How to calculate the mass of gas in a tank?

[Chestermiller]

In the earlier analysis I presented, if we include heat transfer between the tank gas and the surroundings, we obtain:
$$(F_3V-F_4m)\frac{dT}{dt}=\frac{dm}{dt}-\frac{UA}{(h_v-F_2)}(T-T_s)$$where A is the surface area of the tank, U is the overall heat transfer coefficient, and $T_s$ is the temperature of the surroundings; t is time.

 

[Tom.G]

Can anybody recommend a proper scale? One which I can connect to a (Linux) computer, can recalibrate myself and is cheap?

Not at the moment, but if somebody knew what weight range you needed, they could likely do a Google search and find a few. As you are the only one here that would have such information, who do you think would be the most appropriate to do the search? (hint, hint)