Contact and non-contact temperature sensors are distinguished by the detection method of the temperature sensor. The detection part of the contact temperature sensor is in contact with the measured object, and the non-contact temperature sensor and the measured object are not in contact with each other. The non-contact types are mainly infrared thermal imagers and single-point infrared thermal imagers, and their characteristics are as follows:
1) Contact temperature sensor, also known as thermometer, achieves thermal equilibrium through conduction or convection, so that the displayed value of the thermometer can directly represent the temperature of the object to be measured.
Advantages: The measurement accuracy is high, and within a certain range, the thermometer can also measure the temperature distribution inside the object. However, for moving objects, objects with small heat capacity or small size, large measurement errors will occur. Commonly used thermometers include bimetal thermometers, pressure thermometers, resistance thermometers, thermistors and thermocouples, etc. Teppson's temperature sensor is a contact temperature sensor.
Disadvantage: Since the heat of the measured object is transferred to the temperature sensor, the temperature of the measured object is reduced. When the heat capacity of the measured object is small, the measurement accuracy is low. Therefore, when measuring the real temperature of the object in this way, the heat capacity of the measured object must be large enough. When using a contact temperature sensor, it is necessary to consider the physical characteristics of the object to be measured. Due to the limited space of the object to be measured, it is impossible to measure the temperature of objects that cannot be touched.
2) Non-contact temperature sensor, also known as non-contact temperature measuring instrument, can be used to measure the surface temperature of moving objects, objects with small heat capacity or rapid temperature changes, and can also be used to measure the temperature distribution of the temperature field.
Advantages: 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. For high temperatures above 1800 °C, non-contact temperature measurement methods are mainly used.
Disadvantages: The temperature measurement results are easily disturbed by environmental factors, and it is not easy to achieve long-term continuous measurement of the target.
It can be seen that although the two types of temperature sensors differ only by one word, their principles and characteristics are different, and different measurement methods are required for different situations.
