Half Bridge – Thermal Compensating Gage.

In this iLearn video, Darryl explains about temperature compensation by half-bridge strain gage design.

Once an installed strain gage is connected to a strain indicator and the instrument balanced, a subsequent change in the temperature of the gage installation will normally produce a resistance change in the gage. This temperature-induced resistance change is independent of, and unrelated to, the mechanical (stress-induced) strain in the test object to which the strain gage is bonded. It is purely due to temperature change, and is thus called the thermal output of the gage. Thermal output is potentially the most serious error source in the practice of static strain measurement with strain gages. In fact, when measuring strains at temperatures remote from room temperature (or from the initial balance temperature of the gage circuit), the error due to thermal output, if not controlled, can be much greater than the magnitude of the strain to be measured. At any temperature, careful consideration; and it is usually necessary to either provide compensation for thermal output or correct the strain measurements for its presence.

[kennethadams]

Hello, I am working with this half-bridge temperature compensating configuration on a rock sample and expecting the sample to fail in a tensile manner. As such, the strain gauges a positioned in the tensile direction. However, the strain readings on the data acquisition system are showing negative values throughout. Please, is the a reason for this?

[milangeorge]

Can anyone guide me how can i get more informations about strain gauges at Low temperature ?

[GroovesAndLands]

This arrangement is going to create very low full scale output - it only has one "active" gage - so it's really more like a "quarter bridge" in terms of sensitivity. Also of note: the "coupon" of material needs to be robust enough that you have total confidence any force put on it will create NEGLIGIBLE stress. A flimsy coupon of material could be rather sensitive to air currents, or stress/strain on the cabling/wiring.