wtw Oxi 170, Operating Instructions Manual

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Operation Oxi 170
100 ba24105e08 11/2010
4.6.4 Display of the relay states in the operating level
For an active relay the REL 1 or REL 2 status display appears in the
operating level. Depending on the selected switching behavior the relay
contact is either open or closed.
Fig. 4-3 Display of the relay states in the operating mode
4.7 Calibration
Why calibrate? During the operation of a D.O. sensor, the slope of the D.O. sensor
changes with time. The calibration procedure determines the current
slope of the sensor.
When to calibrate? Calibrate before measuring and at regular intervals (depending on the
application).
Calibration procedures Ideally, calibration takes place in water vapor-saturated air. To do this,
position the sensor approx. 2 cm above a water surface, e.g. in a
narrow mouthed bucket or a similar vessel filled with water.
At air temperatures below 5 °C we recommend not to calibrate in air but
in air-saturated water with a higher temperature. Air-saturated water is
generated by vigorously and repeatedly transferring water between 2
vessels.
Note
For calibration, the membrane must always be clean and for calibrating
in air, it must be dry. Clean soiled sensors prior to calibration (see
sensor operating manual).
Note
To guarantee a high accuracy, it is recommended to set the current air
pressure (absolute pressure) under
PPr
before calibrating.
mg/ l
1
1
8 5
°
C
REL1
5 6
O
Relay 1 active Relay 2 inactive