H75.0.01.6C-02
User’s guide GPH 114
Page 6 of 8
2. Care and maintenance:
2.1. Crystallization of the 3 mol/l KCl is not avoidable!
Crystallized KCl at protection cap or closing collar can easily be removed by fingernail or cloth and is no
defect or reason for reclamation.
2.3. Dirty electrodes have to be cleaned. You will find suitable cleaning agents for the pH-glass diaphragm in
the following table:
Contamination
Cleaning agent
Various deposits
Light cleaning agent
Inorganic coatings
Commercial liquids for cleaning of glass
Metal compounds
1 mol/l HCI solution
Oil, grease
Special cleaning agents or solvents
Biological coatings containing proteins
1 % pepsin enzyme in 0.1 molar HCI solution
Resin-lignines
Acetones
Highly resistant deposits
Hydrogen superoxide, sodium hypo chloride
The distinct materials of the electrode have to be considered when choosing the cleaning agent.
E.g. electrodes with plastics shaft must not be cleaned with solvents. In case of doubt please contact the
manufacturer for further advice.
The same has to be considered when using aggressive or other, non water based agents!
5 Calibration of pH-Meter
Accessories required: calibrating solution for pH 7 und pH 4 (resp. special accessories pH 10, pH 12)
How to prepare a calibrating solution: chapter 10 Notes B: preparation of pH buffer solutions
5.1 Calibration of pH-Meters
In order to ensure optimum measuring accuracy, the calibration range should be larger than the measuring
range. We recommend using the following calibration solutions for measurements.
less than pH 7: pH 4,0 and pH 7,0
more than pH 7: pH 7,0 and pH 12,0
Plug in Cinch plug of pH-electrode into corresponding socket and switch on device by means of the lateral
slide switch (a number with decimal point will be displayed on the LCD).
Determine temperature of buffer solution and set accordingly using the central turning knob (controller for
temperature compensation 0 to 90°C): 1 graduation mark = approx.10°C.
Place GPH 114 meter on a solid surface; if possible try to avoid holding the meter in your hand during
calibration (please refer
to “Points to be observed during measuring”).
5.2 Setting of the first calibration point
Carefully remove protection cap from electrode. (Attention: cap contains 3 mol/l KCl).
Rinse electrode with distilled water, dry electrode, place it in buffer solution pH 7.0.
Wait approx. 20 to 30 seconds (for display to show stable value), then use turning knob at the far right side
(pH 7) to set value to 7.00.
5.3 Setting of second calibration point
In order to check calibration repeat procedures for calibration points 1 and 2 using corresponding turning
knob for re-adjustments.
In case you did not prepare pH 4.0 but another buffer solution, e.g. pH 10.0 or pH 12.0, the corresponding
value (pH 10.0 or pH 12.0) can be set (calibration of second calibration point) using the left-hand turning
knob (pH X).
Please note that for each and every calibration procedure the buffer solution value pH 7.0, i.e. 7.00, has to
be set by means of the right-hand turning knob (ph 7).
Note:
We recommend to re-calibrate the measuring device prior to each new measuring series to
ensure optimum accuracy. It has to be considered that the calibration solution and the
media to be measured should had similar temperatures!
After completion of measurements fill electrode protection cap with 3 mol/l KCl solution and slip it back onto
electrode. (Gentle squeezing of the cap displaces air, thus allowing cap to be slipped on easily)
Attention:
pH-electrodes are extremely delicate and sensitive measuring elements. Prior to using the pH
electrode, please carefully read corresponding maintenance and measuring manual!
We shall not assume any warranty if customer fails to use proper care and skill
(e.g. breaking of electrode, drying-out, blocking etc.).
