34 Dräger PEX 1000
Maintenance
3. Apply zero gas to the sensor – either
without calibration adapter:
Ensure that the sensing head is in clean ambient surroundings (no flammable gases or
vapours present),
or
with calibration adapter:
Supply zero gas (clean air) at a flow rate of approx. 0.5 L/min via the calibration adapter.
The display of the PEX 1000 shows the currently measured zero gas concentration which
in general is slightly different from zero. Negative values are displayed up to "–9" %LEL.
4. Wait until the reading has stabilised (max. 3 minutes) and press keys (▲+▼). This converts
the current sensor signal into an updated zero point, also shown on the display (ideally "0“).
5. Press (▲+▼) to save the updated zero point and to terminate the zero point calibration.
6. Press keys (▲+▼) to terminate the zero point calibration. The display shows ZE.
7. Press key ▲ to switch back to the measurement mode or press key ▼ to perform the
sensitivity calibration.
5.1.2 Calibrating sensitivity
Before calibrating the sensitivity the zero point must be calibrated!
1. Navigate by means of keys ▲ or ▼ until the display shows SP (“SPan“)
and press keys (▲+▼) to confirm. The measuring signal is set to
3.4 mA to indicate the calibration mode to the controller unit.
The display shows the test gas concentration used during the previous
calibration in %LEL.
2. By means of the keys ▲ or ▼ the concentration of the currently used test gas can be
adjusted between 20 and 99 % LEL in steps of 1 % LEL.
Pressing the keys for longer activates the repeat function.
Recommended test gas concentration:
3. Press (▲+▼) and – depending on the current sensing head type – apply the recommended
test gas concentration (see table) at a flow rate of approx. 0.5 L/min via the calibration
adapter.
NOTICE
After a sensor replacement the zero point of the PEX 1000 might be misaligned so
much that the display shows “--“. In this case press keys (▲+▼) to save the
preliminary zero point and perform the zero adjustment calibration again, if necessary.
PEX 1000
in combination with:
Full-scale value Test gas concentration
Sensing head SE Ex PR / HT ... DD/DQ
: 100 %LEL 30 to 70 %LEL
CAUTION
The test gas must be a mixture of the gas to be monitored and air! Mixtures with
nitrogen are not suitable!
i
i
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