*Ph probes require periodic calibration to ensure users continue to obtain accurate pH measurements. OF calibration solutions pH 4 & pH 7 are specifially made to allow users to calibrate their probes to the highest possible accuracy.

*Calibration should be performed with at least two standard buffer solutions. As pH 7 is essentially， a "zero point" calibration (similar to zeriong a scale or balance)， calibration at pH7 followed by calibration at pH4 as the second point of reference will enable users to perform a more accurate two point calibration.

*Direction of use:

• Rinse probe in clean water and briefly shake dry
• Switch the pH meter on
• Fill provided measuring cap with OF pH 7 until it reaches the 20ml mark
• Submerge the probe in the pH7 solution until touches the base of the measuring cap and do required calibration
• Rinse probe again in clean water and briefly shake dry
• Fill provided measuring cap with OF pH 4 until it reaches the 20ml mark
• Submerge the probe in the pH 4 solution until it touches the base of measuring cap and do required calibration.