Combo Meter for EC Conductivity, TDS and Temperature PPM PPT uS mS C/F Pen-type 1-Pack with Pouch Measures electrical conductivity (EC): 0~1999 S ; 0~19.99mS Measures total dissolved solids (TDS): 0~1999 ppm ; 0~19.99ppt Automatic Temperature Compensation (ATC) Water Resistance Housing Ideal for all water quality testing, water purification applications, wastewater regulation, aquaculture, hydroponicsnics, colloidal silver, labs & scientific testing, pools & spas,ecology testing, boilers & cooling towers, watertreatment and more.