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 I've been led to believe tells me to calibrate the meter to 1500ppm when using this solution. That's certainly what Einstein told me to do.

However, when I got it home and started using it, it certainly appeared as though it was terribly out of scale, compared to two other reference meters that I use. I eventually became so concerned at the apparent discrepancy between devices (both Oakton) that I called the company's support department to ask for some hand-holding through the calibration process.

Rude awakening #2. The 1500 calibration scale that I and all my cronies so blithely use and assume to be correct is for the NaCl scale, and should only be calibrated to that point if the solution you are measuring is the same. NaCl, for those of us who found Chemistry slightly beyond Wood or Auto Shop, is Sodium Chloride. Salt. Brine, to be more specific. When pressed for my application, hydroponic nutrient measurement, his immediate response was that I should be using the 442 scale to calibrate with, as it is more of a brackish water scale, in line with what I am measuring.

This has two immediate ramifications for me, if it is factual! and that's still a big IF, because, this would seem to mean that I have been far out of calibration with my nutrients for a long time. Specifically, if I have been calibrating my meters to 1500ppm using a calibration fluid that rightfully requires me to calibrate to 2190ppm instead, just what have the values actually been that I have been watering with for so long?

And does any of this really matter? Are we talking about values that are so small to begin with, 600 or 700 parts per MILLION, fer crying out loud, that it's immaterial. Is this just another example of how amazing this plant is in being able to take a tremendous amount of abuse and keep on keeping on?

Or does anybody out there really know if there's something to this different scale business, and I (we) should be looking at how we calibrate our TDS meters differently somehow?

If so, I'm going to be returning a bottle of Calibration Solution that our erstwhile young entrepreneur managed to foist off on me as suitable for my TDS meter. As the meter maxes out at 1999ppm, it's not even able to be calibrated to the 2190 that, supposedly, it should be for all of the purposes that it is sold for at the store I purchased it at.

Anyway, I'd like to hear what any others have to think about this.
DrBoomBoom Reviewed by DrBoomBoom 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