DW1401831 Rev.K1
Sep 18, 2015
2
1.3
EVA-PYH features
* Low profile, stylish appearance
* Soft addressing
* Low monitoring current
* Supplied with protective dust cover
* OMNIVIEW
TM
360
o
LED Indicator for polling and fire alarm indication
* Photoelectric detector, detecting visible particles of combustion
* Heat detector, 8.3 °C (15 °F) rate-of-rise temperature heat detector with 57 °C (135 °F) fixed temperature alarm.
* Automatic compensation for smoke detector contamination
Section 2
–
GENERAL OPERATION
The
EVA-PYH
chamber consists of a light emitting diode (LED) and photodiode arrangement. The chamber contains a
unique design which allows smoke to enter the chamber while preventing external light from affecting the photodiode.
The
EVA-PYH
has chemically etched, stainless steel insect screen therefore reducing the ingress of insects and
airborne contaminants. The chamber is designed so that the light emitted by the LED is not directed to the photodiode.
In the event of fire, particles of smoke enter the chamber and scatter the light in the active area of the chamber. The
scattering effect increases the light in the chamber, causing more light to be detected by the photodiode. The
photodiode input level is sampled to sense smoke density and transmitted as a digitally encoded value to the control
panel. When the smoke density exceeds a preset threshold in the control panel, the control panel indicates a fire alarm
condition.
The control panel can adjust the detector alarm threshold to compensate for contamination that might accumulate in
the chamber within the smoke detector limits.
The
EVA-PYH
heat detector portion initiates an alarm in response to both 8.3 °C
(15 °F) rate-of-rise temperature or a
57 °C (135 °F) fixed temperature alarm point. Heat detector portion incorporates a highly linear thermistor circuit, with
the thermistor mounted externally. The specially designed cover protects the thermistor while allowing maximum air
flow. The thermistor circuit produces a voltage proportional to temperature which is scaled, and transmitted as a
digitally encoded value to the control panel.
