DAQ Assistant Strain Calibration Adjusted Gain

[MoLynch]

I am trying to understand how the DAQ Asst calibrates and offsets a quarter bridge strain gage using a USB NI 9237 on a 9127 chassis....

-how can I tell what the gain is

-what is the "gain adjusted value"

-what known/"simulated" strain is the the 100kOhm shunt supposed to reflect (usually this is 1000microstrain)

-is the output voltage, measured from a DAQ Asst configured to measure strain, scaled with excitation voltage

Maureen

[Brian F.]

Hello. 

Thank you for contacting National Instruments. 

The gain adjust value is the end result of the shunt calibration and is used to scale strain measurements on this channel. Normally, this value is close to 1, which implies that the measured value and simulated value are equal.

You can find out this value by referencing the column labeled "Gain Adj Val" in the Calibration window. You can also retrieve this value programmatically in LabVIEW by placing a DAQmx channel property node and selecting Analog Input>>General Properties>>Signal Conditioning>>Bridge>>Shunt Cal>>Gain Adjustment. 

Also, please refer to the following knowledge base information on how voltage readings on this device can be interpreted. 

http://digital.ni.com/public.nsf/websearch/21CA039D8F43C5188625729F005AC2F7?OpenDocument

Let me know if this clears everything up!

Brian F
Applications Engineer
National Instruments