# Converting Strain gauge reading into torque

Can some one kindly help me understand how strain gauge readings are converted into torque or force readings in general?

Daze101:
Can some one kindly help me understand how strain gauge readings are converted into torque or force readings in general?

Very first thing is to calibrate your strain gauge for various weights within it's range.

Second measure the exact length, center to center, of the arm connecting the strain gauge to the source of your torque.

Third, put your system all together and measure the"'weight" the arm puts on the strain gauge.

Fourth, divide the "weight" by the length of the "arm" and you will have torque. Units you choose are up to you.

Paul

More generally, principles of mechanics of materials are used to convert strain to force or torque (or moment, which has the same units as torque), and vice versa.

This document explains it quite well: https://www.omega.co.uk/techref/pdf/StrainGage_Measurement.pdf

Calibration with a precisely known load or loads is ideal but not always possible. In those cases, indirect calibration is used. This has a good discussion of the issues: Vishay Precision Group - Document - 0 - TN-514 - Shunt Calibration of Strain Gage Instrumentation

Paul_KD7HB:
Fourth, divide the "weight" by the length of the "arm" and you will have torque. Units you choose are up to you.

Paul

No no no, multiply force by arm length. Torque is force x distance from axis. Torque has same units as energy because its an energy per radian of turn. We use Nm rather then J though to make it clear its a torque.
You can actually use J/rad if you like, that also makes it clear its a torque, not an energy.

SI units are the one's to use if possible, really easy to calculate with.

In SI:

power = torque x angular velocity
energy = torque x angle

without conversion factors, just note that angles and angular velocities are always in radians, not degrees, for this to work.