The AquaFX Handheld TDS/TEMP Meter is highly efficient and accurate due to its advanced microprocessor technology. TDS measurement range: 0-9990 ppm. From 0-999 ppm the resolution is in increments of 1 ppm. From 1000-9990 ppm the resolution is in increments of 10 ppm (indicated by a blinking x10 image). Features an integrated digital thermometer with a temperature range of 0-80 degrees Celsius, a hold function that saves measurements for convenient reading and recording, an auto-off function that powers down the meter after 10 minutes of inactivity, and a large and easy-to-read LCD display. Includes a vinyl carrying case with belt clip. Calibrated with a 342 ppm NaCl solution. Can be recalibrated with a mini-screwdriver. TDS Range - 0-9990 ppm (mg/L), Temperature Range - 0-80 degrees Celsius, Accuracy: +/- 2%, Conversion Factor - NaCl (avg. 0.5), Power Source - 2 x 1.5V button cell batteries (included), Battery Life - 1000 hours of usage.