DAQmxPerformBridgeOffsetNullingCal

[querty999]

In LabWindows/CVI, How can I read the voltage across a strain gage in a 1/4 bridge configuration?

I'm using "DAQmxCreateAIStrainGageChan()" to configure the channel. One of the parameters of this function is "Initial Voltage". I want to somehow acquire the initial voltage from the channel with no load on the strain gage so I can insert it into this function call. But how do I read voltage on a strain gage channel?

My hardware is NI 9219.

Also, CVI sample program"ContStrainSamples" uses the following function:

"DAQmxPerformBridgeOffsetNullingCal()"

What does this function do? The help system says it performs a bridge null offset calibration...Gee thanks. What is a null offset calibration? Is this a way to zero a strain gage reading?

What I'm trying to do is read a strain gage output at zero load. Then use this information to offset readings after load is applied.

[Aaron_W.]

Querty,

Thanks for posting on the NI Forums. To read the voltage across the strain gage channel you would need to use a Custom Voltage w/ Excitation task to read the voltage on the channel and then you could use that value as the 'initial voltage'. The initial voltage should be used if you already have some sort of strain on the gauge and want to provide a reference point to adding more strain. 

I would recommend to use the BridgeOffsetNullingCal() function when the voltage level on the strain gauge is just slightly off and you need to have the software take into account this small offset. Hope this helps.