Electrical Resistance of Water

Plumdog_2

what is the relationship between "hardness" and electrical resistance thru water? I'm looking at a liquid level control device that uses probes and an inductive coil (to physically seperate line voltage from the water). The specs show a wide range of resistance thru different liquids; distilled water having very much more resistance than soft water, for example.
Would it be possible to measure resistance and determine hardness? Or relative hardness? The ohmeter creeps towards 39.9 slowly and then pops back to zero.

bobbyg_2

Page 7 of this link shows the relationship.

http://www.mcdonnellmiller.com/prod/Products-LiquidLevel.pdf

Hope this helps!

Plumdog_2

Thanks

the TDS tester is key. Everyday something new.

Bob Harper

electrolytes

When you add minerals such as sodium to water, they act as electrolytes providing ions to conduct current. Same with humans. Water with 0.9% NaCl is isotonic with human blood. FYI, when paramedics defibrillate people, they figure on a 50 Ohm load across the chest but adjust for size.

One measure you may consider when checking for impurities in water as an indicator of hardness is specific gravity. Just as with battery testers (hydrometer), pure water is referenced at 1.0 . A sp. gr. higher than this means the substance will sink while one with a lower sp. gr. will float, such as oil spills. It is also an indicator of concentration. When you don't pee all day, your concentrated urine has a higher sp. gr. than if you've been drinking lots of water. You may find some dipsticks that do what you want. Check lab suppliers. That brings up what is soluble versus insoluble in water such as oil.

To test the water hardness, check with a swimming pool supply co.

HTH,