Short answer: pour a little calibration standard of known value, commonly 1.41 mS/cm, into a clean cup, dip the rinsed probe, and set the meter to match the standard's value (Oklahoma State University Extension). Then rinse the probe again. Why calibration matters...
Short answer: multiply EC in mS/cm by 500 for the 500 scale, or by 700 for the 700 scale. An EC of 1.2 mS/cm is 600 ppm on a 500-scale meter and 840 ppm on a 700-scale meter (Bluelab). Why there are two scales PPM meters do not measure parts per million directly. They...
