The Rapid RH Digital pH Meter comes with calibration solutions that enable you to calibrate the pH sensor before each use. Place deionized water on the concrete for a set amount of time. The probe is then placed on the water spot and will gather the pH readings. Thoroughly clean the probe before putting it back in the case for storage.
For complete instructions on how to use the Rapid RH Digital pH Meter, please download the manual at: https://www.wagnermeters.com/shop/rapid-rh-digital-ph-meter/