The meter has been used for a long time since the last calibration or use. The meter has been used under particularly continuous conditions. Do not press the button for long "Temp / Cal" at ordinary times, otherwise the meter must be recalibrated. The water quality monitor is a professional and useful tool for testing the level of the PH / EC / TEMP solution / TDS It looks like a pen, which is perfect for transport. Excellent for various use, such as drinking water, aquariums, laboratories, water quality control, swimming pools and so on. Range pH: 0.00 ~ 14.00 PH. EC: 0-1999 us / cm 0-19.99 ms / cm. TDS: 0-1999 ppm 0- 19.99 ppt. Resolution Temperature: 0 to 50 C. PH 0.01PH. CE: 1 us / cm (& lt; 1999 us / cm), 10 us / cm (& gt; 1999 us / cm), 0.01 ms / cm. TDS: 1 ppm (& lt; 1999 ppm), 10 ppm (& gt; 1999 ppm), 0.01 ppt. Temperature: 0.1 C. Accuracy pH: 0.02 PH. CE: 2% FS TDS: 2% FS. Temperature: 0.5 C. Compensation Automatic temperature: 0 C to 50 C. Battery type: 3 1.5 V (AG13). Operating temperature: 0 C to 50 C. Calibration: two point (4.01, 6.86) or one point (6.86) calibration Automatic shutdown: after 8 minutes Dimensions: 188 x 35 x 35 mm. Weight: 98 g.