Measure co2 level in the cylinder

[lost66]

Does anyone use any method to check how much co2 is it in the cylinder?
I am thinking about scale which I can automatically turn on once a day and sends an alert in my mobile if the weight drops to certain level. But I don't know if there is such scale with such options. Anyone?

 

[Js.Aqua.Project]

I use the PSI remaining as a general indicator...

I personally have no reason to know the exact amount of gas by volume in this scenario as we are using so little over time. But once there is no longer enough gas to maintain PSI it will start to drop somewhat quickly and I just set a bottom number that I am willing to let that PSI drop to before I swap out my CO2 canister.

I scuba dive and we are taught to monitor by PSI not volume or weight, because pressure changes with depth and the same gas will take up less space under increasing pressure. Since in this scenario you are sitting at a constant pressure I am sure you could calculate exact volume by if you want to.

 

[Js.Aqua.Project]

The math:

One could compare a cylinder of gas at a filled volume (V1 = 660 L) and pressure (P1 = 2200 psi) to the current pressure (P2) read on the cylinder. This would provide the information needed to solve for the current volume (V2) remaining in the tank in liters. The following is the formula: P2/P1 * V1 = V2.

 

[Js.Aqua.Project]

Found this chart:

So if you know your starting weight, temperature, and PSI you can just follow the line to determine how full your tank is.

Also read that if you know your empty canister weight and then have them fill it, you can just measure by loss in weight where you are at.

Note, a 5lb canister will usually not get filled with a full 5lb of gas as room for expansion must be left in place for safety. Most fill places fill by PSI for that very reason.

 

[DCR]

The pressure does not change much until the liquid is gone. For the low use in a Ca reactor, you could probably DIY something with a low pressure switch and have it give you an alarm, but just checking the tank pressure as part of your daily routine would be my choice. I have seen people on freshwater planted tank forums use an inexpensive weigh scale to monitor the level and it works well, but I doubt you could get one with an alarm. Planted tanks use a lot more CO2 than a Ca reactor.