3
2.
ESSENTIAL OPERATING PRACTICE
Gas-Explorer detectors are easy to use. A detector is turned on by pressing the left button;
its operation is controlled by three “
Soft
” buttons whose function is shown on the display. The middle
button generally toggles
“Mute”
on and off in Track Gas mode (see later). Double-clicking the
middle button turns the backlight continuously ON or OFF depending on its previous state. Once
the appropriate display is selected, operation is automatic. However, a few general rules must be
followed to insure reliability.
Pump.
Gas-Explorer detectors have a built-in pump and depend on this pump for their
operation. If the pump is not functioning normally, the instrument will not function properly. It is
therefore essential to check the pump each time the instrument is turned on.
Pump Test:
Connect the probe you plan to use and turn the instrument on. After the display
shows “
Block Intake
”, block the probe at its intake to show
“Pump OK”
.
If
“Pump OK”
does not appear, tighten all connections and repeat the test. If a block
condition is still not observed, remove the probe and block directly the inlet. If
“Pump OK”
still
does not appear, return the instrument for repair.
A pump test can be carried out as above at any time during normal operation of the
instrument.
If there is any indication that the pump is not operating normally, the instrument
should not be used until repaired.
Filters.
Dust and water-block filters protect the sensors and the pump from dust and
accidental intake of liquid water. Just as a car would not be operated without air and fuel filters,
do not operate a detector without a filter on the probe.
Operation without this filter will
eventually degrade the sensors and the pump. It also voids the limited warranty.
It is essential that the filter be replaced monthly or sooner if it turns brown. Operation
without a filter will degrade the natural gas sensor and will void the warranty. Filters are available
from Bascom-Turner in packages of five, Part No. WF-505.
Models VGA-611 and VGA-612 require special filters available from Bascom-Turner in
packages of five, Part No. WF-705.
Zero Check.
All sensors drift to some extent over time. Sensor drift is corrected by zeroing
if the drift is within 0.1% vol. GAS (and 10ppm CO if the unit is equipped with a CO sensor). If
the drift is outside these limits, “
NO GO
” is displayed and the user is asked to autozero the unit in
“clean” outdoor air. The user can override this limit and re-zero the instrument unless the zero has
drifted over 1.0% vol. GAS (or 20ppm CO if the unit is equipped with a CO sensor), in which case
the instrument must be checked by a trained professional (the sensor may need replacement). It is
important that the zero adjustment be done in clean air, for example, outdoors. If the sampled gas
is not clean, a systematic error may be introduced in subsequent measurements.
Test and Calibration.
Gas-Explorer detectors must be checked and calibrated periodically
with gas of known composition. The catalytic combustion, carbon monoxide, and hydrogen sulfide
sensors depend on catalysts which may lose activity or get poisoned during use. When this
happens, there will be diminished response.
The necessary frequency of calibration depends on actual use and on the concentration of
catalyst poisons in the sampled gas. This concentration is, of course, not generally known.
WARNING:
On a call, turn the instrument on outdoors, not indoors.
Summary of Contents for GAS-EXPLORER II EGI-201
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