Table of Contents
Advertisement
DF-30 detectors are designed to protect hazards where an antici-
pated fire will develop quickly with little or no incipient (smoldering)
stage where ignition is virtually instantaneous (e.g., flammable
liquids, combustible gases, etc.).
The DF-30 detectors use a low profile surface mounting base,
Model DB-3S. Each base may be attached to either a 4-inch
octagonal or square electrical box or a single gang switchbox. The
DB-3S base uses screw/clamp terminals for all electrical connec-
tions, self-wiping contacts for reliability, and contains provisions for
an optional concealed locking mechanism to prevent unauthorized
removal.
The DF-30 detectors are capable of operating one remote alarm
indicator or auxiliary relay. These detectors are protected by a
rectifier against input polarity reversal of the supply lines.
DETECTOR OPERATION
The DF-30 detectors use an ultraviolet sensitive gas filled tube
which operates on the Geiger-Mueller principle. This tube con-
sists of an anode and a cathode sensitive to ultraviolet wave
lengths of 1850 to 2600 Angstroms. Both electrodes are energized
by the high voltage generated within the detector from the low volt-
age which is applied to the detector.
When ultraviolet rays (photons) reach the cathode, it ionizes the
gas molecules, causing them to emit electrons. As the number of
ionized particles increases, an electrical current flows between
the electrodes. In this way, the ultraviolet rays generate a pulsed
electrical signal which is digitally counted. If the signal is still pre-
sent when the counting delay cycle is complete, the detector
locks into alarm and must be reset at the control panel by inter-
rupting the power.
The DF-30s are designed to respond in 5 seconds to an 8W
Halogen lamp directly in the line-of-sight at a distance of 50 cen-
timeters. The DF-30As respond in 10 seconds to the same source.
3
Advertisement
Table of Contents
