Tester 2 in 1 Water pH and Chlorine Level Portable Digital pH Meter Pool Spa Analysis Instrument, 190 x 120 mm 1. You both need to prepare a 1.5 ppm chlorine solution for pool water testing2. If your chlorine level is set at 1.5 ppm (unsure or unable to find the calibration point), use conventional test strips 3. Once your calibration works for you, you do not need to recalibrate unless you change the measuring cell to use a different cell water. Brief Description: The Risepro tester is designed for swimming pool or spa home scale (excluding salt lake swimming pools, industrial or scientific use) After the first successful calibration, you can quickly and easily test the chlorine and acid-base levels of pool water. So, with this practical tester, no more complicated and confusing "traditional liquid chloric acid-base sleeves", you can quickly test whether your chlorine and pH levels are within the ideal range of 7.8: chlorine 1.2 1.7 ppm and PH 7.2 lies. If your test results fall outside this range, you have a useful piece of information to adapt to the corresponding chlorine and acid-base pools. This is definitely a great tool you may need to keep your pool water. Specifications: Recommended chlorine levels for swimming pools and spas are 1.2, 1.7 ppm Note: Manual measurement, there may be 1-2cm/1-3g error, which is not a quality problem. Due to different screen displays, there may be a color difference between the real object and the picture. Quantity: 1