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PH Meter

Posted by garf 10b/Fla. (My Page) on
Tue, Oct 5, 10 at 16:49

I have a unit labled pH computer by Accutronics. It is a cheapo 2 prong unit. There are no instructions, just a scotchbrite pad to clean the prongs with. When I first insert the prongs into the soil, it will usually peg the meter then slowly settle down to a reading. Doesn't seem right. Anyone have experience with the 2 prong type meters?

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RE: PH Meter

  • Posted by ericwi Dane County WI (My Page) on
    Wed, Oct 6, 10 at 11:54

I don't own or use a "two prong" pH meter, but I do test for soil pH, using a handheld Hanna Instruments pH meter, the kind with a glass bulb, and calibration pots. This meter can be calibrated using any aqueous solution of known pH, for example, orange juice, vinegar, household ammonia, tap water,...whatever you have available. My understanding is that "glass bulb" type pH meters are ion specific, that is, they sense the concentration of hydrogen ions, which directly correlates with pH. I would guess that metal probe type pH testers are measuring a voltage generated when corrosion takes place on two dissimilar metals. This voltage will change as pH varies, but it can also sense the presence of corrosive salts, like sodium chloride. I don't think that these units are ion specific. The results might be accurate, or they might not. I would try to calibrate the meter using 5% white vinegar, the kind they sell in the grocery store. It should indicate pH around 3.5, and tap water should be around 7. If you have hard water, the pH might be around 7.5.

RE: PH Meter

I got a two prong meter at a yard sale for 25�. I couldn't see any relationship between the readings and pH but it was most useful to determine when houseplants needed to be watered. VBG.

Play with it a bit just for fun.

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