[NAFEX] pH Soil Tester

Jwlehman at aol.com Jwlehman at aol.com
Thu Feb 7 20:54:25 EST 2008

In a message dated 2/7/2008 9:06:28 AM Eastern Standard Time, jfruth at tds.net 

> The thing that works best for cleaning/polishing the soil probe is a Scotch 
> Brite pad, like the one that comes attached to one side of many cellulose 
> dish-washing sponges.  It is easier to use if you just get the Scotch Brite 
> sans sponge.  The best time to take your readings is right after a soaking 
> rainfall or, like I do, I use distilled water to saturate the soil before I test 
> mine.

Do not use sandpaper. That is a very course abrasive and will scratch off the 
special metal alloy coating on the shaft, and once that happens your readings 
will not be accurate. 

Mine did come with operating instructions, then experience via experimenting 
to use it helped. It also helped to understand how it works. That wasn't part 
of the instructions. 

How the thing works is the tip is one alloy that reacts with acid to generate 
a very slight voltage similar to a wet sell battery. The shaft is another 
alloy that generates a voltage of the opposite polarity. Then depending on the 
acidity the meter reads the developed voltage and polarity and the meter is 
calibrated in pH, not microvolts. The metal shaft and tip will not produce a 
sufficient voltage or none at all if oxide is coating the surfaces. Like wise if 
the soil is too dry or other problems that block voltage development. But when 
one gets it right they work great!!! 


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