Dräger PEX 1000 Manual page 30

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Operation
– without calibration adapter: Ensure that the transmitter is in clean
ambient air (no combustible 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 transmitter's display shows the current measured value for zero gas
and for clean ambient air, which generally differs slightly from zero.
Negative values are displayed down to "-5"% LEL for the measuring
range up to 100% LEL or down to "-,9" for the measuring range up to
10% LEL.
– Wait until the reading has stabilised (max. 3 minutes) and press keys
(▲+▼). This converts the current sensor signal to the zero-point, and the
display shows the newly set zero-point (ideally "0").
– Press ( +▼) to save the updated zero-point and to terminate the zero
adjustment.
WARNING
After a sensor replacement, the transmitter's zero-point may initially be
negatively misaligned so much that it cannot be displayed as a negative value.
The display then shows "--". In this case, press keys ( +▼) to save the new
zero-point and perform the zero adjustment again, if necessary.
– Press keys ( +▼) to terminate the zero adjustment. The display shows ZE
once again.
– Press the ▲ key to return to the measuring mode or the ▼ key to calibrate
the sensitivity.
5.3.1.2 Calibrate sensitivity
The zero-point must be calibrated before the sensitivity adjustment!
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– In the calibration menu, navigate using the ▲ or ▼ key until the display
shows SP ("SPan") and confirm by pressing the (▲+▼) keys. The
measured signal is set to 3.4 mA to indicate the calibration mode to the
controller.
 The display shows the test gas concentration used during the previous
adjustment in % LEL.
– Use the ▲ or ▼ key to set the concentration of the test gas currently in use
for the measuring range up to 100% LEL between 20 and 99% LEL in 1%
LEL steps.
– For the measuring range up to 10% LEL, a decimal point appears, i.e. the
concentration of the test gas can be adjusted between 2.0 and 9.9% LEL in
steps of 0.1% LEL.
– Pressing the keys for a longer period activates the repeat function.
Recommended test gas concentration:
Full scale value
100% LEL
10% LEL
CAUTION
The test gas must consist of the gas component to be monitored and air.
Calibration gases filled in nitrogen are unsuitable for this task!
– Press the (▲+▼) keys and – depending on the transmitter type – apply the
recommended test gas concentration (see table) at a flow rate of approx.
0.5 L/min via the calibration adapter.
– Wait until the reading has stabilised (max. 3 min) and press the (▲+▼) keys
to calculate the necessary internal amplification of the transmitter. The
display shows the measured value with the newly calculated amplification
factor; however, this has not yet been saved. The original amplification
factor is restored if the calibration function is automatically exited by waiting
for more than 4 minutes in this status.
Test gas concentration
30 to 70% LEL
3 to 7% LEL
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