I have a TDS meter and I would like to calibrate it so I can verifiy my 4dkh drop checker solution. I want the tds meter to be as close as possible to the actual result. Normally I wouldn't bother calibrating it because I'm usually only interested in TDS deltas rather than the true figure.
My NaCl calibration fluid has mostly evaporated leaving inaccurate results. I need to get more, but I don't want to pay for it. I have aquarium salt and Morton's table salt. Using aquarium salt, or deionized seems to be the way to go. I have a gram scale and 50 mL graduated cylinder to make the solution.
Now just going over this in my head, since the TDS meter reads both positive and negatively charged ions, 1 mg of NaCl in 1L of water should raise the TDS by 1...is this correct?
so if I add 500mg of NaCl to 1L of water the TDS should be 500?