Generally speaking, however, sensors are composed of sensitive elements, sensing elements and other auxiliary elements.
The sensing element directly senses the non-electric quantity and converts it into other quantities (generally still non-electric quantity) which have a definite relationship with the measured quantity according to certain rules. For example, the elastic diaphragm of strain pressure sensor is the sensing element, and its function is to transform pressure into deformation of diaphragm.
Sensing elements are also called sensors. Generally, the output of the sensing element is converted into the output of electric quantity instead of directly feeling the measured. For example, the strain gauge of stress and pressure sensor is used to transform the deformation of elastic diaphragm into the change of resistance value, and the resistance strain gauge is the sensitive element.
There is no strict boundary for this division, and not all sensors must contain sensitive elements and sensing elements. If the sensing element directly outputs electricity, it is also a sensing element; If the sensing element can directly feel the measured non-electric quantity and output the electric quantity which has a definite relationship with it, then the sensor is a sensitive element. Such as piezoelectric crystals, thermocouples, thermistors and photoelectric devices.
Signal conditioning and conversion circuit generally refers to the circuit that can convert the electrical signal output by the sensing element into useful electrical signal which is convenient for display, recording, processing and control. The selection of signal conditioning and conversion circuit depends on the type of sensing element. Common circuits include weak signal amplifiers, bridges, oscillators and impedance converters.
Auxiliary circuits usually include a power supply, and some sensor systems often use batteries for power supply.