HM Digital TDS-3 Handheld TDS Meter with Carrying Case Hold Function: Saves measurements for convenient reading and recording Highly efficient and accurate due to its advanced microprocessor technology. Measurement Range: 0-9990 ppm From 0-999 ppm, the resolution is in increments of 1 ppm * From 1000 to 9990 ppm, the resolution is in increments of 10 ppm, indicated by a blinking 'x10' image