e1901a
6
Fire & Security Products
Siemens Building Technologies Group
06.2001
3
Design
The heart of the PolyRex detectors DOT1151-Ex is a high-quality opto electronic measure-
ment chamber that screens off extraneous light but optimally detects light-colored and dark
smoke particles. The light source, the light stop and the light receiver are arranged in such a
way that the light from the source cannot directly reach the receiver (Fig. 1 and Fig. 2). Only
when smoke particles are present in the optical path does some of the scattered light reach
the receiver and produce an optical signal.
The temperature sensor (NTC) is located in the detector dome.
Due to its optimized optical system, the temperature sensor installed in a protective jacket,
shielded electronics and special circuit board coating this detectors are highly immune to
environmental influences such as temperature, humidity, corrosion and electrical interfer-
ence fields.
Intrinsically safe detectors are marked with the model number and the Ex label.
Light source
Light receiver
Transmitter optics
Smoke particles
Light stop
Fig. 1
Principle of the scattered light measurement
Light source
Light receiver
Labyrinth
Smoke particles
Labyrinth
Light stop
Section A - A’
A
A’
NTC temperature sensor
Fig. 2
Detector design
