Calibrating TDS meter?
Okay, I'm super confused now. I bought an inline TDS meter for my RO filter and a new handheld meter (Aquapro) to replace my TDS-EZ after it began to show 1-2ppm without being submerged in anything (I think the whole thing accidentally got dunked under water, which is why I opted for the water resistant Aquapro to replace it).
I also bought the 342ppm calibration fluid. My old TDS-EZ reads it as 407ppm. My new "factory calibrated" Aquapro reads it at 416ppm. The inline meter (also "factory calibrated") reads this fluid at 558ppm!
Should I recalibrate any of these? I thought if nothing else the calibration fluid would assure me they were accurate, but now I'm less convinced.. all of them say they shouldn't need calibration out of the box. The TDS-EZ is only a few months old (purchased in October).