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6.
INSTRUMENT CHECKS
Pump Checks
If the intake is blocked, the display shows "bloc" (block) and the detector beeps until the
problem is cleared. This check is carried out whether or not a probe is being used. To check for
tight connections, block the probe inlet to sow "bloc" on the display within a few seconds. If
"bloc" fails to appear, there may be a leak (see "Troubleshooting").
WARNING:
The instrument should not be used if it doesn't display "bloc" when the
intake is blocked.
Automatic Zero
To adjust the zero automatically, advance the selector switch to "AUTO ZERO". Zero
adjustment, which takes 25 to 35 seconds, is typically required only once a day.
Display
The oxygen sensor is adjusted to 20.9%.
Air (O
)
2
GAS 1
The zero of the thermal conductivity sensor is adjusted.
CO
The zero of the CO/H
GAS 2
The zero of the combustion sensor is adjusted.
End
The instrument beeps briefly after it has been zeroed and is ready to use.
If automatic adjustment of zero cannot be carried out, for example, because the methane
concentration is too high, or because a sensor has drifted too far from its previous null (zero), the
display will show "nogo" (no go) alternating with the symbol of the gas indicating which sensor
cannot be adjusted.
If an automatic zero attempt leads to "nogo", subsequent selection of some display mode
(% GAS, PPM CO, or % Oxygen) will display "nogo" alternating with the symbol for the
display. The instrument must then be zeroed as described below.
WARNING:
Zero adjustment must be carried out with clean air. If the air is not clean,
a systematic error will be introduced. The instrument will auto zero if
methane is below 0.5% and CO below 35 ppm. At higher concentrations of
methane or CO, the instrument will not change its zero, and the display will
show "nogo" (no go).
Automatic Operation
S sensor is adjusted.
2
13
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