When does the adaptation of the measuring range (gain) makes sense?
Measuring amplifiers for strain gauge bridge circuits have a preset measuring range, which usually fits optimally to commercially available force sensors or torque sensors. The most widely used are measuring amplifiers with a measuring range of + - 2 mV / v because many force sensors have an output signal on the order of 2 mV / v or even exactly 2 mV / v.
Some measuring amplifiers have a larger measuring range of e.g. 3.5 mV / V, another one measuring range of 7 mV / V or even 10 mV / v.
This is because there are some (few) power sensors with a larger output signal of e.g. 3 mV / v at nominal force. Some sensors that are equipped with semiconductor strain gauges have a measuring range from 7 to (in a few individual cases) even 10 mV / v. In these cases, a measuring amplifier is needed with a larger measuring range.
In some documents, the name "Input sensitivity" is used as synomym for "measuring range".
For some measuring amplifiers, especially for measuring amplifiers with analog output, you can adjust the measuring range in steps: 2 mV/V, 1 mV/V, 0.5 mV/V, 0.2 mV/V or possibly even "infinitely" with a 10-speed potentiometer. The adjustment has the effect that a sensor with an output signal of only 1 mV / V with this adjustment also provides an analog output signal of e.g. 10V or 20mA.