3
Triple Plus+ and Triple Plus+ IR
General description
(b) No damage caused by exposure to high gas concentrations
(c) No poisoning effects
(d) Ability to measure at % volume levels as well as %LEL
(e) Fail safe
It must be remembered however that an infrared hydrocarbon sensor will have
no response to hydrogen and is therefore unsuitable for use where hydrogen
forms a significant part of any potential flammable risk. In order to ensure ready
identification of Triple Plus+ IR the membrane switch assembly is yellow in place
of the normal orange and carries the name designation ‘Triple Plus+ IR’.
The infrared sensor module in Triple Plus+ IR will be supplied with a calibration
for one of four hydrocarbon species i.e. methane, propane, butane or ethylene.
This calibration is factory set. Whatever the calibrated species the infrared sen-
sor will respond to any hydrocarbon present, but with differences of response
to different species. However unlike for a pellistor sensor it is not possible to
assign simple correction factors, as the basic relationship between concen-
tration and response of the detector is not linear. An infrared sensor should
therefore always be calibrated for the species to be determined or a suitable
target. If other specific hydrocarbon species need to be detected, please consult
Crowcon as to the optimum calibration.
The infrared sensor in Triple Plus+ IR can be supplied on one of two configura-
tions as follows:
• Single range %LEL
In this case the Triple Plus+ IR can have up to three other sensors from the
standard range of toxic and oxygen sensor modules available.
•
Dual range %LEL and % volume
In this case the sensor module has a second ribbon connector on a side-piece
of PCB, and therefore takes up two display positions on Triple Plus+ IR. This
allows only two other sensor modules from the toxic and oxygen range to be
used. A dual range sensor will always have both ranges calibrated for the same
species, and operates in an auto-ranging mode displaying in %LEL terms with
no numerical display for % volume until the level of gas exceeds 100%LEL,
and in volume terms with no numerical value for %LEL when the level of gas
is above 100%LEL. Note also the lower range will always display as %LEL even
if the gas is detected in an inert background gas where strictly speaking the
mixture cannot be explosive. The display indicates the equivalent %LEL level if
the gas were in an air background.
Note:
It is not possible to have a pellistor or thermal conductivity sensor in a
Triple Plus+ IR.
