MultiRAE - Shawcity Limited

calibration. This is the only way to positively differentiate between a faulty sensor and a
real background signal. If you obtain a good calibration with “zero” air, and then recheck
the zero with the same bottle of “zero” air, then you can have confidence that the
instrument is working properly and the background signal you are seeing is caused by
something in the environment.
2.6.3 If, after a “zero” air calibration, you do not obtain a stable zero when applying the
“zero” air to the instrument, then the sensor does not have a stable zero point and must be
replaced.
2.7 Pump Stall Adjustment.
2.7.1 The Pump alarm can occur if the pump current exceeds the stall threshold value or
if the pump current is 0. The pump current may increase over the threshold value as the
pump ages or if the diaphragm is stiff due to cold temperatures. It may be necessary to
adjust the pump stall threshold when switching from low to high pump speed or when
adding additional lengths of tubing (Rev. D boards). Pump current may also increase if
the inlet is blocked or the vapor trap filter is clogged. Before adjusting the pump stall
threshold, make sure the flow path is not obstructed. Do not attempt to clean a clogged
filter: it must be replaced.
2.7.2 Turn on the unit in Diagnostic Mode (Section IV). The pump alarm is disabled in
Diagnostic Mode. Press the [MODE] key repeatedly until you get to the “Pump =”
screen. The top line is the measured pump current, and the bottom line is the threshold
value at which the pump will stall in normal operating mode. When operating properly
the stall threshold should be 6 - 10 counts higher than the operating current (typically 20 -
30 counts).
2.7.3 If the pump current is 0 then check for loose or broken wires. If the wires are
intact, check the voltage between the red and black wires. It should be 3.5V. If the
voltage is correct, then replace the pump assembly. If the voltage is not correct, then the
unit will have to return to the factory for repair.
2.7.4 If the pump is operating, block the inlet with your finger and observe the change in
pump current:
No change or only a few counts:
1) Pump current < stall current means there is a leak in the flow path
between your finger and the pump intake. Check the filter assembly, the
inlet valve, the internal tubing, the pump inlet nipple, and the pump
diaphragm. Clean or replace any parts that are dirty or leaking
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