Chapter 2
Connecting the Signals
©
National Instruments Corporation
2-3
SCXI-1502 User Manual
Front Connector Signal Descriptions
Analog Input Signal Connections
The signal terminals for the negative input channel are located in column B
of the connector. The signal terminal for each corresponding positive input
channel is located in column C of the connector. Each input goes to a
separate filter and amplifier that is multiplexed to the module output
buffer. If the terminal block has a temperature sensor, the sensor
output—connected to pins A3 and/or A4 (CJ SENSOR)—is also filtered
and multiplexed to the module output buffer.
The differential input signal range of an SCXI-1502 module input channel
is ±10 V when using a gain of 1 or ±0.1 V when using a gain of 100. This
differential input range is the maximum measurable voltage difference
between the positive and negative channel inputs. The common-mode input
signal range of an SCXI-1502 module input channel is ±10 V. This
common-mode input range for either positive or negative channel input is
the maximum input voltage that results in a valid measurement. Each
channel includes input protection circuitry to withstand the accidental
application of voltages up to ±42 VDC powered on or ±25 VDC powered
off.
Table 2-2.
Front Connector Signals
Pin
Signal Name
Description
A1
+5 V
+5 VDC Source—Used to power circuitry on the
terminal block. 0.1 mA of source not protected.
A2, A5, A16,
A24, A32
GND
Ground—Tied to the SCXI module ground.
A3, A4
CJ SENSOR
Cold-Junction Temperature Sensor
Input—Connects to the temperature sensor of
the terminal block.
B1–B32
CH 31 – through CH 0 –
Negative Input Channels—Negative side of
differential input channels.
C1–C32
CH 31 + through CH 0 +
Positive Input Channels 31 through 0—Positive
side of differential input channels.
A19, A20, A25
to A28
RSVD
Reserved—Reserved for use by the SCXI-1502.
