TDS Meter Calibration Issues

[Help_Needed]

Mine is their TDSTestr Low, which is still pretty basic. All I know is that I've been using the same GH calibration and calibrating it to 1500ppm. If it's really a 0.7 conversion, that explains a lot.

I've mainly been seeing Mg deficiencies in mid-late flowering. I'm using the Lucas formula, and I know Lucas has stated that the Mg deficit is usually the first to show when your concentrations aren't high enough, since the formula has *just* enough Mg for the needs of the plant. The LF recommends a nute concentration of ~950ppm @0.5, and ~1330ppm @0.7. I had my white widows on my most recent grow running between 1050 and 1100 (on my meter, whatever it actually is lol) throughout almost the entire grow, and WW is supposed to be fairly nute sensitive. If my meter is really a 0.7 conversion, that explains why my widows liked the concentration so "high".

[PlantHeadJ]

Ok my meter is .5 conversion...What the hell does that mean? I never new there was a diff. Shucks hope someone can tell me if my ppm's are too low because it's a .5? Thanks.