Smoke detector with test means for simulating a predetermined co

Details Smoke detector with test means for simulating a predetermined co Smoke detector with test means for simulating a predetermined co

1977-11-29

1979-03-13

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

340515, G01N 2126

Patent

active

041444582

ABSTRACT:
A smoke detector of the photo-electric type having a photo-responsive device viewing a volume illuminated by a light beam, in which a test member is provided for being temporarily positioned in the light beam so that one side of said member is exposed to the light and the other side is in the view of the photo-responsive device.
The test member has an area near the forward edge which is thin in relation to the thickness of the rest of the test member. In one embodiment of the invention this area is thin enough to be translucent, so that the translucent area illuminated by the beam simulates a predetermined percentage of smoke in the beam with a high degree of accuracy, since the transmission characteristics of the translucent area can be consistently maintained within production tolerances, and the exact position of the translucent area in the light beam for the smoke simulation is not critical. In another embodiment of the invention, the thin area may or may not be translucent, and a small hole is provided therein extending completely through the thin area to pass a predetermined amount of light from one side of the thin area to the other.

REFERENCES:
patent: 3868184 (1975-02-01), Marsocci
patent: 4053785 (1977-10-01), Lee et al.

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