Can a data logger measure strain gauges?

Yes. A Wheatstone bridge is often used to enable instruments with low sensitivity measurement capability to measure the small impedance changes common in strain measurements. Instruments with high resolution impedance measurement capability, such as the internal DMM of the 34980A Multifunction SourceMeter module, can directly measure small impedance changes with high accuracy and linearity using the 4-wire Ohms function.

A Wheatstone bridge can be used to enable the instrument to measure small impedance changes common in strain measurements.

As shown below, using the Mx+B math function, the strain and unstrained impedance of the strain gage can be measured and the strain value can be easily obtained as a strain unit:

M = 1 / (GF * R0)
B = -1 / GF

GF – Gain factor of the strain gage (provided by the strain gage manufacturer)
R0 – Reference measurement provided by the initial unstrained measurement

For example, for a strain value of 350 ohms (the unstrained value of the strain gauge) and a strain value of 350.1 ohms, when the GF value is equal to 2, the calculated strain will be:

M = 1 / (GF * R0) = 1 / (2 * 350) = 1 / (700) = 0.001428571
B = -1 / GF = - (1 / 2) = -0.5

The strain value ε obtained from the 350.1 ohm strain measurement (350.1 ohm is the x value in the Mx + B formula) is:

ε = Mx + B = (0.001428571 * 350.1) + (-0.5) = 0.5001427 - 0.5 = 0.0001427