Bridge Excitation and Measuring Range with Strain Gauge
Strain gauge bridges provide signals that depends on bridge excitation. Therefor the bridge signal is expressed in mV/V (ratiometric measurement).
Often strain gauge device have only one range (gain) and specify different spurious ranges just by changing the bridge excitation:
8 mV/V at 5V, 16 mV/V at 2.5 V, 40 mV/V at 1 V and 80 mV/V at 0.5 V.
Indeed the gain is fix, thats a mess.
This fact provides big problems when measuring strain with small gauges on composite material. A small excitation voltage is needed but the Signal also require a sensitive range. With the above kind of device an excitation of 1 V constrain a range of 40 mV/V, means 80000 µm/m with single strain gauge application. A 1000 µm/m Signal just use the range of 1.25 %. Smaller strain signals are very close to noise and drift. Excitation voltage has to be selected because of range and not because of application.
Gantner´s Q.series A116 offeres beside different bridge excitation voltages also REAL GAIN selection. Small excitation with a sentitive range is possible as well as high excitation in a very wide input range. That optimizes the signal to noise ration and provides best results. Range is independent on bridge excitation.