There are many kinds of temperature sensors, such as thermocouple sensor using thermoelectric effect, metal thermistor sensor and semiconductor thermistor sensor using thermal resistance effect, transistor PN junction temperature sensor, integrated temperature sensor and optical fiber temperature sensor developed in recent years, etc.
Humidity sensor can sense atmospheric humidity and convert it into appropriate electrical signal. According to the principle of sensors, the commonly used humidity sensors are divided into sintered semiconductor ceramic humidity sensor, porous oxide humidity sensor, junction and MOS humidity sensor, lithium chloride humidity sensor, hydroxyethyl cellulose carbon humidity sensor and polymer electrolyte humidity sensor.
Gas sensors can detect specific components in gas (mostly air) and convert them into corresponding electrical signals for output. Gas sensors can be divided into semiconductor gas sensors, solid electrolyte gas sensors, concentration cell gas sensors and combined potentiometer gas sensors, among which the most commonly used is semiconductor gas sensors.
The pH sensor is based on the potential measurement method in electrochemistry, which can be used to measure the pH of solution online. It is generally composed of measuring electrode and reference electrode. The measuring electrode is usually glass electrode, and the reference electrode is calomel electrode and silver silver chloride electrode.
There are many kinds of photoelectric sensors, including phototube and photomultiplier tube using external photoelectric effect, semiconductor photosensitive resistor using photoconductive effect, photodiode, photosensitive triode and photocell using photovoltaic effect, optical fiber sensor using total reflection of light, and CCD sensor (also called charge coupled device) based on MOS integrated circuit technology And so on.
There are many sensors that can measure the pressure, such as the strain resistance sensor based on the resistance strain effect, the piezoresistive sensor based on the piezoresistive effect, the piezoelectric sensor based on the piezoelectric effect, the inductive sensor and the capacitive sensor.
Biosensors are widely used in clinical diagnosis, industrial control, food and drug analysis, environmental protection, modern agriculture, biotechnology, biochip and so on. Biosensors can be divided into five categories according to different molecular recognition elements (i.e. sensitive elements): enzyme sensors, microbial sensors, cell sensors, tissue sensors and immunosensors.