Chapter 1 Routing Signals with Your NI2501/2503
©
National Instruments Corporation 1-9 NI 2501/2503 User Manual
Table 1-1. Front Connector Signal Description
Signal Name Type 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
nextscan entry.
SCAN_ADV Output Scanner Advanced—Trigger to an instrument
that indicated the switch card has advanced to
thenext 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>± (twowire)
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± (fourwire)
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
canbe connected to any column.