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13.1
Important information
13.2
General information
13.2.1
Calibration methods for Redox sensors
Zero-point calibration
Two-point Calibration
WARNING!
During the calibration, the relays and analog output signals assume the states
configured for the calibration! The response of the output signals is set for each
output in its "Response at calibration" configuration point.
⇨
Chapter 10.7 "Analog outputs of base unit and optional boards", page 28
The calibration of Redox sensors is based on measurements in test solutions
with a defined Redox potential.
This calibration method is used to determine the redox zero point.
A test solution with a defined redox potential is needed as a reference.
"mV" must be set as the redox unit in the configuration of the redox measure-
ment input (analysis input or input for digital sensors).
⇨
Chapter 10.6.4 "pH/Redox/NH3 analysis inputs", page 21
This calibration is used to establish an application-specific measurement char-
acteristic curve where redox potentials are represented as a percentage of con-
centration values. The redox potentials of 2 solutions are measured.
Concentration values in percent are then assigned to the measured values by
the user.
Two process-typical sample solutions are needed as calibration solutions as a
reference.
"Percent" must be set as the redox unit in the configuration of the redox mea-
surement input (analysis input or input for digital sensors).
⇨
Chapter 10.6.4 "pH/Redox/NH3 analysis inputs", page 21
Example: In a detoxification plant, the toxicity of a liquid is to be measured on
the basis of the Redox potential. The calibration requires 2 solutions:
•
the concentration of the highly toxic solution is given as 80 % by the user, for
instance
•
the concentration of the detoxified solution is given as 10% by the user, for
instance
Using the redox potential, the toxicity can now be measured and displayed in
percent.
13 Calibrating redox sensors
63
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