KROHNE OPTISENS OAS 2000 EN - Manual (Page 31)

OPERATION
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OPTISENS OAS 2000
www.krohne.com 07/2010 - MA OAS 2000 R02 en
5.3.1 Calibration Points
To calculate the consistency or concentration out of the loss of light the sensor uses a calibration
curve. The curve is built up of the zero calibration point and at least one calibration point.
Each point has a sample value and a consistency value. To be used a point needs both values.
The sample value is set by Calibrate > Take sample
Calibrate > Take sample Calibrate > Take sample Calibrate > Take sample in the calibration menu. The consistency
value is manually entered in the same menu after having analysed the actual consistency at the
time the sample was taken.
A calibration point can be disabled by setting the consistency value to zero. In most applications
one calibration point in addition to the zero sample is the best solution, adding more samples
then just confuses the measurement. Only in the following cases a multipoint calibration is
needed:
1. The measurement turns out to be non linear.
2. The sensor needs to be very accurate at widely separated consistencies.
The zero calibration defines the zero point used as a reference for all other calibration points.
The other points define the relation between loss of light and real consistency.
5.3.2 Negative values
The sensor continuously compares the loss of light to its calibrated points. If, for some reason,
the loss of light is less than when the sensor was zero-calibrated, the sensor shows a negative
consistency. This is not a fault, it just indicates the liquid in the sensor absorbs less light than the
liquid used as zero reference. Please contact the manufacturer if this is a problem for you.
Figure 5-1: Example of a calibration curve
1 Loss of light
2 Consistency
0
1
2
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