ATC FUNCTION: The multi-function test pen OW-100 measures salinity, TDS, EC, and temperature, with simultaneous temperature display on the LCD. Features automatic temperature compensation (ATC). LCD DISPLAY: Large, easy-to-read LCD screen with two-line display and backlight. Designed with a scientific and ergonomic structure. 4 IN 1 MULTI FUNCTION: A fast, efficient, accurate, and portable test pen that combines salinity, TDS, EC, and temperature measurement to meet various testing needs. WIDE APPLICATION: Suitable for use in aquariums, aquaculture, laboratories, chemical processes, food brewing, water purification, swimming pools, and educational institutions. ENVIRONMENTALLY FRIENDLY ABS: Constructed from high-quality ABS material, offering durability, impact resistance, scratch resistance, and environmental safety. Item Type: Water Quality Meter Model: S-100 Battery: 3 x LR44 (not included) Material: ABS Uses: Suitable for aquariums, aquaculture, laboratories, chemical processes, food brewing, water purification, swimming pools, and educational institutions. Basic Parameters: Measuring Range: Salinity: 0.00–25.00% / 10.1–200 ppt TDS: 0–10000 ppm / 10.1–200 ppt EC: 1–10000 μs/cm; 10.01–19.99 ms; 20.1–400 ms/cm Temperature: 0.1–60 ℃ Package Includes: 1 x Water Quality Meter 1 x User Manual