Fangrui Product Details How To Calibrate The Orp Meter:1. On/off Button To Turn On The Meter, The Protective Cap And Rinse Off The Probe With Pure Water And Dry It. 2. The Mode/cal Button To Set The Orp Mode; The Word Mv Be Displayed At The Top Right Of The Screen. Put The Probe Into 222mv Calibration Solution And Shake It Gently. 3. Wait Until The Reading Is Stable, Then Long Mode/cal For 5 Seconds And Release; Cal Is Displayed On The Screen, Then A Value Flash 3 Times On The Screen, When The Value Starts To Fiash, Mode/cal Button ( Lf The Flashing Value Is Higher Than 222mv ) Or Hold/temp Button ( Lf The Flashing Value Is Lower Than 222mv ). 4. After Adjusting The Displaying Value To 222mv Then Release The Button, Waiting The Reading Stop Flashing,the Calibration Is Finished, Rinse Off The Probe With Water. Storage: Buffer Solutions Should Be Stored In A Dark, Cool Place (not In The Refrigerator And At Temperatures No Higher Than 25c) Away From Direct Sunlight To Prevent Photochemical Degradation. In Addition, Buffer Calibr