Seaside Aquatics Salinity/Temperature/TDS Digital Pocket TesterSame as most digital meters, this meter apply a work theory which is measuring the liquid conductance to determine its TDS TEMP Salinity value. Compared with regular digital meters, this one measure the frequency of input probe rather than measure voltage or current of probe to measure the conductance, and the probe use copper with platinum plating, by this way, minimize the polarization and platinum plating probe is pretty stable and fit for food