Hi Bob and Dan, When I try to measure CS with a DC ohm meter it acts like either a capacitor or a battery which makes sense. I've got two electrodes in an electrolyte so it is either charging or discharging through the meter (which is supplying current to make the measurement). Just the process of making CS is charging up the "battery" so current restart Bob mentioned makes sense.
Measuring the AC impedance rather than the DC resistance (as Ole Bob suggests) would also seem to make more sense. I would assume that the commercial units with automatic shutoff are measuring current by using a voltage divider and a comparator. When a set value is reached they turn off. I doubt that they measure the initial starting current and adjust for variations of DW conductivity. Of course, if the generator runs on a timer, it's probably garbage. Good questions to ask the manufacturer if they provide an "auto shutoff feature." Ole Bob - Just out of curiosity, what kind of variations are you seeing between batches when you try to keep everything exactly the same? Best Regards, Andy From: Robert Berger Hi Dan, With our posteriors exposed we find that when using a DC ohm meter it is necessary to swish the electrodes in short rapid strokes to keep the reading from climbing. Generally when measuring a resistance of a liquid or soil it is done with an AC ohmmeter and preferably one running at 180 Hertz or faster. The commercial units do measure conductivity to determine when the proces is finished. The generators will not start if the conductivity of the DW is above a certain limit. Are you enough of a computer "geek" so that if I sent you off line a program Wplot32.exe that you would install it on the desk top, and then create a file folder "My wplots" under "My documents" to store some files that I would send to you? If you could I would like to send you some data plots of runs that I have made so that you can see some of the strange things that go on with this process. First offf the conductance changes with time i.e. at the end of a run it might be 75 uS/cm and24 hours later if might be 40 uS/cm. If you stop a process for several minutes to wipe the electodes then the current on restart will be 20 to 30% lower. In fact just stopping for a minute and restarting without doing anything and the current readings will drop. "Ole Bob"
