Almost all sensors have a millivolt output, or voltage amplification, or milliamps, or frequency output. The type of output you choose depends on the distance between your sensor and system control or display components, noise, and other electrical disturbances, as well as whether you need to zoom in, optimally position the amplifier, and more. For many original equipment manufacturers, their control elements and sensors are very short, so millivolt output is generally sufficient and less expensive.
If you need to amplify the sensor output, it is easier to use another sensor with a built-in amplifier. In long-distance cables, or in areas with large electrical noise, mA output or frequency output is required. In environments with high levels of RF interference and electromagnetic interference, you need to consider adding additional shielding or filtering equipment outside of the milliamp and frequency output.