Ladies and gentlemen, please ask me about the working principle of the temperature sensor

The principle of temperature sensing deformation of bimetal sheets.

temperature measuring elements, protection devices, transmission devices; Some have a fixed method, with a junction box, and some will have a meter display that is also called a temperature sensor.

What you normally see is that the temperature sensor for the motor is a stainless steel protective tube (inside is a platinum RTD temperature measuring element), a fixing screw, and then the lead wire is led to the junction box.

For other temperature sensors, the temperature measuring element may be very small, and the volume of the protection device is not large after installation, but the main structure is basically the same, temperature measuring element + protection + lead.

It is a thermistor sensor, and the three are placed in the three-phase winding part of the motor and connected in series.

He selected the model according to the insulation grade of the motor, and the winding temperature reached the upper limit of the thermistor, and the resistance value of the thermistor rose sharply, with the matching overheat protector. Cut off the power and give an alarm.

The resistance of PT100 varies linearly with temperature, which is proportional. Unlike thermistors, the resistance has a sharp turn.

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A temperature sensor is a sensor that senses temperature and converts it into an output signal. Temperature sensors are the core components of temperature measuring instruments, and there are many types. According to the measurement method, it can be divided into two categories: contact temperature sensors and non-contact temperature sensors, and according to the characteristics of materials and electronic components, it can be divided into two categories: thermal resistance and thermocouple.

1.Contact Temperature Sensor:

The detection element of the contact temperature sensor is in good contact with the object being measured. It brings it to thermal equilibrium by conduction or convection, so that the displayed value of the thermometer can directly represent the temperature of the object being measured.

2.Non-contact temperature sensor:

The sensitive elements of non-contact temperature sensors do not come into contact with the object to be measured. The sensor is generally used to measure the surface temperature of moving objects, small targets, and objects with small heat capacity or rapid temperature changes, and can also be used to measure the temperature distribution of a temperature field. .

3.RTD Temperature Sensor:

A RTD temperature sensor is a sensor that measures temperature using the principle that the resistance value of a conductor or semiconductor changes with its temperature. For different conductors (semiconductors), when the temperature changes by 1 degree, the resistance value changes differently, and the resistance value can be directly used as the output signal.

4.Thermocouple Sensors:

A thermocouple is a loop formed by connecting two conductors with different components. When the junction temperature is different, a thermal electromotive force is generated in the circuit. This phenomenon is called the thermoelectric effect.

Among them, one end that is directly used to measure the temperature of the medium is called the measuring end, and the other end is called the compensation end; Compensated termination display gauge that indicates the thermal electromotive force generated by the thermocouple. Thermocouples made of different materials are used in different temperature ranges and have different sensitivities. The metal materials used to make thermocouples must have good ductility, so thermocouple temperature sensors have an extremely fast response time and can measure the process of rapid temperature changes.

In general, the principle of temperature sensor is based on the physical properties of thermal expansion and contraction of materials (such as the thermostat of household refrigerators), the temperature characteristics of the resistivity of materials (thermistors), and the temperature difference thermocouple, that is, when the temperature of two different metal connection points changes, the corresponding electromotive force appears at the other end (cold end) to reflect the temperature change. Mainly these three.

From the perspective of microstructure, when the temperature of the object increases, the kinetic energy of the molecule increases, and the average free path of the molecule increases, so it is manifested as thermal expansion; In the same way, when the temperature of the object decreases, the kinetic energy of the molecule decreases, and the average free path of the molecule decreases, so it behaves as cold contraction. This is the real reason for thermal expansion and contraction, and it is also how thermometers work.

A temperature transducer is a sensor that senses temperature and converts it into a usable output signal. Temperature sensors are the heart of temperature measuring instruments and come in a wide variety of varieties. According to the measurement method, it can be divided into two categories: contact and non-contact, and according to the characteristics of sensor materials and electronic components, it can be divided into two categories: thermal resistance and thermocouple.

Pressure sensor is a common sensor in industrial practice, and has a wide range of applications in various industrial automation environments, such as water conservancy and hydropower, railway transportation, aerospace and other fields. Pressure sensors are used in different locations and have different performance metrics. Therefore, when selecting a pressure sensor, it is necessary to understand the performance indicators and application scope of the sensor.

Below, I will introduce to you the performance index parameters of the pressure sensor. Rated pressure range The rated pressure range is the pressure range that meets the specified values of the standard. That is, between high and low temperatures, the sensor outputs a pressure range that conforms to the specified operating characteristics.

In practice, the pressure measured by the sensor is within this range. Maximum Pressure Range The maximum pressure range is the maximum pressure that the sensor can withstand for a long time.