Long Range Scanning; Dealing With False Detections - Teledyne GAS LASER Operator's Manual

GAS LASER

Long Range Scanning

Gas Laser can detect
methane up to 100' away.
Actual distance may vary due to
target surface and environmental
conditions.
As scanning distance increases,
the returning laser light
decreases. As the
distance is approached, a "low
return signal" tone is heard. You will
need to move in closer.
Scanning Distance of 50'+
- Slow down the scanning rate.
- Take care in pointing the laser.
- Use the spotter laser or IMAGE
mode to ensure proper scanning
of the target area.
- Be aware of the ground elevation.
Scanning across the top of a knoll
or past the edge of a structure
can result in beam skip (a sudden
change in distance) which may
give you a false detection.
- Obstructions or variations in the
landscape can cause a dark zone
(an area where the laser doesn't
scan). Look for the best angle to
thoroughly scan these areas. Scan-
ning up a hillside may cause beam
skip or dark zones around the
foundation of a structure.

Dealing With False Detections

Several conditions may occur
that will cause the algorithm
to give a detection indication.
The most common are:
• Abrupt or jerky motions cause
the scanning distance to rapidly
change.
• Overly strong returns due to
strong reflectors.
The laser light is selective to methane, and will not false-alarm on other hydrocarbons.
Doc No. 16162 Rev A, GAS LASER Operator Manual
- Dark Zone is an area where the laser doesn't scan.
They are caused by obstructions such as rocks, trees,
level
maximum
(an area where the
laser doesn't scan)
False detection most commonly occurs in the 50 feet (15 m) range, due to the
beam footprint becoming very large. Abrupt motion, and change in terrain
or distance to an object may cause the DMD to give a short low detection.
To verify if the detection is due to a leak, pause at this distance, aim off
to the side, and re-sweep across the area to determine if gas is present.
Scanning from a long range to short range will also minimize false detection.
Strong reflections off certain surfaces (e.g., black garbage bags, water drop-
lets, glass, polished surfaces, stones, license plates, reflectors, etc.) may give
a false detection. Re-scan the area from a slightly different angle.
- Beam Skip is a sudden change in distance.
structures, and uneven landscape.
Dark Zone
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Operator's Manual
Beam Skip
(a sudden change
in distance)