081211-1129 EST
Some comments on water conductivity. Currently our air is quite dry and many years ago I gave up on furnace humidifiers. I am use an ultrasonic room type unit now, and also a big pot on the stove.
I really need to use pure water in the ultrasonic unit to avoid calcium dust on everything.
I am not sure of the calibration factor for my test probe, but I am guessing at 10. The resistance measurements are at 1 kHz and the probe capacitance in free air is about 34 pfd including the leads. In distilled water it is about 117 pfd and D=20.
The resistivity measurements are:
800,000 ohm-cm for distilled water
90,000 ohm-cm for recent rain water
44,000 ohm-cm for recent snow water
1,400 ohm-cm for room temp tap water
170 ohm-cm for boiled and hot --- may be about a days worth of cooking and refill several times
310 ohm-cm for the same water but at room temperature
85 ohm-cm after another day's worth of cooking and at room temperature
An interesting reference on water purity:
http://www.lenntech.com/deionised-demineralised-water.htm
Thus, it looks like my grocery store distilled water is what might be expected for ordinary distillation.
My resistivity measurement of tap water would be useful in the discussion with the person and his horse watering problem, but he has not responded with more information. Critical to that discussion is what is the voltage variation from different points in the water in the bowl to the wall of the stainless bowl. My off hand guess it is near zero and the problem is really the voltage between the earth and the bowl.
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