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NOTICE
After sensor replacement, the internal amplification of the transmitter can be so
high that the measured value cannot be displayed. The display will then show
"99" or "9.9". In this case, press the keys (▲+▼) to recalculate the necessary
internal amplification, save it, and repeat the sensitivity adjustment.
–
Press the (▲+▼) keys. This finally saves the newly calculated amplification.
The display shows a reference value for the sensitivity (sensitivity) of the
sensor (constantly amplified bridge signal). If this reference value is lower
than 10 it is displayed with a decimal point.
–
The actual sensitivity of the sensor in mV per % LEL can be obtained by
multiplying the reference value by a factor 2 and dividing it by 100 (or for the
measuring range up to 10% LEL, dividing it by 10), e.g.:
–
Measuring range up to 100% LEL: If, following an adjustment by means
of 52% LEL propane, a reference value of 45 is displayed, the true
sensitivity of the DrägerSensor PR M DQ for propane is 45 * 2 / 100 =
0.9 mV/%LEL.
–
Measuring range up to 10% LEL: If, after adjusting with 4.4% LEL
ethanol, a reference value of 32 is displayed, the actual sensitivity of the
DrägerSensor LC M for ethanol is 32 * 2 / 10 = 6.4 mV/% LEL. This
value is higher by a factor of 5 than for the DrägerSensor PR M DQ
because of the internal amplification of the DrägerSensor LC M.
–
The reference value and/or the actual sensor sensitivity should always be
recorded in mV/% LEL for test purposes.
NOTICE
If the reference value is less than half the value recorded during commissioning
of the sensor or if the measured value does not stabilise within 3 minutes, the
sensor should be replaced.
–
Press the (▲+▼) keys to exit the sensitivity adjustment.
–
Press the ▲ key twice to return to measuring mode. The flashing point on
the bottom right is deactivated.
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5.3.1.3
After completing the adjustment
–
The display shows the current gas concentration in % LEL and the
transmitter once again emits the concentration-dependent 4 to 20 mA
signal.
–
Refit the upper part of the casing, ensuring that the atmosphere is free of
dust and fasten the cover screws.
5.4
Operation
In line with the gas concentration, the current loop produces a current between
4 and 20 mA, or
Current
Meaning
0 mA
Cable is broken or power supply has failed
1 mA
Fault (see "Troubleshooting", page 31)
3.4 mA
Calibration signal
3.8 mA to 20.5 mA
Measured signal in normal operation
4 mA
Measured signal zero-point
20 mA
Measured signal full scale value
20.5 mA
Over range by more than 3% of full scale value
6
Troubleshooting
Fault
Cause
Display off
Cable faulty
Transmitter cannot be
Sensor faulty or poi-
calibrated
soned
Measuring current is
Transmitter signals a
1 mA, display shows E0,
fault
E1, .... or E8
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en
Troubleshooting
Remedy
Check cable to the con-
troller.
Replacing the sensor.
See following table.
31
