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2.3 Principle of Operation
All objects above absolute zero emit infrared energy. The amount of energy emitted is
proportional to the body's temperature. The QUASAR M8100-EXP collects this energy by means
of a focusing optical system concentrating the energy from a body onto a sensitive infrared
detector. Specialized amplification circuitry converts the signal received by the detector into a
DC level to activate relay and mA outputs for monitoring. The M8100-EXP utilizes amplitude
correction circuitry which, when initially set, will automatically correct for diminishing radiation
amplitude due to varying and/or adverse weather conditions.
2.3.1
Alarm Set Point
PM/FM - If the instrument detects a loss of signal fault, an adjustable delay timing circuit starts a
countdown to activate a "loss of signal" alarm. This delay circuit allows for loss of signal due to
wind or adverse conditions for a time period of two seconds to two minutes. This allows the
monitor to reacquire the flame before an alarm signal is sent, limiting false alarms due to
weather conditions. The alarm provides status by LED and Relay contacts.
SM - The alarm set point has no delay and activates in real time.
2.3.2
Relay Contacts
Denoted by their non-energized states, Normal Open (N.O.) and Normal Closed (N.C.) contacts
are common to a single Relay Common (Com), also known as "single pole double throw"
contacts.
4-20mA Outputs
•
PM & FM: 4 or 20mA circuit outputs 4mA or 20mA depending on a preset signal level.
Standard output provides 4mA with a flame present, 20mA without a flame present.
This is a switched output.
•
SM: mA circuit outputs a signal proportional to the relative amount of smoke detected.
2.4 Signal Path
Infrared (IR) energy is focused onto the detector through a rotating chopper wheel. The
chopper wheel provides the ability to stabilize and improve noise rejection. IR filters are
employed for the FM, PM, and SM models. By virtue of these select, application-specific IR filters,
the desired IR energy is allowed to pass and be amplified by the detector. Filters are located on
the chopper wheel for the SM and are located on the detector for the FM and PM.
The rotating chopper wheel creates a pulsing (on/off) signal, which is then selectively amplified
by the detector. The detector's amplified signal is conditioned by chopper synchronized,
automatic amplitude control and stabilization circuits. This allows for compensation for
diminishing IR radiation due to climate conditions and is accomplished without operator
intervention.
After the signal is conditioned, it is further filtered and provides the input to subsequent; relay
driver, time delay and 4 ... 20mA output control circuits.
2.4.1
SM: Smoke Monitor's Dual Wavelength (2 color)
Unique to the QUASAR M8100SM-EXP is the use of 2 filters at separate wavelengths or colors.
These filters located on the chopper wheel, allow the electronics to selectively amplify the IR
energy of interest over the background IR energy, thus allowing the Smoke Monitor to
distinguish particulate (smoke) from the background flame that is present.
E
T QUASAR Flare Monitors Operation Manual
2
Introduction • 13
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