I’m often asked whether the Prosig systems support strain gauges. And what configuration of strain gauge bridges are supported? The answer is all types of all configurations.
Bridge Completion Configurations
Prosig hardware supports
- 1/4 bridge completion
- 1/2 bridge completion
- Full bridge completion
Bridge Completion Resistances
And the following bridge completion resistances are supported
- 120?
- 350?
- 1000?
Regarding calibration of bridges, each channel on the front end has its own internal, low tolerance shunt resistor (120k?).
Generally, a 1/4 bridge is a 3-wire configuration. It can be used in a 2-wire configuration, but this does reduce the accuracy slightly.
1/2 bridge is usually a 5-wire configuration but can be used as a 3-wire configuration if desired, but as above is slightly less accurate.
The full bridge can be used as a 6-wire or a 4-wire configuration, but with the same issue as above when used as a 4-wire device.
The 2 wires discussed above that can be ‘removed’ (actually, they are shorted to the supply) are the sense wires. These wires sense the excitation at the bridge and not at the front end. So, in the case of long thin wires, the voltage drop is taken into account in the calculation of microstrain.
Prosig front ends usually support 3 different strain gauge excitation voltages; 0V, 5V and 10V.
Prosig hardware can support from +/-10V input range down to +/-10mV. The smaller measurement range is often required as the voltage changes when using strain gauges are so small. Additionally, there is a benefit to using the full 24 bits of the ADC resolution across a small range.
James Wren
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