LABEC M-MIA-A - Manual (Page 84)

Ultrasonic milk analyser
APPENDIX 7 PH MEASURING
1. General information
PH probe is a unit, measuring the solution acidity or alkalinity degree. It is
measured on scale of 0 to 14. The term pH is derived from "p", the
mathematical symbol for the negative logarithm, and "H", the chemical
symbol of Hydrogen. The formal definition of pH is the negative logarithm of
the Hydrogen ion activity.
2. pH Electrode
For pH measurement the milk analyzer needs a combination electrode,
compatible with most pH electrodes that have BNC connectors and zero
potential (the pH where the mill volt output of the electrode equals 0) near 7
pH.
2.1. Electrode part
The electrode is the most important part of the pH measurement. The
electrode glass membrane is fragile and must be handled with care. To
protect the glass membrane and to maintain activation, a protective rubber
cap containing a suitable storage solution covers the glass membrane.
2.2. Electrode care & Electrode maintenance
pH Electrodes are susceptible to dirt and contamination and need to be clean
regularly depending on the extent and condition of use. At no time should one
touch or rub the glass bulb as this causes the build-up of electrostatic charge.
2.3. Storage
For best results, always keep the pH bulb wet. An optimal storage solution for
combination electrode is pH 4 buffer with 225 grams of KCl per liter. Table
salt, NaCl, can be used if KCl is not really available. Other pH buffers or tap
water are also acceptable storage media, but avoid storage in de-ionized
water. The protective rubber cap filled with the buffer solution provides ideal
storage for long periods.
2.4. After Use
After measurement is completed, follow the sequence below for storage.
- Wash the electrode and reference junction in de-ionized water.
- Close the refilling hole by returning its rubber sleeve or stopper cap.
(Necessary for only refillable electrode).
- Store the electrode as mentioned above (see section Storage).
Operation manual MRC.VER.01-02.10