National Instruments 321906B-01 用户手册

Chapter 1

Routing Signals with Your NI 2501/2503

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 National Instruments Corporation

1-9

Table 1-1.  Front Connector Signal Description

+5 V

Output

+5 VDC Source—Powers the temperature sensor 
on the terminal block. 0.2 mA of source protected 
by a resettable poly fuse.

GND

Output

Ground

CJS

±

Input

Cold-junction Temperature Sensor Input— 
Connects to the temperature sensor of the 
terminal block.

1_WIRE_LO_REF

Input

The common reference signal used in one-wire 
mode.

EXT_TRIG_IN

Input

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)

COM<0..3>

± 

(two wire)

COM<0..1>A

± 

(four wire)

COM<0..1>B

± 

(four wire)

Input/Output

Common—The common for each bank.

AB0

± 

(one wire)

AB<0..1>

± 

(two wire)

AB0A

± 

(four wire)

AB0B

± 

(four wire)

Input/Output

Analog Bus—Used to wire multiple switch cards 
to an instrument such as a DMM.

COL<0..5>

±

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>

±

Input/Output

Rows—Where signals are connected to the 
switch card. In matrix configuration any row 
can be connected to any column.