A boxed 16 bridge inputs card which you need when monitoring strain gauge bridges and balanced bridges such as pressure transducers. Also provides screw terminations to allow signals into the USB units to be permanently wired. Used with the 751, 752 or 851 data acquisition units.
Strain gauges need an external excitation voltage to supply sufficient current to keep all the bridge circuits energised. Four sets of 16 screw terminals give + and - excitation and + and - signals for each of 16 bridges. Two 1 kOhm termination resistors are mounted in half bridge configuration whilst high quality 350 and 120 Ohm resistors can be provided for the completion of quarter bridges. The auxiliary channel of a 751, 752 or 851 unit, is used to monitor the excitation voltage. The analogue-to-digital converter on the 751, 752 or 851 unit is suitable for direct measurement of voltage imbalance, provided you choose a high resolution.
When a bridge input is selected the software automatically monitors excitation voltage and performs the bridge calculation to produce a reading in microstrain. You can set a zero reference level and monitor changes relative to that level.
With the 594 unit you can configure individual channels to accept any one of the following inputs.
| voltage input |
| quarter bridge | single strain gauge |
| half bridge | tensile + compressive strain gauge |
| half bridge | normal + transverse strain gauge |
| full bridge | two tensile + two compressive gauges |
| full bridge | two normal + two transverse gauges |
| full bridge | tensile normal + compressive normal + tensile transverse + compressive transverse gauge |
More information about measuring strain, and tips on implementing a computerised strain measurement system, is on our Data Acquisition Intelligence site.
