Direct reading pH meter:

1. Put on the selector switch to suitable pH range (0-7 for acidic or 7-14 for basic solutions) and adjust set buffer knob in manner that the pointer reads the pH of the standard buffer solution (placed in the beaker).

2. Put the selector switch back to zero position.  Remove the electrodes from the buffer solution and wash the electrodes along with distilled water and after that wipe them gently with tissue paper.

3. Immerse the electrodes in a second buffer below pH 10, around 3 pH units various from the first one; the reading should be inside 0.1 units for the pH of the second buffer. (0.1 pH unit from expected value seems for trouble along with the electrodes or ph meter if the meter response shows a difference greater.

4. Transport the standard buffers back to the storage bottle and wash the beaker well with distilled water.

5. Take the sample solution in the beaker. Begin the electrodes within the solution and swirl it gently.

6. Set the selector switch within the suitable range position and read the pH on the scale.

7. Put the selector switch back to zero position.  Remove the electrodes from the solution, wash them with distilled water and keep the electrodes in distilled water, while not in use.

Figure:  A direct reading pH meter (front view) legend:

I. On/off switch  II. Set zero    III. Selector   IV. Electrode support V. Temperature compensation     VI. Set buffer       VII. Meter