Introduction to the Steps and Methods for Calibrating a pH Meter
1. Laboratory pH meter | Acidity meter calibration:
When calibrating commonly used laboratory pH meters, the slope of the instrument should be adjusted to the maximum and the rubber plug on the upper part of the electrode should be opened to expose the small hole. Otherwise, negative pressure will be generated during calibration, which will cause the solution to not perform ion exchange properly and result in inaccurate measurement data.
Remove the electrode from the beaker containing distilled water and use filter paper to absorb any remaining distilled water on the electrode. Then put the electrode into the beaker with the mixing phosphoric acid basin, wait for more than 15 min, and then adjust the positioning knob on the instrument to make the instrument display 6.86 pH. This is the first time to set the reference point for the instrument. After setting the reference point, take out the electrode from the beaker containing the mixed phosphoric acid solution, wash the electrode with distilled water, and place it in the beaker containing distilled water. Wait for about 3 minutes to dissolve the residual part of the mixed phosphoric acid solution.
2. Later, remove the electrode from the beaker containing distilled water and use filter paper to absorb any remaining distilled water on the electrode. Then place the electrode in a solution containing potassium hydrogen phthalate or borax, wait for more than 15 minutes, and observe whether the instrument displays a pH of 4.00 or 9.18. If not, adjust the slope knob on the instrument to display a pH of 4.00 or 9.18, which is the commonly used two-point calibration. If three-point calibration is required, simply repeat the same steps for the other solution. This is the calibration method for acidity meters.
3. After calibration, insert the rubber stopper back. If not in use temporarily, remember to fill the protective cover of the electrode with a saturated solution to keep the electrode moist. This can extend the lifespan of the electrode and reduce its asymmetric potential. Electrodes have a lifespan and are fragile, so laboratories need to replace them frequently. Don't think that just because the electrodes are not damaged during use, they won't be replaced.
