LabVIEW
How to programmatically create a Strain Gage Calibration Wizard?
Hello,
I have a requirement to build a Strain Data acquisition Systems using LabVIEW with all the Signal Conditioning Facilities available with PXIe-4331.
So the main attractive feature for the customer is the Offset Nulling and Shunt Calibration.
The DAQMX does have two VIs for this, DAQmx Perform Bridge Offset Nulling Calibration.vi and DAQmx Perform Shunt Calibration (Strain).vi
and both works very well..
But my problem is .. Customer is more interested in knowing the exact initial offset voltage and the Gain adjustments made by Shunt Calibration vi.
The Strain Gage Calibration Wizard in MAX has the similar feature available.
But I couldn't find a way to implement the same in LabVIEW.
Any Ideas?
Thanks and Regards,
Mirash
Hello Mirash,
You can't run the DAQ Assistant's strain calibration wizard from your program, but you can query the offset and gain adjust programmatically through the API after performing the calibration:
AI.Bridge.InitialVoltage is the offset (in volts*) from the offset nulling procedure, and AI.Bridge.ShuntCal.GainAdjust is the gain adjustment factor from the shunt cal procedure.
* The PXIe-4331 doesn't actually measure volts. The PXIe-4331 performs ratiometric measurements, so AI.Bridge.InitialVoltage is based on measuring the voltage ratio Vch/Vex, then multiplying it by the ideal Vex value. The PXIe-4331 never measures Vch or Vex separately, only as a ratio. If you need to compare the initial voltage to an independent measurement (from another instrument), it is probably better to query AI.Bridge.InitialRatio, which tells you what the PXIe-4331 actually measured, then measure Vch and Vex independently and calculate their ratio.
Brad
