Dräger PEX 3000 Manual Del Usuario página 37

5.3.1 Turning on the supply voltage
– After turning on the supply voltage, all 14 LED segments including both
points are activated for approx. 5 seconds to make sure that they are not
faulty ("Lamp test"). Internal test routines run in the transmitter during this
period, the transmitter's output signal is 1 mA.
– After this, the display changes, with approx. 1 Hz, between two horizontal
lines and the currently measured gas value. During this time the
transmitter's output is 3.4 mA.
– After one minute the transmitter is ready for operation. If the zero-point is
not undercut by more than 5% LEL or 1% LEL, it displays the current
measured value, and the output signal corresponds to the measured value.
– Type XTR 0090 or XTR 0091 with sensing head SE Ex LC M ...DD: Adjust
sensor current to 276 mA by means of the function "CU – Sensor Current
Adjustment" ((see "CU – Adjust the sensor current", page 32)).
– Allow the transmitter to warm up before adjustment: DrägerSensor PR M
DQ for at least 30 minutes (warm-up time of the sensor), DrägerSensor LC
M for at least 120 minutes (warm-up time of the sensor)
5.3.2 Calibrating the transmitter
For this chapter:
– Mentioning type XTR 0000 also includes type XTR 0001 as well as the
transmitters type XTR 0090 or XTR 0091 with remote sensing head Polytron
SE Ex PR ... DQ or HT M DQ (100% LEL).
– Mentioning type XTR 0010 also includes type XTR 0011 as well as the
transmitters type XTR 0090 or XTR 0091 with remote sensing head Polytron
SE Ex LC ... DD (10% LEL).
5.3.2.1 Calibrate zero-point
To enter the calibration menu, press the ▼ key for more than one second but
less than three seconds. The display shows ZE and a flashing point on the
bottom right indicating the calibration mode.
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– Confirm with keys (▲+▼). The measured signal is set to 3.4 mA to indicate
the calibration mode to the controller.
– Apply gas to the sensor – either
– 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 down to "–5"% LEL or "–,9"% LEL (type XTR 0010) are
displayed.
– 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.
5.3.2.2 Calibrate sensitivity
The zero-point must be calibrated before the sensitivity adjustment!
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Operation
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