H80.0.02.6C-16
Operating Manual GMH 5530
page 10 of 20
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6.5 Calibration of pH measurement
The electrode data of pH electrodes are subject to fluctuation due to ageing and manufacturing tolerances.
Therefore it is necessary to check the calibration with buffer solutions before measurements take place. If
deviations are too large, a recalibration is necessary. See also: Chapter 10 GLP
Buffer solutions are liquids with an accurate pH-value. The following buffers can be used for calibration:
- Technical buffer series
PHL
(ready to use, pH 4.01, pH 7.00 und pH 10.01)
- Standard series
GPH
(buffer capsules to be mixed with water pH 4.01, pH 7.00 and pH 10.01)
- DIN series
CAL dIn
(pH 1.68 (A), pH 4.01 (C), pH 6.87 (D), pH 9.18(F) und pH 12.45(G))
- Arbitrary buffer
CAL Edit
(neutral buffer ranging from 6.5 ... 7.5pH)
Service life of a buffer solution is limited and will be further reduced unless the electrodes are
properly rinsed and dried when changing over the solutions. This may even result in incorrect
calibration! We recommend to use new buffer solution for calibration, as far as possible, and to
rinse with deionized or distilled water.
6.5.1 How to prepare calibration buffers of standard GPH series (capsules)
See Notes B.
6.5.2 Automatic temperature compensation during calibration
Both the signal of the pH-electrode and the pH-buffer are depending on temperature. If a temperature probe
is connected, the temperature influence of the electrode is compensated automatically during measuring as
well as during calibration. Otherwise enter actual buffer temperature as accurate as possible (see below).
When working with the standard or DIN-buffer series, the influences of buffer temperature are also
compensated. If buffers are entered manually, make sure to enter the pH-values of the buffers at the relevant
temperature to ensure optimum calibration of the device.
6.5.3 How to carry out calibration
Please note: the calibration can only carried out at a temperature range of 0 - 60°C !
If you have not yet done so set device to measuring mode ’pH’. Make sure that either the
1-, 2- or 3- point
calibration
(whichever is required) and desired buffer series (
PHL, GPH, dIn
or
Edit
) the has been activated
(further information in chapter 7
“Configuration”).
Carefully remove electrode safety cap (Attention! Contains 3 mol KCl!).
Rinse electrode with distilled water and dry it carefully.
How to start calibration: press
key for 2 seconds.
The display will prompt you to measure the first calibration solution.
You can abort calibration at any time by pressing
key. In such a case the last calibration before this one
remains valid.
1. Calibration point 1:
‘Pt. 1’
*1)
Place electrode and temperature probe
(if any) in the neutral solution stirring
gently.
(For 1-point calibration: solutions with
arbitrary pH value (e.g. pH 4) can be uses)
As soon as the measured pH value got
stable the next calibration step will be
displayed.
No temperature sensor:
manual input of
temperature of buffer 1
Use
or
to enter the temperature of
the buffer solution.
Use
to confirm the value; the next
calibration step is displayed.
If 1-point calibration is chosen the calibration is already done at this point, the bar graph display on the left
shows the electrode’s state rating.
2. Rinse electrode in distilled or deionized water, dry electrode
