YSI NiCaVis 701 IQ NI - Manual (Page 29)

NiCaVis 70x IQ NI
Measuring / Operation
4 - 5 ba76132e01 03/2013
4.3.2 User calibration
Calibration points and
value pairs
The adjustment is carried out at one or two points within the measuring
range. A value pair is determined at each point. Each value pair
consists of the raw value of the UV sensor and the corresponding refer-
ence value.
Each value pair has to be determined at the same time and place as
the test sample as possible. At the time of the calibration, the test
sample should be in a condition that is typical of the application.
Selection of calibration
points
If the required accuracy is low, the default setting of the first value pair
can be adopted unchanged. The first value pair is equivalent to the zero
point in this case. The second value pair should be close to the working
point of the application. This method results in a single-point calibra-
tion.
If the application has to cover a wide value range with high measuring
accuracy, both value pairs should be used for calibration. When doing
so, the calibration value pairs should be determined and input at the
limits of the application range as possible.
You obtain samples of different concentrations e. g. by taking two
samples during clearly different conditions of the plant (dry period and
rain period).
The measurement results will be ever more accurate the closer the
composition of the test sample corresponds to the status at the time of
the calibration. If there is a fundamental change of the characteristics
of the sample, a new calibration may be necessary.
Storage location of user
calibration data
The calibration data of the user calibration are stored in the IQ Sensor
Net controller. They are loaded into the sensor during operation and
automatically assigned to the replacement sensor if the sensor is
exchanged.