Siemens QFM1660 Duct Humidity and Temperature Sensor
Overview: Dual Humidity and Temperature Monitoring in One Duct Sensor
The Siemens QFM1660 Duct Sensor is an active sensor for acquiring both air humidity and temperature directly inside an HVAC ventilation duct, delivering two independent 0…10 V analog output signals from a single compact probe. Part of Siemens QFM duct sensor family, the QFM1660 gives building automation and process control systems continuous visibility into duct-level air conditions without requiring two separate sensor bodies.
As an authorized supplier of Siemens building automation and process instrumentation, Seven Star LLC sources and supplies the QFM1660 duct sensor to facility management contractors, HVAC integrators, and industrial plants across Oman and the wider GCC. Customers purchasing through Seven Star LLC receive genuine Siemens hardware with full manufacturer specification and regional technical support.
Measurement Principle
The QFM1660 combines a capacitive humidity-sensing element with a temperature-sensing element in a single probe body, converting both measured parameters into proportional analog voltage signals. The humidity channel measures relative humidity across a 10 to 90% r.h. range with a stated accuracy of plus or minus 5% r.h. across that band at 20-25 degrees C, while the temperature channel provides a proportional 0…10 V output corresponding to the sensors rated temperature span, with an accuracy of plus or minus 0.8 K at 25 degrees C.
Because both signals are delivered as separate, independent 0…10 V outputs, the QFM1660 integrates directly with standard building management system (BMS) or PLC analog input cards without requiring a communications protocol or gateway, a straightforward wiring approach that suits retrofit installations onto existing analog-based control panels as much as new-build HVAC automation projects.
Engineering Design of the QFM1660
The QFM1660 is housed in a compact plastic enclosure measuring 222 x 56 x 72 mm, with a probe shaft designed for direct insertion into the ventilation duct wall so the sensing elements sit within the moving air stream rather than in a stagnant side-mounted pocket. The sensor operates from an AC 24V supply, matching the standard low-voltage control power widely used across commercial and industrial HVAC control panels.
Siemens recommends mounting the QFM1660 in the extract air duct for applications involving dew point shifting, and cautions against connecting voltmeters or ohmmeters directly at the sensing element during wiring checks, since this can disturb the calibrated sensing surface. The sensor is part of the broader QFM family, which also includes Modbus RTU (RS-485) variants and models targeting higher-accuracy demanding requirements applications, giving specifiers a range of communication and precision options within the same physical mounting concept.
Key Features
The QFM1660 Duct Sensor provides reliable, dual-parameter duct monitoring in a single compact device. Key characteristics include:
- Combined humidity and temperature sensing in one duct-mounted probe.
- Independent 0…10 V analog outputs for both humidity and temperature channels.
- Humidity measuring range of 10 to 90% r.h. with plus or minus 5% r.h. accuracy.
- Temperature accuracy of plus or minus 0.8 K at 25 degrees C.
- AC 24V operating voltage, compatible with standard HVAC control power.
- Compact 222 x 56 x 72 mm housing for straightforward duct-wall installation.
- Direct compatibility with standard analog BMS and PLC input cards, no communications gateway required.
Industrial Applications
The QFM1660 is deployed across commercial building HVAC systems, industrial ventilation and air conditioning plant, and process facilities where duct-level humidity and temperature must be continuously monitored to support demand-controlled ventilation, humidity control sequences, or general environmental monitoring within air handling units. Its analog output design makes it a straightforward retrofit option for existing control panels built around conventional 0…10 V instrumentation.
Seven Star LLC supports facility management contractors, HVAC integrators, and industrial plant maintenance teams across Oman, Muscat, Sohar, and the broader GCC region with sourcing of Siemens QFM duct sensors, helping projects maintain accurate environmental monitoring across their ventilation infrastructure.
Technical Specifications
The table below summarizes the core specifications of the Siemens QFM1660 Duct Sensor as supplied by Seven Star LLC.
| Parameter | Specification |
|---|---|
| Model | Siemens QFM1660 (Manufacturer No. S55720-S198) |
| Measured Parameters | Air humidity and temperature |
| Humidity Range | 10 to 90% r.h. |
| Humidity Accuracy | plus or minus 5% r.h. (20-25% and 10-90% r.h. bands, at 25 degrees C) |
| Temperature Accuracy | plus or minus 0.8 K at 25 degrees C |
| Output Signal (Humidity) | DC 0…10 V |
| Output Signal (Temperature) | DC 0…10 V |
| Operating Voltage | AC 24 V |
| Dimensions (W x H x D) | 222 x 56 x 72 mm |
| Mounting | Duct wall insertion probe |
Why Choose Seven Star LLC for HVAC Duct Sensor Sourcing
A duct humidity and temperature sensor’s accuracy depends on correct duct placement – Siemens’ own guidance to mount in the extract air duct for dew-point-shifting applications is easy to miss if a contractor treats this as a generic sensor drop-in rather than a placement decision tied to the actual control sequence. Seven Star LLC’s engineers confirm mounting location and whether the analog 0-10V output or a Modbus RTU variant from the broader QFM family better suits the customer’s BMS architecture before the QFM1660 is ordered. We also help facility management contractors and HVAC integrators across Oman plan retrofit installations onto existing analog control panels without a full BMS redesign, and coordinate delivery for commercial and industrial ventilation projects across Muscat, Sohar, and the wider GCC.
Request a Quote for Siemens QFM1660 Duct Humidity and Temperature Sensor
Seven Star LLC supplies the Siemens QFM1660 duct humidity and temperature sensor with full manufacturer documentation and regional technical support. Contact our instrumentation division for a formal B2B quotation, to confirm compatibility with your HVAC control panel, or to obtain the complete technical datasheet. Seven Star LLC ensures every unit shipped across Oman and the GCC is genuine Siemens hardware, correctly specified, and backed by local support.
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