BOREAL LASER GasFinderMC-2, Operation Manual

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3.3
Boreal Laser Inc. GasFinderMC Operation Manual— Installation July 17th 2017
Retrorefl ectors (Retros)
The Retro is a vital part of the system and choosing the correct type is necessary for the correct
operation of the system. Refer to page 3.2 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 provided this does not degrade the R
2 value.
Where Retros are used on longer paths, these may be mounted in an enclosure on a •
tripod, or the enclosure placed in any convenient location.
Purge air may be required for Retros used in ducts. •
Where long paths are measured in metal buildings, the Remote Head may go out of •
alignment as a result of solar heating deforming the structure. The preferred solution is
to use multiple Retros. See page 7.7
The • GasFinderMC does not require any changes when different path lengths are
measured unless ppm values are needed, in which case the distance must be set and an
appropriate Retro used.
Light Values
The type of Retro used will depend on the path length, atmospheric conditions such as dust or
fog, the type of head 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 dew point. This may 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 or rain hood over the enclosure to shield the window from radiation cooling at night. •
This also prevents rain from striking the window.
Use a desiccant pack inside the enclosure. This will only prevent •
condensation on the inside.
Place a heater in the enclosure. The heater can be 12W to 50W •
depending on the size of the enclosure and the conditions of operation
and is controlled by a thermostat to prevent overheating. The heater raises
the temperature of the enclosure and prevents condensation forming
either on the inside or the outside of the window. To minimise heat loss
the enclosure is insulated. This option requires power to be supplied and
there are heaters available for use in hazardous areas.
Two Enclosures with
Heaters and Rain Hoods
Radiation Shield
4 Retros 4 Retros
Heater Heater
Thermostat Thermostat
4 Retros and Heater in
insulated Enclosure