It is essentially the same thing.so looks like i need to get a tds meter too, is this a must?
thanks so i take it you can calculate the tds from the other readings.It is essentially the same thing.
EC=Electrical Conductivity
PPM= Part per million, calculated either by ECx500, ECx640, ECx700 depending on the brand of meter you buy
TDS=total dissolved solids, http://en.wikipedia.org/wiki/Total_dissolved_solids
You really only need to measure one of these, i prefer EC because it is a universal rate and doesnt fluctuate based on brand of meter.