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Soil PH Tester


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#1 smegma

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Posted 08 March 2005 - 03:13 PM

Do the cheap ones that are a metal probe with a plastic meter work?

Example:

Posted Image

#2 cutty

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Posted 08 March 2005 - 03:17 PM

Do the cheap ones that are a metal probe with a plastic meter work?

Example:

Posted Image


Excellent Q I just bought one exactly like that and I have no clue how to use it...I was told they work but I have no experience using it yet.

#3 smegma

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Posted 08 March 2005 - 03:22 PM

Excellent Q I just bought one exactly like that and I have no clue how to use it...I was told they work but I have no experience using it yet.


I really want to know if it is at all accurate.

IME hygrometers are ALL OVER THE MAP and was wondering if the same was true of my new POS PH meter.

Mine also supposedly measures "wetness" and light. All for $7... Yeah, I bet.

I have 3 VERY different hygrometers, cheap, moderate and expensive. Sitting RIGHT NEXT TO EACHOTHER they read currently: 72%, 88%, 100%.

So I generally just average. :)

#4 nomoreusmc

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Posted 08 March 2005 - 03:49 PM

I wonder which one is correct? but avarging is probibly the best way to do it in that circumstance

#5 vp7

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Posted 08 March 2005 - 03:56 PM

i have one of those.(similar) actually just used the thing like 10 mins. ago. I never actually checked the accuracy against ph paper or anything, but it seems to work well. you have to let the thing sit in your material for several minutes to get an accurate reading. it may not be a perfect measure, but it sure beats guessing.

#6 smegma

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Posted 08 March 2005 - 04:03 PM

i have one of those.(similar) actually just used the thing like 10 mins. ago. I never actually checked the accuracy against ph paper or anything, but it seems to work well. you have to let the thing sit in your material for several minutes to get an accurate reading. it may not be a perfect measure, but it sure beats guessing.


Is there an easy way to test it without strips?

Like "distilled water should be 7.0" (EXAMPLE ONLY) or something like that?

#7 Guest_golly_*

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Posted 08 March 2005 - 04:17 PM

Orange juice - 4.4 Ph
Apple cider - 4.8
human spit - 5.4
baking soda - 8.5
Hope this helps...

#8 smegma

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Posted 08 March 2005 - 04:33 PM

Orange juice - 4.4 Ph
Apple cider - 4.8
human spit - 5.4
baking soda - 8.5
Hope this helps...

Seriously?

#9 Guest_golly_*

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Posted 08 March 2005 - 06:47 PM

seriously...!

#10 Guest_Peter Cottontail_*

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Posted 08 March 2005 - 07:27 PM

Seriously,
That thing is a piece of shit. It's totally useless. They don't even work well for soil. I have several of those, including a $100 one. They all read differently and no real way to calibrate them. The PH of various juices won't help because those type testers won't read liquid anyway.

If you'll look at the end of the probe, it has an insulator, and the lower part of the probe is a different electrode from the rest. These are two dissimilar metals and in the presence of acid(soil in this case) it becomes a battery. The voltage is what is read on the meter. The issue is if your soil is compact, more of it is in contact with the probe and if your soil is loose as in casing material, not much is in contact with the probe. This effects the reading irregardless of soil PH. The only accurate way I know of to measure ph is to squeeze out some liquid and read it with a test strip. Now, in the absence of test strips, just use hydrated lime in the amount of 5% of the compost or peat moss. Don't count the amount of verm when you figure the 5%. This means that for every 2 cups of peat in your casing, use 1 tablespoon of hydrated lime. Ditto for compost. If you use one cup of compost and one cup of verm, use 1/2 tablespoon of hydrated lime. If you'll use this formula, you don't need to test each batch. There isn't going to be that much variance in water ph from location to location and peat/compost will always be slightly acidic. I haven't had my test strips out in months.

As for hygrometers, the good ones have an adjustment screw on the back to calibrate them. Here's how: Wrap the hygrometer up in a damp bath towel. The towel shouldn't be dripping wet, but very damp. Squeeze out all water that will wring out of it and wrap the hygrometer up inside several layers. Leave this to sit for at least half an hour. When you come back, adjust the screw so the dial reads 98%. You should do this at least monthly. The hair that is used to sense humidity is under tension and will naturally stretch over time, requiring re-calibration.

#11 destroy_erase_improve

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Posted 08 March 2005 - 07:56 PM

i had a few hygrometers that were digital that i got from a cigar shop. it was pretty reliable as far as reading in the high 90s. the only bad thing is if it got too saturated with water it would shut down. i learned to mist around it and keep it elevated.

#12 smegma

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Posted 09 March 2005 - 08:32 AM

Seriously, That thing is a piece of shit. It's totally useless.


:D

I almost dropped one when I read that.

I kind of figured as much. I am not a rocket scientist, but could kind of tell it is a conductivity measurement device and that wetness, density, etc. would skew it.

So, the PH of the liquid in the sub = the PH of the sub? I will get the test strips and rock them out.

Thanks!

#13 Guest_pissybee_*

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Posted 09 March 2005 - 09:44 AM

You can make your own test strips by chopping up red cabbage and boiling it for about 20-30 mins, then strain the cabbage, and you can use small amounts of liquid in a glass. Just add a drop or two of the liquid to be tested to the purple cabbage juice, or do what I do and dip coffee filters in it then cut into strips and let them dry. This will give you PH paper. I posted some color charts in the attachments...

Attached Thumbnails

  • ph-cabbage.gif
  • Organph.jpg


#14 smegma

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Posted 09 March 2005 - 09:51 AM

You can make your own test strips by chopping up red cabbage and boiling it for about 20-30 mins, then strain the cabbage, and you can use small amounts of liquid in a glass. Just add a drop or two of the liquid to be tested to the purple cabbage juice, or do what I do and dip coffee filters in it then cut into strips and let them dry. This will give you PH paper. I posted some color charts in the attachments...


You sir are a gentleman and a scholar.

This should be the first thing in the archives for PH.

#15 Forager

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Posted 09 March 2005 - 02:37 PM

Rodger said: "for every 2 cups of peat in your casing, use 1 tablespoon of hydrated lime."

According to my calculations, for dry materials, 2c=472ml. 5% of 472ml = 23.6 ml. 1tablespoon=15ml, therefore this is actually closer to 3%. But whatever, close enough, I know. Trust Rodger, it works.

If you are also supplementing with calcium carbonate in the form of crushed oyster shells, what would be the recommended amount? I have been using 1% hydrated lime + 3% oyster shell. This works out to about 2 teaspoons (10 ml) hyd. lime and 2 tablespoons (30 ml) oyster shell per quart (about 4cups or 944ml).

It would be good to have all the common concentrations and measures for the various materials used in this hobby listed in a single reference in the archives somewhere.

I like the red cabbage idea. I've also been using one of those cheap pH testers. I knew it was shit, but I 'calibrated' it to test strips. You can compress the medium around the probe to get a more accurate reading. Make sure no part of the probe is touching metal.

#16 Lazlo

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Posted 09 March 2005 - 04:37 PM

:D

I almost dropped one when I read that.

I kind of figured as much. I am not a rocket scientist, but could kind of tell it is a conductivity measurement device and that wetness, density, etc. would skew it.

So, the PH of the liquid in the sub = the PH of the sub? I will get the test strips and rock them out.

Thanks!


Don't feel bad. RR set me straight too!




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