Water Quality Test Pen - Purpose: TDS meter tester to assess filter water quality and purity. Helps you drink safe and pure water and protect your health. - Hold function: locks the readings for convenient reading and recording. Provides quick measurements, taking about five seconds per reading. - Automatic temperature compensation: maintains accuracy as temperature changes. Includes a temperature unit switch between Celsius and Fahrenheit for easy viewing by different users. - Sensitive probe operation: press the switch and submerge the probe in the water to be tested. A lower TDS value indicates fewer dissolved solids and higher water purity; the purity level is visibly reflected in the reading. 2-3 practical use scenarios - Home use: verify the quality of filtered drinking water from a pitcher or faucet to ensure safety and purity. - Travel or remote locations: quickly check water quality when using water from hotels, public sources, or unfamiliar bottled options. - Filter maintenance: monitor TDS before and after replacing filter cartridges to assess filter effectiveness and determine when replacement is needed.