Key facts
- Brand
- Siemens
- Model
- QFM21
- Documents
- 2
- Languages
- ZH · JA
- Last added
- 2011-10-16
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Siemens QFM21 Duct Sensor Manual
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.
Siemens QFM21 specifications
| 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 |
Source: Siemens QFM21 Duct Sensor Manual
All Siemens QFM21 documents by type
Day-to-day operation, settings and troubleshooting. Start here if the product is already set up.
Questions answered in these manuals
What is the required power supply for the QFM21 sensor?
The sensor can be powered from AC 24 V ±20 % or DC 13.5 … 35 V.
How should the sensor be installed to maintain its IP54 rating?
The cable entry must face downwards and the sensor should be mounted where it can be easily accessed for debugging.
What is the operating voltage for the QFM21 sensor?
The sensor can be powered from AC 24 V or DC 13.5 V to 35 V.
What signal outputs are available for humidity measurement?
Humidity can be output as either DC 0–10 V or a 4–20 mA current loop.