Calibration Redox (Mv); Calibration Procedure; Calibration Errors; Determining The Redox (Mv) Setpoint - Bayrol PoolManager Chlorine User Manual

13
13.4

Calibration redox (mV)

The calibration for redox measurement is performed as 1-point
calibration. A buffer solution with a known redox value (e.g. 465 mV) is
used.
TIP
Redox calibration
Depending on water quality and the state of the
electrode, it can occur that the redox electrode reacts
very slowly if it is moved from the buffer solution back
into the measuring water after calibration. In
disadvantageous conditions, it may take several hours
until the measured redox value stabilises again and is
displayed correctly.
During that time, reasonable configuration and
activation of redox control is not possible.
Therefore, it is recommended to only perform redox
calibration when necessary, such as when it is
suspected that the electrode could be defective.
Calibration can be omitted for the following reasons in
order to avoid potential problems with running-in time:
Functioning redox electrodes generally have a tight
tolerance range, such that calibration only changes the
display value by a few mV.
The absolute redox value is not of significant. Assigning
the redox value to the chlorine value in the pool is more
important; see section Determining the redox (mV)
setpoint.
13.4.1

Calibration procedure

Redox (mV) calibration can be found in the following menu:
Calibration Redox (mV)
Calibration is carried out as follows:

Select 1-point Calibration Redox (mV)

Calibration is a menu sequence, i.e. it goes through a series of
menus step-by-step.
13.4.1.1 Calibration Data
The following parameters are displayed in the calibration menu:
Calibration value
For calibration value, enter the reference value for calibration, i.e. the
redox value of the buffer solution being used (e.g. 465 mV).
Current value
This is the current measured value calculated using the parameters
from the last calibration, which are still valid. This value may deviate
from the actual value. It is only displayed to give you a certain level of
orientation throughout calibration.
Using the measured value, you can see when measurement has
stabilised when you place the electrode into the buffer solution.
13.4.1.2 Calibration results
At the end of calibration, the calibration parameters calculated are
displayed:
Offset
Offset is the zero point shift calculated from calibration. It is indicated
in [mV].
Current value
The redox (mV) measured value is now calculated using the
parameters from the current calibration. The measured value
displayed should therefore be consistent with the calibration value
entered.
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13.4.1.3 Step by step
1-point calibration with buffer solution (e.g. 465 mV)
1. Block the measuring water
2. Separate the electrode cable from the controller
3. Unscrew the redox electrode from the measurement chamber
4. Rinse the redox electrode off with (distilled) water
5. Carefully dab the redox electrode dry using a cloth (free from
grease and fluff)
6. Connect the electrode cable to the controller again.
7. In the menu, select the function 1-point Calibration Redox (mV)
8. Enter the buffer solution's redox value as the calibration value
(e.g. 465 mV)
9. Dip the redox electrode into the buffer solution (e.g. 465 mV)
and stir it carefully and briefly.
10. If the measured value displayed has stabilised and is no longer
changing in a relevant manner, then confirm calibration by
pressing Next.
11. Check the calibration results displayed and close calibration by
pressing Ready.
12. Place the redox electrode back into the measurement chamber
13. Open the shut-off valves for the measuring water
13.4.2

Calibration errors

During calibration, various plausibility criteria are checked. If one of the
criteria is not met, then a corresponding error message appears and
calibration is not executed.
The following criteria have to be met for successful calibration:

The offset calculated (zero point shift) has to be in the range of
±100 mV. The offset is generally close to 0 for flawless
electrodes.
13.5

Determining the redox (mV) setpoint

Electrode calibration is not of decisive importance for redox control.
Correct determination of the redox setpoint is.
After all, redox control should provide the desired level of chlorine /
bromine in the pool. As long as water quality and other general
conditions do not change significantly, the redox value measured is
directly dependent upon the concentration of free chlorine / bromine. A
change in chlorine / bromine concentration always results in a change
in the redox potential measured. Conversely, this means that the
chlorine / bromine concentration remains constant if the control system
is providing a constant redox value. It counteracts a sinking redox
value immediately by dosing chlorine / bromine, thereby maintaining a
constant redox value at the configured setpoint.
IMPORTANT NOTICE!
Determining the correct redox setpoint
The redox value for the desired chlorine / bromine
value can vary widely from pool to pool.
Therefore, the correct redox setpoint must be
determined individually for each pool.
Values experienced in the past are surely helpful for
orientation. However, the redox setpoint cannot be
configured based solely on values experienced in the
past, as the correct redox setpoint in an individual case
can deviate significantly from values experiences in the
past.