RAEGuard
S
EC / LEL / IR User’s Guide
3. Theory of Operation
The
RAEGuard
S
EC
uses electrochemical sensors. The electrons
generated at the working electrode travel via the contact pins to be
measured at the external circuit and are returned to the counter
electrode to complete the circuit, The current of the sensor response
is proportional to the related EC sensors’ gas concentration.
The
RAEGuard
S
IR
is based on the patented technology of non-
dispersive infrared (NDIR) for hydrocarbon, carbon dioxide and other
gas detection. After sample gas diffuses into the infrared optical gas
sensor, the electro-magnetic radiation cause oscillation on gas
molecules. If this happens the oscillation reduces the amount of
radiation, it absorbs a certain degree of radiation. The absorbance at
specified wavelength is a measure of the present gas concentration.
The
RAEGuard
S
LEL
uses a highly poison-resistant catalytic bead
lower explosion limit (LEL) sensor. After sample gas diffuses through
the metal sinter into the combustion chamber, a pair of combustion
elements inside the combustion chamber burns the combustible gas
and generates an electrical signal.
The RAEGuard
S
is a microcontroller-based instrument. After the
electrical signal is conditioned and converted to digital, the
microcontroller processes the data, which displays the results locally
and reconstructs the digital data into a standard 4-20 mA analog
current output signal and RS-485 digital output signal.
The instrument has three magnetic sensing keys. The user may
calibrate the transmitter and change the alarm level setting via the
magnetic front-panel key pad.
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