How the humidity sensor works

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REVIEW: The humidity sensor is a very important sensors are widely applied in people's lives, what works and humidity sensor that is it what works so that humidity sensors have so much to do here let small series?? Let me introduce you.

1. Humidity sensor working principle - introduction

The humidity sensor, known in English as the humidity transducer, is a sensor that senses the water vapor content of the gas and converts it into an available output signal. Mainly used in mechanical engineering, sensors, gas and humidity sensors. In most cases, if there is no precise temperature control, or the measured space is unsealed, the accuracy of ±5% RH is sufficient. For applications requiring precise control of constant temperature, constant humidity local space, or where it is necessary to track and record humidity changes at any time, select ±3% RH.

2. Humidity sensor working principle - characteristics

The humidity sensor is the simplest humidity sensor. The humidity sensor is mainly of two types: resistive and capacitive.

Humidity-sensitive resistor: The characteristic of the humidity-sensitive resistor is that the substrate is covered with a film made of a moisture-sensitive material. When the water vapor in the air is adsorbed on the moisture-sensitive film, the resistivity and the resistance value of the element change. Use this feature to measure humidity. The advantage of the humidity sensitive resistor is its high sensitivity. The main disadvantage is the poor linearity and interchangeability of the product.

Humidity Sensitive Capacitors: Humidity sensitive capacitors are usually made of polymer film capacitors. When the ambient humidity changes, the dielectric constant of the humidity sensitive capacitor changes, and its capacitance also changes. The amount of capacitance change is proportional to the relative humidity. The main advantages of the humidity sensitive capacitor are high sensitivity, good product interchangeability, fast response, small hysteresis of humidity, ease of manufacture, easy miniaturization and integration, and its accuracy is generally lower than that of the humidity sensitive resistor.

3. Humidity sensor works

Select the measurement range - just like measuring weight and temperature, first select the humidity sensor to determine the measurement range. In addition to meteorological and scientific research departments, temperature and humidity measurement and control generally do not require full wet range measurement. In today's information age, sensor technology is closely integrated with computer technology and automatic control. The purpose of the measurement is to control, the measurement range and the control range are collectively used.

Selecting the measurement accuracy - the same as the measurement range, the measurement accuracy is the most important indicator of the sensor. Every increase is a percentage point. For the sensor, it is the last step, even the previous level. Because of the different precisions, the manufacturing costs vary widely, and the selling price is far from the same.

Consider drift and warm drift - almost all sensors have drift and temperature drift. Since the humidity sensor must be in contact with moisture in the atmosphere, it cannot be sealed. This determines its stability and longevity is limited.

Expand reading:

1. Principle and application of temperature and humidity sensor

2. How to choose temperature and humidity sensor

3. Capacitive humidity sensor basics

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