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Temperature Sensor


According to the measurement method, it can be divided into two categories: contact type and non-contact type.

1. Contact

The detection part of the contact temperature sensor has good contact with the measured object, also known as a thermometer.

The thermometer achieves thermal equilibrium through conduction or convection, so that the indication value of the thermometer can directly represent the temperature of the measured object.

Generally, the measurement accuracy is high. In a certain temperature measurement range, the thermometer can also measure the temperature distribution inside the object. However, for moving objects, small targets or objects with small heat capacity, large measurement errors will occur. Commonly used thermometers include bimetal thermometers, glass liquid thermometers, pressure thermometers, resistance thermometers, thermistors and thermocouples. They are widely used in industry, agriculture, commerce and other sectors. These thermometers are also often used in daily life.

2. Non-contact

Its sensitive element and the measured object do not contact each other, also known as non-contact temperature measuring instrument. This instrument can be used to measure the surface temperature of moving objects, small targets and objects with small heat capacity or rapid temperature changes (transient), and can also be used to measure the temperature distribution of temperature fields.

The most commonly used non-contact thermometers are based on the basic law of blackbody radiation, called radiation thermometers. Various radiation temperature measurement methods can only measure the corresponding photometric temperature, radiation temperature or colorimetric temperature. Only the temperature measured for a black body (object that absorbs all radiation and does not reflect light) is the true temperature. To determine the true temperature of an object, the surface emissivity of the material must be corrected. The surface emissivity of materials depends not only on temperature and wavelength, but also on surface state, coating film and microstructure, etc., so it is difficult to measure accurately.

The advantage of the non-contact temperature sensor is that the upper limit of measurement is not limited by the temperature resistance of the temperature sensing element, so there is no limit to the maximum measurable temperature in principle.