IM 12B6C2-E-H
1. What is manual calibration?
Manual calibration or process calibration is
the calibration executed with a freshly taken
sample from the process.
This sample is then measured with an off
line instrument and the value obtained is
programmed into the EXA PH200 transmit-
ter.
Manual calibration can be used for calibra-
ting the sensors with a buffer solution spe-
cially made for this purpose.
NOTE:
This routine can also be used to calibrate
with two points as an alternative to automa-
tic calibration e.g. for occasional use of not
programed buffers.
2. How does it work?
1. Take a sample from the process.
2. Measure the pH with an off-line pH meter
which has been previously calibrated with
standard buffers and is equiped with an
automatic temperature compensation.
3. Adjust the value of the in-line EXA PH200
transmitter to the measured value.
4. Any values outside the normal operating
range of the instrument are signal led by
Error 19.
3. Example
The EXA PH200 indicates a process value of
pH 6.54 at 50°C.
A freshly calibrated portable pH-meter inser-
ted into a hot sample reads 6.62 pH at
50°C.
The value is adjusted to the process value at
manual calibration to bring the values in
agreement.
A laboratory check of the same sample
shows the value to be pH 6.612 at 25°C.
The difference is due to the change of pH of
this particular sample with temperature.
21
5-2. Manual calibration
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