Dräger Polytron 8900 UGLD Instructions For Use Manual page 15

Sensor The current and the highest sensor tem-
tempera-
perature is displayed.
ture
Data logger
Logger Display the data-logger status (active or
status non-active)
Graph Displays the history of the past 15 minutes
on a time/concentration graph.
7 Calibration
Obey the safety statements mentioned in 1 Safety-related
information!
A bump test (calibration check) and adjustment of the
measurement accuracy can be performed with the Dräger
Polytron 8900 UGLD Calibration Kit. Only the sensor span
should be calibrated if the bump test result is out of spec.
Severe ambient conditions or physical impacts to the sensor
may cause sensor drifts. Sensor drifts have a negative impact
on the measurement accuracy. Calibrations restore this
accuracy.
Dräger ultrasonic sensors are life-time calibrated. Under
normal conditions sensor drifts should not occur and a
recalibration should not be necessary.
To verify the sensor is providing correct measurement data,
the sensor should undergo a regular bump test utilizing the
calibration kit.
In general calibration is not necessary. To check whether a
calibration is necessary, first perform a bump test.
7.1 Test gas
The acoustic sound pressure emitted by a leak varies by the
type of target gas, the leak size and the distance to the
device.
Test gas for ultrasonic sensors is compressed air or nitrogen.
The calibration adapter generates the ultrasonic sound
pressure at defined flow rate.
Thus, the calibration adapter generates the needed ultrasonic
signal to calibrate the system span.
7.2 Performing a bump test
Once installed, the instrument typically does not need regular
calibrations. Nevertheless, the calibration can be checked and
performed if a deviation outside the acceptable tolerance is
detected.
A bump test checks alarm activation and sensor sensitivity
without setting off the alarms.
Prerequisites:
– Background noise is < 80 dB.
– Environmental temperatures within 0 °C to 40 °C (+32 °F
to +104 °F).
Calibration equipment:
– Dräger Polytron 8900 UGLD Calibration Kit (8328042)
Instructions for use |
Dräger Polytron
®
8900 UGLD Firmware version ≥ 4.0.x
To perform a bump test:
1. Place the calibration adapter onto the sensor up to the
stop.
2. Enter the menu, see 6.6.3 Entering the menu.
3. Select Settings > Instrument > Bump test and confirm.
 The maintenance symbol is displayed
 The analog output is set to the maintenance signal.
4. Open calibration gas cylinder valve.
 After a short period of stabilization time (~ 10 s), the
displayed value should stabilize at the dB number (or
percentage of measurement range) that is indicated on
the calibration adapter.
 If the value deviates by > 3 dB (or 6 %), perform a
span calibration.
5. Press OK to return to measurement.
The calibration adapter must not be soiled. Store the
calibration adapter in a clean environment. Dräger
recommends storing the calibration adapter in the calibration
kit case.
7.3 Preparing a calibration
A calibration needs to be performed in a controlled
environment with the following prerequisites:
– Background noise is < 70 dB.
– Environmental temperatures within +15 °C to +35 °C
(+59 °F to +95 °F).
Calibration equipment:
– Dräger Polytron 8900 UGLD Calibration Kit (83 28 042)
To prepare a calibration:
1. Remove the sensor from the instrument or the remote
sensing head.
2. Take the sensor to a controlled environment.
3. In the controlled environment insert the sensor into a
Polytron 8900 UGLD instrument.
4. Calibrate the sensor by using the calibration kit.
● Performing a zero calibration, see 7.4 Performing a
zero calibration.
● Performing a span calibration, see 7.5 Performing a
span calibration.
5. Re-insert the sensor in it's previous location.
6. Re-integrate the instrument into the alarming system.
7.4 Performing a zero calibration
NOTICE
Zero calibrations may cause malfunctions
Zero calibrations should not be necessary.
Zero calibrations set the zero point of the measurement
range.
The zero point of the measurement is < 54 dB and should only
be calibrated if background noise is < 54 dB.
► Do not calibrate the zero point at the installation site with
background noise present.
| en
Calibration
15