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

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DAS-16 Series
User’s Manual
A GREATER MEASURE OF CONFIDENCE
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WARRANTY
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.
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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.
Limitation of Liability
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.
Keithley Instruments, Inc. • 28775 Aurora Road • Clev eland, OH 44139 • 440-248-0400 • F ax: 440-248-6168 • http://www.keithley.com
BELGIUM: Keithley Instruments B.V. Bergensesteenweg 709 • B-1600 Sint-Pieters-Leeuw • 02/363 00 40 • Fax: 02/363 00 64 CHINA: Keithley Instruments China Y uan Chen Xin Building, Room 705 • 12 Yumin Road, Dewai, Madian • Beijing 100029 • 8610-62022886 • Fax: 8610-62022892 FRANCE: Keithley Instruments Sarl 3, allée des Garays • 91127 Palaiseau Cedex • 01-64 53 20 20 • Fax: 01-60 11 77 26 GERMANY: Keithley Instruments GmbH Landsberger Strasse 65 • 82110 Germering • 089/84 93 07-40 • Fax: 089/84 93 07-34 GREAT BRITAIN: Keithley Instruments Ltd The Minster • 58 Portman Road • Reading, Berkshire RG30 1EA • 0118-9 57 56 66 • Fax: 0118-9 59 64 69 INDIA: Keithley Instruments GmbH Flat 2B, WILOCRISSA • 14, Rest House Crescent • Bangalore 560 001 • 91-80-509-1320/21 • Fax: 91-80-509-1322 ITALY: Keithley Instruments s.r.l. Viale S. Gimignano, 38 • 20146 Milano • 02-48 39 16 01 • Fax: 02-48 30 22 74 NETHERLANDS: Keithley Instruments B.V. Postbus 559 • 4200 AN Gorinchem • 0183-635333 • Fax: 0183-630821 SWITZERLAND: Keithley Instruments SA Kriesbachstrasse 4 • 8600 Dübendorf • 01-821 94 44 • Fax: 01-820 30 81 TAIWAN: Keithley Instruments Taiwan 1 Fl. 85 Po Ai Street • Hsinchu, Taiwan, R.O.C. • 886-3572-9077• Fax: 886-3572-903
09/00
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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
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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: (440) 248-6168
Visit our website at http://www.keithley.com
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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: (440) 248-0400 • FAX: (440) 248-6168
http://www.keithley.com
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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
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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
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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
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x
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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
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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
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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
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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
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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
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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
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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
Page 19
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
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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
Page 21
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
Page 22
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
Page 23
Figure 2-1. DAS-16/16F Functional Block Diagram
2-2 Functional Description
Page 24
Figure 2-2. DAS-16G1/G2 Functional Block Diagram
2-3
Page 25
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
Page 26
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
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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
Page 28
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
Page 29
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
Page 30
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
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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
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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
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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
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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
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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
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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
Page 37
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
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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
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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.
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
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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
Page 41
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
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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
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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
Page 44
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
Page 45
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
Page 46
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
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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
Page 48
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
Page 49
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
Page 50
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
Page 51
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 (800) 468-3548
Harris Semiconductor Literature Department
P.O. Box 883, MS CB1-28 Melbourne, FL 32901 (407) 724-3739
Newbridge Microsystems
603 March Road Kanata, Ontario Canada K2K 1X3 (613) 592-0714 (800) 267-7231
2-30 Functional Description
Page 52
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
Page 53
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
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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
Page 55
2-34 Functional Description
Page 56
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
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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
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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
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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
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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
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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
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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
Page 63
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
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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
Page 65
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
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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
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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
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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
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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
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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
Page 71
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
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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
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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
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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
Page 75
3-20 Setup and Installation
Page 76
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
Page 77
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
Page 78
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
Page 79
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
Page 80
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
Page 81
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
Page 82
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
Page 83
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
Page 84
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
Page 85
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
Page 86
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
Page 87
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
Page 88
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
Page 89
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
Page 90
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
Page 91
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
Page 92
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
Page 93
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
Page 94
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 100, 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 100, 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
Page 95
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
Page 96
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
Page 97
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
Page 98
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
Page 99
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
Page 100
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
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