The output signal of a force sensor or a Wheatstone bridge is dependent on the level of the supply voltage.
The higher the supply voltage, the higher the output signal
By specifying the output per volt supply voltage, you can compare the sensors themselves.
Sensors with strain gauges deliver approximately 0 mV / V in the unloaded condition and-depending on the sensor approximately 0.5 mV / V to 3,5mV / V at full load.
The measuring amplifiers are designed for this signal level: measuring amplifier with a supply voltage of 5V, for example, handle input voltages between -17,5mV to + 17,5mV
The technical datasheets of bridge amplifiers do not specify the amplification factor and the supply voltage.
Imagine a sensor with 2 mV/V bridge output (at 100% load), and an amplifier with 5V bridge supply:
2 mV / V x 5V supply voltage = 10mV
multiplied with a gain of 1000
10mV x 1000
results in 10 V output voltage of the amplifier
Instead it is easear to define as follows
2 mV / V output signal of the sensor (at full load)
2 mV / V input sensitivity, the amplifier
fits -> 100% output of the amplifier at 100% load on the sensor.
The characteristic value of a sensor is the change of the output signal at 100% load.
The term is defined in the VDI guideline 2638: output signal at rated force, decreased by the zero signal ...
The output signal is expressed in mV per volt bridge voltage (mV/V).
Typical characteristic values of sensors are 2 mV/V, or 1 mV/V, or 0.5 mV/V, partly also 3 mV/V. A sensor with sensitivity 2 mV/V (at nominal force) therefore provides 10mV output signal with an amplifier of 5V bridge supply voltage (as differential voltage between + bridge output and - bridge output)
The terms are defined in the VDI 2638 (for force sensors) and VDI 2639 (for torque sensors).
the characteristic value is the actual output of the sensor. So this is defined in the test report or in the calibration certificate.
The rated characteristic value (or rated sensitivity) is the "target" (theoretical value) for the characteristic value. The rated sensitivity is therefore defined in the generally technical data sheet for this sensor type (not in the protocol for a specific and real sensor).
Strain is a measure of the relative change in length Δl/l
The units of strain are: m/m,μm/m, ppm (parts per million), %, ‰