Does anyone have suggestions for a good quality PH meter.......Digital or analog meter, doesn't matter, provided that it is reliable. The one I got from my local garden center reads 7 for all areas of my garden. I knew it was a dud when I placed it in pure lime juice, and it still read a PH of 7.
Any ideas would be greatly appreciated.
Deight.
All the meters that I know work on the same principle - bascially, they read the electric potential between two parts (metals) of the shaft, or the electric potential between two side-by-side different-metal shafts, using the soil. Ph 7 is no potential (zero voltage).
It's a very small potential, and there has to be enough of a current flow in the meter bridge to register. The oxide on the metal and/or the lack of fluid in the path both reduce the flow available for the meter. However, too damp soil or a dirty insulator, and the path is primarily in the fluid/dirt on the insulator instead of primarily through the meter.
First, you need to wipe the stem clean before using, but not damage it or smear metal or dirt across the insulator separating the two metals. Wipe off the crud at the insulator with a wet kleenex, wipe dry, and then use a dollar bill or brown paper toweling to remove the oxides right before reading. Turn around the shaft to wipe it, rather than wipe along the shaft.
Second, the soil needs to be damp but not wet. The meters don't read mud well. City tap water has a ph around 8.4- 8.7, depending on the time of year, so if you put it in the soil with tap water, you can read higher ph than the soil. I read a day or so after a rain (NOT sprinklered), or I put a few drops of distilled water in the soil and mix it up before reading.
Third, if you don't get a reading, the soil is too dry, too wet, the probe is dirty, or the meter is broken..
So wipe it per above and dampen the soil with distilled water, and if it still won't read, then test it by wrapping it with a damp napkin sprinkled with baking soda (ph about 9-10) - and then clean it and test it again using a napkin dampened with vinegar, soft drink, or beer (ph 3-4). If it doesn't read a damp napkin, take it back to the store with a damp soil sample, and get one that works on the sample.
fwiw
AFAIK there aint no such animal except in a laboratory. The little portable probe ones rely on the moisture in the soil to get a reading and since that is not constant they are unreliable. I recommend a dye indicator test kit. These are cheap, easy to use and reliable. IIRC lime juice is about pH 3 or
4 so take it back for a refund.David
Check out this site for pH meter and pH measurements details:
The soil type pH meters are not accurate in most situations. You should get a real pH meter (Daigger has good prices) or some soil test kits. If you get a pH meter, you need a calibration standard too. You can mix your soil with about 2x amount of water thouroughly, let the soil settle, and measure the pH of the water.
real pH meter (Daigger has good prices) or some soil test kits. If you get a pH meter, you need a calibration standard too.
Calibration procedure in details:
As described here:
Mr.pH
Get one of the test tube tests, more accurate.
Fast, cheap, and more than accurate enough for gardening: pHydrion paper.
Interesting site. How is it relevant to the original question? Are there any glass electrode portable systems suitable for use in the garden? How much do they cost? For garden or agricultural purposes why would you need accuracy down to decimal points of a pH unit?
David
Although the site is somewhat user hostile, there are explanations of pH strips and pH papers/indicators. Plus, I see no reason a 'pen' or probe type device couldn't be used in a soil slurry or other very wet, soil derived solutions. And it IS likely, especially given the difficulty of soil testing as provided in the other ratehr good link, that decimal point accuracy means little - but if it comes along with an inexpensive, convenient, long shelf life piece of test equipment, I see no problem with that. Some folks may find a way to use a pen or probe for multiple duty - soil, tropical fish, pond, etc.
Carl
Bottom line for me - I have two portable probe-type "garden-style" ph meters - neither works in water (tried them for fish tank, tap water, boiler water, etc.), but both work just fine in moist mediums.
Why is that? I believe the reason the portable non-battery probes don't work well in fluids is for the same reason they don't work with well with a dirty probe - Using a dirty probe defeats the insulator because it provides a current path across the insulator, just as immersing the probe in a conducting fluid defeats the insulator because it also provides a path across the insulator.
---------- As I said, the portable types (without batteries) need a certain current flow through the meter to make the meter move, and that flow is from the potential difference in the two measuring elements, flow caused by the imbalance in the hydrogen and hydroxyl in the measured medium (we are trying to measure the "free" hydrogen). The probe materials each gather their hydogen or hydroxyl, and the meter reads the draining of those two pools of different charges through the meter circuit.
Water is hydrogen hydroxyl ( H+ OH-, or more commonly H20). It is a conducting medium. Having the probe insulator immersed in fluid water will have the same effect on the insulator and circuit as having a dirty probe insulator -
fwiw
And it IS likely, especially given the difficulty of
Partially only, but it is a good introduction to pH measurements. IMHO it is better to know a little bit too much, then not enough :)
Google for pHC2051 made by Radiometer - that's the electrode. pH meter is a separate thing, there are battery field units available from many manufacturers.
One decimal point my be important, as soil pH changes in rather small range - and the difference between 6.5 and 7.5 is rather important, while every soil in this range will be measured as just 7 (perfectly neutral) without any decimal digits. But IMHO you don't need the pH meter in a garden, for most cases pH stripes will be enough. Especially if you will use not universal ones (0-14) but some for smaller range. See examples at
Care to drop me a line and explain why do you think so?
There is one problem - glass electrode (or more precisely the bubble at the end) is made of extremally thin glass, thus it is very fragile. But that's not a problem you can't overcome with good engineering. Note, that due to the way pH electrodes are made they will age - at best they can be used for about a year (gell type). Flowing electrodes can be used much longer, but they are difficult to maintain.
See my other reply - one decimal digit is important. I wonder if the difference between 6.5 and 7.5 won't be large enough for the hydrangea to change flower color.
Yes - and soil electrode (while best for soil pH measurements) can be used for such applications as well. But it will be probably overkill, IMHO pH stripes will do in all these cases.
Mr. pH
I just found it tricky to find links to pH strips and info thereon and generally 'search' for specific subjects. It's there I'm sure - but some of it felt 'buried'. I've seen much worse. Generally, folks patience with a website goes down exponentially with the number of pages they must click thru.
Carl
I think it MAY be helpful if one were trying amend the soil. One could track changes over time.
i dunno
Carl
Seems fair. Such would probably be cheaper and easier to use too.
David
Thanks to all for your responses to my PH question. I am truly a lot better educated now. My inclination is tending towards the color indicator using a sample of the soil with a measured amount of water, and then comparing the color to that of a chart. I was looking at the meter option for the convenience of being able to test multiple areas quickly.
I know that my gardens require an application of lime, and I want to be able to do it accurately and know when I've added enough without having to guess.
"Cyberiade.it Anonymous Remailer" wrote in message news: snipped-for-privacy@remailer.cyberiade.it...
Yes, I know the standard pHydrion roll you're likely to get if you don't specify anything is fairly wide range; however, they also make very nice shortrange papers, e.g., pH 3.0 - 7.5, pH 6.0-8.0, 6.5-9.5: hundreds of tests for under $10.
Kay
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