Single-range pocket TDS tester, 1 point calibration, suitable for measuring total dissolved solids in pure water, range 0.5 to 100.0 ppm.

Single-range pocket TDS tester, 1 point calibration, suitable for measuring total dissolved solids in clean water, range 5 to 1000 ppm.

Single-range pocket TDS tester, 1 point calibration, suitable for measuring total dissolved solids in natural water, range 0.05 to 10.00 ppt.

Multi-range pocket TDS tester, 1 to 3 points calibration, selectable TDS conversion factor, setup menu contains 5 options, range 0 to 20 ppt.