Reducing excitation voltage for bridge measurements

[mortalwombat]

Hello,

I'm using a National Instruments Compact DAQ System for measuring strain gauges. The system allows an excitation voltage of 2V (minimum) for my half-bridge.
Unfortunately the strain gauges I have to use aren't able to stand this voltage and allow only 1V (maximum) excitation voltage.
Is it possible to reduce the excitation voltage between strain gauge and DAQ-System by an stable potential divider e.g. an resistance with 0,01% accuracy in both sides of the half bridge?
Any tip will be helpful...

Karsten

 

[analogkid2digitalman]

Which module are you using? The 9235, which has the 2V excitation, is for quarter-bridge 120 ohm strin gauges- you mentioned you were using a half-bridge.

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[mortalwombat]

I'm using the NI 9237. According to NI it is not possible to go under 2V excitation voltage...
For this I want to reduce the voltage between 9237 and strain gauge...

 

[roydm]

It should be OK if the NI card can be wired to measure the voltage applied to the bridge (not before the dropping resistor). The V in/mV out is linear for a strain gauge.
I presume NI measures the V and mV as part of it's calculation.
Roy

 

[mortalwombat]

According to NI the 2V-limit is given by the ADC.
This will be the lowest value for all cases.

What I'm thinking about is putting two extra resistors in the circuit of the half bridge. One after excitation (+) and before strain gauge 1 and one after strain gauge 2 and excitation (-). The measured value will then be wrong - but linear wrong.
To correct the value I could calculate a correction factor and apply the factor in the software after the data acqusistion. There is a formula for correcting the errors coming from cable-resistance.
If I interpret the two extra resistors as cables I will get the right values... hopefully