Calibration of Strain Gauges

[stressmerchant]

Following a work discussion today:

If one wishes to use strain gauge data as part of certification data, how does one calibrate the strain gauge?

If the data involves airspeed, the certification authority would expect to see some form of calibration of the airspeed recording against an established standard. Similarly for masses, pressures and so on. So how is a strain gauge calibrated?

My thoughts were:
- statistically, from the factors supplied by the manufacturer
- some form of additional resistance added temporarily across the terminals (shunt?)
- similar installation technique / bridge circuit on a dogbone specimen

Or are they accepted "as-is"?

Does anyone have some advice on this issue?

Thanks in advance