52
Operating and functions
• In order not to interrupt the process, activate the HOLD function (see chap. 9.12.1).
• Before each calibration, correctly clean the electrode with a suitable product.
• In a 2-point calibration, the buffer solutions used must be at the same temperature.
• Set the periodicity of calibrations in the "Interval" function in the sub-menu "Calib interval" (see previous
page): each time a calibration is due, the transmitter generates a "maintenance" event and a "warning"
event.
1-point calibration
The 1-point calibration procedure is used for quick calibration by adjusting the offset of the measurement graph
with a buffer respectively a calibration solution with a known pH (to calibrate a pH sensor: see page 54)
respectively a known oxidation reduction potential (to calibrate a Redox sensor: see page 53).
2-point calibration
The 2-point calibration procedure for a pH sensor is used for the precise calibration of the offset and the gradient
("span") of the sensor measurement graph.
This operation requires 2 buffer solutions: in general a first solution with a pH of 7 and a second solution with a
pH very close to that of the process value to be measured. See page 54.
At the end of calibration of the pH sensor, two types of messages may be displayed:
Message "span" value "offset" value
Possible
cause
Recommended
action
"Warning:Span/
offset out of
range"
50 mV/pH < span < 53 mV/pH
or
63 mV/pH < span < 65 mV/pH
-60 mV < Offset < -35 mV
or
35 mV < Offset < 60 mV
Error in
the buffer
solution.
→ Use the correct
buffer solution.
The
probe has
reached
halfway in
its lifespan
→ The values can
be saved or
not.
"Error:Span/
offset out of
range"
< 50 mV/pH
or
> 65 mV/pH
< -60 mV
or
> 60 mV
The probe
must be
replaced.
→ Replace the
probe.
→ Calibrate the
transmitter
again when the
new probe is in
place
Table 1: Warning and error messages during pH sensor calibration
English
Type 8202 ELEMENT
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