The document introduces Symaro™ duct-type sensor QFM21, which is used to measure relative humidity and temperature. Its features include operating voltage of AC 24 V or DC 13.5-35 V, signal output of DC 0.10 V/4-20 mA for relative humidity and DC 0.10 V/4-20 mA or T1 or LG-Ni 1000 for temperature. The sensor can be used for controlling supply and exhaust air, reference sensors, limit sensors, etc.
This manual describes the Siemens Symaro™ QFM21 series duct sensors used for measuring relative humidity and temperature in ventilation and air‑conditioning equipment. It covers the sensor’s operating principle, signal outputs, measurement ranges, accuracy, and environmental ratings.
The document includes installation guidance, engineering notes on power supply and cabling, construction details, connector terminal assignments, and a full table of technical data for each reference model (e.g., QFM2100, QFM2120, QFM2140). This manual is written in Chinese.
| Working voltage | AC 24 V ±20 % or DC 13.5 … 35 V |
|---|---|
| Humidity measurement range | 0 % … 100 % RH |
| Signal output (humidity) | DC 0 … 10 V or 4 … 20 mA |
| Signal output (temperature) | DC 0 … 10 V |
| Accuracy (humidity) | ±3 % RH in comfort range |
The sensor can be powered from AC 24 V ±20 % or DC 13.5 … 35 V.
The cable entry must face downwards and the sensor should be mounted where it can be easily accessed for debugging.
It outputs a linear DC voltage of 0 … 10 V (or 4 … 20 mA) proportional to 0 % … 100 % RH.