How Does The Gas Laser Measure Gas - Teledyne GAS LASER Operator's Manual

GAS LASER

How Does the Gas Laser Measure Gas?

The Gas Laser uses infrared
(IR) laser technology known
as Tunable Diode Laser
Absorption Spectroscopy
(TDLAS).
TDLAS enables the Operator to
safely scan:
- Hard to reach areas
- Plumes up to 100' away
(actual distance may vary
due to surface condition)
- Through windows
WARNING
WARNING - The Gas Laser is
capable of scanning through
windows to possibly detect methane
gas. However, scanning through
windows is not guaranteed. False
positives and negatives may occur.
AVERTISSEMENT
AVERTISSEMENT : Le Gas Laser
est capable de balayer les fenêtres
pour éventuellement détecter du
méthane. Cependant, le balayage
des fenêtres n'est pas garanti. Des
faux positifs et des faux négatifs
peuvent être obtenus.
NOTICE
NOTICE: There is always a small
amount of methane in the air.
This natural methane background
is also measured by the Gas Laser.
The PPM-M reading will then
increase as the scanning distance
increases.
NOTICE: The nature of a gas plume
is highly variable. The above/right
illustrations are intended to convey
the basic theory. Some leaks may
have a high surface concentration
with little to no measurable plume
above the surface.
Doc No. 16162 Rev A, GAS LASER Operator Manual
22"
100' 75'
Infrared beam width is about 22" at 100 feet. It is important to note that the laser
beam "footprint" width increases as the distance increases. This is why it is much
easier to detect natural gas from a distance of 10 to 15 feet and beyond.
When the laser passes through a gas plume, a portion of the light is
absorbed by methane, while some of the light is reflected back to the
Gas Laser. The reflected light is collected and processed so the Gas Laser
can report methane concentrations in parts-per-million-meter or PPM-M.
B
A
a) Gas cloud of 1000 PPM is about ½ meter in width (the distance the
infrared beam passes through the plume).
B
b) Average concentration of gas cloud is 20 PPM and is about
two (2) meter in width.
plus 15 PPM-M background level, displaying a total value of 55 PPM-M.
25
Operator's Manual
50' 25'
A
Gas Laser
measures 500 PPM-M.
Gas Laser
measures 40 PPM-M,
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