User Manual

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Siemens Building Technologies Duct sensor QFM66/C CM1N1863E
HVAC Products 05.05.2003
Ordering and delivery
Indicate device name and type designation on order: Duct Sensor QFM66/C.
The coupling of the circular connector (Lumberg RKC 50/11) and the installation flange
are delivered uninstalled.
Equipment combinations
All systems and devices that are capable of acquiring and handling the sensor’s
DC 0...10 V output signals.
Technical design
The sensor senses relative humidity via a capacitive humidity measuring element
whose capacitance varies according to the relative humidity of the ambient air.
An electronic circuit converts the sensor's signal to a continuous DC 0...10 V signal,
corresponding to a relative humidity of 0...100 %.
The sensor senses the temperature via a Pt1000 thin-film measuring element whose
electrical resistance varies according to the temperature of the ambient air.
This variation is converted to two mutually independent DC 0...10 V signals. One signal
corresponds to the 0...50 °C temperature range, the other to the −35...+35 °C range.
Mechanical design
The duct sensor comprises a housing with a removable cover and an immersion sensor
stem. The housing and stem are made of plastic and are inseparably connected to
each other.
Between the housing and the cover there is a seal which is required to ensure degree
of protection IP 65.
The sensing elements are installed in the end of the stem, protected by a screw-on cap
with a Coretex filter.
The housing accommodates the measuring circuit and the connection terminals. The
cable is connected via a circular connector with a screwed plug.
The connector consists of a built-in plug with Pg 11 screw connection and a coupling
with a screw fastening. The built-in plug is installed on the housing and electrically con-
nected inside.
The sensor is designed for duct mounting. It can be installed in either of the following
ways:
• Using the installation flange supplied (flange is fitted over the stem and clamped at
the required insertion depth)
• Without the installation flange (to utilise the maximum immersion depth)
The sensor is serialised, registered and calibrated before delivery. The corresponding
calibration certificate is enclosed.
Engineering notes
Use a safety extra-low voltage (SELV) transformer that has separate windings and is
designed for 100 % duty.
The mandatory safety specifications at the plant location shall apply to sizing and pro-
tecting the transformer.
The connection of the sensor is described in the data sheets of those devices it is to be
connected to (connection of active sensors).
The maximum permissible cable lengths are mandatory.
Relative humidity
Temperature
Calibration certificate