Simple design for a pH referenced.doc

Here's a simple generalized design for a pH probe and reference KH solution to measure CO2 accurately in an aqurium with tannins, ADA soil, or weird tap water with non bicarbonate alkalinity.

The larger the tank -ref solution interface/surface area, the faster and better the response times will be.

Interference with the CO2 mist rising into the catch part of the air gap can produce false positives, but never false negatives.

This means you will read more CO2 than is truly in solution, rather than the reverse!

Regards,
Tom Barr

Where's the Illustration ?

click on the file

Regards,
Tom Barr

Click-ed File. I see words without illustration ? Wonder if my word program is shhcrewwy ? No Joy...

Tom,
I've got a modification to your schematic that may appeal to those who want less to show up in their tanks. Specifically, make this to hang over the edge of the tank like a HOB filter or overflow. Something like this (CD-790065 at DrsFosterSmith.com) should give an idea of what I'm talking about.

The reference solution and probe can be outside the tank, while only a little would reach inside.

Tom,

Where is the water sample measure? I don't get it.

Thanks

David

No, you don't want the reference solution and probe outside the tank. Unless the reference solution is at the same temperature as the tank water at all times there will be distillation going on, with water moving from the warmer water to the colder water. That would alter the KH of the reference solution. Much better to just minimize the size of the unit in the water.

Tom, it is likely to take more than a grommet to adequately seal the point where the probe enters the drop checker. That connection has to be air tight, or the device doesn't work. Something more like the sealing nuts used for wires going into a sealed device would be best. And, given the relatively short life of the probes, you can't just use silicone sealant to seal it. I think the best design would be made from two sizes of acrylic pipe - the inner one about twice the diameter of the probe, the outer one about twice the diameter of the inner one, and the inner one with a bottom piece that extends to attach the two together. At the top would be a solid piece of acrylic with a liquid tight pass thru fitting from Heyco, Handles, Thumb Screws Captive Panel Screws, Stand offs, Handles, Connector Hardware, Lyn-Tron, Inc. - Spacers, Thumb Screws, Captive Panel Screws, Standoffs, Handles, Connector Hardware - Bolt Products Inc., Fasteners, Cable Ties, Distributor Standar, which fits the probe diameter.

Vaughn,

I have 500 grommets that are rated at 30 psi sittng here, they are very air tight!

I used them on the CO2 reactors I use to make.

They fit the probe nicely.
I'll make on and show folks how to with some pics.

Regards,
Tom Barr