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Discussion Starter · #241 ·
I like this design as I have all the supplies to do this one but I can't figure out where the reading is coming from... Is it just the sandwiched Tyvek membrane spaced from the O ring that is allowing the exchange in reading ? Or am I missing something as to where membrane is exposed to the water ?
One flat piece of acrylic has a hole in it. The membrane goes across the hole, over the O-ring, and then between the two pieces of acrylic. That leaves a disc consisting of membrane, piece of sponge soaked with KH reference water, acrylic, with the O-ring sealing in the KH reference water. I wasn't too happy with this design, and I'm not all that sure the tyvek membrane doesn't leak a bit. Personally, I am giving up the quest for faster response, preferring the simplicity of not using the membrane.
 

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Hoppy Wrote:
> I'm not all that sure the tyvek membrane doesn't leak a bit

Tyvek is only a one way street when a liquid with surface tension (like water with no surfacants) is only on one side, and air on the other. It is ALWAYS permeable to water vapor. Only surface tension of the water resisting against the small pores in the polyester allows it to hold water- but not permanently. It is a two-way street for water and even much larger molecules when wet through. Its pore size is not regular, there are larger and smaller holes. I know from experience with sterile cultures that it can only be effective in keeping out viruses and even some bacteria when it is dry on both sides. Those are obviously much larger than organic acid molecules of all kinds. It worked for you temporarily, but I think the true semipermeable membranes with the right structure for the job would be the only long-term solution (pun intended).

But I agree with you now that the hassle doesn't sem to be worth the gain over the regular partial pressure gas exchange testers the thread started with... now off to make one for myself (yeah, when I get around to it... :))
 

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Whipped this DIY Drop Checker together in about 5 minutes with stuff I already had. Doesn't look too bad in the aquarium, now we'll see how it works. I just put it in so the regent is still blue. It's the air type rather than the membrane type so it'll take a couple of hours.
 

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Nice job on the "3-jigger drop checker"
 

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Discussion Starter · #247 ·
Wow! What a neat and easy way to make one of these gadgets. The only suggestion I have is to keep the quantity of water in it to a minimum to speed up the reaction time.
 

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Whipped this DIY Drop Checker together in about 5 minutes with stuff I already had. Doesn't look too bad in the aquarium, now we'll see how it works. I just put it in so the regent is still blue. It's the air type rather than the membrane type so it'll take a couple of hours.
Not bad! What a simple but effective idea. :D

I assume that's silicone you used to put it all together?
 

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Wow! What a neat and easy way to make one of these gadgets. The only suggestion I have is to keep the quantity of water in it to a minimum to speed up the reaction time.
Hoppy - I suspect it (speed) may also be a function of surface area than of volume in the "air gap" checkers. I've got one (air-gap one) that holds <2mL of indicator solution but it's in a tall, thin shell vial. It reacts slower than the membrane one (inverted bottle w/ hole in cap) in the same tank.

Once, it went yellow so I pulled it and stuck it to the outside of my tank, it took 3 days to change back to green. My membrane one went from blue to green in 3-4 hours when I added it to my 5g tank.

I need to refill the one in my 46g tank as the 96W light has not been kind to the indicator dye. I think I'll mount it a lot lower in the tank when I refill it (maybe in some shade provided by the sword that's taking over).
 

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Not bad! What a simple but effective idea. :D

I assume that's silicone you used to put it all together?
Yup, just some silicone. Took less than 5 minutes to put together, then a couple of days waiting for the silicone to cure. I took quite a bit longer mixing up the 4 dkh solution and ensuring it was EXACTLY 4 dkh. The package said fully cures in 24 hours so I gave it 48. Seems to work great so far.
 

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Discussion Starter · #253 ·
The real breakthrough in that shot glass design is thinking outside the box, by noting that there is no good reason to keep the two parts concentric. That suggests getting two sizes of test tubes, cutting them shorter and glueing the small diameter one inside the large diameter one as you did. Even doing the non-concentric thing when making one from acrylic tubes would be much easier. One could also experiment by making the air chamber glass much bigger than the water chamber glass, to see if that speeds up the reaction. Now I think anyone can make one of these, even the all thumbs people.
 

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The real breakthrough in that shot glass design is thinking outside the box, by noting that there is no good reason to keep the two parts concentric. That suggests getting two sizes of test tubes, cutting them shorter and glueing the small diameter one inside the large diameter one as you did. Even doing the non-concentric thing when making one from acrylic tubes would be much easier. One could also experiment by making the air chamber glass much bigger than the water chamber glass, to see if that speeds up the reaction. Now I think anyone can make one of these, even the all thumbs people.
I agree about making the air chamber larger (in terms of horizontal area, not height) and the water chamber smaller to make the air/water interchange area as large as possible to hopefully speed up the reaction. My next one will be the same design but using an old test kit test tube inside one of the larger sized shot glasses. I could use an even larger sized glass of some kind but I don't want the thing too ridiculously large in my aquarium. It'll be interesting to time this and see if it improves reaction time.
 

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http://img479.imageshack.us/img479/5952/20070122fts5g3pz.jpg

^pic featuring a poorly designed air-gap DC - it's super slow to respond to change because of the ~3mm diameter at the top of a ~3cm column of indicator solution. Something along the lines of the shot glass design featuring a short, wide column of indicator solution should respond a lot faster (I feel another science fair project idea coming on).
 

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I have an ADA knock off drop checker and a Red Sea drop checker.
Plus I have made about 10 others with different designs.

The test tube drop checkers work but they are slow to respond. You don't even have to
attach the bottom test tube it will just float in place (see picture below).

When I first started using a drop checker I made one big enough to pull out and measure
the 4 dKH water with my pH meter. It wasn't something I wanted in my tank forever, I just
did it so I would feel confident that the pH indicator solution was correct. Here's a link showing
how I put it together, you might be able to attach the shot glasses together like this so they
would be straight.
http://www.plantedtank.net/forums/g...70-co2-measurement-checking-drop-checker.html

Bill
 

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after having read this thread a few times, i'm going to be making a drop checker myself, probably starting off with something similar to billionzz's idea.

but all i have to say is, i didn't realize how little baking soda is needed to make a kH solution. since i don't have any sort of scale to use, it's pretty hard. instead i'm using a trimmed off/flattened wooden toothpick, i've pretty well gotten the measurements worked out to get 4-5dkH.

starting off with .25 tsp of baking soda to 1 ounce water, pretty well have me liquid rock, and blue fingers... don't ask :p
 

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Sorry, been gone for a while. Trying to get my big tank back in order. Found this idea yesterday. Made one today. Went with the Shot Glass and Test Tube method.



Thanks for the awesome idea! Off to watch Borat and see if it changes color. I know there's more liquid than needs to be in there... but it's there now, it'll just take a smidge longer.

-MT
 

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I'm sure I'm missing something obvious, but as I understand it, atmospheric CO2 concentration is somewhere north of 300 ppm. Why then are drop checkers supposed to be blue when they are sitting out, and not yellow?

I say "supposed" because I think I "broke" mine when I tried adding pH drops to intensify the color, and after a few days it assumed a yellow color that has stuck, whether in or out of the tank.

I wish I paid more attention in chemistry.
 

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I'm sure I'm missing something obvious, but as I understand it, atmospheric CO2 concentration is somewhere north of 300 ppm. Why then are drop checkers supposed to be blue when they are sitting out, and not yellow?

I say "supposed" because I think I "broke" mine when I tried adding pH drops to intensify the color, and after a few days it assumed a yellow color that has stuck, whether in or out of the tank.

I wish I paid more attention in chemistry.
No, there's only about 3 ppm of CO2 in the atmosphere.

It should definitely be blue if it's exposed to the air for an hour or so.
 
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