wtw inoLab 740, Operating Manual

Page: 140 / 274

Dissolved oxygen (D. O.)
140
8.2 Calibrating for D. O. measurements
Why calibrate? D. O. probes age. This changes the slope of the D. O. probe.
As a result, an inexact measured value is displayed.
Calibration determines the current slope of the probe and
stores this value in the instrument.
After calibrating the D. O. probe in the air calibration vessel,
the measuring system displays a value of approx. 102%
oxygen saturation. If the value of the oxygen saturation
obtained by checking the probe in the air calibration vessel
is different from this, it is necessary to calibrate or clean the
probe.
If possible, check the probe signal in the air calibration
vessel before each series of measurements.
When to calibrate?
l
At regular intervals (14 days)
l After connecting another D. O. probe
Calibration
procedures
The calibration is performed in water vapor saturated air.
Use the OxiCal
®
-SL air calibration vessel for calibration
(accessory).
AutoRead The calibration procedure automatically activates the
AutoRead function. The
h
display indicator flashes. The
calibration process is finished when
h
stops flashing.
Calibration record The calibration record contains the calibration data of the
current calibration. You can call up the calibration record by
outputting the data storage (section 11.3).
Note
You can automatically print a calibration record after the
calibration. To do so, switch on the printer before calibrating
(print LED lights up green). After a valid calibration, the
record is printed.