Can I measure dynamic strain with a SCXI-1531 and how steady is the excitation current?

Question

I am looking at the possibility of using an SCXI-1531 module to take measurements from a single strain gauge. I am only interested in the dynamic content of the signal and so am considering using the constant current excitation method which does not require bridge completion. Is there anyone out there that has tried this or could advise me as to whether this module is suitable?
Having read the spec of the module, it looks promising except for the data on the excitation current which states:
"Accelerometer input excitation current: 4mA +/-10%, 24V compliant."
Now, does that mean that the current will be steady at a value in the range 3.6 - 4.4mA or that it may fluctuate within this range during measurement? The latter would not be acceptable for my application as this would be indistinguishable from a variation in strain.
Thanks for any help.
CAS

Answer 1

Hi CAS,
Essentially the excitation provided by the module will not allow you to acquire as you would like.
However, the good news is that you are able to disable the excitation provided by the module, and provide your own external excitation. You should then be able to acquire the signal using the SCXI-1531.
To disable the excitation in LabVIEW using DAQm, place down a DAQmx Create Channel.vi and then configure it for Strain measurements. Then you can create a control/constantto wire to the Bridge Information Terminal by right-clicking on the terminal and selecting control/constant. Within this cluster control/constant will be an enum element where you can specify the voltage excitation source to be external.
I have attached an example VI demonstrating this.
Hope this helps.
Steve
Attachments:
Excitation Example.vi ‏18 KB