235
17 Calibrating Ci conductivity sensors
17.1 Important information
17.2 General information
The calibration of Ci sensors is based on measurements in test solutions with a
defined electrolytic conductivity. Since the electrolytic conductivity of liquids is
temperature dependent, the temperature of the test solution must be sensed.
This requires either manual entry or measurement with the aid of a temperature
sensor.
17.2.1 Calibration methods for Ci conductivity sensors (inductive)
Rel. cell constant
The deviation from the nominal cell constant of a Ci sensor is described by the
relative cell constant. The rel. cell constant is determined by making a measure-
ment in a test solution with a defined conductivity.
Temperature coefficient
The temperature coefficient is a measure of the temperature dependence of the
electrolytic conductivity of a liquid. Is used to compensate for the effect of tem-
perature when measuring the electrolytic conductivity. When making a tempera-
ture-compensated conductivity measurement, the measuring value of the
conductivity is always given on the basis of the fixed, preset reference tempera-
ture. With the aid of the temperature coefficient, the value of the electrical con-
ductivity at the reference temp. is calculated from the current values of
conductivity and temperature measured for the liquid and then displayed.
Reference temperature is set in the configuration of the individual Ci analysis in-
put.
v Chapter 10.5.6 "CR/Ci analysis inputs (conductive/inductive conductivity)",
Page 148
The temperature coefficient is determined from 2 measurements in a test solu-
tion at different temperatures (reference and operation temp.).
WARNING!
During the calibration, the relays and analog output signals assume the config-
ured states! The response of the output signals is set for each output in its "Re-
sponse at calibration" configuration point.
⇨ Chapter 10.5 "Analog inputs", Page 139
NOTE!
If the temperature coefficient of a sample solution is known, it can be entered
directly.
v Chapter 12.2.1 "General procedure for calibration", Page 205
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