Brand: Siemens

Siemens QFM1660 Duct Humidity and Temperature Sensor

Name: Siemens QFM1660 Duct Humidity Sensor – Datasheet & Quote
Brand: Siemens

Description

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 a trusted 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 datasheet 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 supplies this item on request with the manufacturer documentation, and availability and lead time are confirmed at quotation.

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About brand

Siemens is the German technology group whose industrial products include SIMATIC controllers and HMIs, SINAMICS drives, SIRIUS and SENTRON switching and protection devices, SIPROTEC protection relays, SITRANS process instruments, SCALANCE networks and process analysers. It was founded in Berlin on 12 October 1847 by Werner von Siemens and the precision mechanic Johann Georg Halske as Telegraphen-Bauanstalt von Siemens & Halske, to build Siemens's newly designed pointer telegraph. Siemens AG is headquartered in Munich and listed on the Frankfurt Stock Exchange; its energy business was spun off as Siemens Energy in 2020.

Siemens company profile

Founded	12 October 1847, Berlin, Germany, as Telegraphen-Bauanstalt von Siemens & Halske, with 10 employees
Founders	Werner von Siemens (1816–1892) and Johann Georg Halske (1814–1890)
First product	The pointer telegraph designed by Werner von Siemens
Headquarters	Munich, Germany (Siemens AG)
Ownership	Public company listed in Frankfurt; Siemens Energy (2020) and Siemens Healthineers are separately listed companies
Businesses acquired that appear in our range	Moore Products (bought in 2000; APACS and QUADLOG control systems), Applied Automation (Maxum process gas chromatographs); small industrial gas turbines such as the SGT-300 came with Alstom's industrial turbine business in 2003
Product families	SIMATIC S7 PLCs, ET 200 distributed I/O and HMI panels, TIA Portal software, SINAMICS drives, SIMOTICS motors, SIRIUS and SENTRON low voltage devices, SIVACON switchboards, SIPROTEC relays, SITRANS instruments, SCALANCE network components, building technology valves and sensors

Milestones

1847: Siemens & Halske starts work in Berlin with 10 employees.
1848: The company wins the contract for Europe's first long-distance telegraph line, Berlin to Frankfurt am Main.
1856: 330 employees, two-thirds of them working on telegraph networks in Russia.
1866: Werner von Siemens describes the dynamo-electric principle, the basis of the electric generator.
1958 onwards: The SIMATIC name is used for Siemens industrial automation; S7 PLCs follow in the 1990s and S7-1500 in 2012.
2020: Siemens Energy is spun off and listed separately.

Choosing Siemens automation products

A Siemens order number (MLFB) identifies the exact product: 6ES7 is SIMATIC automation, 6AV is HMI, 6GK is industrial communication, 6SL is SINAMICS drives, 3R is SIRIUS control and 5SY is SENTRON miniature circuit breakers. For PLCs, S7-1200 is the compact controller for small machines, S7-1500 is the current mid-to-high range controller, and S7-300 and S7-400 are older platforms still running in many plants; S7-300 is being phased out, so spares and migration to S7-1500 are common requests. When replacing a CPU or module, the full order number including the version digits matters, because firmware and hardware versions affect compatibility with the existing project.

Where Siemens products are used

In Oman and the GCC, Siemens automation runs in oil and gas, power and desalination plants, water networks, cement and process industries. Maxum gas chromatographs analyse gas composition in gas plants and refineries, SIPROTEC relays protect substations, SGT-300 turbines drive generators and compressors, and Siemens building valves are used in HVAC systems.

Siemens products we list

Family	Examples
SIMATIC controllers and I/O	S7-1500, CPU 1515-2 PN, S7-1200, CPU 1214C, S7-300, S7-400H CPU 412-5H, ET 200SP, IM 153-2
HMI and networking	KTP700 Basic, TP700 Comfort, TP1200 Comfort, SCALANCE XC208, SCALANCE WAM766, PROFIBUS OLM
Drives, motors and power distribution	SINAMICS G120C, SINAMICS G120X, 1LA7 motor, SIVACON S8, SIPROTEC 7SJ85, 5SY4510-7 MCB
Process instruments	SITRANS P320, MAG 5100W, SITRANS TH320, SITRANS TS500, SITRANS TR200
Maxum II analyser spares	FID 302A detector, FPD II assembly, filament detector, Model 50 valve, SYSCON kit, air bath heater
APACS and QUADLOG spares	QLCCM24AAN, QLSAMBAN, QLSDM024DCCBN, 39SAMCAN, 16137-151 M-BUS cable
Building technology	VPI46 PICV, VPF44, QFM1660 sensor

Ordering Siemens products: what we need

Send the full order number from the label (for example 6ES7214-1AG40-0XB0) and, for PLC and HMI parts, the hardware and firmware version (FS and V numbers). For Maxum II and APACS spares, send the Siemens part number such as 2021651-002. For drives, add the motor power and supply voltage.

Facts checked against Siemens's published history timeline, October 2026.

FAQ

Questions about the Siemens QFM1660 Duct Humidity and Temperature Sensor

Answers from our engineering team on installation, compatibility and integration.

01What does the QFM1660 measure?

The QFM1660 measures both air humidity (10-90% r.h.) and temperature inside an HVAC duct, providing two independent 0...10 V analog output signals.

02What power supply does the QFM1660 require?

The QFM1660 operates from an AC 24 V supply, matching standard low-voltage HVAC control panel power.

03Where should the QFM1660 be mounted for dew point shifting applications?

Siemens recommends fitting the sensor in the extract air duct for applications involving dew point shifting.

04Does the QFM1660 require a communications gateway?

No, the QFM1660 uses independent 0...10 V analog outputs, integrating directly with standard BMS or PLC analog input cards without a fieldbus gateway.

05Does Seven Star LLC supply this part across the GCC?

Yes, Seven Star LLC sources and supplies the Siemens QFM1660 duct sensor to HVAC integrators and industrial facilities across Oman and the wider GCC region.