BOREAL LASER GasFinder2, Operation Manual

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3.3
Boreal Laser Inc. GasFinder2 Operation Manual — Installation July 17th 2017
Fixed Location
Retrorefl ectors (Retros)
The retrorefl ector is a vital part of the system and choosing the correct type
is necessary for the correct operation of the system. Refer to page 3.4 for
details on choosing a retro. For short paths where refl ective tape is used, the
tape can be attached to the back of an enclosure which is fi tted to a tripod
or placed on a wall in any convenient location. The angle of the tape can be
adjusted to give an adequate signal return.
Where longer paths are measured, the retros can be mounted in an •
enclosure placed in any convenient location with access for cleaning.
Where long paths are measured in metal buildings, the • GasFinder2
may go out of alignment as a result of solar heating deforming the building structure.
The preferred solution is to use multiple retros. See page 7.7.
Light Values
The type of retro used will depend on the path length, atmospheric conditions such as dust
or fog, and the type of laser. When choosing a retro, the prime concern should be to keep the
returning light level value between the preferred values of 4,000 and 8,000. The range of the
value is between 1000 and 16,368. Below 1000 the display will indicate “Low Light”. There is
no indication that the returning light has exceeded 16,368. When this happens the receiver
saturates and the displayed light value could read very low (<200). In this situation the gas
concentration readings will be in error and it is also possible to cause damage to the optical
components. The light value can be adjusted with the use of different retros.
Note: Care should be taken to ensure that the returning light does not exceed 14,000.
Condensation
Condensation on the surface of the window is caused by the window
temperature falling below the dewpoint. This may be occur in areas of
high humidity or large temperature differences between day and night.
The enclosures are well sealed but condensation can sometimes occur on
the inside of the window. Condensation can usually be controlled by the
following measures:
Fasten a cover over the enclosure to shield the window from the effect of •
radiation cooling at night. It also prevents rain from striking the window.
Use a desicant pack inside the enclosure. This will only prevent •
condensation inside the enclosure.
Place a heater in the enclosure. The heater can be from 12W to 50W •
depending on the size of the enclosure and the conditions of operation
and is controled by a thermostat to prevent overheating. The heater
raises the temperature of the enclosure and prevents condensation
from forming either inside or outside the window. To minimise heat loss
the enclosure is insulated.
Radiation Shield
Enclosures with
heaters and rain hoods
4 Retros
Heater
Thermostat
4 retros and heater in
insulated enclosure