Background I have a strain gauge that I need to obtain measurements from. The product page indicates that the sensor is a half bridge configuration (one active/one compensating element). The sensor has three wires: White (common), Red (active) and Black (compensating). I have never used a strain gauge before, so I may have some fundamental misconceptions about how it works.
My Understanding of the gauge is that I need to measure the resistance and use the equation: \$strain = (R - R_0)/(G*R_0)^2\$, where \$R\$ is the measured resistance, \$R_0\$ is the gauge resistance, and \$G\$ is the gauge factor. I do this for both leads (active and compensating) and subtract the two to find the actual strain.
What I have Tried Using an Agilent Data Acquisition unit, I have successfully measured the resistance of both leads as ~120\$\ \Omega \$, which is expected, and calculated a strain of essentially zero.
My Problem started when I tested the sensor by heating the it (attached to a metal plate) to 50C. I expected the strain to increase, but was surprised to see that it actually decreased. Now I am questioning my basic understanding of how this sensor works. The change was very small, but distinct from the noise (below image).
Additionally, the noise I am getting from the sensor is less than ideal. I suspect some of it is caused by the furnace I am using, as there is a noticeable increase in noise when I turned it on (below image). Update The increased noise level remains even after de-energizing the furnace, so I now believe the increase is caused by the temperature.
- Shouldn't strain increase as the temperature increases?
- Is this level of noise normal? How can I reduce it?
- Am I using the strain gauge correctly?