Waterbear;

You need to work up an account of the calibration process that you can post everytime somebody starts dreaming about all-electronic testing. People get tired of hearing it from me, but they also forget that 'all-electronic' testing STILL has to have a wet-end somewhere!

I was gullible enough, years ago, to sail to the that 'all-electronic' siren song, wasting a lot of time and money on the way.

I finally threw out some old boxes of useless (!) Hanna ORP, pH and TDS meters, replacement electrodes of various types, and several flavors of ORP and pH controllers. Some ORP controllers have a valid place in commercial operation . . . but Hanna Instruments' products? -- faugh, a plague upon them!

Ben