The pH meter is calibrated to accurately measure pH . Three standard buffers ( 7, 4, 10) are used for this purpose. First the pH prov has to be cleaned with distilled water. The pH meter is then standardized with buffer- 7 solution and rinsed again. In the same process, pH meters need to be standardized for buffer 4 and 10 , respectively. This is how the pH meter is calibrated with the help of buffer solution and prepared for reading.