Question : What is the best supply voltage for the strain gages sensors ?

Answer :

The value is mentioned on the calibration certificate delivered with the sensor.
For sensors without amplifier, the best common setting is 10V . It’s the voltage that is used to calibrate the load cell in the factory.
The maximum voltage allowed is 15V (350 ohms bridges) or 20V (700 Ohms bridges), depending on the model.

Remarks:
For some small models (eg 5932, 5962), it may be preferable to use a lower voltage (eg 5V) in order to limit the temperature rise of the sensor.
Some battery-operated signal conditioners use smaller voltages to save energy.