PORTABLE DESIGN: Portable pen and compact case, easy to store in your pocket or bag or anywhere. Auto Calibration: Calibration can be completed by pressing the auto calibration button without any calibration (no calibration powder/liquid) ATC function: automatic temperature compensation, which can automatically solve temperature changes. Lightweight and easy to carry. Ideal for home and laboratory pH testing applications including drinking water and swimming pools. , aquarium, hydroponics and more. Widely used in: pure water production and consumption, electroplating solution, boiler water, aquarium water, pool water, photographic hunting well water, deep water, laboratory, aquaculture, food processing.