PC1021 swimming pool water quality tester. You must prepare a 1.5 ppm chlorine solution, the purpose of inspecting your pool water2. If you are at 1.5ppm chlorine level or not (don't know if it is or can't find the calibration point), please use the traditional test strip3. Once you are satisfied with your calibration, you do not need to recalibrate unless you change the measuring pool to use a different pool water. A brief description: The design of the tester is suitable for swimming pools or SPAs family ratios (excluding salt lake water pools, industrial or scientific use). After the first successful calibration, you can test the chlorine and acid-base levels of your pool water in a quick and easy way. Therefore, there is no need for complicated and messy "traditional liquid chlorine and acid-base combinations"! With this handy tester, you can quickly test whether your chlorine and pH are within the ideal range of 7.8: chlorine 1.2 1.7 ppm and pH 7.2 lied. If your test results are beyond this range, please leave you a useful information and a corresponding pool that adapts to chlorine, acid and alkali. It is definitely a great tool you may need to keep pool water. Specification: The recommended chlorine level for swimming pool and SPA is 1.2, 1.7 ppm It is recommended that the level of chlorine the swimming pool and SPA PH is 7.2, 7.8Size (CM):Host: 190 x 120 mmProbe with handle: 150 mm long Probe (only): 48 MM long (black strap not included in supply) Cable (only): 130 mm long Power supply: 1 x 1.5V AA alkaline battery, does not contain Weight: 160g (without battery) Note: The data is all measured manually, please allow 1-3cm error, due to the difference in light and display, there will be a certain color difference, the actual item received shall prevail.