The temperature and humidity sensor is one of the sensors. It passes the temperature and humidity in the air through a certain detection device. After measuring the temperature and humidity, it converts into an electrical signal or other required form of information output according to a certain rule to meet user needs. .
Because temperature and humidity have a close relationship from both the physical quantity itself and the actual people's life, a temperature and humidity integrated sensor will be generated accordingly. Temperature and humidity sensor refers to a device or device that can convert temperature and humidity into electrical signals that can be easily measured and processed. The temperature and humidity sensors on the market generally measure temperature and relative humidity.
Modern temperature and temperature sensors vary widely in principle and structure. How to properly select a temperature and humidity sensor according to the specific measurement purpose, measurement object and measurement environment is the first problem to be solved when measuring a certain quantity. After the temperature and humidity sensor is determined, the measurement method and measurement equipment to be matched with it can be determined. The success or failure of the measurement results depends to a large extent on the selection of temperature and humidity sensors.
1. Frequency response characteristics:
The frequency response characteristic of the temperature and humidity sensor determines the frequency range to be measured. It must maintain undistorted measurement conditions within the allowable frequency range. In fact, the sensor's response always has a fixed delay. It is hoped that the shorter the delay time, the better. The frequency response of the sensor is high, and the measurable signal frequency range is wide. Due to the influence of structural characteristics, the inertia of the mechanical system is large, and the frequency of the measurable signal of the sensor with a low frequency is low. In dynamic measurement, the response characteristics of the signal (stable, transient, random, etc.) should be used to avoid production errors.
2. Linear range:
The linear range of the temperature and humidity sensor refers to the range where the output is proportional to the input. In theory, within this range, the sensitivity remains constant. The wider the linear range of the sensor, the larger the range and the certain measurement accuracy. When selecting a sensor, when the type of sensor is determined, first of all, it depends on whether its range meets the requirements.
3. Determine the type of sensor according to the measurement object and measurement environment:
To carry out a specific measurement, we must first consider the principle of temperature and humidity sensors, which need to be analyzed after determining many factors. Because, even if measuring the same physical quantity, there are multiple principles of sensors to choose from, which one is more suitable, you need to consider the following specific issues according to the characteristics of the measurement and the conditions of use of the sensor: the size of the range; Requirement of the measured position on the volume of the sensor; the measurement method is contact or non-contact; the method of signal extraction, wired or non-contact measurement; the source of the sensor, domestic or imported, whether the price can be afforded, or developed by itself.
4. Selection of sensitivity:
Generally, in the linear range of a temperature and humidity sensor, it is desirable that the higher the sensitivity of the sensor, the better. Because only when the sensitivity is high, the value of the output signal corresponding to the measured change is relatively large, which is conducive to signal processing. However, it should be noted that the sensitivity of the sensor is high, and external noise that is not related to the measurement is also easily mixed in, and it will be amplified by the amplification system, affecting the measurement accuracy. Therefore, the sensor itself is required to have a high signal-to-noise ratio, and every effort is made to reduce plant disturbance signals introduced from the outside.
The ability of a temperature and humidity sensor to maintain its performance after a period of time is called stability. In addition to the structure of the sensor itself, the factors affecting the long-term stability of the sensor are mainly the environment in which the sensor is used. Before selecting a sensor, it should investigate its use environment, and choose the appropriate sensor according to the specific use environment, or take appropriate measures to reduce the environmental impact. There is a quantitative indicator for the stability of the sensor. After the period of use, the calibration should be performed before use to determine whether the performance of the sensor has changed.