ive recently purchased a so called EC/TDS/PPM meter and purchased a bottle of ionic conductivity standard reading 2.76 MS/CM. Simple so now i follow the instructions i got with my meter which is one with a srewdriver adjustment on the back to calibate it, now this is the confusing part. are we ready so i turn my meter on it shows three zeros with the one in front slightly more over i pressume this is a decimal point yes still with me i hope, i dip it in my water and it reads 080 and my meter tells me the measuring range is 0 to 1999 US/CM and the resolution ? is 1US/CM the u is shown back to front on the instructions so this is where im confused. but wats worse i put it in the ionics conductivity standard and it reads 1640 odd, now what i wanted to no was PPM and TDS so i tried finding a chart to convert the us/cm reading on my meter as i cannot go down to this number in fact no were near this number while the meter is in the solution, so now ive found a converting chart and it has everything but US btu other things with s like S/cm mS/cm AND microS/cm so i assume its one of these three. SIEMENS WHICH STANDS FOR THE S IS A UNIT OF THE ELECTRICAL CONDUCTIVITY. THE CONDUCTIVITY OF WATER IS MEASURED WITHIN A CERTAIN DISTANCE THUS THE INPUT IS IN S/cm or mS/cm.OTHER CONDUCTIVITY UNITS ARE Mho cm ,CF in (America and Australia) en EC. The term EC IS USED AS A GENERAL TERM FOR ELECTRICAL CONDUCTIVITY ON SOME CONDUCTIVITY METERS THE ACTUAL CONDUCTIVITY IS PRESENTED IN EC UNITS WHERE 1 EC CORRESPONDS WITH microS/cm still with me, so i type in 2.76 on the converter hoping ill figre it out when it shows what 2.76 mS/cm the conductivity standard, with the readin on my meter of 1640 something, the results were: S/cm 0.00276 mS/cm 2.76 microS/cm 2.76e+3 mS/cm 1 EC 2.76 CF 27.6 mho/cm 0.00276 mho/m 0.0000276 ppm/TDS 1.77e+3 which isnt really helping me atall the thing is doing my head in and all i want to no is when i start my hydro again how much nutrints is in the reservoir which is not as simple as i thought. can anyone tell me if they no what ineed to do. ive found more instuctions that tells me i need 1413 us/cm calabration fluid can anyone kindly help