OPERATION OF MULTIRAE PLUS
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2.8 Integrated Sampling Pump
The MultiRAE PLUS Multi-gas Monitor includes an
integrated sampling pump. This is a diaphragm pump
providing about 300 cc per minute flow rate at the high
setting with the standard filters in place.
A low pump speed of about 200 cc per minute is the factory
default setting, which will increase the battery life by about
5% and result in an increased LEL sensor lifetime (see
Chapter 4 or 5 for details of how to select the pump speed).
The high pump speed setting is required for vapors that are
especially reactive or adsorb easily to instrument surfaces.
Such vapors include Cl
2
, PH
3
, NH
3
, HCN, and semi-volatile
organic compounds like diesel fuel and jet fuels. For such
compounds it is helpful to remove the water trap filter for
normal calibration and operation, which will increase the
pump speed to about 350 cc/min. It is also desirable to use
inert connecting and sampling tubing, such as Teflon instead
of Tygon, and to make connections as short as possible.
The pump is turned on automatically when the monitor is
turned on and remains on during normal operation.
If liquid or other objects are sucked into the water trap in the
inlet port and cause the pump to stall, the electronics of the
monitor will detect the obstruction and shut down the pump
immediately. The alarm will be activated and a flashing error
message “Pump” will be also displayed in the LCD display.
