What is a sensor? What are the classifications of sensors?
What is a sensor? A sensor (Transducer/Sensor) is a detection device that can feel the measured information, and can transform the sensed information into an electrical signal or other required forms of information output according to certain rules, so as to meet the needs of information transmission, Processing, storage, display, recording and control requirements.
What is a sensor? A sensor (Transducer/Sensor) is a detection device that can sense the measured information and convert the sensed information into electrical signals or other required forms of information according to certain rules. output to meet the requirements of information transmission, processing, storage, display, recording and control.
The characteristics of sensors include miniaturization, digitization, intelligence, multi-function, systematization and networking. It is the first link to realize automatic detection and automatic control. The existence and development of sensors allow objects to have senses such as touch, taste, and smell, making objects gradually come alive. Usually according to its basic perception function, it is divided into more than ten categories such as thermal sensor, light sensor, gas sensor, force sensor, magnetic sensor, humidity sensor, sound sensor, radiation sensor, color sensor and taste sensor. . This chapter will focus on two types of sensors: temperature sensors and pressure sensors.
The function of the temperature sensor is to sense the temperature and convert the temperature into an electrical signal, which is transmitted to the processing mechanism for corresponding display or control. There are four main types of temperature sensors used in industry: thermistor temperature sensors, thermal resistance temperature sensors, thermocouple temperature sensors and integrated circuit temperature sensors.
Thermistor temperature sensor
Thermistors are characterized by temperature sensitivity and exhibit different resistance values at different temperatures. They are divided into positive temperature coefficient thermistors (PTC) and negative temperature coefficient thermistors (NTC). . The higher the temperature of the positive temperature coefficient thermistor, the greater the resistance value, and the higher the temperature of the negative temperature coefficient thermistor, the smaller the resistance value. The main material of the positive temperature coefficient thermistor is sintered by barium titanate mixed with rare earth elements; the main material of the negative temperature coefficient thermistor is the mixed sintering of transition metal oxides such as manganese, cobalt, nickel, iron, copper, etc. made.
The probe of the thermistor temperature sensor is packaged with a negative temperature coefficient thermistor (NTC). The packaging forms mainly include resin packaging, copper shell packaging, stainless steel shell packaging, etc., which are often used for temperature measurement and control of household air conditioners, car air conditioners, refrigerators, cabinets, water heaters, water dispensers, heaters, dryers, etc.
Pyroelectric temperature sensor
Thermal resistors are resistors whose resistance value changes with temperature. The thermal resistance temperature sensor is a sensor that uses the principle that the resistance value of a conductor (such as metal platinum, copper, iron, nickel) changes with temperature to measure temperature.
Thermal resistance is widely used to measure the temperature in the range of -200~+850°C. In a few cases, the low temperature can be measured to 1K (-272.15°C), and the high temperature can reach 1000°C.
The thermal resistance sensor is composed of thermal resistance, connecting wires and display instrument. The thermal resistance can also be connected with a temperature transmitter to convert the temperature into a standard current signal output.
The material used to manufacture thermal resistance should have as large and stable temperature coefficient of resistance and resistivity as possible, the output should be linear, stable physical and chemical properties, good reproducibility, etc. At present, the most commonly used thermal resistances are thermal resistances of two metal materials: platinum thermal resistance and copper thermal resistance.
Platinum thermal resistance, there are mainly two kinds of Pt100 and Pt1000, 100 and 1000 after Pt means that the resistance value at 0 ℃ is 1002 and 1000 respectively; copper thermal resistance, there are two kinds of Cu50 and Cu100, 50 after Cu and 100 mean that the resistance values at 0°C are 50 and 1000, respectively.