Measuring Operation; Automatic Switchover To Other Measuring Ranges; Exceeding The Lower Explosion Limit And Alarm Signal - Herth+Buss ELPARTS 95980002 Notice D'emploi

E L PA RTS
Operating manual
SelectH selective gas detector
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2.4

Measuring operation

The temporal progress of the heat-up phase can be seen on the basis
of the analogue bar that progresses from left to right. After the heat-
up phase, the sensor zero point is determined and used as the fresh-
air reference value for the rest of the measuring operation.
All threshold LEDs are only active at the beginning. The first roughly
estimated measuring value is available after about 12 seconds and
can only be indicated by the threshold LEDs.
When the heat-up phase is completed, the device switches to measu-
ring mode immediately. Here, a low gas concentration of under 999
is indicated in ppm and a value over 999 ppm in Vol.%, starting with
0.1 Vol.%.
In an atmosphere free of the target gas, the device should indicate
0 ppm.
2.5 Functional test before starting to work
If the device has been stored in highly contaminated, soiled air for
a longer period, a background concentration can be indicated on
account of particle deposits on the sensor.
The sensor only becomes clean gradually after longer operation and
achieves its original zero value again.
The diffusion surface on the sensor head must be kept clean and
remain free of oils or greases. Spraying on evaporating liquids or
gases falsifies the later measuring results.
2.6 Automatic switchover to other
measuring ranges
Up to 999 ppm, the gas concentration is displayed in this unit value.
When 999 ppm is exceeded, the concentration is displayed in the unit
Vol.% from 1000 ppm = 0.1 Vol.% onwards.
Concentrations are now shown in steps of 0.1%. The analogue bar
reaches the whole display width at 1.0 Vol.%.
2.7 Exceeding the lower explosion limit
and alarm signal
The lower explosion limit is indicated when the lower explosion limit
is exceeded. In line with the numeric concentrations, the "threshold
LEDs" switch on after 10, 100, 1000 ppm and 1 Vol.%. In measuring
mode, the analogue bar has the function of an additional concentra-
tion indicator and is right across the display when 1 Vol.% is reached.
The bar indicator has a linear resolution range.
An acoustic signal can be heard which becomes faster as the
concentration increases and turns into a permanent acoustic alarm
when the lower explosion limit has been exceeded. If the lower
explosion limit is reached during measurement, the lower explosion
limit remains visible on the display when the gas concentration falls
again. This state can only be reset to the normal measuring mode by
switching the device off and on again or by pressing the right-hand
button (2x sound signal).
Note: If a certain concentration below the lower explosion limit is in-
dicated in a room or container, an explosive gas-air mixture can still
exist elsewhere in the room or container – on account of light gases
rising and heavy gases falling.
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