HM Digital AP-1 + 1382 ppm Solution, AquaPro TDS/&ordm;C/&ordm;F Meter/Tester/Thermometer Measures total dissolved solids (TDS) and temperature. Automatic Temperature Compensation (ATC) * Water-resistant housing Measurement Range: 0-5000 ppm * Digital Calibration (push button) Auto-off function, data-hold function and low-battery indicator. Display: large and easy-to-read LCD screen includes simultaneous temperature reading.