Types of sensors, application and principle description

What is a sensor?

A sensor (English name: transducer/sensor) is a detection device that can feel the measured information, and can transform the sensed information into electrical signals or other required forms of information output according to a certain rule to meet the information Requirements for transmission, processing, storage, display, recording and control.

The characteristics of sensors include: miniaturization, digitization, intelligence, multi-function, systemization, and networking. It is the first link to realize automatic detection and automatic control. The existence and development of sensors give objects the senses of touch, taste and smell, and make objects slowly become alive. According to its basic perception function, it is usually divided into ten categories: heat sensitive components, photosensitive components, gas sensitive components, force sensitive components, magnetic sensitive components, humidity sensitive components, acoustic components, radiation sensitive components, color sensitive components, and taste sensitive components. .

The composition of the sensor: generally composed of four parts: sensitive components, conversion components, conversion circuits and auxiliary power supply.

The sensitive element directly senses the measured and outputs a physical quantity signal that has a definite relationship with the measured; the conversion element converts the physical quantity signal output by the sensitive element into an electrical signal; the conversion circuit is responsible for amplifying and modulating the electrical signal output by the conversion element; the conversion element and The conversion circuit generally needs auxiliary power supply.

Types of sensors:

1. Resistive sensor: A resistive sensor is a device that converts physical quantities such as displacement, deformation, force, acceleration, humidity, temperature, etc., into resistance. There are mainly resistance strain sensors, piezoresistive sensors, thermal resistance sensors, thermal sensors, gas sensors, and humidity sensors.

2. Variable-frequency power: The variable-frequency power sensor performs AC sampling on the input voltage and current signals, and then connects the sampled value to the digital input secondary instrument through a transmission system such as cables and optical fibers. The digital input secondary instrument measures the voltage and current Calculate the sampled value of, you can get the voltage RMS, current RMS, fundamental voltage, fundamental current, harmonic voltage, harmonic current, active power, fundamental power, harmonic power and other parameters.

3. Weighing: The load cell is a force → electricity conversion device that can convert gravity into electrical signals

4. Thermal resistance: Thermal resistance temperature measurement is based on the characteristic that the resistance value of the metal conductor increases with the increase in temperature for temperature measurement. Thermal resistors are mostly made of pure metal materials. Divided into positive temperature coefficient sensors and negative temperature coefficient sensors.

5. Laser: a sensor that uses laser technology for measurement. It consists of a laser, a laser detector and a measuring circuit. The laser sensor is a new measuring instrument.

6. Hall: Hall sensor is a kind of magnetic field sensor made according to Hall effect. Hall sensors are divided into linear Hall sensors and switching Hall sensors. Linear Hall sensor is composed of Hall element, linear amplifier and emitter follower, it outputs analog quantity. The switch-type Hall sensor consists of a voltage regulator, a Hall element, a differential amplifier, a Schmitt trigger and an output stage, and it outputs a digital quantity.

Principles of some sensor applications

1. Resistive type: when the metal conductor undergoes mechanical deformation under the action of external force, its resistance value changes with the change of mechanical deformation

2. Hall: change due to Hall effect (Hall effect: metal or semiconductor sheet is placed in a magnetic field, when a current passes through, an electromotive force will be generated in the direction perpendicular to the current and the magnetic field).