“EC” stands for Electrical Conductivity. Electrical conductivity is defined as the ability of a substance to conduct an electrical current. Conductivity in a solution is directly proportional to the concentration of salts. Conductivity is temperature dependent and will rise in proportion to a temperature increase.
EC is recorded in mS (milliSiemens) or µS (MicroSiemens).
1 mS = 1000 µS
TDS (Total Dissolved Solids) is a proportion of EC and is usually recorded in ppm (parts per million). Three common proportion multiplying factors are: 0.7 (hydroponics), 0.64 (soil science), and 0.5 are used to convert EC to TDS. For example, if the measured EC is 1000 µS, this can be converted by multiplying it by 0.7 (hydroponics) which equals 700 ppm.
Four-ring conductivity probes utilize a potentiometric approach to measure EC. An alternating current is applied to the outer two “drive” electrodes to induce a current in the solution. The voltage is measured between the inner pair of electrodes in solution. The voltage is proportional the conductivity of the sample. This technology extends the linear range of measurement, and reduces polarization effects.
The four-rings in the HI76310 are made with platinum and the body of the electrode is made of Polyetherimide (PEI) plastic that is resistant to many harsh chemicals. The four-ring design allows for this probe to be used over a wide range of measurements.