Functional Check Before Starting Work; Automated Switching To Other Measuring Ranges; Exceeding The Lel And Alarm Signal - Herth+Buss SelectH2 Instrucciones De Manejo

Operating Instruction

2.5 Functional check before starting work

If the device was kept in highly contaminated
impure air for a long time, an underground
concentration may be displayed due to the
accumulation of particle deposits on the sen-
sor. The sensor only becomes clean gradu-
ally after longer periods of use, reaching its
original zero point value again.
The sensor head's diffusion area must be
kept clean and free of oil and grease. Spray-
ing with vaporised liquids or gases distorts
the subsequent measurement results.
2.6 Automated switching to other
measuring ranges
Gas concentrations of up to 999 ppm are
shown using this value. If 999 ppm is excee-
ded, the volume is shown in vol% as of 1000
pm = 0.1 vol%.
The concentrations are now displayed in in-
tervals of 0.1%. At 1.0 vol%, the analogue bar
reaches the full width of the display.
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2.7 Exceeding the LEL and alarm signal

LEL is displayed if the LEL of the gas is ex-
ceeded. In line with the concentration shown
numerically, the "threshold LEDs" switch to
10, 100, 1000 ppm and 1 vol%. In measuring
mode, the analogue bar functions as an ad-
ditional concentration display and is shown
in full once 1 vol% is reached. The bar dis-
play has a linear resolution range.
An uninterrupted acoustic signal can be
heard. Its speed increases at higher con-
centrations and it becomes a continuous
tone once the LEL threshold is exceeded. If
the LEL is reached when measuring, LEL re-
mains shown in the display, even if the gas
concentration falls again. Resetting this sta-
tus in normal measuring mode is only pos-
sible by switching the device off and restar-
ting it or by pressing the right-hand button
(2x signal tone).
Warning: If a specific concentration under
the LEL is displayed in a room or container,
it is still possible that an explosive gas-air
mixture exists at another point due to light
gas rising or heavy gas "flowing off" .
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