Chad Westport
10 minutes
TDS Meters Convert Conductivity to ppm Using a 500 or 700 Scale
TDS pens measure EC and multiply by a factor: \( \text{ppm} = \text{EC (mS/cm)} \times 500 \) on the NaCl scale or \( \times 700 \) on the 442/KCl scale. So EC 1.6 reads 800 ppm on one pen and 1120 ppm on another.