Chapter 4
Connecting and Using Accessories and Transducers
©
National Instruments Corporation
4-15
Using Strain Gauges with the SCXI-1520
The SCXI-1520 allows you to set the voltage excitation level over the range
0 to 10 V at 0.625 V resolution. To prevent the module from overheating,
the voltage should not be set greater than
(total load resistance per channel)
×
(28.6 mA)
Table 4-3 shows maximum allowable excitation voltages for standard
bridge configurations and gauge resistances.
Figures 4-8, 4-9, and 4-10 show examples of quarter-bridge, half-bridge,
and full-bridge strain gauge connections, respectively, to the SCXI-1520
through the accessory SCXI-1314 terminal block. The quarter-bridge
completion resistor and shunt calibration resistors are in sockets. You can
change the quarter-bridge completion resistor to match the resistance of
your strain gauge without resoldering. Half-bridge completion is provided
inside the SCXI-1520 module. You configure the module for half-bridge
completion under software control.
Table 4-3.
Excitation Voltage Ranges for Configuration and Gauge Resistances
Configuration/Sensor
Resistance
Excitation Voltage Range
Quarter or Half Bridge
120
Ω
0 to 6.250 V
350
Ω
0 to 10 V
1000
Ω
0 to 10 V
Full Bridge or
Full-Bridge Sensor
120
Ω
0 to 3.125 V
350
Ω
0 to 10 V
1000
Ω
0 to 10 V