You can choose between 2 diff. types:
- an EC-meter, that measures electric conductivity in the unit MicroSiemens (µS).
- a TDS-meter, that measures total dissolved solids (TDS) in ppm (parts per million
A TDS meter and an EC-meter is the same device, they just show different
units. TDS meter and an EC meter both measures the water's electrical
conductivity. Total Dissolved Solids (TDS) is the number of charged
ions (minerals, salts and metals) that is dissolved in a given quantity of water
expressed in mg/l, also referred to as parts per million (ppm).
HM Digital uses in TDS-meters a
calibration, that converts from µS to the unit for a TDS-meter: ppm
with factor 2, that is:
1ppm = 2µS (maybe not true for other manufacturers)
It is recommended to buy a meter to check the water in different situations. You
can see how well the filter and membrane are working, and thereby evaluate, when
it is time to change or membrane filters.