Sensitive elements are components that can sensitively sense the measured variable and respond. Such as: elastic membrane box can feel the pressure caused by deformation, the extent of deformation is the response to the pressure level, therefore, the elastic membrane box is a pressure sensitive element.
The sensor should not only be sensitive to measurement, but also have the function of transmitting it to the measured response. In other words, the sensor is not only a general sensitive element, but its output response must also be a physical quantity that is easy to transmit. For example, the output response of an appealing elastic bellows is a deformation, which is a small geometric quantity and is not convenient for transmission to distant places. If the displacement of the center of the capsule is converted into the change in the gap of the capacitor plate, the output response is the capacitance of the pressure sensor.
Since the electrical signal is most convenient for transmission, the output of most sensors is in the form of electrical quantities such as voltage, current, resistance, inductance, capacitance, frequency, and the like.
Transmitters are developed from sensors. Sensors that can output standard signals are called transmitters. (The standard signal is a signal in which the physical quantity and the numerical range are in conformity with international standards. For example, DC 4 to 20 mA) With a uniform signal form and numerical range, it is easy to integrate various transmitters and other instruments into a detection system or a regulation system. .
Sensors that are output as non-standard signals must be matched with specific instruments or devices to achieve detection or regulation functions. In order to enhance versatility and flexibility, the output of some sensors can be converted by the converter to convert the non-standard signal to a standard signal, which can be matched with an input circuit or interface meter with a standard signal. Different standard signals can also be converted to each other by means of converters. For example, using an air/electric converter, it is possible to convert an air pressure of 20 to 100 kPa into a direct current of 0 to 10 mA.