# Signal Conditioning

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## Expected Shunt Calibration Factors

I am trying to shunt calibrate (using a SCC-SG11) a rectangular rosette strain gage wired to an SCC-SG01 module. I'm using an SC-2345 hooked up to a laptop with a DAQCard-6036E. I am reading in an analog voltage with the SG11 engaged and subtracting the value w/o it engaged. The expected value of Vexpected=(R3*Vex*(Rshunt+R4))/(R4+Rshunt+R3*(Rshunt+R4)) is then divided by this difference to obtain the correction factor. For the Vexpected, R3=R4 correct? I am getting a correction factor value of less than 1 (~.97), which to me doesn't make sense, as the shunt calibration is supposed to correct for the wire resistance. Am I understanding this correctly that the correction factor should be >1?

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Accepted by topic author William Stewart

## Re: Expected Shunt Calibration Factors

Hi William,

If we look at what's going on internally in the SCC-SG11 by looking at pg 17-18 in the manual, it shows a diagram and a sample equation. Set all values to 120 to calculate your expected measurement and then vary it from 119 to 121 and divide by the expected value. If the resistance is higher than 120, you will get a lower measured voltage and a ratio >1. If the resistance is lower than 120, you will get a higher measured voltage and a ratio of <1.

Jake H | Product Manager
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## Re: Expected Shunt Calibration Factors

Well, that was easy. Thank you Jake.

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