A sensor or transducer is a measuring device that converts a measured quantity into a specific physical quantity with a defined corresponding relationship and is easy to apply with a certain degree of accuracy. Its input quantity can be force, temperature, light, sound, or chemical composition, which it converts into electrical quantities such as voltage, current, capacitance, or the on-off state of a circuit according to certain rules. When selecting a sensor, it is important to have a sufficient understanding of its performance characteristics. For simple applications, you can choose a sensor by understanding its performance indicators. However, if the application requirements are high and the environment is complex, it is also necessary to evaluate the sensor's performance from the perspective of its principle. This includes analyzing the working principle of the sensor, considering the potential load effect on the measured object, and determining which sensor is most suitable.