KROHNE OPTISENS OAS 2000 EN - Manual (Page 34)

5
OPERATION
34
OPTISENS OAS 2000
www.krohne.com 07/2010 - MA OAS 2000 R02 en
5.3.5 Statistic adjustment
Statistic adjustment of the lab sample value is a much better way to good measurement than
frequent calibration. This is done comparing the lab results with the instrument reading over
time. If a systematic discrepancy is detected, change accordingly the value of the lab sample
used in the converter by using the Adjust
Adjust Adjust Adjust function in the calibration menu.
If, for example, several lab results for a period of time in average show 5 % more than the
instrument, the sample value in the converter shall be increased by 5% of its value. E.g. if the
sample value is 10000 mg/l, it shall be changed to 10500 mg/l.
Using the statistic method will increase the accuracy and reliability of the measurement as time
passes while new calibrations will start from scratch. An Excel sheet to help doing statistical
adjustment of the calibration can be obtained from the manufacturer.
Running a statistic adjustment
• Select the sensor to be calibrated in the menu by using ↑ or ↓.
• Press ^ for approximately 5 seconds to enter the sensor menu.
• Select Calibrate > Adjust
Calibrate > Adjust Calibrate > Adjust Calibrate > Adjust and then Lab Lab Lab Lab using ↑ and ↓.
• Press ^.
• Press ↑ to key in a value.
• Key in the result of the statistical calculation, then press ^.
i The converter will show current and suggested new value for "Sample 1".
• Acknowledge the change by pressing ^ or abort using ↑ or ↓.
5.3.6 Zero calibration
The sensor is zero-calibrated at the factory and does not often need to be zero-calibrated.
Before doing a zero calibration, always check that it is really needed. Make sure the lenses are
clean, and use clean de-aerated water to check the sensor reading. Tap water is best de-aerated
by leaving the water in an open bucket for at least two hours.
CAUTION!
Even though the sensors have daylight-filters, they are sensitive to the infrared parts of the
sunlight. Always cover the sensor and the bucket before calibration.
.book Page 34 Friday, July 2, 2010 1:49 PM