On Tue, 6 Apr 2010 19:28:32 +0000 (UTC), Elmo
wrote:

So, with my new carbon dioxide tank, I'm not sure how I tell how much co2
is left in the tank. Does anyone know how you tell when it's getting low?

Ummm... arithmetic? Weigh the empty tank (or ask the supplier for the
empty weight). Weigh the tank with whatever amount of C02 you have
left. The difference is how many pounds of C02 you have left.

You can also sorta do it the same way as with a propane tank. Get a
liquid crystal thermometer strip and glue it vertically to the side of
the tank. Leak a little gas and you should see the warm/cold liquid
dividing line. The problem is that the propane tank is quite thin
compared to most CO2 tanks, thus making the thicker CO2 tank more
difficult to see the dividing line. It also works best with steel
tanks, and doesn't work at all with aluminum.
http://www.google.com/patents/about?id=gTkeAAAAEBAJ&dq=4358955
You can also use an IR thermometer to locate the liquid level.

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