Ok....I have no clue what you just said.....but I have an oakton tds basic and I asked my hydro guy (whom I would trust with my firstborn) what to calibrate it with and he told me 1500/tds solution (which is what he then sold me). I unscrew the little top and press the buttons to calibrate. I've never had a problem with it and I've been using it for a couple months now.

That's my story and I'm sticking to it.
Weedhound Reviewed by Weedhound on . TDS Meter Calibration Issues I'm hoping that there are some really smart folks out there that can help me understand something of the world of meter calibration. After making my purchase of an Oakton TDSTestr11, I asked the young genius behind the counter for an appropriate calibration solution, for which he hands me General Hydroponics Standard Calibration Solution. Here's where the confusion starts, as the package indicates that it calibrates to 1500ppm (NaCl), 2190ppm (442), and 2930S (microSiemens). So everything Rating: 5