National Instruments Home Theater Server 321906B 01 User Manual

Computer-Based  
Instruments  
NI 2501/2503 User Manual  
24-Channel Two-Wire Multiplexer  
NI 2501/2503 User Manual  
July 1998 Edition  
Part Number 321906B-01  
 
 
Important Information  
Warranty  
The NI 2501 and NI 2503 are warranted against defects in materials and workmanship for a period of one year from the  
date of shipment, as evidenced by receipts or other documentation. National Instruments will, at its option, repair or  
replace equipment that proves to be defective during the warranty period. This warranty includes parts and labor.  
The media on which you receive National Instruments software are warranted not to fail to execute programming  
instructions, due to defects in materials and workmanship, for a period of 90 days from date of shipment, as evidenced  
by receipts or other documentation. National Instruments will, at its option, repair or replace software media that do not  
execute programming instructions if National Instruments receives notice of such defects during the warranty period.  
National Instruments does not warrant that the operation of the software shall be uninterrupted or error free.  
A Return Material Authorization (RMA) number must be obtained from the factory and clearly marked on the outside  
of the package before any equipment will be accepted for warranty work. National Instruments will pay the shipping costs  
of returning to the owner parts which are covered by warranty.  
National Instruments believes that the information in this manual is accurate. The document has been carefully reviewed  
for technical accuracy. In the event that technical or typographical errors exist, National Instruments reserves the right to  
make changes to subsequent editions of this document without prior notice to holders of this edition. The reader should  
consult National Instruments if errors are suspected. In no event shall National Instruments be liable for any damages  
arising out of or related to this document or the information contained in it.  
EXCEPT AS SPECIFIED HEREIN, NATIONAL INSTRUMENTS MAKES NO WARRANTIES, EXPRESS OR IMPLIED, AND SPECIFICALLY DISCLAIMS  
ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. CUSTOMERS RIGHT TO RECOVER DAMAGES CAUSED  
BY FAULT OR NEGLIGENCE ON THE PART OF NATIONAL INSTRUMENTS SHALL BE LIMITED TO THE AMOUNT THERETOFORE PAID BY THE  
CUSTOMER. NATIONAL INSTRUMENTS WILL NOT BE LIABLE FOR DAMAGES RESULTING FROM LOSS OF DATA, PROFITS, USE OF PRODUCTS,  
OR INCIDENTAL OR CONSEQUENTIAL DAMAGES, EVEN IF ADVISED OF THE POSSIBILITY THEREOF. This limitation of the liability of  
National Instruments will apply regardless of the form of action, whether in contract or tort, including negligence.  
Any action against National Instruments must be brought within one year after the cause of action accrues. National  
Instruments shall not be liable for any delay in performance due to causes beyond its reasonable control. The warranty  
provided herein does not cover damages, defects, malfunctions, or service failures caused by owner’s failure to follow  
the National Instruments installation, operation, or maintenance instructions; owner’s modification of the product;  
owner’s abuse, misuse, or negligent acts; and power failure or surges, fire, flood, accident, actions of third parties,  
or other events outside reasonable control.  
Copyright  
Under the copyright laws, this publication may not be reproduced or transmitted in any form, electronic or mechanical,  
including photocopying, recording, storing in an information retrieval system, or translating, in whole or in part, without  
the prior written consent of National Instruments Corporation.  
Trademarks  
CVI, LabVIEW, NI-SWITCH, and PXIare trademarks of National Instruments Corporation.  
Product and company names listed are trademarks or trade names of their respective companies.  
WARNING REGARDING MEDICAL AND CLINICAL USE OF NATIONAL INSTRUMENTS PRODUCTS  
National Instruments products are not designed with components and testing intended to ensure a level of reliability  
suitable for use in treatment and diagnosis of humans. Applications of National Instruments products involving medical  
or clinical treatment can create a potential for accidental injury caused by product failure, or by errors on the part of the  
user or application designer. Any use or application of National Instruments products for or involving medical or clinical  
treatment must be performed by properly trained and qualified medical personnel, and all traditional medical safeguards,  
equipment, and procedures that are appropriate in the particular situation to prevent serious injury or death should always  
continue to be used when National Instruments products are being used. National Instruments products are NOT intended  
to be a substitute for any form of established process, procedure, or equipment used to monitor or safeguard human health  
and safety in medical or clinical treatment.  
 
Compliance  
FCC/DOC Radio Frequency Interference  
Class A Compliance  
This equipment generates and uses radio frequency energy and, if not installed and used in strict accordance  
with the instructions in this manual, may cause interference to radio and television reception. Classification  
requirements are the same for the Federal Communications Commission (FCC) and the Canadian  
Department of Communications (DOC). This equipment has been tested and found to comply with the  
following two regulatory agencies:  
Federal Communications Commission  
This equipment has been tested and found to comply with the limits for a Class A digital device, pursuant  
to part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful  
interference when the equipment is operated in a commercial environment. This equipment generates,  
uses, and can radiate radio frequency energy and, if not installed and used in accordance with the instruction  
manual, may cause harmful interference to radio communications. Operation of this equipment in a  
residential area is likely to cause harmful interference in which case the user will be required to correct the  
interference at his own expense.  
Notices to User: Changes or modifications not expressly approved by National Instruments could void  
the user’s authority to operate the equipment under the FCC Rules.  
This device complies with the FCC rules only if used with shielded interface cables  
of suitable quality and construction. National Instruments used such cables to test  
this device and provides them for sale to the user. The use of inferior or nonshielded  
interface cables could void the user’s authority to operate the equipment under the  
FCC rules.  
If necessary, consult National Instruments or an experienced radio/television technician for additional  
suggestions. The following booklet prepared by the FCC may also be helpful: Interference to Home  
Electronic Entertainment Equipment Handbook. This booklet is available from the U.S. Government  
Printing Office, Washington, DC 20402.  
Canadian Department of Communications  
This Class A digital apparatus meets all requirements of the Canadian Interference-Causing Equipment  
Regulations.  
Cet appareil numérique de la classe A respecte toutes les exigences du Règlement sur le matériel brouilleur  
du Canada.  
 
Conventions  
The following conventions are used in this manual.  
<>  
Angle brackets containing numbers separated by an ellipsis represent a  
range of values associated with a port, bit, or signal name (for example,  
CH<0..7> stands for the signals CH0 through CH7).  
This icon to the left of bold italicized text denotes a note, which alerts  
you to important information.  
This icon to the left of bold italicized text denotes a caution, which  
advises you of precautions to take to avoid injury, data loss, or a  
system crash.  
!
This icon to the left of bold italicized text denotes a warning, which advises  
you of precautions to take to avoid being electrically shocked.  
bold italic  
Bold italic text denotes a note, caution, or warning.  
italic  
Italic text denotes variables, emphasis, a cross reference, or an introduction  
to a key concept. This font also denotes text from which you supply the  
appropriate word or value, as in CHx.  
 
Chapter 1  
Routing Signals with Your NI 2501/2503  
About the NI 2501/2503 ................................................................................................1-1  
Analog Bus......................................................................................................1-2  
Triggers............................................................................................................1-2  
Cold-Junction Sensor Channel ........................................................................1-3  
NI 2501 Amplifier...........................................................................................1-3  
Connecting Signals ........................................................................................................1-4  
Contact Protection..........................................................................................................1-10  
Terminal Blocks.............................................................................................................1-10  
NI-SWITCH Driver Software .........................................................................1-10  
National Instruments Application Software....................................................1-11  
Third Party Software .......................................................................................1-11  
Chapter 2  
NI 2501/2503 Operation  
Functional Overview......................................................................................................2-1  
Multiplexer.....................................................................................................................2-4  
Two-Wire Mode..............................................................................................2-4  
Four-Wire Mode..............................................................................................2-5  
Matrix Mode....................................................................................................2-5  
Switch Control Circuitry................................................................................................2-5  
Random Scanning..........................................................................................................2-5  
Triggers............................................................................................................2-6  
External Trigger Input.......................................................................2-6  
Modes................................................................................................2-7  
Initiating Scanning...........................................................................................2-8  
Multicard Triggering .......................................................................................2-8  
Appendix A  
Specifications  
© National Instruments Corporation  
vii  
NI 2501/2503 User Manual  
 
Contents  
Appendix B  
Accessories  
Appendix C  
Customizing Your Card  
Appendix D  
Architecture Drawings  
Appendix E  
Customer Communication  
Glossary  
Index  
Figures  
Figure 1-2.  
Figure 1-4.  
Front Connector Pinout Assignments for One-Wire Mode .................. 1-6  
Front Connector Pinout Assignments to Create a 6 x 4 Matrix............ 1-8  
Figure 2-2.  
NI 2503 Module Block Diagram .......................................................... 2-3  
Figure D-1. NI 2501 Switch Architecture ................................................................ D-2  
Figure D-2. NI 2503 Switch Architecture ................................................................ D-3  
Tables  
Front Connector Signal Description .................................................... 1-9  
NI 2501/2503 User Manual  
viii  
© National Instruments Corporation  
 
1
Routing Signals with Your  
NI 2501/2503  
This manual describes the electrical and mechanical aspects of the  
NI 2501 FET multiplexer and the NI 2503 mechanical relay multiplexer  
and contains information concerning their installation and operation.  
This manual uses the term NI 2501/2503 whenever information applies  
to both instruments.  
About the NI 2501/2503  
This section summarizes the features and operation of the NI 2501/2503  
switch card. Refer to Chapter 2, NI 2501/2503 Operation, for more  
complete details. In addition, refer to Appendix A, Specifications,  
for detailed specifications of the two switch cards.  
The NI 2501 is a FET switch card, and the NI 2503 is an armature  
relay switch card. Each consists of a 24 x 1 two-wire multiplexer in  
PXI/Compact PCI format. You can take advantage of the switch card’s  
flexibility to handle a wide variety of test systems through the use of  
various accessories and software configurations. You can use the National  
Instruments NI-SWITCH software included with your kit to configure and  
operate the NI 2501/2503 switch card.  
The NI 2501/2503 can also operate as two 12 x 1 or four 6 x 1 two-wire  
multiplexers. You can use software-configurable switches to configure  
the switch card as a 48 x 1 one-wire multiplexer for making large numbers  
of common referenced measurements. In addition, the NI 2501/2503 can  
operate as a 12 x 1 four-wire multiplexer to handle resistive measurements,  
such as thermistors or RTDs. Finally, you can use a National Instruments  
TB-2606 terminal block to further configure the NI 2501/2503 as a 6 x 4  
two-wire matrix.  
The Connecting Signals section of this chapter contains more information  
on one-wire, two-wire, four-wire, and matrix configurations, and includes  
diagrams of the pinout connections to make.  
© National Instruments Corporation  
1-1  
NI 2501/2503 User Manual  
 
     
Chapter 1  
Routing Signals with Your NI 2501/2503  
Refer to Appendix B, Accessories, for more information on terminal blocks  
you can order from National Instruments.  
You can also use multiple NI 2501/2503 cards together to expand the size  
of the multiplexer or matrix. For example, you can connect two cards to  
create a 48 x 1 two-wire multiplexer or a 12 x 4 two-wire matrix.  
Caution  
The maximum voltage is different for the NI 2501 and NI 2503 switch cards.  
If you intend to use more than one type of card, be sure you do not exceed the  
maximum voltage of any card in your system. Refer to Appendix A, Specifications,  
for information.  
!
Analog Bus  
The NI 2501/2503 works with a four-wire analog bus. You connect the  
analog bus to the switch card through its main front-panel connector.  
You can use the analog bus to simplify connecting multiple cards to an  
instrument such as a digital multimeter (DMM). This bus makes it possible  
to create large systems using multiple switch cards.  
For example, if you have two NI 2501/2503 cards—or one of each—in two  
adjacent slots, you can connect them through the analog bus and create a  
48 x 1 two-wire multiplexer. With this flexibility, you keep the wiring of  
the modules to a minimum while you create large switching solutions. In  
such cases, the scanning architecture uses some of the PXI trigger lines for  
synchronization and delivers full access to all of the scanning features for  
the cards. The National Instruments software you receive with the  
NI 2501/2503 handles the complexity of programming the cards.  
Triggers  
Two triggers are used to handshake the NI 2501/2503 switch with PXI  
instruments or other external instruments. The Scanner Advanced trigger  
indicates when the card has closed all the necessary switches for the next  
scan and the switches have settled, or debounced. This trigger is typically  
wired to a measurement device, such as a DMM, which is configured to  
take a reading when it receives the trigger.  
The External Trigger Input trigger is sourced by another instrument, such  
as the DMM, and causes the NI 2501/2503 to advance to the next entry  
in the scan list. The triggers can be routed to the front connector of the  
NI 2501/2503, to any of the PXI TTL triggers, or to the PXI star trigger. If  
no external trigger input is available, you can have the software trigger the  
NI 2501/2503 to advance to the next entry in the scan list.  
NI 2501/2503 User Manual  
1-2  
© National Instruments Corporation  
 
 
Chapter 1  
Routing Signals with Your NI 2501/2503  
Refer to Chapter 2, NI 2501/2503 Operation, for more information on  
triggers.  
Cold-Junction Sensor Channel  
For low-voltage measurements, such as those provided by thermocouples,  
the NI 2503 has very low thermal offset—less than 2 µV—to ensure  
accurate measurements. For cold-junction compensation when switching  
thermocouples, the NI 2501/2503 has a dedicated channel for a  
temperature sensor. The National Instruments TB-2605 and TBX-68S  
terminal blocks both have onboard temperature sensors that connect to the  
dedicated cold-junction sensor channel.  
NI 2501 Amplifier  
The NI 2501 has an amplifier with a gain of 1. This amplifier can be  
switched in-line before the COM0 signal and the AB0 signal. The amplifier  
helps to decrease the settling time of the FET switch. The amplifier’s  
high impedance isolates the FET from the resistance, capacitance,  
and inductance in the external wiring. This isolation decreases the  
resistance/capacitance time constant seen by the FET, which improves  
settling time.  
The amplifier has an offset that should be calibrated for more accurate  
measurements. The calibration data can be stored into and retrieved from  
the EEPROM on the board. The software you received with your switch  
card includes API function calls to retrieve and store calibration data.  
When the amplifier is used, the switch card becomes directional, where  
CHx is for signal inputs and COM0 or AB0 are for signal outputs.  
The NI 2501 also has an amplifier in the CJS0+ to COM0+ signal path.  
This amplifier in the cold-junction sensor signal path is used to improve  
settling time performance. It prevents the impedance of the cold-junction  
sensor from increasing the settling time when switching the CJS channel.  
As a result, when scanning thermocouples, the settling time for the  
cold-junction sensor channel should be about the same as for the channels  
with the thermocouples.  
© National Instruments Corporation  
1-3  
NI 2501/2503 User Manual  
 
 
Chapter 1  
Routing Signals with Your NI 2501/2503  
Connecting Signals  
This section describes the signal connections to the NI 2501/2503 module  
via the module front connector. This section also includes specifications  
and connection instructions for the signals on the NI 2501/2503 module  
connectors.  
Caution  
Static electricity is a major cause of component failure. To prevent damage to the  
electrical components in the module, observe antistatic precautions whenever  
removing a module from the chassis or whenever working on a module.  
!
Front Connector  
depending on the wiring mode you use. The following four diagrams show  
the pin assignments for two-wire mode, one-wire mode, four-wire mode,  
and matrix mode, respectively. Two-wire mode is shown first because it is  
the most common configuration. Table 1-1, following the diagrams,  
describes the connector signals. For more information on the wiring modes,  
refer to the Multiplexer section in Chapter 2, NI 2501/2503 Operation.  
Warning Any connections that exceed the maximum settings for the NI 2501/2503 can  
result in an electrical shock hazard and damage to the NI 2501/2503 module and  
any or all of the boards connected to the PXI backplane. National Instruments  
is NOT liable for any damages or injuries resulting from exceeding maximum  
voltage ratings. Refer to Appendix A, Specifications, for information.  
NI 2501/2503 User Manual  
1-4  
© National Instruments Corporation  
 
   
Chapter 1  
Routing Signals with Your NI 2501/2503  
34 68  
CH0– 33 67  
CJS0–  
CJS0+  
CH0+  
CH1+  
CH2+  
CH3+  
CH4+  
CH5+  
COM0+  
COM1+  
32 66  
31 65  
30 64  
29 63  
28 62  
CH1–  
CH2–  
CH3–  
CH4–  
CH5–  
COM0– 27 61  
COM1– 26 60  
CH6–  
CH7– 24 58  
25 59 CH6+  
CH7+  
CH8–  
23 57 CH8+  
1_WIRE_LO_REF1  
22 56  
21 55  
GND  
CH9–  
CH9+  
CH10– 20 54  
CH10+  
CH11+  
AB0+  
19 53  
18 52  
17 51  
16 50  
15 49  
CH11–  
AB0–  
AB1–  
AB1+  
CH12–  
CH13–  
CH12+  
CH13+  
CH14+  
CH15+  
CH16+  
CH17+  
COM2+  
COM3+  
SCAN_ADV  
CH14– 14 48  
CH15– 13 47  
CH16– 12 46  
CH17–  
COM2–  
COM3–  
+5 V  
11 45  
10 44  
9
8
7
6
5
4
3
2
1
43  
42  
41  
40  
39  
38  
37  
36  
35  
GND  
CH18–  
CH19–  
CH20–  
CH21–  
CH22–  
CH23–  
EXT_TRIG_IN  
CH18+  
CH19+  
CH20+  
CH21+  
CH22+  
CH23+  
1not used in two-wire mode  
Figure 1-1. Front Connector Pinout Assignments for Two-Wire Mode  
© National Instruments Corporation  
1-5  
NI 2501/2503 User Manual  
 
   
Chapter 1  
Routing Signals with Your NI 2501/2503  
CJS–1  
CJS+1  
34 68  
CH24 33 67  
CH0  
32 66  
31 65  
30 64  
29 63  
28 62  
CH25  
CH26  
CH27  
CH28  
CH29  
CH1  
CH2  
CH3  
CH4  
CH5  
COM0– 27 61  
COM1– (CH30–CH35)1 26 60  
CH30  
CH31 24 58  
COM0+  
COM1+ (CH6–CH11)1  
25 59 CH6  
CH7  
CH32  
23 57 CH8  
22 56  
21 55  
1_WIRE_LO_REF  
CH33  
GND  
CH9  
CH34 20 54  
CH10  
19 53  
18 52  
17 51  
16 50  
15 49  
CH35  
AB0–  
AB1–1  
CH36  
CH37  
CH11  
AB0+  
AB1+1  
CH12  
CH13  
CH38 14 48  
CH39 13 47  
CH40 12 46  
CH14  
CH15  
CH16  
CH41  
COM2– (CH36–CH41)1  
COM3– (CH42–CH48)1  
+5 V  
11 45  
10 44  
CH17  
COM2+ (CH12–CH17)1  
COM3+ (CH18–CH23)1  
SCAN_ADV  
9
8
7
6
5
4
3
2
1
43  
42  
41  
40  
39  
38  
37  
36  
35  
GND  
CH42  
CH43  
CH44  
CH45  
CH46  
CH47  
EXT_TRIG_IN  
CH18  
CH19  
CH20  
CH21  
CH22  
CH23  
1not used in one-wire mode  
Figure 1-2. Front Connector Pinout Assignments for One-Wire Mode  
NI 2501/2503 User Manual  
1-6  
© National Instruments Corporation  
 
   
Chapter 1  
Routing Signals with Your NI 2501/2503  
CJS–1  
CJS+1  
34 68  
CH0A– 33 67  
CH0A+  
CH1A+  
CH2A+  
CH3A+  
CH4A+  
CH5A+  
COM0A+  
COM1A+  
32 66  
31 65  
30 64  
29 63  
28 62  
CH1A–  
CH2A–  
CH3A–  
CH4A–  
CH5A–  
COM0A– 27 61  
COM1A– 26 60  
CH6A–  
CH7A– 24 58  
25 59 CH6A+  
CH7A+  
CH8A–  
23 57 CH8A+  
1_WIRE_LO_REF1  
22 56  
21 55  
GND  
CH9A–  
CH9A+  
CH10A+  
CH11A+  
AB0A+  
CH10A– 20 54  
19 53  
18 52  
17 51  
16 50  
15 49  
CH11A–  
AB0A–  
AB0B–  
CH0B–  
CH1B–  
AB0B+  
CH0B+  
CH1B+  
CH2B+  
CH3B+  
CH4B+  
CH5B+  
COM0B+  
COM1B+  
SCAN_ADV  
CH2B– 14 48  
CH3B– 13 47  
CH4B– 12 46  
CH5B–  
COM0B–  
COM1B–  
+5 V  
11 45  
10 44  
9
8
7
6
5
4
3
2
1
43  
42  
41  
40  
39  
38  
37  
36  
35  
GND  
CH6B–  
CH7B–  
CH8B–  
CH9B–  
CH10B–  
CH11B–  
EXT_TRIG_IN  
CH6B+  
CH7B+  
CH8B+  
CH9B+  
CH10B+  
CH11B+  
1not used in four-wire mode  
Figure 1-3. Front Connector Pinout Assignments for Four-Wire Mode  
© National Instruments Corporation  
1-7  
NI 2501/2503 User Manual  
 
 
Chapter 1  
Routing Signals with Your NI 2501/2503  
CJS–1  
CJS+1  
COL0+  
34 68  
COL0– 33 67  
32 66  
31 65  
30 64  
29 63  
28 62  
COL1–  
COL2–  
COL3–  
COL4–  
COL5–  
COL1+  
COL2+  
COL3+  
COL4+  
COL5+  
ROW0– 27 61  
ROW1– 26 60  
ROW0+  
ROW1+  
COL0–  
25 59 COL0+  
COL1– 24 58  
COL1+  
COL2–  
23 57 COL2+  
1_WIRE_LO_REF1  
22 56  
GND  
21 55  
COL3+  
COL3–  
COL4– 20 54  
COL4+  
19 53  
18 52  
17 51  
16 50  
15 49  
COL5–  
AB0– (ROW0–)  
AB1– (ROW2–)  
COL0–  
COL5+  
AB0+ (ROW0+)  
AB1+ (ROW2+)  
COL0+  
COL1–  
COL1+  
COL2– 14 48  
COL3– 13 47  
COL4– 12 46  
COL2+  
COL3+  
COL4+  
COL5–  
ROW2–  
ROW3–  
+5 V  
11 45  
10 44  
COL5+  
ROW2+  
9
8
7
6
5
4
3
2
1
43  
42  
41  
40  
39  
38  
37  
36  
35  
ROW3+  
SCAN_ADV  
GND  
COL0–  
COL1–  
COL2–  
COL3–  
COL4–  
COL5–  
EXT_TRIG_IN  
COL0+  
COL1+  
COL2+  
COL3+  
COL4+  
COL5+  
1not used in matrix mode  
Figure 1-4. Front Connector Pinout Assignments to Create a 6 x 4 Matrix  
For matrix mode, connect all pins with the same name together external to  
the switch card. The National Instruments TB-2606 terminal block  
connects the necessary pins to create the 6 x 4 matrix.  
NI 2501/2503 User Manual  
1-8  
© National Instruments Corporation  
 
   
Chapter 1  
Routing Signals with Your NI 2501/2503  
Table 1-1. Front Connector Signal Description  
Signal Name  
Type  
Output  
Description  
+5 V  
+5 VDC Source—Powers the temperature sensor  
on the terminal block. 0.2 mA of source protected  
by a resettable poly fuse.  
GND  
Output  
Input  
Ground  
CJS±  
Cold-junction Temperature Sensor Input—  
Connects to the temperature sensor of the  
terminal block.  
1_WIRE_LO_REF  
EXT_TRIG_IN  
Input  
Input  
The common reference signal used in one-wire  
mode.  
External Trigger Input—Trigger from an  
instrument to advance the switch card to the  
next scan entry.  
SCAN_ADV  
Output  
Scanner Advanced—Trigger to an instrument  
that indicated the switch card has advanced to  
the next scan and relays are debounced.  
CH<0..47> (one wire)  
CH<0..23>± (two wire)  
CH<0..11>A± (four wire)  
CH<0..11>B± (four wire)  
Input/Output  
Channels—Where signals are connected to the  
switch card. CHx+ and CHx– are switched  
together.  
COM0± (one wire)  
Input/Output  
Input/Output  
Common—The common for each bank.  
COM<0..3>± (two wire)  
COM<0..1>A± (four wire)  
COM<0..1>B± (four wire)  
AB0± (one wire)  
Analog Bus—Used to wire multiple switch cards  
to an instrument such as a DMM.  
AB<0..1>± (two wire)  
AB0A± (four wire)  
AB0B± (four wire)  
COL<0..5>±  
Input/Output  
Input/Output  
Columns—Where signals are connected to the  
switch card. The card behaves as a matrix when  
proper external wiring is added.  
ROW<0..3>±  
Rows—Where signals are connected to the  
switch card. In matrix configuration any row  
can be connected to any column.  
© National Instruments Corporation  
1-9  
NI 2501/2503 User Manual  
 
   
Chapter 1  
Routing Signals with Your NI 2501/2503  
Contact Protection  
Caution  
When inductive loads are connected to the relays, a large counter electromotive  
!
force may occur at relay switching time due to the energy stored in the inductive  
load. These flyback voltages can severely damage the relay contacts and greatly  
shorten the life of the relay.  
It is best to limit flyback voltages at your inductive load by installing a flyback  
diode for DC loads or a movistor for AC loads.  
Terminal Blocks  
Several terminal blocks with screw terminals are available for easy signal  
connection to the NI 2501/2503 inputs. Refer to Appendix B, Accessories.  
Software Choices  
You have several options to choose from when programming your National  
Instruments switch card. You can use the NI-SWITCH driver software, or  
National Instruments application software.  
NI-SWITCH Driver Software  
The NI-SWITCH instrument driver is an Intelligent Virtual Instrument  
(IVI) compliant instrument driver that is bundled with NI-SWITCH cards  
at no cost.  
NI-SWITCH features a set of operations and attributes that exercise all  
the functionality of the switching hardware, including configuration,  
opening/closing, and scanning. In addition, NI-SWITCH comes with  
an interactive soft front panel and online documentation.  
NI-SWITCH eliminates the need to understand complex register  
programming and interrupt handling in the Microsoft operating systems,  
and frees you to focus on creating your test system.  
NI 2501/2503 User Manual  
1-10  
© National Instruments Corporation  
 
 
Chapter 1  
Routing Signals with Your NI 2501/2503  
National Instruments Application Software  
LabVIEW and LabWindows/CVI are innovative program development  
software packages for data acquisition and control applications. LabVIEW  
uses graphical programming, whereas LabWindows/CVI enhances  
traditional programming languages. Both packages include extensive  
libraries for data acquisition, instrument control, data analysis, and  
graphical data presentation. Using LabVIEW or LabWindows/CVI can  
significantly reduce the development time for your data acquisition and  
control application.  
LabVIEW features interactive graphics, a state-of-the-art user interface,  
and a powerful graphical programming language. The LabVIEW  
NI-SWITCH VI Library, a series of virtual instruments (VIs) for using  
LabVIEW with National Instruments switch hardware, is included with  
the NI-SWITCH driver.  
LabWindows/CVI features interactive graphics, a state-of-the-art user  
interface, and uses the ANSI standard C programming language. The  
LabWindows/CVI NI-SWITCH Library, a series of functions for using  
LabWindows/CVI with National Instruments switch hardware, is included  
with the NI-SWITCH driver.  
Third Party Software  
The NI-SWITCH instrument driver also includes support files for  
Microsoft Visual C++ and Microsoft Visual Basic. Please see the  
NI-SWITCH readme file for version support information.  
© National Instruments Corporation  
1-11  
NI 2501/2503 User Manual  
 
 
2
NI 2501/2503 Operation  
This chapter contains a functional overview of the NI 2501/2503  
module and explains the operation of each functional unit making up  
the NI 2501/2503 module.  
Functional Overview  
The block diagrams on the following pages illustrate the key functional  
components of the switch card modules. Figure 2-1 shows the NI 2501 and  
Figure 2-2 shows the NI 2503.  
The major components of the NI 2501/2503 modules are as follows:  
Multiplexer  
Relay/FET switch control circuitry  
Random scanning  
PXIbus interface  
Triggers  
© National Instruments Corporation  
2-1  
NI 2501/2503 User Manual  
 
     
Chapter 2  
NI 2501/2503 Operation  
Analog Bus0  
Com0  
CH0  
One Wire /  
Two Wire  
Select  
Unity Gain  
Amplifier  
Select  
CH5  
AISENSE  
Cold Junction Sensor  
Com1  
CH6  
CH11  
Analog Bus1  
Com2  
CH12  
CH17  
Com3  
CH18  
CH23  
Figure 2-1. NI 2501 Module Block Diagram  
NI 2501/2503 User Manual  
2-2  
© National Instruments Corporation  
 
   
Chapter 2  
NI 2501/2503 Operation  
Analog Bus0  
Com0  
CH0  
One Wire /  
Two Wire  
Select  
CH5  
AISENSE  
Cold Junction Sensor  
Com1  
CH6  
CH11  
Analog Bus1  
Com2  
CH12  
CH17  
Com3  
CH18  
CH23  
Figure 2-2. NI 2503 Module Block Diagram  
© National Instruments Corporation  
2-3  
NI 2501/2503 User Manual  
 
   
Chapter 2  
NI 2501/2503 Operation  
Multiplexer  
The relay multiplexer consists of four banks of six channels. The switches  
for the six channels in each bank connect the channels to a common output  
for each bank.  
Bank 0 consists of Channels 0–5 and Common 0.  
Bank 1 consists of Channels 6–11 and Common 1.  
Bank 2 consists of Channels 12–17 and Common 2.  
Bank 3 consists of Channels 18–23 and Common 3.  
Each channel connects to the corresponding bank common by closing its  
relay/FET switch. You can have multiple channels connected to the bank  
common at the same time. Bank connection relay/FET switches can  
combine the commons of the four banks. See Appendix D, Architecture  
Drawings, for illustrations of the NI 2501 and NI 2503 architecture.  
The NI 2503 relays are single-side stable. When power is removed from the  
relay coil, the relay returns to its de-energized state. The de-energized state  
opens all the relays, disconnecting the device from external inputs and  
outputs.  
See Figures 1-1 through 1-4 in Chapter 1, Routing Signals with Your  
NI 2501/2503, for the pin names used for the different modes of operation.  
Different names are used for the pin assignments in the different modes to  
better reflect the operation in the different modes and to simplify the task  
of wiring.  
Two-Wire Mode  
One-Wire Mode  
Two-wire mode is the default and most common configuration for the  
NI 2501/2503 switch cards. The CHx+ and CHx– channels are switched  
together to the COMx+ and COMx– signals for the corresponding bank.  
One-wire mode doubles the channel count of what is available in two-wire  
mode. However, the signals connected to the switch card need a common  
reference. For one-wire measurements, Bank 0 includes extra relays  
between the multiplexed channel relays and COM0. The 1WIRE relay  
switch connects COM0– to the 1-Wire Lo Ref signal. The HLSELECT  
relay connects COM0+ to either CHx+ or CHx–. The de-energized states  
for these relays configure the device for two-wire measurements.  
NI 2501/2503 User Manual  
2-4  
© National Instruments Corporation  
 
   
Chapter 2  
NI 2501/2503 Operation  
Four-Wire Mode  
Matrix Mode  
Four-wire mode is typically used for resistance measurements. In this  
mode, CHxA+, CHxA–, CHxB+, and CHxB–, are switched together to  
COMxA+, COMxA–, COMxB+, and COMxB–.  
By adding some external wiring, you can configure the switch card as  
a two-wire 6 x 4 crosspoint matrix. (See Figure 1-4 in Chapter 1.) The  
TB-2606 terminal block simplifies your wiring task by connecting the  
necessary pins on the switch card’s front connector to create the 6 x 4  
matrix.  
In the matrix configuration, you can connect any ROWx signal to any COLx  
signal.  
Switch Control Circuitry  
The switch control circuitry (SCC) is responsible for opening and closing  
FET switches on the NI 2501 or relays on the NI 2503. You can load  
commands for the SCC into memory storage using the driver software  
you received with your kit. Consult the online help or your software  
documentation for specific information on the appropriate commands.  
There are two reasons for storing the commands in memory before the  
SCC can process them:  
The operate/release time for the NI 2503 is 3 to 5 ms. Using memory  
storage, the software can send multiple commands to the SCC without  
having to wait for a relay action to complete.  
The memory is used to store a scan list necessary for hardware random  
scanning.  
Random Scanning  
The NI 2501/2503 can perform random scanning. In random scanning,  
the switch card can scan the channels in any order.  
The scan list is downloaded to onboard memory. Commands in the scan  
list can:  
Open or close relays  
Wait for an external trigger  
© National Instruments Corporation  
2-5  
NI 2501/2503 User Manual  
 
 
Chapter 2  
NI 2501/2503 Operation  
Generate a scanner advanced trigger  
Generate a breakpoint interrupt  
You can use the driver software to configure the switch card for continuous  
or one-time scanning. In continuous scanning, the switch card cycles  
through the scan list until you disable scanning. For one-time scanning, the  
switch card cycles through the scan list only once.  
You can also use software commands to clear the scan list or reset it to the  
beginning at any time.  
The onboard control logic for the NI 2501/2503 switch card gives you  
direct access to open and close the relays, and also the capability to  
download up to 1024 random scanning instructions. The software included  
with the card automatically configures the NI 2501/2503 and downloads  
the scan list to hardware for you. The scan list itself downloads directly into  
the memory of the card to deliver the fastest scan possible with no  
controller intervention. You can configure the switch card to process the  
scan list once or to continuously loop through the scan list.  
When configured to operate as a single switch card with multiple  
multiplexers—such as four 6 x 1 two-wire multiplexers—the scan  
architecture makes it possible for each multiplexer to have its own parallel  
scan list (which must be triggered together). Also, if the switch card is  
configured as a matrix, the scanning architecture scans the matrix through  
a series of user-definable states.  
PXI Interface  
The NI 2501/2503 switch card has a PXI interface through which you  
can use your driver software to configure and control the card. The  
NI 2501/2503 takes advantage of PXI features. It uses the PXI TTL triggers  
to synchronize scanning with a measurement device such as a National  
Instruments NI-4060 PXI digital multimeter (DMM).  
Triggers  
External Trigger Input  
The NI 2501/2503 can use an external trigger input to advance between  
scan setups in a scan list. Using the driver software, you can configure the  
switch card to route the external trigger from any of the PXI TTL trigger  
lines, the PXI star trigger, or the EXT TRIG IN pin on the front connector.  
Alternatively, you can use a software command to trigger the switch card.  
NI 2501/2503 User Manual  
2-6  
© National Instruments Corporation  
 
 
Chapter 2  
NI 2501/2503 Operation  
Routing the external trigger from the front connector to the PXI trigger  
lines gives you the capability to trigger multiple switch cards with only one  
board connected to the external trigger from the measurement device.  
All external trigger lines are compatible with TTL voltage levels and are  
edge sensitive.  
The external trigger from the front connector requires a minimum pulse  
width of 500 ns. The line has a low pass filter to prevent false triggering.  
The minimum pulse width from the PXI TTL triggers and PXI star trigger  
is 70 ns.  
Scanner Advanced  
The NI 2501/2503 can generate a scanner advanced trigger to indicate  
when the switch card is set up and ready to take measurements. Using the  
driver software, you can configure the switch card to route the scanner  
advanced (SCANADV) trigger to any PXI TTL trigger line, the PXI star  
trigger, or the SCAN_ADV pin on the front connector. You can configure  
the switch card to generate the SCANADV trigger when a relay has settled  
(or debounced).  
All SCANADV trigger lines are compatible with TTL voltage levels.  
Because the NI 2501/2503 has open collector drives on the PXI TTL trigger  
lines, you can have multiple switch cards using the same trigger line in the  
multicard SCANADV mode.  
Modes  
SCANADV has two modes of operation. In its default mode, the  
SCANADV trigger asserts for 1 µs after the relay has debounced. You  
can also configure the switch card for handshaking mode, in which the  
SCANADV trigger goes high after a relay settles, and the SCANADV  
trigger goes low after the external trigger input asserts. Use this  
handshaking mode for multicard scanning.  
Note  
The NI 2501/2503 ignores external triggers when it is not in a wait-for-trigger  
state while scanning.  
© National Instruments Corporation  
2-7  
NI 2501/2503 User Manual  
 
 
Chapter 2  
NI 2501/2503 Operation  
Initiating Scanning  
When you use the NI 2501/2503 to initiate a scan, make sure the  
measurement device is armed (waiting for trigger) before enabling  
scanning on the switch card. Enabling scanning causes the first switch(es)  
in the scan list to close and generates a scanner advanced trigger after the  
relay/FET switches have settled or debounced.  
When you use the measurement device to initiate a scan, make sure  
scanning is enabled on the NI 2501/2503 before the measurement device  
starts to take measurements. This ensures that the switch card has the  
correct signal routed and that the switch card is waiting for an external  
trigger from the measurement device.  
Always configure the triggers in a system before configuring the  
measurement device or the NI 2501/2503 for scanning. When triggers are  
configured, a state change or pulse could occur on the trigger line. This is  
also possible when you reset the switch card.  
Multicard Triggering  
You can use multiple NI 2501/2503 switch cards together in conjunction  
with an instrument such as a DMM. In multiple switch-card systems,  
be sure to identify one switch card as the master switch card.  
All other switch cards for the system are identified as slave switch cards.  
The master switch card can route an external trigger from the front  
connector to a PXI backplane trigger. In addition, the master switch card  
can route the SCANADV trigger from the PXI backplane to the front  
connector. This functionality makes it possible to wire external triggers  
from/to only one switch card in the system, which simplifies the wiring  
scheme.  
For more information, refer to the NI-SWITCH Software User Manual.  
NI 2501/2503 User Manual  
2-8  
© National Instruments Corporation  
 
 
A
Specifications  
This appendix lists the specifications for the NI 2501 and NI 2503  
switch cards. These specifications are typical at 25° C unless otherwise  
noted.  
NI 2501  
Input Characteristics  
Number of Channels .............................. 24  
Maximum Working Voltage .................. ± 10 VDC from chassis ground  
Overvoltage Protection  
Signals CH<0..23>, COM<0..3>  
Powered on or off .................... ± 25 VDC  
Signals AB<0..1>  
Powered on .............................. ± 25 VDC  
Powered off.............................. ± 15 VDC  
FET Switch On Resistance  
Typical ............................................ 50 Ω  
Max @ 25° C.................................. 85 Ω  
Max @ 85° C.................................. 100 Ω  
Total Signal Path Resistance (Channel x to Analog Bus x)  
Typical ............................................ 1650 Ω  
Maximum........................................ 1900 Ω  
Total Signal Path Resistance (Channel x to Common x)  
Typical ............................................ 1900 Ω  
Maximum........................................ 2150 Ω  
© National Instruments Corporation  
A-1  
NI 2501/2503 User Manual  
 
     
Appendix A  
Specifications for NI 2501  
Transfer Characteristics  
Channel Amplifier (Unity Gain)  
Offset Voltage (Differential) ..................1.2 mV max  
Cold-Junction Sensor Channel Amplifier (Unity Gain)  
Offset Voltage  
Maximum ........................................60 µV  
Frequency Bandwidth (50 Ω source, 1 M25 pF load)  
–3 dB ...............................................400 KHz  
–10 dB .............................................1 MHz  
Channel to Channel  
Crosstalk/Isolation..................................50 dB  
Dynamic Characteristics  
Operating Speed  
Typical.............................................25,000 cycles/s  
Maximum ........................................250,000 cycles/s  
Settling Time (+5 V to –5 V Step) 6 in. AB connector to PXI-MIO  
0.012% Accuracy  
With output buffer selected......8.5 µs  
Without output buffer...............9.0 µs  
0.006% Accuracy  
With output buffer selected......10 µs  
Without output buffer...............11.5 µs  
0.0015% Accuracy  
With output buffer selected......16 µs  
Without output buffer...............18 µs  
Settling Time (+5 V to –5 V Step) 3 m cable to PXI-MIO  
0.012% Accuracy  
With output buffer selected......21 µs  
Without output buffer...............45 µs  
NI 2501/2503 User Manual  
A-2  
© National Instruments Corporation  
 
Appendix A  
Specifications for NI 2501  
0.006% Accuracy  
With output buffer selected ..... 30 µs  
Without output buffer .............. 60 µs  
0.0015% Accuracy  
With output buffer selected ..... 80 µs  
Without output buffer .............. 160 µs  
Note  
Settling time is greatly affected by the external wiring to the switch card. You can  
improve the settling time by minimizing the wiring from the analog bus connection  
to the measurement device.  
PXI Bus Interface  
PXI Trigger Bus  
Slave  
Trigger Lines.......................................... 8  
Star Trigger ............................................ 1  
Power Requirement  
+5 V  
Typical ............................................ 300 mA  
+12 V  
Typical ............................................ 30 mA  
–12 V  
Typical ............................................ 30 mA  
Physical  
Dimensions............................................. 10 by 16 cm (3.9 by 6.3 in.)  
Weight.................................................... 0.254 kg (0.56 lb.)  
I/O Connector......................................... 68-pin male SCSI  
© National Instruments Corporation  
A-3  
NI 2501/2503 User Manual  
 
Appendix A  
Specifications for NI 2501  
Environment  
Operating Temperature ........................ 0° to 50° C  
Storage Temperature............................ –55° to 150° C  
Relative Humidity...................................5% to 90% non-condensing  
Shock and Vibration  
Functional Shock  
MIL-T-28800E Class 3 (30 g half-sine shock pulse)  
Also meets IEC 60068-2-27  
Random Vibration  
MIL-T-28800E, MIL-STD-810E Category 1  
Operational...............................5 to 500 Hz, 0.3 grms  
Non-operational........................5 to 500 Hz, 2.4 grms  
Certifications and Compliances  
CE Mark Compliance  
This product meets applicable EU directives as follows:  
Safety Isolation................................low-voltage safety,  
EN 61010-1:1993  
EMC Directive  
Immunity..................................EN 50082-1:1992  
Emissions .................................EN 55011:1991,  
Group 1 Class A at 10 m  
NI 2501/2503 User Manual  
A-4  
© National Instruments Corporation  
 
Appendix A  
Specifications for NI 2503  
NI 2503  
Input Characteristics  
Number of Relays Available  
as Channels ............................................ 24  
Common Mode Voltage  
Channel to Channel......................... 30 Vrms/60 VDC  
Channel to Earth ............................. 30 Vrms/60 VDC  
Maximum Allowed Voltage—Differential Mode or Single ended  
AC................................................... 30 Vrms  
DC................................................... 60 VDC  
Maximum Switching Capacity—Differential Mode or Single ended  
DC................................................... 1 A @ 30 VDC  
Maximum Switching Power per  
Differential Channel or Single ended..... 60 VA, 30 W  
Contact on Resistance (Initial)............... 100 mΩ  
Contact Material..................................... Gold-clad Silver Alloy  
Transfer Characteristics  
Thermal E.M.F. (Differential)................ <2 µV  
Maximum Frequency Bandwidth 50 Ω Termination  
Worst case channel ......................... 35 MHz  
© National Instruments Corporation  
A-5  
NI 2501/2503 User Manual  
 
Appendix A  
Specifications for NI 2503  
Channel to Channel Crosstalk/Isolation  
Differential..............................................50 Ω termination  
Frequency  
10 KHz  
Crosstalk  
< –100 dB  
< –80 dB  
< –55 dB  
< –30 dB  
< –25 dB  
100 KHz  
1 MHz  
10 MHz  
35 MHz  
Dynamic Characteristics  
Maximum Operating Speed....................200 cycles/s  
Relay Operate Time (@ 20° C)..............3 ms typical, 5 ms max  
Relay Release Time (@ 20° C)..............1.5 ms typical, 5 ms max  
Expected Life  
Mechanical (@ 180 cpm) ................5 × 107 operations  
Electrical at Maximum Load...........2 × 106 operations  
PXI Bus Interface  
PXI Trigger Bus  
Slave  
Trigger Lines ..........................................8  
Star Trigger.............................................1  
Power Requirement  
+5 V  
Typical.............................................370 mA  
Maximum ........................................700 mA  
NI 2501/2503 User Manual  
A-6  
© National Instruments Corporation  
 
Appendix A  
Specifications for NI 2503  
Physical  
Dimensions............................................. 10 by 16 cm (3.9 by 6.3 in.)  
Weight.................................................... 0.118 kg (0.4 lb.)  
I/O Connector......................................... 68-pin male SCSI  
Environment  
Operating Temperature.........................0° to 50° C  
Storage Temperature ............................–55° to 150° C  
Relative Humidity.................................. 5% to 85% non-condensing  
Shock and Vibration  
Functional Shock  
MIL-T-28800E Class 3 (30 g half sine shock pulse)  
Also meets IEC 60068-2-27  
Random Vibration  
MIL-T-28800E, MIL-STD-810E Category 1  
Operational .............................. 5 to 500 Hz, 0.3 grams  
Non-operational....................... 5 to 500 Hz, 2.4 grams  
Certifications and Compliances  
CE Mark Compliance  
This product meets applicable EU directives as follows:  
Safety Isolation ............................... low-voltage safety,  
EN 61010-1:1993  
EMC Directive  
Immunity ................................. EN 50082-1:1992  
Emissions................................. EN 55011:1991,  
Group 1 Class A at 10 m  
© National Instruments Corporation  
A-7  
NI 2501/2503 User Manual  
 
B
Accessories  
This appendix lists various National Instruments products you can use with  
your NI 2501/2503 module.  
The TB-2605 terminal block has screw terminal connections for all  
channels, bank commons, analog bus, and trigger signals. You can use  
this card for multiplexer switching applications. The terminal block  
has a temperature sensor that is used for thermocouple cold-junction  
compensation.  
The TB-2606 terminal block converts the switch card to a 6 x 4  
two-wire matrix configuration. This terminal block creates the matrix  
configuration by connecting channels (0, 6, 12, 18) (1, 7, 13, 19) …  
(5, 11, 17, 23).  
Analog bus connectors plug into TB-2605 and TB-2606 terminal  
blocks. These analog bus plugs connect the analog bus of two cards  
and terminate in banana plugs.  
The TBX-68S I/O connector block is a DIN rail-mounted terminal  
block with screw terminal connections you can use for all channels,  
bank outputs, analog bus, and trigger signals. You can use this card  
for multiplexer switching applications. The terminal block has a  
temperature sensor that is used for thermocouple cold-junction  
compensation. This is connected to the switch card through the  
SH68-68S cable.  
SH68-68S shielded 68-conductor cable connects the NI 2501/2503 to  
the TBX-68S, TBX-68LP, or TBX-68LPR.  
The TBX-68LP and TBX-68LPR are low-cost termination accessories  
with 68 screw terminals.  
CA-1000 is a configurable signal conditioning enclosure. It uses the  
TBX-68LPR terminal block.  
Contact National Instruments for more specific information about these  
products.  
© National Instruments Corporation  
B-1  
NI 2501/2503 User Manual  
 
     
C
Customizing Your Card  
This appendix describes options for customizing your NI 2501/2503 card.  
Current-Loop Receivers  
The NI 2501/2503 modules have sockets for transforming individual  
channels to current-to-voltage converters. National Instruments offers  
a process-current pack of four 249 , 0.1%, 5 ppm, 0.25 W resistors.  
The reference designator format for the current-loop resistors is such that  
for input channel x, the resistor is RCLx. For example, the resistor for  
channel 14 is RCL14.  
Caution  
Before installing the resistors in your module, make sure that no signals are  
connected to your module front connector.  
!
Before installing your module in the PXI chassis, you must install the  
resistors by performing the following steps:  
1. Ground yourself via a grounding strap or a ground connected to  
your PXI chassis. Properly grounding yourself prevents damage to  
your PXI module from electrostatic discharge.  
2. Bend and trim the resistor lead as shown in Figure C-1. Be sure that  
the resistor does not extend more than 0.5 in. above the surface of the  
circuit board.  
3. Insert the resistor into the appropriate socket, labeled RCLx.  
© National Instruments Corporation  
C-1  
NI 2501/2503 User Manual  
 
 
Appendix C  
Customizing Your Card  
Figure C-1. Bent and Trimmed Resistor  
NI 2501/2503 User Manual  
C-2  
© National Instruments Corporation  
 
   
D
Architecture Drawings  
This appendix contains architecture drawings for the NI 2501 and NI 2503  
switch cards. The drawings show the signal names that are used when the  
boards are in two-wire mode. To make these drawings relevant for  
one-wire mode, four-wire mode, or 6 x 4 matrix mode, use the signal names  
shown in Figures 1-2 through 1-4, respectively, in Chapter 1, Routing  
Signals with Your NI 2501/2503.  
Relay or switch names are based on the signal names where applicable. For  
example, the switch that connects CH9+ to COM1 and CH9– to COM1– is  
named CH9.  
For the other configuration relays, the names are as follows:  
For the relays that connect banks, the switch name is BCx-y, where  
x and y are the bank numbers that are being connected.  
For the relay that switches 1-Wire Lo Ref to COM0–, the name is  
1WIRE.  
For the relay that switches CHx+ or CHx– to COM0+, the name is  
HLSELECT.  
For the Amp Select switches (NI 2501 only), the names are AMP0 and  
AMP1.  
© National Instruments Corporation  
D-1  
NI 2501/2503 User Manual  
 
     
Appendix D  
Architecture Drawings  
CH11+  
CH11–  
CH10+  
CH10–  
CH9+  
CH9–  
Bank1  
CH8+  
CH8–  
CH7+  
CH7–  
COM1+  
COM1–  
CH6+  
CH6–  
BC01  
CH5+  
CH5–  
CH4+  
CH4–  
AB0  
CH3+  
CH3–  
AB0+  
AB0–  
Bank0  
CH2+  
CH2–  
HLSELECT  
AMP1  
AMP0  
COM0+  
COM0–  
CH1+  
CH1–  
1WIRE  
CH0+  
CH0–  
1-Wire Lo Ref  
CJS+  
CJS–  
AB1  
AB1+  
AB1–  
BC02  
CH12+  
CH12–  
COM2+  
COM2–  
CH13+  
CH13–  
CH14+  
CH14–  
Bank2  
CH15+  
CH15–  
CH16+  
CH16–  
CH17+  
CH17–  
BC23  
CH18+  
CH18–  
COM3+  
COM3–  
CH19+  
CH19–  
CH20+  
CH20–  
Bank3  
CH21+  
CH21–  
CH22+  
CH22–  
CH23+  
CH23–  
Figure D-1. NI 2501 Switch Architecture  
NI 2501/2503 User Manual  
D-2  
© National Instruments Corporation  
 
 
Appendix D  
Architecture Drawings  
CH11+  
CH11–  
CH10+  
CH10–  
CH9+  
CH9–  
Bank1  
CH8+  
CH8–  
CH7+  
CH7–  
COM1+  
COM1–  
CH6+  
CH6–  
BC01  
CH5+  
CH5–  
CH4+  
CH4–  
CH3+  
CH3–  
Bank0  
CH2+  
CH2–  
AB0  
AB1  
HLSELECT  
AB0+  
AB0–  
CH1+  
CH1–  
1WIRE  
COM0+  
COM0–  
CH0+  
CH0–  
1-Wire Lo Ref  
CJS+  
CJS–  
AB1+  
AB1–  
BC02  
CH12+  
CH12–  
COM2+  
COM2–  
CH13+  
CH13–  
CH14+  
CH14–  
Bank2  
CH15+  
CH15–  
CH16+  
CH16–  
CH17+  
CH17–  
BC23  
CH18+  
CH18–  
COM3+  
COM3–  
CH19+  
CH19–  
CH20+  
CH20–  
Bank3  
CH21+  
CH21–  
CH22+  
CH22–  
CH23+  
CH23–  
Figure D-2. NI 2503 Switch Architecture  
© National Instruments Corporation  
D-3  
NI 2501/2503 User Manual  
 
 
E
Common Questions  
This appendix addresses common questions you may have while using  
your NI 2501 or NI 2503 switch card.  
How fast can I scan with the NI 2501 switch card?  
The NI 2501 can be scanned as fast as 250 Kscans/s. However, at faster  
scan rates, the accuracy of the card declines due to the settling time of the  
card. National Instruments recommends you set the scan rate to allow for  
enough settling time to ensure the desired accuracy.  
How fast can I scan with the NI 2503 switch card?  
The NI 2503 uses relays that have typical operate and release times of 3 ms.  
In addition to the operate and release times, the NI 2503 also requires from  
0.5 to 1.0 ms for the relay contacts to stop bouncing. The combination of  
these two times are known as debounce time. The default debounce time for  
the NI 2503 switch card is set to just under 5 ms. This setting allows the  
card to be scanned at 200 scans/s. However, if the software implements  
break-before-make, this would reduce the scan rate to 100 scans/s.  
Typically, when using a DMM to make accurate measurements, the DMM  
requires hundreds of ms. Consequently, the DMM becomes the limiting  
factor in determining the scan rate.  
What should I do if the software detects the board but the switches do  
not switch?  
Verify that the switches do not switch. Close your application program  
and then launch the soft front panel as described in the Setup and Test  
document you received with your kit. The soft front panel shows the  
state of each relay or FET switch on the board. Try closing and opening  
the switches.  
Also be sure to check the return codes of the NI-SWITCH operation to  
ensure that there are no errors (negative value) or warnings (positive  
value). You can also use the NI-Spy utility to check for error codes.  
© National Instruments Corporation  
E-1  
NI 2501/2503 User Manual  
 
 
Appendix E  
Common Questions  
Finally, verify that your code is correct. For reference, see the  
examples described in the NI-SWITCH Software User Manual. The  
NI-SWITCH driver also ships with several examples in source code.  
Compare your algorithm to the ones in the examples.  
What should I do if scanning does not work?  
First, ensure that you have configured the switch card and the  
instrument to match trigger lines. The output trigger of the instrument  
should connect to the trigger input of the switch card. In addition, the  
scanner advanced trigger of the switch card should be connected to the  
input trigger of the instrument.  
If the switch card is used to initiate the scan, make sure the DMM is  
waiting for a trigger before enabling scanning on the switch card. This  
is the recommended method for hardware scanning.  
If the DMM is used to initiate the scan, enable scanning on the switch  
card before configuring the DMM to start taking measurements.  
Also be sure to check the return codes of the NI-SWITCH operation to  
ensure that there are no errors (negative value) or warnings (positive  
value). You can also use the NI-Spy utility to check for error codes.  
Finally, verify that your code is correct. For reference, see the  
examples described in the NI-SWITCH Software User Manual. The  
NI-SWITCH driver also ships with several examples in source code.  
Compare your algorithm to the ones in the examples.  
Do I need to program the switch card myself?  
The NI 2501/2503 comes with the NI-SWITCH driver software, which  
exports the full functionality of the card. NI-SWITCH handles the complex  
issues of direct memory access, interrupts, and operating system  
interfacing.  
NI 2501/2503 User Manual  
E-2  
© National Instruments Corporation  
 
F
Customer Communication  
For your convenience, this appendix contains forms to help you gather the information necessary  
to help us solve your technical problems and a form you can use to comment on the product  
documentation. When you contact us, we need the information on the Technical Support Form and  
the configuration form, if your manual contains one, about your system configuration to answer your  
questions as quickly as possible.  
National Instruments has technical assistance through electronic, fax, and telephone systems to quickly  
provide the information you need. Our electronic services include a bulletin board service, an FTP site,  
a fax-on-demand system, and e-mail support. If you have a hardware or software problem, first try  
the electronic support systems. If the information available on these systems does not answer your  
questions, we offer fax and telephone support through our technical support centers, which are staffed  
by applications engineers.  
Electronic Services  
Bulletin Board Support  
National Instruments has BBS and FTP sites dedicated for 24-hour support with a collection of files  
and documents to answer most common customer questions. From these sites, you can also download  
the latest instrument drivers, updates, and example programs. For recorded instructions on how to use  
the bulletin board and FTP services and for BBS automated information, call 512 795 6990. You can  
access these services at:  
United States: 512 794 5422  
Up to 14,400 baud, 8 data bits, 1 stop bit, no parity  
United Kingdom: 01635 551422  
Up to 9,600 baud, 8 data bits, 1 stop bit, no parity  
France: 01 48 65 15 59  
Up to 9,600 baud, 8 data bits, 1 stop bit, no parity  
FTP Support  
To access our FTP site, log on to our Internet host, ftp.natinst.com, as anonymous and use  
your Internet address, such as [email protected], as your password. The support files and  
documents are located in the /support directories.  
© National Instruments Corporation  
F-1  
NI 2501/2503 User Manual  
 
 
Fax-on-Demand Support  
Fax-on-Demand is a 24-hour information retrieval system containing a library of documents on a wide  
range of technical information. You can access Fax-on-Demand from a touch-tone telephone at  
512 418 1111.  
E-Mail Support (Currently USA Only)  
You can submit technical support questions to the applications engineering team through e-mail at the  
Internet address listed below. Remember to include your name, address, and phone number so we can  
contact you with solutions and suggestions.  
Telephone and Fax Support  
National Instruments has branch offices all over the world. Use the list below to find the technical  
support number for your country. If there is no National Instruments office in your country, contact  
the source from which you purchased your software to obtain support.  
Country  
Telephone  
Fax  
Australia  
Austria  
Belgium  
Brazil  
Canada (Ontario)  
Canada (Québec)  
Denmark  
Finland  
03 9879 5166  
0662 45 79 90 0  
02 757 00 20  
011 288 3336  
905 785 0085  
514 694 8521  
45 76 26 00  
09 725 725 11  
01 48 14 24 24  
089 741 31 30  
2645 3186  
03 6120092  
02 413091  
03 5472 2970  
02 596 7456  
5 520 2635  
03 9879 6277  
0662 45 79 90 19  
02 757 03 11  
011 288 8528  
905 785 0086  
514 694 4399  
45 76 26 02  
09 725 725 55  
01 48 14 24 14  
089 714 60 35  
2686 8505  
France  
Germany  
Hong Kong  
Israel  
Italy  
Japan  
03 6120095  
02 41309215  
03 5472 2977  
02 596 7455  
5 520 3282  
Korea  
Mexico  
Netherlands  
Norway  
Singapore  
Spain  
Sweden  
Switzerland  
Taiwan  
0348 433466  
32 84 84 00  
2265886  
91 640 0085  
08 730 49 70  
056 200 51 51  
02 377 1200  
01635 523545  
512 795 8248  
0348 430673  
32 84 86 00  
2265887  
91 640 0533  
08 730 43 70  
056 200 51 55  
02 737 4644  
01635 523154  
512 794 5678  
United Kingdom  
United States  
NI 2501/2503 User Manual  
F-2  
© National Instruments Corporation  
 
Technical Support Form  
Photocopy this form and update it each time you make changes to your software or hardware, and use  
the completed copy of this form as a reference for your current configuration. Completing this form  
accurately before contacting National Instruments for technical support helps our applications  
engineers answer your questions more efficiently.  
If you are using any National Instruments hardware or software products related to this problem,  
include the configuration forms from their user manuals. Include additional pages if necessary.  
Name __________________________________________________________________________  
Company _______________________________________________________________________  
Address ________________________________________________________________________  
_______________________________________________________________________________  
Fax ( ___ ) ________________Phone ( ___ ) __________________________________________  
Computer brand____________ Model ___________________Processor_____________________  
Operating system (include version number) ____________________________________________  
Clock speed ______MHz RAM _____MB  
Display adapter __________________________  
Mouse ___yes ___no Other adapters installed_______________________________________  
Hard disk capacity _____MB Brand_________________________________________________  
Instruments used _________________________________________________________________  
_______________________________________________________________________________  
National Instruments hardware product model _____________ Revision ____________________  
Configuration ___________________________________________________________________  
National Instruments software product ___________________ Version _____________________  
Configuration ___________________________________________________________________  
The problem is: __________________________________________________________________  
_______________________________________________________________________________  
_______________________________________________________________________________  
_______________________________________________________________________________  
_______________________________________________________________________________  
List any error messages: ___________________________________________________________  
_______________________________________________________________________________  
_______________________________________________________________________________  
The following steps reproduce the problem: ___________________________________________  
_______________________________________________________________________________  
_______________________________________________________________________________  
_______________________________________________________________________________  
_______________________________________________________________________________  
 
NI 2501/2503 Hardware and Software  
Configuration Form  
Record the settings and revisions of your hardware and software on the line to the right of each item.  
Complete a new copy of this form each time you revise your software or hardware configuration, and  
use this form as a reference for your current configuration. Completing this form accurately before  
contacting National Instruments for technical support helps our applications engineers answer your  
questions more efficiently.  
National Instruments Products  
Using NI 2501 or NI 2503?_________________________________________________________  
Hardware revision ________________________________________________________________  
Switching mode__________________________________________________________________  
List National Instruments Software Installed and Version  
NI-SWITCH version ______________________________________________________________  
LabVIEW version ________________________________________________________________  
LabWindows/CVI version __________________________________________________________  
Other National Instruments software version ____________________________________________  
________________________________________________________________________________  
Programming choice _______________________________________________________________  
Other Products  
PXI Chassis make and model _______________________________________________________  
Microprocessor __________________________________________________________________  
Clock frequency or speed __________________________________________________________  
Type of video board installed _______________________________________________________  
Operating system version __________________________________________________________  
Operating system mode____________________________________________________________  
Programming language ____________________________________________________________  
Programming language version______________________________________________________  
Switch accessories________________________________________________________________  
_______________________________________________________________________________  
Instruments connected to switch _____________________________________________________  
_______________________________________________________________________________  
 
List All Boards in PXI Mainframe  
PXI Slot  
Manufacturer, Description, and Function  
1
2
3
4
5
6
7
8
 
Documentation Comment Form  
National Instruments encourages you to comment on the documentation supplied with our products.  
This information helps us provide quality products to meet your needs.  
Title:  
NI 2501/2503 User Manual  
Edition Date: July 1998  
Part Number: 321906B-01  
Please comment on the completeness, clarity, and organization of the manual.  
_______________________________________________________________________________  
_______________________________________________________________________________  
_______________________________________________________________________________  
_______________________________________________________________________________  
_______________________________________________________________________________  
_______________________________________________________________________________  
_______________________________________________________________________________  
If you find errors in the manual, please record the page numbers and describe the errors.  
_______________________________________________________________________________  
_______________________________________________________________________________  
_______________________________________________________________________________  
_______________________________________________________________________________  
_______________________________________________________________________________  
_______________________________________________________________________________  
_______________________________________________________________________________  
Thank you for your help.  
Name _________________________________________________________________________  
Title __________________________________________________________________________  
Company _______________________________________________________________________  
Address ________________________________________________________________________  
_______________________________________________________________________________  
E-Mail Address __________________________________________________________________  
Phone ( ___ ) __________________________ Fax ( ___ ) _______________________________  
Mail to: Technical Publications  
National Instruments Corporation  
Fax to: Technical Publications  
National Instruments Corporation  
512 794 5678  
6504 Bridge Point Parkway  
Austin, Texas 78730-5039  
 
Glossary  
Prefix  
n-  
Meanings  
nano-  
Value  
10–9  
10– 6  
10–3  
103  
µ-  
micro-  
milli-  
m-  
k-  
kilo-  
M-  
G-  
mega-  
giga-  
106  
109  
Symbols  
°
degrees  
%
±
ohms  
percent  
plus or minus  
A
A
amperes  
AC  
ANSI  
alternating current  
American National Standards Institute  
B
breakpoint  
a specified point in program code where the program pauses to perform  
some action; a breakpoint interrupt can be added to a scan list for  
debugging or other special needs.  
© National Instruments Corporation  
G-1  
NI 2501/2503 User Manual  
 
 
Glossary  
bus  
the group of conductors that interconnect individual circuitry in a computer.  
Typically, a bus is the expansion vehicle to which I/O or other devices are  
connected. Examples of PC buses are the ISA and PCI bus.  
C
C
Celsius  
channel  
pin or wire lead on the multiplexer to which you apply or from which you  
read the analog or digital signal. Signals can be single-ended or differential.  
cold-junction  
compensation  
a method of compensating for inaccuracies in thermocouple circuits  
contact bounce  
the intermittent switching that occurs when the movable metal parts of a  
relay make or break contact  
D
DC  
direct current  
debounced  
device  
indicates when the contact bounce has ended. See contact bounce.  
a plug-in board, card, or pad that can contain multiple channels and  
conversion devices. Some examples of devices are computers,  
multimeters, multiplexers, oscillators, operator interfaces, and  
counters.  
digital multimeter  
a multifunction meter used to make measurements such as voltage, current,  
resistance frequency, temperature, and so on  
DIN  
Deutsche Industrie Norme  
DMA  
direct memory access—a method by which data can be transferred to/from  
computer memory from/to a device or memory on the bus while the  
processor does something else. DMA is the fastest method of transferring  
data to/from computer memory.  
DMM  
See digital multimeter.  
drivers/driver software  
software that controls a specific hardware device such as a switch card  
NI 2501/2503 User Manual  
G-2  
© National Instruments Corporation  
 
Glossary  
E
external trigger  
a voltage pulse from an external source that triggers an event such as  
A/D conversion  
F
FET  
Field Effect Transistor  
H
handshaking  
the use of two trigger lines between two instruments, such as a switch and  
a DMM, to synchronize their actions  
Hz  
hertz—the number of scans read or updates written per second  
I
in.  
inches  
I/O  
input/output—the transfer of data to/from a computer system involving  
communications channels, operator interface devices, and/or data  
acquisition and control interfaces  
Intelligent Virtual  
Instrument  
an advanced architecture for instrument drivers that includes features such  
as simulation and state caching  
ISA  
IVI  
Industry Standard Architecture  
See Intelligent Virtual Instrument.  
M
MB  
megabytes of memory  
matrix  
superset of multiplexer; consists of connected rows and columns that  
allows for a direct connection from any row to any column  
movistor  
transient suppression device  
© National Instruments Corporation  
G-3  
NI 2501/2503 User Manual  
 
Glossary  
multiplexer  
a switching device with multiple inputs that sequentially connects each  
of its inputs to its output, typically at high speeds, in order to measure  
several signals with a single analog input channel  
mux  
See multiplexer.  
N
NI-SWITCH  
an IVI-based instrument driver that supports the National Instruments line  
of switch cards  
P
PXI  
PCI with extensions for instrumentation  
R
random scanning  
scanning the channels in a mux in any order  
relay  
a switch that connects or disconnects the signal to a common through the  
physical movement of a metal arm  
RMA  
rms  
Return Material Authorization  
root mean square—the square root of the average value of the square of the  
instantaneous signal amplitude; a measure of signal amplitude  
RTD  
resistance temperature detector—a metallic probe that measures  
temperature based upon its coefficient of resistivity  
S
s
seconds  
scan  
the data acquisition of signals connected to multiple channels of a  
multiplexer. Typically, the measurement device uses a trigger to  
advance the multiplexer to the next channel in the scan.  
scan list  
a list of channels supplied to NI-SWITCH that indicates the order in which  
channels will be scanned  
NI 2501/2503 User Manual  
G-4  
© National Instruments Corporation  
 
Glossary  
scanner advanced  
trigger  
the trigger generated by the switch card when scanning. The trigger occurs  
after the switch card has closed a switch and the switch has settled.  
sensor  
a device that responds to a physical stimulus (heat, light, sound,  
pressure, motion, flow, and so on), and produces a corresponding  
electrical signal  
settling time  
the amount of time required for a voltage to reach its final value within  
specified limits  
soft front panel  
a graphical program included with NI-SWITCH that you can use to  
interactively control the switch  
T
TBX  
Terminal Block Extension  
terminal block  
thermistor  
an accessory containing wire connection points, typically screw terminals  
a semiconductor sensor that exhibits a repeatable change in electrical  
resistance as a function of temperature. Most thermistors exhibit a  
negative temperature coefficient.  
thermocouple  
a temperature sensor created by joining two dissimilar metals. The  
junction produces a small voltage as a function of the temperature.  
trigger  
TTL  
any event that causes or starts some form of data capture  
Transistor-Transistor Logic  
V
V
volts  
VDC  
VI  
volts, direct current  
virtual instrument—(1) a combination of hardware and/or software  
elements, typically used with a PC, that has the functionality of a classic  
stand-alone instrument (2) a LabVIEW software module (VI), which  
consists of a front panel user interface and a block diagram program  
© National Instruments Corporation  
G-5  
NI 2501/2503 User Manual  
 
Glossary  
W
W
watts  
wire  
data path between nodes  
NI 2501/2503 User Manual  
G-6  
© National Instruments Corporation  
 
Index  
COM<0..1>Α± signal (table), 1-9  
COM<0..1>B± signal (table), 1-9  
COM0± signal (table), 1-9  
Numbers  
1_WIRE_LO_REF signal (table), 1-9  
+5 V signal (table), 1-9  
common questions, E-1 to E-2  
connecting signals. See signal connections.  
contact protection (caution), 1-10  
conventions used in this manual, v  
current-loop receivers, C1 to C-2  
customer communication, F-1 to F-2  
customizing NI 2501/2503, C1 to C-2  
A
AB<0..1>± signal (table), 1-9  
AB0± signal (table), 1-9  
AB0A± signal (table), 1-9  
AB0B± signal (table), 1-9  
accessories for NI 2501/2503, B-1  
amplifier for NI 2501, 1-3  
analog bus, 1-2  
D
debounced switches, 1-2  
dynamic characteristics  
NI 2501, A-2 to A-3  
NI 2503, A-6  
analog bus connectors, for terminal blocks, B-1  
architecture drawings, D-1 to D-3  
B
block diagrams  
E
NI 2501 module, 2-2  
NI 2503 module, 2-3  
bulletin board support, F-1  
electrical hazards  
exceeding maximum settings (warning), 1-4  
static electricity (caution), 1-4  
electronic support services, F-1 to F-2  
e-mail support, F-2  
environmental specifications  
NI 2501, A-4  
C
CA-1000, B-1  
cable, SH68-68S, B-1  
NI 2503, A-7  
calibration data, storing in EEPROM, 1-3  
CE Mark Compliance, A-4, A-7  
CH<0..23>± signal (table), 1-9  
CH<0..47> one-wire signal (table), 1-9  
CH<0..11>A± signal (table), 1-9  
CH<0..11>Β± signal (table), 1-9  
CJS± signal (table), 1-9  
COL<0..5>± signal (table), 1-9  
cold-junction sensor channel, 1-3  
COM<0..3>± signal (table), 1-9  
external trigger input, 1-2, 2-6 to 2-7  
EXT_TRIG_IN signal (table), 1-9, 2-6  
F
fax and telephone support numbers, F-2  
Fax-on-Demand support, F-2  
flyback voltages (caution), 1-10  
four-wire multiplexer, 1-7, 2-5  
© National Instruments Corporation  
I-1  
NI 2501/2503 User Manual  
 
 
Index  
front connector  
N
pinout assignments  
National Instruments application  
software, 1-11  
NI 2501/2503. See also operation of  
NI 2501/2503.  
four-wire mode (figure), 1-7  
matrix mode (figure), 1-8  
one-wire mode (figure), 1-6  
overview, 1-4  
accessories, B-1  
two-wire mode (figure), 1-5  
signal descriptions (table), 1-9  
FTP support, F-1  
architecture drawings, D1 to D-3  
block diagrams  
NI 2501 module, 2-2  
NI 2503 module, 2-3  
common questions, E-1 to E-2  
customizing, C1 to C-2  
features, 1-1 to 1-2  
G
GND signal (table), 1-9  
functional overview, 2-1  
maximum voltage (note), 1-2  
overview, 1-1 to 1-2  
signal connections, 1-4 to 1-9  
software choices, 1-10 to 1-11  
specifications  
I
initiating scanning, 2-8  
input characteristics  
NI 2501, A-1  
NI 2503, A-5  
NI 2501, A-1 to A-4  
NI 2503, A-5 to A-7  
NI-SWITCH driver software, 1-10, E-1 to E-2  
I/O connector blocks  
TBX-68LP, B-1  
TBX-68LPR, B-1  
TBX-68S, 1-3, B-1  
O
one-wire multiplexer, 1-6, 2-4  
operation of NI 2501/2503, 2-1 to 2-8  
block diagrams  
L
LabVIEW software, 1-11  
LabWindows/CVI software, 1-11  
NI 2501 module, 2-2  
NI 2503 module, 2-3  
functional overview, 2-1  
multiplexer, 2-4 to 2-5  
PXI interface, 2-6 to 2-8  
initiating scanning, 2-8  
multicard triggering, 2-8  
triggers, 2-6 to 2-7  
M
matrix mode, 1-8, 2-5  
maximum voltage (note), 1-2  
modes of operation, 2-7  
multicard triggering, 2-8  
multiplexer, 2-4 to 2-5  
four-wire, 2-5  
random scanning, 2-5 to 2-6  
switch control circuitry, 2-5  
matrix mode, 2-5  
one-wire, 2-4  
two-wire, 2-4  
NI 2501/2503 User Manual  
I-2  
© National Instruments Corporation  
 
Index  
P
S
physical specifications  
NI 2501, A-3  
SCAN_ADV signal (table), 1-9, 2-7  
scanner advanced trigger, 1-2, 2-7  
scanning  
NI 2503, A-7  
pinout assignments for front connector  
four-wire mode (figure), 1-7  
matrix mode, (figure), 1-8  
one-wire mode (figure), 1-6  
overview, 1-4  
two-wire mode (figure), 1-5  
power requirements  
NI 2501, A-3  
failure to scan, E-2  
initiating, 2-8  
random scanning, 2-5 to 2-6  
speed of scanning, E-1  
SH68-68S shielded cable, B-1  
shock and vibration specifications  
NI 2501, A-4  
NI 2503, A-7  
NI 2503, A-7  
product compliance specifications  
NI 2501, A-4  
signal connections, 1-4 to 1-9  
exceeding maximum settings  
(warning), 1-4  
front connector pinout assignments  
four-wire mode (figure), 1-7  
matrix mode (figure), 1-8  
one-wire mode (figure), 1-6  
overview, 1-4  
NI 2503, A-7  
PXI interface, 2-6 to 2-8  
initiating scanning, 2-7 to 2-8  
multicard triggering, 2-8  
specifications  
two-wire mode (figure), 1-5  
signal descriptions (table), 1-9  
software choices  
NI 2501, A-3  
NI 2503, A-6  
triggers, 2-6 to 2-7  
external trigger input, 2-7  
modes, 2-7  
National Instruments application  
software, 1-11  
NI-SWITCH driver software, 1-10  
third-party software, 1-11  
specifications  
scanner advanced, 2-7  
PXI trigger bus specifications  
NI 2501, A-3  
NI 2501, A-1 to A-4  
NI 2503, A-6  
CE mark compliance, A-4  
dynamic characteristics, A-2 to A-3  
environment, A-4  
input characteristics, A-1  
physical, A-3  
Q
questions and answers, E-1 to E-2  
power requirements, A-3  
PXI bus interface, A-3  
PXI trigger bus, A-3  
shock and vibration, A-4  
transfer characteristics, A-2  
R
random scanning, 2-5 to 2-6  
relay multiplexer, 2-3 to 2-5  
resistors, installing, C1 to C-2  
ROW<0..3>± signal (table), 1-9  
© National Instruments Corporation  
I-3  
NI 2501/2503 User Manual  
 
Index  
NI 2503, A-5 to A-7  
technical support, F-1 to F-2  
telephone and fax support numbers, F-2  
terminal blocks  
CE mark compliance, A-7  
dynamic characteristics, A-6  
environment, A-7  
input characteristics, A-5  
physical, A-7  
analog bus connectors, B-1  
availability, 1-10  
TB-2605, 1-3, B-1  
power requirements, A-7  
PXI bus interface, A-6  
PXI trigger bus, A-6  
TB-2606, 1-1, 1-8, 2-5, B-1  
transfer characteristics  
NI 2501, A-2  
shock and vibration, A-7  
transfer characteristics, A-6  
NI 2503, A-6  
triggers  
static electricity, component failure due to  
(caution), 1-4  
external trigger input, 1-2, 2-6 to 2-7  
modes, 2-7  
switch control circuitry, 2-5  
switch failure, E-1 to E-2  
multicard triggering, 2-8  
overview, 1-2  
scanner advanced, 1-2, 2-7  
two-wire multiplexer, 1-5, 2-4  
T
TB-2605 terminal block, 1-3, B-1  
V
TB-2606 terminal block, 1-1, 1-8, 2-5, B-1  
TBX-68LP I/O connector block, B-1  
TBX-68LPR I/O connector block, B-1  
TBX-68S I/O connector block, 1-3, B-1  
voltage  
flyback voltages (caution), 1-10  
maximum voltage (note), 1-2  
NI 2501/2503 User Manual  
I-4  
© National Instruments Corporation  
 

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