Using The Internal Half-Bridge Completion; Temperature Sensor Connection; Figure 3-7. Connecting A Quarter-Bridge Strain Gauge To Channel 0; Table 3-1. Maximum Load Per Excitation Channel - National Instruments SCXI -1122 User Manual

Chapter 3

Using the Internal Half-Bridge Completion

Your SCXI-1122 includes half-bridge completion for half-bridge and quarter-bridge setups. The
completion network consists of two 2.5 k
coefficient of 2 ppm/ C. These resistors are connected in series. To use the network, connect
the VEX/2 screw terminal on the terminal block to the negative input of the channel of interest.

Figure 3-7. Connecting a Quarter-Bridge Strain Gauge to Channel 0

Note: When using the half-bridge completion network with a quarter-bridge setup, you must
use an extra resistor to complete the bridge. Place this resistor on the terminal block
between the positive input channel and the negative excitation output.

Temperature Sensor Connection

Pins A1 and A3 are for connecting the isolated temperature sensor located on the SCXI-1322
terminal block for cold-junction compensation (CJC) of thermocouples connected to the
SCXI-1122. The connection is overvoltage-protected to 250 Vrms with power on and off.
Warning: Exceeding the overvoltage protection on the temperature connections can damage
the SCXI-1122, the SCXIbus, and the DAQ board. National Instruments is
liable for any damages resulting from such signal connections.
© National Instruments Corporation

Table 3-1. Maximum Load per Excitation Channel

Excitation Level
3.333 V
1 mA
120
Strain
Gauge
120
Dummy
Resistor
Maximum Load
225 mA
5 k
0.02% ratio tolerance resistors with a temperature
VEX+
CH+0
CH-0
VEX/2
VEX-
SCXI-1322 Terminal Block
3-9
Signal Connections
NOT
SCXI-1122 User Manual