Configuring Strain Gage Bridge Type in FlexLogger

Updated Jan 15, 2020

Reported In

Software

  • FlexLogger

Issue Details

I have previously used the NI-DAQmx driver to take data from strain gages. When configuring my acquisition task, I would use the Bridge Type configuration as described in the Measuring Strain with Strain Gages White Paper. How can I configure the bridge type of strain gage in my FlexLogger?

Solution

FlexLogger uses industry terms for strain gage configuration types that are different from how these configurations were named previously in NI-DAQmx. The following table shows you FlexLogger gauge type corresponding to NI-DAQmx bridge configuration.
 
Bridge Configuration FlexLogger Gage Type
Quarter Bridge Type ISingle Element
Half Bridge Type ITwo Poisson Elements
Half Bridge Type IITwo Elements Opposite Sign
Full Bridge Type IFour Element Uniaxial
Full Bridge Type IIFour Element Poisson Opposite Sign
Full Bridge Type IIIFour Element Poisson Same Sign

For more details about FlexLogger strain gage configurations, please refer to Selecting a Strain Gage - FlexLogger 2020 R1 Manual.

Additional Information

To configure a Quarter Bridge Type II in FlexLogger, you would use the following configuration:
  • Bridge Configuration: Half Bridge
  • Gage Type: Two Poisson elements
  • Poisson's ratio: 0
This results in a Half Bridge configuration where only one gage is actively measuring strain. The other gage is not bonded to the sample, so it is just compensating for temperature.