count value of 3

3 2 1

Figure 2-10. Programmable One-Shot Mode

2-22 Functional Description

• Rate generator (Mode 2) — This mode is useful for generating a
real-time clock interrupt. The output is initially high. A trigger loads
the initial count value into the counter. At the next clock pulse after
the trigger, the counter starts counting down. When the counter
reaches one, the output goes low for one clock pulse and then goes
high again. The counter is then reloaded with the initial count value
and the process repeats.

A high gate input enables counting; a low gate input disables
counting. If the gate goes low during an output pulse, the output is set
high immediately; this allows you to use the gate input to synchronize
the counter.

Writing a new count to the counter while counting does not affect the
current counting sequence. In this mode, a count of 1 is illegal.

Figure 2-11 illustrates rate generator mode.

Clock pulse

Output

Trigger loads initial
count value of 3

3 2

Figure 2-11. Rate Generator Mode

1 3 2 1 2

Counter/Timer Features 2-23

• Square-wave generator (Mode 3) — This mode is useful for
square-wave generation. The output is initially high. A trigger loads
the initial count value into the counter. At the next clock pulse after
the trigger, the counter starts counting down. When half the initial
count has elapsed, the output goes low for the remainder of the count.
When the total count elapses, the counter is reloaded with the initial
count value, the output goes high again, and the process repeats. If the
initial count is odd, the output is high for (n + 1) / 2 counts and low
for (n

− 1) / 2 counts, where n indicates the loaded count.

A high gate input enables counting; a low gate input disables
counting. If the gate goes low while the output is low, the output is set
high immediately; this allows you to use the gate input to synchronize
the counter.

Figure 2-12 illustrates square-wave generator mode.

Clock pulse

Output

Trigger loads initial
count value of 4

4 3 2 1 4 3 2 1

Figure 2-12. Square-Wave Generator Mode

2-24 Functional Description

Clock pulse

• Software-triggered strobe (Mode 4) — The output is initially high.
Writing the initial count through software loads the initial count value
into the counter at the next clock pulse, but the counter does not start
counting. At the next clock pulse, the counter starts counting down.
When the counter reaches zero, the output goes low for one clock
pulse and then goes high again. Note that the output does not go low
until n + 1 clock pulses after the initial count is written, where n
indicates the loaded count.

A high gate input enables counting; a low gate input disables
counting. The gate input has no effect on the output.

Figure 2-13 illustrates software-triggered strobe mode.

Software writes initial
count value of 3

Output

Figure 2-13. Software-Triggered Strobe Mode

Software loads counter
with initial count

3 2

1

Counter/Timer Features 2-25

Clock pulse

• Hardware-triggered strobe (Mode 5) — The output is initially
high. A rising edge of the gate input acts as a trigger. The counter is
loaded with the initial count value on the next clock pulse after the
trigger, but the counter does not start counting. At the next clock
pulse, the counter starts counting down. When the counter reaches
zero, the output goes low for one clock pulse and then goes high
again. Note that the output does not go low until n + 1 clock pulses
after the trigger event occurs, where n indicates the loaded count.

After the trigger event occurs, the gate input has no effect on the
output. Writing a new value during counting does not affect the
counting sequence.

Figure 2-14 illustrates hardware-triggered strobe mode.

Rising edge of gate
input acts as trigger

Output

Figure 2-14. Hardware-Triggered Strobe Mode

Counter is loaded with
initial count value of 3

3 2

1

2-26 Functional Description

Using the Timer-Counter Enable with the Counter

The Timer Counter Enable register is a 2-bit Write Only register located
at BASE ADDRESS +Fh. The register is described in more detail in
Appendix C. If the least significant bit, C0, is high, it allows IP0/TRIG0
to control the gates of Counters 2 and 3. This provides a means of holding
off trigger pulses to the A/D from the programmable timer until IP0 is
taken high. If C0 is low, then IP0 has no control over the programmable
interval timer.

The second bit, C1, controls the source of the clock input for Counter 0. If
C1 = 0, then the external clock input, COUNTER 0 IN, is enabled. If
C1 = 1 then Counter 0 is connected to a stable 100KHz internal crystal
clock source. This is useful if Counter 0 is used for pulse width
measurement, delay generation, frequency synthesis, or a secondary
timer.

Generating Square Waves of Programmed Frequency

Both the Counter 1 and 2 combination and Counter 0 may be used to
generate square waves of programmable frequency. With the C1 bit of the
Timer Counter Enable register set high and Counter 0 clock input open or
high, Counter 0 is internally connected to a 100KHz crystal signal source.
Counter 0 can be operated in Mode 3 (square wave generator) with a
maximum divisor of 65,536. The lowest output frequency obtainable
from Counter 0 directly will be about 1.5Hz (100000 / 65535). The
minimum divisor can be as low as 2 to obtain a maximum output
frequency of 50KHz.

Use DriverLINX to select the square wave configuration. Counters 1 and
2 provide considerable flexibility in frequency range, a minimum division
ratio of 4 (2 x 2) with a 10Mhz clock providing a 2.5MHz output at one
extreme, and a division ratio of 232 (65,535 x 65,535) with a 1MHz clock
providing an output of about 1 pulse/hour at the other extreme.

In practice, to obtain a symmetrical square wave, the divisor loaded into
the counter should be an even number. If it is an odd number, one half of
the square wave will be 1 input clock pulse period longer than the other
half.

Counter/Timer Features 2-27

Calculating the divisor is straightforward. Assume you desire an output
frequency of 1KHz. The input frequency to the Counter 0 is 100Khz so
you must divide this by 100 to obtain 1Khz.

Measuring Frequency and Period

It is possible to use the 82C54 to measure frequency by raising the gate
input of Counter 0 for some known interval of time, say 10, 100, or
1000ms and counting the number of pulses clocked into the counter for
that interval. The gating signal can be derived from Counters 1 and 2
operating in square–wave mode. Also, the computer has to be informed
about the start and finish of the measurement cycle, so one of the DAS-16
digital inputs can be used to monitor the gate input to achieve this
requirement.

Counter 0 can also be used to measure pulse width or half period of a
periodic signal. The signal should be applied to the gate input of Counter
0 and a known frequency applied to Counter 0 clock input (100KHz)
from the internal crystal. During the interval when the gate input is low,
Counter 0 is loaded with a full count, 65,536. The gate input then goes
high at the beginning of the measurement, and the counter decrements
until the gate input goes low at the end of the pulse. The counter is then
read and the change in the count is the duration of the gate input signal. If
Counter 0 is fed with 10 microsecond duration clock pulses (100KHz),
the maximum pulse duration that can be measured is 65,535*10 = 655
milliseconds. Longer pulse durations can be measured using Counters 1
and 2 as an input clock source for Counter 0. One of the digital inputs
should also be connected to the gate of Counter 0 to synchronize the
loading and reading operations.

2-28 Functional Description

Frequency Measurement

Without external hardware, support of frequency measurement using the
DAS-16 hardware configuration is limited. Frequency measurement
requires an external connection between two counters.

Frequency measurement requires two counter/timers used as
measurement and gating counters. The unknown frequency is input as the
clock source to the measurement counter. The gate input of the
measurement counter is then activated for a known interval as timed by
the gating counter. The gating counter is clocked from a known internal
crystal reference clock.

Gating Counter

Internal Clock

Unknown Frequency

Figure 2-15. Counter Setup for Frequency Measurement

Gate
Clock In

Measurement Counter

Gate
Clock In

Clock Out

Clock Out

The unknown input frequency is then calculated as

""Frequency

Measured count

--------------------------------------=
Gate time

The accuracy of the measurement is a function of the unknown input
frequency and the gate time. As the input frequency decreases, the gate
time must increase to preserve accuracy. It is the responsibility of the
application program to chose the gate time. To measure a 0.1Hz signal,
the gate time should be approximately three minutes.

In DriverLINX for the DAS-16, logical counter 0 is the measurement
counter and logical counter 1 is the gating counter. Therefore, the
operation is only defined for logical counter 1 which uses the 1/10 MHz
internal clock. The output of logical counter 1 (Counter 2 Out [pin 20])
must be externally connected to the gate input of logical counter 0 (Gate

Counter/Timer Features 2-29

0/IP2 [pin 24]). The frequency to be measured is fed to the clock input of
logical counter 0 (Counter 0 In [pin 21], active low). Remember the
signal must be TTL (0 to 5 volts). Do not exceed this voltage range as
damage to the counter could result.

Clock pulses are defined as a falling edge followed by a rising edge. This
is a function of the Intel 82C54 hardware and cannot be changed without
external hardware.

Refer to 82C54 documentation for information on programming the
82C54 counter/timer circuitry for general-purpose tasks. Table 2-1 lists
several companies that provide documentation for the 82C54.

Table 2-1. Sources for 82C54 Documentation

Company Address and Telephone Number

Intel Corporation Literature Sales

P.O. Box 7641
Mt. Prospect, IL 60056-7641
[phone]

Harris Semiconductor Literature Department

P.O. Box 883, MS CB1-28
Melbourne, FL 32901
[phone]

Newbridge
Microsystems

603 March Road
Kanata, Ontario
Canada K2K 1X3
[phone]
[phone]

2-30 Functional Description

Triggering the A/D Periodically

When you are using the A/D converter, one of the key uses for the 82C54
programmable interval timer is in providing trigger pulses for starting the
A/D to perform periodic samples.

Figure 2-16. Using Counter 0 to Generate a Delayed Start

You can set up any given output frequency to load Counters 1 and 2 with
the required divisors. As an example, let us set up a trigger rate of

8.3KHz. First, work out the overall division ratio from 1MHz or 10MHz
(depending on setting of TIMER jumper block):

1,000,000 / 8300 = 120.48 (for 1MHz clock)

The closest frequency obtainable will be:

1,000,000 / 120 = 8.333 KHz

Next, apportion the divisor between the 2 counters:

If we had used the 10MHz clock source we could get closer to the desired
frequency of 8.300KHz with the limitation of integer division ratios of the
counters:

10,000,000 / 8300 = 1204.8 (for 10MHz clock)

The closest frequency obtainable will be:

10,000,000 / 1205 = 8.299KHz

Counter/Timer Features 2-31

Note that a counter cannot divide by one; the minimum divisor is two, and
the maximum 65,536. Initialize Counters 1 and 2 to the Rate Generator
configuration with a division ratio of 1,000. You can change the frequency
(division ration) while not altering the counter configuration.

Generating Interrupts with the Counter/Timer

DAS-16 architecture does not allow direct generation of an interrupt from
the Counter/Timer. However, it is easy to set up the A/D to be triggered by
the Counter/Timer and in turn have the A/D generate an interrupt at the
end of its conversion cycle (a constant delay of 8-12 microseconds). This
setup is performed through the DAS-16 control register. Indirectly, this
accomplishes the desired result of generating a periodic interrupt from the
timer, and you can then install any desired interrupt routine to service the
interrupt.

Note also that it is possible to trigger the A/D any other way (externally or
by a programmed write to an I/O port) and invoke an interrupt at the end
of A/D conversion in the same way.

An interrupt request level in the range 2–7 must be selected in the
DriverLINX software. Interrupt lines can be shared so long as two devices
sharing an interrupt will not be used concurrently.

2-32 Functional Description

Wait State Selection

Although most current-generation PCs and compatibles extend bus cycles
during 8-bit data transfers, the DAS-16 Series provides a
jumper-configurable option that allows you to enable or disable wait
states that extend bus cycles during 8-bit data transfers.

Inclusion of this option maintains backward compatibility with boards
that may be used in early generation machines.

Power

+5V power is available from the main I/O connector. The +5V supply is
brought out from your host computer.

Wait State Selection 2-33

2-34 Functional Description

Setup and Installation

Read this section and all related DriverLINX documentation before you
attempt to install and use your DAS-16 Series board.

Unwrapping and Inspecting Your Board

After you remove the wrapped board from its outer shipping carton,
proceed as follows:

1. Your board is packaged at the factory in an anti-static wrapper that
must not be removed until you have discharged any static electricity
by either of the following methods:

– If you are equipped with a grounded wrist strap, you discharge

static electricity as soon as you hold the wrapped board.

3

– If you are not equipped with a grounded wrist strap, discharge

static electricity by holding the wrapped board in one hand while
placing your other hand firmly on a metal portion of the computer
chassis (your computer must be turned off but grounded).

2. Carefully unwrap your board from its anti-static wrapping material.
(You may store the wrapping material for future use.)

3. Inspect the board for signs of damage. If damage is apparent, arrange
to return the board to the factory (see Section 7).

4. Check the remaining contents of your package against the packing
list to be sure your order is complete. Immediately report any missing
items.

5. When you are satisfied with the inspection, proceed with the software
and hardware setup instructions.

Unwrapping and Inspecting Your Board 3-1

Note: DAS-16 Series boards are factory calibrated; they require no

further adjustment prior to installation. If at a later time you decide to
recalibrate the board, refer to Section 6 for instructions.

Standard Software for DAS-16 Series Boards

Important: As a precaution against a system crash the first time you

install and test any new hardware, you should exit all other programs and,
if you use a disk cache, disable write caching. If the system does crash
and you’re using disk compression software or a disk cache utility, as a
precaution after any crash, run the utility that checks the directory
structures.

This section describes how to install the DAS-16 Series standard software
package. The contents of these software packages are described as
follows:

● DAS-16 Series standard software package — Shipped with

DAS-16 Series boards. Includes DriverLINX for Microsoft Windows
and function libraries for writing application programs under
Windows in a high-level language such as C/C++, Turbo Pascal, and
Visual Basic; Delphi, Test Point, LabVIEW support files; utility
programs; and language-specific example programs.

● DriverLINX — The high-performance real-time data-acquisition

device drivers for Windows application development includes:
– DriverLINX API DLLs and drivers supporting the DAS-16 Series

hardware.

– Analog I/O Panel — A DriverLINX program that verifies the

installation and configuration of DriverLINX to your DAS-16
Series board and demonstrates several virtual bench-top
instruments.

– Learn DriverLINX — An interactive learning and demonstration

program for DriverLINX that includes a Digital Storage
Oscilloscope.

– Source Code — for the sample programs.

3-2 Setup and Installation

– DriverLINX Application Programming Interface files — for the

DAS-16 Series compiler.

– DriverLINX On-line Help System — provides immediate help as

you operate DriverLINX.

– Supplemental Documentation — on DriverLINX installation and

configuration; analog and digital I/O programming; counter/timer
programming; technical reference; and information specific to the
DAS-16 Series hardware.

● DAS-16 Series utilities — The following utilities are provided as

part of both the DAS-16 Series standard software package:
– DriverLINX Calibration Utility
– DriverLINX Test Utility

● LV-16 — LabVIEW driver for the DAS-16 Series boards.

Standard Software for DAS-16 Series Boards 3-3

Installing the Software

Note: Install the DriverLINX software before installing the DAS-16

Series board. Otherwise, the device drivers will be more difficult to
install.

Software Options

Users of DAS-16 Series boards have the following two software options.
In both cases, the software interfaces with your system via the
DriverLINX software provided with your board.

● The user can run a fully integrated data-acquisition software package

such as TestPoint or LabVIEW.

● The user can write and run a custom program in Visual C/C++, Visual

Basic, or Delphi, using the programming support provided in the
DriverLINX software.

The DAS-16 Series has fully functional driver support for use under
Windows 95/98/NT.

DriverLINX driver software for Windows 95/98/NT

DriverLINX software, supplied by Keithley with the DAS-16 Series
board, provides convenient interfaces to configure analog and digital I/O
modes without register-level programming.

Most importantly, however, DriverLINX supports those programmers
who wish to create custom applications using Visual C/C++, Visual Basic,
or Delphi. DriverLINX accomplishes foreground and background tasks to
perform data acquisition. The software includes memory and data buffer
management, event triggering, extensive error checking, and context
sensitive on-line help.

DriverLINX provides application developers a standardized interface to
over 100 services for creating foreground and background tasks for the
following:

3-4 Setup and Installation

● Analog input and output

● Digital input and output

● Time and frequency measurement

● Event counting

● Pulse output

● Period measurement

In addition to basic I/O support, DriverLINX also provides:

● Built-in capabilities to handle memory and data buffer management.

● A selection of starting and stopping trigger events.

● Extensive error checking.

● Context-sensitive on-line help system.

DriverLINX is essentially hardware independent, because its portable
APIs (Application Programming Interfaces) work across various
operating systems. This capability eliminates unnecessary
programming when changing operating system platforms.

TestPoint

TestPoint is a fully featured, integrated application package that
incorporates many commonly used math, analysis, report generation, and
graphics functions. The TestPoint graphical drag-and-drop interface can
be used to create data acquisition applications, without programming, for
IEEE-488 instruments, data acquisition boards, and RS232-485
instruments and devices.

TestPoint includes features for controlling external devices, responding to
events, processing data, creating report files, and exchanging information
with other Windows programs. It provides libraries for controlling most
popular GPIB instruments. OCX controls plug directly into TestPoint,
allowing additional features from third party suppliers.

TestPoint interfaces with your DAS-16 Series board through DriverLINX,
using a driver that is provided by the manufacturer.

Installing the Software 3-5

LabVIEW

LabVIEW is a fully featured graphical programming language used to
create virtual instrumentation. It consists of an interactive user interface,
complete with knobs, slide switches, graphs, strip charts, and other
instrument panel controls. Its data-driven environment uses function
blocks that are virtually wired together and pass data to each other. The
function blocks, which are selected from palette menus, range from
arithmetic functions to advanced acquisition, control, and analysis
routines. Also included are debugging tools, help windows, execution
highlighting, single stepping, probes, and breakpoints to trace and
monitor the data flow execution. LabVIEW can be used to create
professional applications with minimal programming.

A Keithley VI palette provides standard virtual instruments (VIs) for
LabVIEW that interface with your DAS-16 Series board through
DriverLINX. The needed driver is provided on your DriverLINX
CD-ROM.

3-6 Setup and Installation

Installing DriverLINX

Refer to the instructions on the Read this first sheet and the manuals on
the DriverLINX CD-ROM, both shipped with your board, for information
on installing and using DriverLINX.

Installing Application Software and Drivers

Installing the TestPoint software and driver

The DriverLINX driver for TestPoint is provided as part of the TestPoint
software. The driver therefore installs automatically when you install
TestPoint.

You can install TestPoint application software at any time before or after
installing DriverLINX and the DAS-16 Series board. For TestPoint
installation instructions, consult the manual provided with TestPoint.

Note: Before using TestPoint with the DAS-16 version of DriverLINX,

check with Keithley to ensure that your version of TestPoint is compatible
with DriverLINX.

Installing the LabVIEW software and driver

A DriverLINX driver for LabVIEW is provided on your DriverLINX
CD-ROM. The LabVIEW driver does not install automatically when you
install DriverLINX and your board. You must first install the LabVIEW
application program, then install the DriverLINX driver. Access the
LabVIEW driver installation routine by starting setup.exe on the
DriverLINX CD-ROM, then selecting LabVIEW Support from the Install
These DriverLINX components screen.

Consult the manual provided by National Instruments for LabVIEW
installation instructions.

Installing DriverLINX 3-7

Setting Switch-Configurable Options

This section contains information and illustrations that you can use to
verify default switch configurations and reconfigure switch-configurable
options. Sections 1 and 2 contain information about product features that
help you determine the board configuration that best suits the needs of
your application.

Be sure to make note of the configuration of all switches and jumpers on
the board. You will use this information to enter the correct configuration
parameters using DriverLINX. Also locate any information or notes about
the interrupt and DMA channels used by the other hardware devices in
your computer system.

Figure 3-1 shows the switches for DAS-16/16F Series boards; Figure 3-2
shows the switches for the DAS-16G1/G2 Series boards. The remaining
subsections describe the switches and how to configure them.

Figure 3-1. Default Switch Configuration for DAS-16/16F Series Boards

3-8 Setup and Installation

Figure 3-2. Default Switch Configuration for DAS-16G1/G2 Series Boards

Table 3-1. Default Switch Settings

Switch/Jumper Default

Base Address 300H
DMA Channel 3
A/D Mode 16-Channel Single-Ended
A/D Input Range ±10V
A/D Coding Straight Binary
Timer Source Clock 1MHz

Setting Switch-Configurable Options 3-9

DAS-16 must be configured for operation via several on-board switches,
as follows:

Wait State
Base Address
Channel/System Configuration
Unipolar/Bipolar Modes
DMA Level Select
Gain (DAS-16/16F only)

Except for Base Address, none of these functions requires immediate
attention.

Base Address Switch

Figure 3-3. Base Address Switch

The DAS-16 is factory-configured for a Base Address of 300 Hex (768
decimal). If this Base Address is already occupied, you will need to
change the Base Address switch setting. (Figure 3-3 shows the Base
Address Switch.) It is essential that each peripheral device, such as a
DAS-16, be assigned a unique Base Address within the range of 200 to
3F0 (512 to 1008 Decimal) and that the address is on a 16-byte boundary.
Use Table 3-2 as an aid to selecting an unoccupied Base Address.

3-10 Setup and Installation

Table 3-2 lists I/O addresses commonly used by IBM PC/XT, AT, and
compatible computers. Determine an even boundary of eight I/O
addresses within the range of 000H to 3F8H that are not being used by
another resource in your system (including another DAS-16 Series
board), and set the switches to the appropriate base address.

Table 3-2. I/O Address Map (000H to 3FFH)

Address Range Use

000H to 00FH 8237 DMA #1
020H to 021H 8259 PIC #1
040H to 043H 8253 timer
060H to 063H 8255 PPI (XT)
060H to 064H 8742 controller (AT)
060H to 06FH 8042 Keyboard controller
070H to 071H CMOS RAM and NMI mask register (AT)
080H to 08FH DMA page registers
0A0H to 0A1H 8259 PIC #2 (AT)
0A0H to 0AFH NMI mask register (XT)
0C0H to 0DFH 8237 DMA #2 (AT - word-mapped)
0F0H to 0FFH 80287 numeric processor (AT)
170H to 177H Hard disk controller #1
1F0H to 1F8H Hard disk controller #2
1F0H to 1FFH Hard disk controller (AT)
200H to 2FFH Game / control
210H to 21FH Expansion unit (XT)
238H to 23BH Bus mouse
23CH to 23FH Alternate bus mouse
278H to 27FH Parallel printer
2B0H to 2DFH EGA
2E0H to 2EFH GPIB (AT)
2E8H to 2EFH Serial port

Setting Switch-Configurable Options 3-11

Table 3-2. I/O Address Map (000H to 3FFH) (cont.)

Address Range Use

2F8H to 2FFH Serial port
300H to 31FH Prototype card
320H to 32FH Hard disk (XT)
370H to 377H Floppy disk controller #2
378H to 37FH Parallel printer
380H to 38FH SDLC
3A0H to 3AFH SDLC
3B0H to 3BBH MDA
3BCH to 3BFH Parallel printer
3C0H to 3CFH VGA EGA
3D0H to 3DFH CGA
3E8H to 3EFH Serial port
3F0H to 3F7H Floppy disk controller #1
3F8H to 3FFH Serial port

Channel (System) Configuration Switch

This slide switch is used to select whether 8 differential or 16
single-ended analog input channels are to be used. On the DAS-16/16F,
this switch is marked CHAN CONF. On the DAS-16G, it is marked SYS
CONFIG. On either switch, to select eight differential input channels,
move the switch to the right (towards the 8 designator). Likewise, to
select 16 single-ended analog input channels, move the switch to the left
(towards the 16 designator).

DMA Level Switch

This slide switch selects the DMA level. This two-position slide switch
selects the DMA as 1 or 3. Some early PC’s utilize Channel 3 for their
hard drives. If this is the case, you cannot choose DMA Channel 3 for
your DAS-16. More information regarding DMA is provided in Appendix
D.

3-12 Setup and Installation

A/D Switch

This slide switch controls the input range. When moved to the UNI
(unipolar) position, inputs can be positive only (ranges are from zero to
some positive full-scale voltage). When moved to the BIP (bipolar)
position, inputs can range from equal negative to positive full scale limits.

GAIN Switch (DAS-16/16F Only)

This switch is a 5-position DIP switch and is found only on the
DAS-16/16F boards. The five positions on the switch are marked A, B,
C, D, and USER. These are used to set the range as shown in Table 3-3.

Table 3-3. DAS-16/16F Gain Switch Positions

A B C D USER UNIPOLAR BIPOLAR
OFF OFF OFF OFF OFF N/A ± 10V
ON OFF OFF OFF OFF 0-10V ± 5V
ON ON OFF OFF OFF 0-5V ± 2.5V
ON OFF ON OFF OFF 0-2V ± 1V
ON OFF OFF ON OFF 0-1V ± 0.5V
ON OFF OFF OFF ON User Set User Set

Setting Switch-Configurable Options 3-13

Jumpers

The DAS-16/16F has only one jumper block: the TIMER jumper block.
The DAS-16G has two jumper blocks: the TIMER and WAIT STATE
jumper blocks.

The TIMER Jumper

This jumper selects a timer input frequency of 10MHz or 1MHz. For most
applications, 10MHz is more useful and will give a finer time interval
resolution at higher conversion rates.

The WAIT STATE Jumper

This jumper, when set to ON, will cause the DAS-16G to generate a
450ns wait state on I/O accesses. This jumper will only need to be set to
ON, if you have built your own computer and know that the I/O read and
write pulses will be less than 210ns duration.

Generally, this jumper should be in the OFF position. Most computer
manufacturers include internal wait states on all I/O accesses to maintain
compatibility with other standard peripherals.

3-14 Setup and Installation

Main I/O Connector

Analog and Digital I/O occurs through a 37-pin, D-type connector that
projects through the computer case at the rear of the board. The mating
connector for DAS-16 is a standard, 37-pin D-type female such as an
ITT/Cannon #DC-37S for soldered connections. Insulation displacement
(flat cable) types are readily available (for example, Amp #745242-1).
Other manufacturers make equivalent parts. This connector and its signal
conductor functions are described in Figure 3-4.

Figure 3-4. Main I/O Connector

Note: Pins 11 through 18 perform a double function depending on the

setting of the channel configuration switch. In 8-channel differential
configuration, these pins provide the low inputs of Channels 0 – 7
corresponding to the high inputs of these channels on Pins 30 – 37. In 16
channel single-ended configuration, they provide additional channel high
inputs for Channels 8 – 15.

Main I/O Connector 3-15

Setting up the Computer

Caution: To prevent damage that can occur when handling electronic

equipment, use a ground strap or similar device when performing this
installation procedure.

Caution: Installing or removing a board while power is on can damage

your computer.

1. Turn off the computer.

2. Turn off all peripherals (printer, modem, monitor, and so on)
connected to the computer.

3. Unplug the computer and all peripherals.

4. Remove the cover from you computer. Refer to your computer’s user
manual for instructions.

Selecting an Expansion Slot

1. Select a 32-bit or 64-bit ISA expansion slot.

ISA slots are longer than PCI slots. One of the ISA slots may be a
shared ISA/PCI slot. If a PCI board exists in the shared slot, you
cannot use the slot for an ISA board; if an ISA board exists in the
shared slot, you cannot use the slot for a PCI board.

2. Remove the cover plate from the selected expansion slot. Retain the
screw that held it in place; you will use it later to install the board.

3-16 Setup and Installation

Installing the Board

Note: You must observe the current-capacity limits of the PC supply;

allow for the power used by any other boards that may be in use. See
Appendix A for DAS-16 Series power requirements.

1. Make sure the option switch settings match the settings shown in the
configuration-utility switch diagram.

2. Carefully lower the board into the ISA expansion slot using the card
guide to properly align the board in the slot. When the bottom of the
board contacts the bus connector, gently press down on the board
until it clicks into place.

Caution: Do not force the board into place. Moving the board from side

to side during installation may damage the bus connector. If you
encounter resistance when inserting the board, remove the board and try
again.

3. Secure the board in place at the rear panel of the system unit using the
screw removed from the slot cover.

4. Replace the computer cover.

5. Turn on power to the computer.

DAS-16

Series Board

ISA Expansion Slot

Bus Connector

Figure 3-5. Installing the DAS-16 Series Board

Rear of Computer

Installing the Board 3-17

Configuring DriverLINX

After you have successfully installed the DAS-16 Series board in your
computer, start Windows to install DriverLINX. For detailed instructions
on installing DriverLINX, see the documentation provided on the
DriverLINX CD-ROM; especially the DriverLINX Installation and

Configuration Guide and Appendix F: Configuration and Implementation
Notes—for Keithley DAS-16/1600 manuals.

Run “Learn DriverLINX” (LearnDL.exe) from the DriverLINX
program group to tell DriverLINX how you configured your DAS-16
Series board and to verify that everything is properly installed
and configured.

1. Start Windows as you normally would and select the Program
Manager window. Install DriverLINX if you have not previously
done so.

2. Select the “Learn DriverLINX” icon created when you installed
DriverLINX. You may also use the Command Line edit box activated
by selecting Run... option from the File menu. Enter
“<drive>:/DRVLNX/LEARNDL” in the command line edit box
(<drive> is the letter of the hard disk drive where DriverLINX is
installed).

3. Immediately after loading Learn DL, the Open DriverLINX DLL
dialog box appears. Select the name of the hardware-specific DLL
from the list for your DAS-16 board. The name is an abbreviation of
the board’s model number.

4. From the main menu bar of Learn DL, select the Device menu and

choose Select....

5. Select the Logical Device you wish to configure and then click on the
OK button (return).

6. Again select the Device menu and then choose the Configure... option
to display the Device Configuration Dialog Box.

7. From the Model list, select the model name for your DAS-16 Series
board you are configuring.

8. If the value displayed in the Address edit box is not correct, type the
correct value into the box. You may enter the address in decimal or

3-18 Setup and Installation

hexadecimal using the c-notation for hex, (that is, 768 decimal =
0x300 hexadecimal).

9. Choose the correct options for the Analog, Digital, and
Counter/Timer Sections by first clicking on the appropriate radio
button in the middle of the dialog box and then completing the group
of dialog fields in the lower third of the dialog box. Be sure to click on
both the Input and Output radio buttons for the Analog and Digital
groups to see all the dialog fields.

10. After you have made your selections, save the configuration
parameters by clicking on the OK button. This will create or update
the configuration file in the Windows directory.

11. Repeat the preceding steps, starting at step 5, for each Logical Device
you wish to configure.

You can use DriverLINX to verify board operation:

1. To physically initialize the DAS-16, select Device/Initialize from the
main menu in Learn DriverLINX.

2. The first time the DAS-16 is initialized, or after a configuration
change, DriverLINX runs a diagnostic program to verify the
operation and accuracy of the configuration settings.

You can use the control panel (see Section 5 to verify board operation).

Configuring DriverLINX 3-19

3-20 Setup and Installation

4

Cabling and Wiring

In most applications, you use accessories to connect external I/O devices
to the DAS-16 Series boards. Keithley accessories extend signals from the
main I/O connector to corresponding screw terminals of the accessory.

This section describes the cabling and accessories required for attaching
field wiring to your DAS-16 Series boards.

Caution: To avoid electrical damage, turn off power to the computer and

any attached accessories before making connections to DAS-16 Series
boards.

4-1

Attaching Screw Terminal Accessories

You can use the following screw terminal connectors and accessories to
simplify connection of field wiring to DAS-16 Series boards:

● STC-37 screw terminal connector; when using a DAS-16 Series

board, your application may require two connectors.

● STP-37 screw terminal panel; when using a DAS-16 Series board,

your application may require two panels.

● STA-16 screw terminal accessory.

● STA-U universal screw terminal accessory.

The following sections describe how to attach these accessories to
DAS-16 Series boards.

Attaching an STC-37

The screw terminals on the STC-37 screw-terminal connector allow you
to connect field wiring to a DAS-16 Series board. The screw terminals
accept wire sizes 12 – 22 AWG.

To connect an STC-37 to the main I/O connector of a DAS-16 Series
board, attach the 37-pin connector on the STC-37 directly to the main I/O
connector. Figure 4-1 illustrates the connection of an STC-37 to a
DAS-16 Series board.

4-2 Cabling and Wiring

STC-37 Screw Terminal

Connector

21

17

16

DAS-16 Series Board

5
4

Pin 1

1

Figure 4-1. Attaching an STC-37 Screw Terminal Connector

37

34

33

22

Strain Relief

The screw terminals are labeled from 1 to 37 and correspond directly to
the functions of the pins on the main I/O connector (see Figure 4-2). For
example, since pin 25 is assigned to IP0/TRIG 0, use screw terminal 25 to
attach a digital signal to bit 0 of the standard digital input port.

Attaching Screw Terminal Accessories 4-3

Figure 4-2. Pin Assignments of the Main I/O Connector.

Attaching an STP-37

The screw terminals on the STP-37 screw terminal panel allow you to
connect field wiring to DAS-16 Series boards. The STP-37 contains the
following components:

● A 37-pin male connector for cabling to the main I/O connector of a

DAS-16 Series board.

● Labeled screw terminals for connecting sensor outputs and test

equipment. These terminals accept wire sizes 12 through 22 AWG.

You attach an STP-37 screw terminal panel to the main I/O connector on
the DAS-16 Series board with a C-1800 or S-1800 cable. The C-1800 is
the unshielded version of the cable; the S-1800 is the shielded version of
the cable. Figure 4-3 shows how to attach an STP-37 to a DAS-16 Series
board.

4-4 Cabling and Wiring

C-1800 / S-1800 Cable

J1

1

19

20

38

DAS-16 Series Board

Figure 4-3. Attaching an STP-37 to the Main I/O Connector

The screw terminals are labeled 1 to 38 and correspond directly to the
functions of the main I/O connector. See Figure 4-2 for the pin
assignments of the main I/O connector.

Attaching an STA-16

The screw terminals on the STA-16 screw terminal accessory allow you to
connect field wiring to DAS-16 Series boards. The STA-16 contains the
following components:

● Two 37-pin male connectors. One for cabling to the main I/O

connector of a DAS-16 Series board and a second for daisy-chaining
additional accessories.

● Labeled screw terminals for connecting sensor outputs and test

equipment. These terminals accept wire sizes 12 through 22 AWG.

STP-37

● A breadboard area for user-installed circuitry.

Attach an STA-16 screw terminal accessory to the main I/O connector on
the DAS-16 Series board with a C-1800 or S-1800 cable. The C-1800 is
the unshielded version of the cable; the S-1800 is the shielded version of
the cable. Figure 4-4 shows how to attach an STA-16 to a DAS-16 Series
board.

Attaching Screw Terminal Accessories 4-5

C-1800 / S-1800 Cable

J1

J2

DAS-16 Series Board

Figure 4-5 shows the screw terminal names on the STA-16.

0 LO /

HI

GND

8 HI

LL

OP 3

CH 1HI1 LO /

OP 2

OP 1

CH 0

J2J1

+5 V

Pin 1

Pin 1

Figure 4-4. Attaching an STA-16

12 HI

OUT

CTR 2

CH 4HI4 LO /

GND

OUT

CTR 0

9 HI

OP 0

LL

GND

GND

CH 2

HI

IP 3

10 HI

LL

2 LO /

IP 3

GND

CH 3HI3 LO /

IP 3

IP 3

11 HILLGND

GND

GND

LL

0

CTR

CH 5

IN

HI

5 LO /

1

USER

USER

13 HI

LL

LL

2

GND

CH 6

GND

D/A 0

STA-16

HI

14 HILLGND

6 LO /

OUT

REF IN

D/A 0

VREF

-5 V

15 HILLGND

CH 7HI7 LO /

OUT

D/A 1

REF IN

D/A 1

GND

Figure 4-5. STA-16 Terminal Names

4-6 Cabling and Wiring

Attaching Expansion Accessories

You can use the following expansion accessories to increase the number
of channels available and add signal conditioning to your application:

● EXP-16

● EXP-16/A

● EXP-GP

The following section describes how to attach these expansion
accessories to DAS-16 Series boards.

Attaching an EXP-16 or EXP-16/A Expansion Accessory

Each expansion multiplexer/amplifier accessory provides up to 16 analog
input channels (labeled 0 to 15). Table 4-1 lists the terminal names used
on EXP-16 and EXP-16/A expansion accessories.

Table 4-1. EXP-16 and EXP-16/A Terminal Names

Terminal Name Signal

LL GND low-level ground
CHn HI positive input; where n indicates the channel number
CHn LO negative input; where n indicates the channel number

To connect an EXP-16 or EXP-16/A to a DAS-16 Series board, you must
first connect an STA-16 or STA-MB accessory, as shown in Figure 4-6.

Attaching Expansion Accessories 4-7

DAS-16 Series

Board

C-1800

or

S-1800

S-1600

STA-16

or

STA-MB

Figure 4-6. Attaching an EXP-16 or EXP-16/A Expansion Accessory

Note: The S-1600 cable must be used to connect the first EXP to the

DAS-16 Series board.

Refer to the EXP-16 and EXP-16/A expansion board documentation for
more information about these accessories and instructions for installing
the PG-408A option on the board.

Attaching an EXP-GP Expansion Accessory

Each EXP-GP expansion multiplexer/signal conditioner board provides
up to eight analog input channels (labeled 0 to 7). Table 4-2 lists the
terminal names used on each EXP-GP channel.

EXP-16 or
EXP-16/A

Table 4-2. EXP-GP Terminal Names

Terminal Name Signal

+IEXC positive current excitation
+SENSE positive input

−P negative voltage excitation

IEXC negative current excitation

−

−SENSE negative input

+P positive voltage excitation

4-8 Cabling and Wiring

To connect an EXP-GP to a DAS-16 Series board, attach one end of an
S-1600 cable to the DAS-16 Series main I/O connector and the other end
of the cable to the J1 connector on the EXP-GP. Figure 4-7 illustrates the
connection of an EXP-GP to a DAS-16 Series board.

DAS-16 Series

Board

C-1800

or

S-1800

STA-16

or

STA-MB

Figure 4-7. Attaching an EXP-GP Expansion Accessory

Refer to the EXP-GP expansion board documentation for more
information about this expansion accessory.

Attaching Multiple Expansion Accessories

You can cascade up to eight EXP-16, EXP-16/A, and/or EXP-GP
expansion accessories to provide up to 128 analog input channels.

Figure 4-8 shows how to attach multiple EXP-16, EXP-16/A, and
EXP-GP accessories to a DAS-16 Series board.

S-1600

EXP-GP

Notes: In a mix of EXP-16, EXP-16/A, and EXP-GP accessories,

the EXP-16 and EXP-16/A accessories must be placed ahead of the
EXP-GP accessories.

All multiple EXP-16 and EXP-16/A accessories attached to a DAS-16
Series board, as shown in Figure 4-8, must contain a PG408A accessory.

Attaching Expansion Accessories 4-9

DAS-16 Series

Board

C-1800

or

S-1800

S-1600

C-1800 or
S-1800

C-1800 or
S-1800

STA-16

or

STA-MB

EXP-16 or
EXP-16/A
with PG408

EXP-16 or
EXP-16/A
with PG408

EXP-GP

Figure 4-8. Attaching Multiple EXP-16, EXP-16/A, and /or EXP-GP Accessories

Notes: Each EXP-16, EXP-16/A, or EXP-GP expansion accessory is

associated with an analog input channel on a DAS-16 Series board. You
specify the associated DAS-16 input channel by setting a jumper on each
expansion accessory. Use a unique jumper setting for each expansion
accessory you are using. Refer to your expansion board documentation
for more information.

4-10 Cabling and Wiring

Attaching an MB Series Backplane

MB Series modules are ideally suited to applications where monitoring
and control of temperature, pressure, flow, and other analog signals are
required. Figure 4-9 shows a block diagram of a typical MB Series
measurement and control application.

mV, V, Thermocouple,

RTD, Strain Gauge,

4–20mA / 0–20mA

Sensors,
Monitors

Process or
Equipment

Controls

(Valves, etc.)

Figure 4-9. Typical Measurement and Control Application

Input

Module

MB SERIES

MODULES

Output Module

4–20mA / 0–20mA

0 to +5V / ±5V

A/D

Analog I/O

D/A

0 to +5V / ±5V

Computer

Table 4-3 provides a brief summary of the backplanes available for use
with MB Series modules.

Attaching an MB Series Backplane 4-11

Table 4-3. MB Series Backplanes

Model Description

MB01 Holds up to 16 modules and mounts in a 19-inch equipment rack.

Provides direct channel-to-channel connection to a DAS-16
Series board.

MB02 Holds up to 16 modules and mounts in a 19-inch equipment rack.

Up to four MB02s can be multiplexed together, providing a total
of 64 channels. This makes it suitable for larger systems.

MB05 Functionally equivalent to half an MB01, the MB05 backplane

accepts eight modules. Provides direct channel-to-channel
connection to a DAS-16 Series board.

STA-MB Holds up to four modules and provides general-purpose screw

terminal connections for all other signals on the DAS16 Series
board.

Attaching an MB01/05 Backplane

Use the C16-MB1 cable to connect a DAS-16 Series board to an
MB01/05 backplane. This cable connects MB01/05 channels 0 through
15 to analog input channels 0 through 15 on the DAS-16 Series board.
Refer to Figure 4-10 for a cabling diagram.

DAS-16

Series

Figure 4-10. Attaching an MB01/05 Backplane

Note: The channel connections are single-ended. Make sure that

C16-MB1

MB01/05

Use connector P1 or P2
(identical pinouts)

the DAS-16 Series board is set for 16-channel, single-ended operation.

4-12 Cabling and Wiring

Attaching an MB02 Backplane

Figure 4-11 shows how to connect a DAS-16 Series board to up to four
MB02 backplanes. The STA-SCM16 interface connects one MB02 board
to one analog input channel of the DAS-16 Series board. One C-2600
cable connects each MB02 to the STA-SCM16, and the C-1800 cable
connects the STA-SCM16 to the DAS-16 Series board.

DAS-16 Series

board

C-1800

STA-SCM16

MB02

MB02

MB02

C-2600 (four
cables)

MB02

Figure 4-11. Attaching Multiple MB02 Backplanes

Figure 4-12 shows how the STA-SCM16 connects DAS-16 Series boards
with MB02 backplanes.

Attaching an MB Series Backplane 4-13

A/D CH 0 IN

D/A CH 0 OUT

A/D CH 1 IN

D/A CH 1 OUT

A/D CH 2 IN
A/D CH 3 IN

MB02 Backplane Interfaces

Vread

Vwrite

Vread

Vwrite

Vread

Vread

DAS-16 Series Board

0123

Backplane Connectors

STA-SCM16

Figure 4-12. MB02 I/O Connections

The four digital output lines on the DAS-16 Series boards select one of
the 16 MB02 channels. For example, if you set the digital output lines to
1000 (8 decimal), MB02 channel 8 is selected on all four backplanes.
Analog input channels 0 to 3 on the DAS-16 Series board map directly to
the connectors labeled 0 to 3 on the STA-SCM16. In this arrangement, the
channel connections are single-ended. Make sure that the DAS-16 Series
board is set for single-ended, 16-channel operation. Refer to the MB
Series User’s Guide for more information.

4-14 Cabling and Wiring

Attaching an STA-MB

The screw terminals on the STA-MB screw-terminal accessory accept
field wiring to up to four MB Series modules whose outputs are brought
through an C-1800/S-1800 cable to the main I/O connector of a DAS-16
Series board.

The STA-MB contains the following components:

● Two 37-pin male connectors. One for cabling to the main I/O

connector of a DAS-16 Series board and a second for cascading
additional accessories.

● Labeled screw terminals for connecting sensor outputs and test

equipment. These terminals accept wire sizes 12 through 22 AWG.

● Mounts for up to four MB Series modules.

Attach an STA-MB screw terminal accessory to the main I/O connector
on the DAS-16 Series board with a C-1800 or S-1800 cable. The C-1800
is the unshielded version of the cable; the S-1800 is the shielded version
of the cable. Figure 4-13 shows how to attach an STA-MB to a DAS-16
Series board.

DAS-16 Series Board

C-1800 / S-1800 Cable

Pin 1

Pin 1

J1

J2 J3

STA-MB

Figure 4-13. Cabling and Connections for Attaching an STA-MB

Attaching an MB Series Backplane 4-15

Connecting Analog Input Signals

This section shows circuits for wiring signal sources to input channels of
DAS-16 Series boards. While the circuit diagrams show direct
connections to channel input pins of the main I/O connector, you must
make actual connections through corresponding inputs of an accessory,
such as a screw terminal panel.

The circuit diagrams represent a single signal source wired to a single
channel (channel n). In reality, you can wire eight separate signal sources
to eight differential inputs or 16 separate signal sources to 16
single-ended inputs.

If you expect to use a DAS-16G1 board at high gain, read the
precautionary information in “Precautions for Operating at High Gains”
on page 4-24. Other considerations for I/O connections are offered under
“Additional Precautions” on page 4-25.

Connecting a Signal to a Single-Ended Analog Input

Figure 4-14 shows the connections between a signal source and a
channel of a DAS-16 Series board configured for single-ended input
mode.

DAS-16 Series
Board

Figure 4-14. Connections for Wiring a Signal Source to a DAS-16

Series Board Configured for Single-Ended Inputs

CHANNEL n

HIGH

LL GND

+

−

Signal
Source

4-16 Cabling and Wiring

The main I/O connector contains the following two ground connections:

● POWER GND is the noisy or “dirty” ground that carries all digital

signal and power supply currents.

● LL GND or low level ground is the ground reference for all analog

input functions and it only carries signal currents that are less than a
few mA.

Contact resistance and cable resistance can make a voltage difference of
many millivolts between the two grounds although they are connected to
each other.

Note: When you wire signals to the analog input channels, you are

advised to wire all unused channels to LL GND. This action prevents the
input amplifiers from saturating, and it ensures the accuracy of your data.

Connecting a Signal to a Differential Analog Input

Figure 4-15 shows three methods of wiring a signal source to a channel of
a DAS-16 Series board configured for differential input mode.

Connecting Analog Input Signals 4-17

DAS-16 Series
Board

Channel n High
Channel n Low

R

LL GND

b

Where Rs > 100 ohms Rb
= 2000 R

s

+

Signal

R

s

R

b

Source

−

DAS-16 Series

Channel n High
Channel n Low

+

Board

R

LL GND

b

−

Where Rs < 100 ohms Rb

DAS-16 Series
Board

> 1000 R

Channel n Low

LL GND

s

R

a

R

x

R

a

arm

R

a

Channel n High

Figure 4-15. Three Methods of Wiring Differential Inputs

R

Signal

s

Source

bridge

null

+

Supply

−

DC

4-18 Cabling and Wiring

The upper two circuits of the diagram require the addition of resistors to
provide a bias-current return. You can determine the value of the bias
return resistors (R

) from the value of the source resistance (Rs), using the

b

following relationships:

● When R

is greater than 100Ω, use the connections in the upper

s

circuit. The resistance of each of the two bias return resistors must
equal 2000 R

● When R

.

s

is less than 100Ω, use the connections in the middle circuit.

s

The resistance of the bias return resistor must be greater than 1000 R

In the lower circuit, bias current return is inherently provided by the
source. The circuit requires no bias resistors.

Avoiding a Ground Loop Problem

Very often, the signal-source ground and the DAS-16 Series board ground
are not at the same voltage level because of the distances between
equipment wiring and the building wiring. This difference is referred to as
a common-mode voltage (Vcm) because it is normally common to both
sides of a differential input (it appears between each side and ground).

Using a differential input lets you avoid a ground loop problem. Since a
differential input responds only to the difference in the signals at its high
and low inputs, its common-mode voltages cancel out and leave only the
signal. However, if your input connections contain a ground loop, your
input could see incorrect data readings resulting from the sum of the
signal-source and common-mode voltages. Figure 4-16 shows the proper
way to connect a differential input while Figure 4-17 illustrates the effect
of a ground loop on a differential channel converted to a single-ended
channel by the installation of a wire jumper between Channel n Low and
LL GND on the DAS-16 board side of the cable. Figure 4-17 also
illustrates the ground loop problem for a channel already configured in
the configuration utility as single-ended.

.

s

Avoiding a Ground Loop Problem 4-19

DAS-16 Series
Board

CHANNEL n HIGH
CHANNEL n LOW

V

LL GND

V

g2

cm

R

wire

+

E

s

−

Signal

Signal
Source

Source

Do not connect n LOW to LL
GND at the computer

V

cm =

g1 -

g2

Ground

V

g1

V

V

Figure 4-16. A Differential Input Connection that Avoids a Ground Loop Problem

DAS-16 Series
Board

CHANNEL n HIGH

CHANNEL n LOW

LL GND

V

g2

V

cm =

V

cm

R

wire

V

V

g2

g1 -

+

E

s

−

Signal
Source
Ground

V

g1

Signal
Source

Figure 4-17. Differential or Single-Ended Input Connection that Introduces a Ground

Loop Problem

4-20 Cabling and Wiring

Connecting Analog Output Signals

Make the D/A output connections from the appropriate D/A output and
LL GND, as shown in Figure 4-18.

JUMPER

Figure 4-18. D/A Converter Connections

The D/A reference inputs can be connected to the –5V reference signal on
the rear connector. In this case, the D/A output scaling will be 0 to +5V. It
is also possible to connect the reference inputs to an external reference
signal whether it be AC or DC.

DAS-16 Series boards include two DACs. Refer to the specifications in
Appendix A for voltages, current limits, and other loading information.
Make your connections to the DAC output terminals through

Connecting Analog Output Signals 4-21

corresponding screw terminals of your accessory. Table 4-4 lists the input
and output connections of the DACs in the DAS-16 Series boards.

Table 4-4. DAC Input and Output Connections

Signal Main I/O Connector

D/A 0 User Reference Voltage In pin 10
D/A 1 User Reference Voltage In pin 26
D/A 0 Out pin 9
D/A 1 Out pin 27

Measuring Current and 4–20mA Current Loops

Process control current loop transducers are easily interfaced to DAS-16
by adding a suitable shunt resistor across the input. Since the maximum
current will be 20mA, the precision shunt resistor should have a
resistance in ohms of 50 * Vfs. The resistor should be of
low–temperature, coefficient–metal film or wirewound construction for
stability with time and temperature. Using this interface, the 4–20mA
working range of the current loop corresponds to 80% of the normal
resolution; about 3,277 bits for unipolar ranges and 1,638 bits for bipolar
ranges.

Non–ground referred currents outside the common–mode range can also
be measured with a suitable shunt. Non–ground referred currents can be
measured through an isolation amplifier, DC, or Hall Effect current
transformer.

The D/A Voltage Reference

A –5V stable reference voltage (Vref) is brought out for users. This
voltage is derived from the A/D converter reference. Apart from its use as
a D/A reference, it can also be used for offsetting signals, powering
bridge transducers, etc. The maximum available output source/sink
current is 5mA.

4-22 Cabling and Wiring

Interface to Transducers, Thermocouples, etc.

Low level transducers such as thermocouples and strain gauge bridges
(load cells, pressure and force transducers) require amplification before
applying to the high level DAS-16 inputs. The EXP-16 expansion
multiplexer incorporates an instrumentation amplifier that can provide
stable amplification and also includes circuitry that allows cold junction
compensation of thermocouples. EXP-16 will handle most interfacing
requirements to DC output transducers and also includes spaces for
filters, shunts, and attenuators.

For inexpensive temperature measurement in the –50 to +125˚C
temperature range, semiconductor temperature transducers are a good
choice. The most popular types are the AD590/592 (Analog Devices)
which behave like a constant current source with an output of 273µA at
0˚C and a scaling of 1µA/ ˚C and the LM335 (National Semiconductor)
that has an output of 2.73 volts at 0˚C and a temperature coefficient of
10mV/ ˚C.

For measuring high temperatures, up to 1800˚C or more, thermocouples
are the most satisfactory solution. The base metal thermocouples (types J,
K, T, and E) have outputs around 40 microvolts/ ˚C while the platinum
and tungsten types are used for the highest temperature measurement.
Thermocouple types S, B, and R tend to have lower outputs––in the 6 to
12 microvolt/ ˚C range. A further complication encountered in the use of
thermocouples is the “cold–junction” compensation. Where the
thermocouple wire is terminated to the copper EXP–16 connections, an
unwanted thermocouple junction is formed. As the connector
temperature varies, this introduces an error. The error can be bucked out
by sensing the connector temperature using a semiconductor sensor on
another channel, and correcting the thermocouple readings in software.
This is required only at the highest levels of accuracy, since in most cases
connector temperature (usually room temperature) varies little. EXP–16
provides the sensing hardware needed to perform this correction.

Interface to Transducers, Thermocouples, etc. 4-23

Precautions for Operating at High Gains

Operating DAS-16G1 boards at gains of 100 or 500 can lead to problems
if your application is unable to cope with noise. At a gain of 500, with a
bipolar input range of
corresponds to 10
bandwidth of this board, analog noise and performance degradation come
easily unless you take precautions to avoid them. The following collection
of ideas and suggestions is aimed at avoiding these problems:

● Operate DAS-16G1 boards in 8-channel differential mode. Using the

board in 16-channel, single-ended mode at high gains introduces
enough ground-loop noise to produce large fluctuations in readings.

● Minimize noise from crosstalk and induced-voltage pickup in the flat

cables and screw terminal accessories by using shielded cable.
Connect the shield to LL GND and the inner conductors to Channel
LO and HI. Channel LO and LL GND should have a DC return (or
connection) at some point; this return should be as close to the signal
source as possible. Induced noise from RF and magnetic fields can
easily exceed tens of microvolts, even on one- or two-foot cables;
shielded cable eliminates this problem.

−10.0V to +10.0V, each bit of A/D output

µV of analog input. Thus, with the high speed and

● Avoid bi-metallic junctions in the input circuitry. For example, the

kovar leads, used on reed relays, typically have a thermal emf to
copper of 40

µV/˚C. Thermals can introduce strange random

variations caused by air currents and so on.

● Consider filtering. This approach can use hardware (resistors,

capacitors, and so on) but is often accomplished more easily with
software. Instead of reading the channel once, read it 10 or more
times in quick succession and average the readings. If the noise is
random and Gaussian, it will be reduced by the square-root of the
number of readings.

4-24 Cabling and Wiring

Additional Precautions

Do not mix your data acquisition inputs with the AC line, or you risk
damaging the computer. Data acquisition systems provide access to
inputs of the computer. An inadvertent short between data and power lines
can cause extensive and costly damage to your computer. The
manufacturer can accept no liability for this type of accident. To prevent
this problem, use the following precautions:

● Avoid direct connections to the AC line.

● Make sure all connections are tight and sound so that signal wires are

not likely to come loose and short to high voltages.

● Use isolation amplifiers and transformers where necessary.

Additional Precautions 4-25