Oakton Waterproof TDSTestr 11 Plus Pocket Meter, 0 to 200 ppm; 0 to 2000 ppm; 0 to 10.00 ppt TDS Range Pocket-sized total dissolved solids (TDS) tester that floats for use in a tank or pond Automatic temperature compensation, single or one point per range calibration Low battery indicator and error messages Replaceable sensor with stainless steel electrodes Waterproof and dustproof, with IP67 ratings