First of all, the structure of the sensor must be selected so that the temperature of the measured fluid or the measured surface can be reached within the specified measurement time of the sensitive element. The output of the temperature sensor is simply the temperature of the sensitive element. In practice, it is often difficult to ensure that the temperature indicated by the sensor is the temperature of the object being measured.
In most cases, the selection of temperature sensors should consider the following aspects:
(1) Whether the temperature of the measured object needs to be recorded, alarmed and automatically controlled, and whether it needs to be measured and transmitted remotely.
(2) The size and accuracy requirements of the temperature measurement range.
(3) Whether the size of the temperature measuring element is appropriate.
(4) In the case where the temperature of the measured object changes with time, whether the lag of the temperature measuring element can meet the temperature measuring requirements.
(5) Whether the environmental conditions of the measured object damage the temperature measuring element.
(6) What is the price and whether it is convenient to use.
The choice of temperature sensor is mainly based on the measurement range. When the measurement range is expected to be within the total range, platinum resistance sensors can be selected. The narrower ranges generally require that the sensor must have a fairly high base resistance in order to obtain a sufficiently large resistance change. The sufficiently large resistance change provided by thermistors makes these sensitive elements ideal for narrow measurement ranges. Thermocouples are more suitable if the measurement range is relatively large. It is best to include the freezing point in this range, since thermocouple scales are based on this temperature. Sensor linearity over a known range is also an additional condition for selecting a sensor.
