Category: Temperature Sensor

A Relative Humidity Sensor with Analog Output is a type of sensor used to measure the relative humidity (RH) of the air and convert that measurement into an analog electrical signal. This signal can then be sent to a control system, such as a PLC (Programmable Logic Controller), SCADA (Supervisory Control and Data Acquisition) system, or other monitoring systems for further processing and control.

How it Works:

1. Humidity Sensing:
   • The sensor uses a sensing element (typically capacitive, resistive, or hygroscopic) to detect the amount of moisture in the air.
   • Capacitive sensors measure changes in capacitance as humidity levels change.
   • Resistive sensors detect variations in resistance caused by moisture absorption by the sensor material.
   • Hygroscopic sensors rely on materials that absorb moisture and change their properties, providing an indication of the humidity level.
2. Signal Conversion:
   • The sensor measures the relative humidity in the air and converts it into an analog signal (such as 0-10V or 4-20mA).
   • 0-10V output means that the sensor provides a voltage signal that varies between 0V (0% RH) and 10V (100% RH).
   • 4-20mA output is commonly used in industrial settings, where the current signal varies between 4mA (0% RH) and 20mA (100% RH). The 4mA minimum is used as a "live zero" to indicate a working sensor and avoid issues with signal loss.
3. Output Signal:
   • The analog signal generated by the sensor is directly proportional to the measured humidity value. This allows real-time monitoring and enables integration with systems like HVAC, industrial controllers, and automated systems.
   • Analog outputs are especially useful in applications where continuous, real-time data is necessary, and where older or simpler control systems without digital communication protocols (like Modbus) are used.
4. Typical Use in Systems:
   • The analog signal is fed into a controller or monitoring system, which processes the signal and can trigger actions such as adjusting air conditioning, turning on humidifiers, activating alarms, or controlling other processes that rely on humidity control.
   • For instance, in a greenhouse, if the humidity sensor detects that the humidity has dropped below a set threshold, the system can trigger a humidifier to restore optimal conditions.