Can an Ultrasonic wave penetrate a LPG cylinder

[Baluncore]

The external temperature difference sensed is driven either by the internal evaporation of gas as gas is used or by externally applied hot water when gas is not being used.
A system to measure liquid level when gas is not being used will need to apply external heat. The challenge will be to apply the external heat evenly and then sense the temperature profile as it returns to ambient conditions.

 

[sophiecentaur]

The external temperature difference sensed is driven either by the internal evaporation of gas as gas is used or by externally applied hot water when gas is not being used.
A system to measure liquid level when gas is not being used will need to apply external heat. The challenge will be to apply the external heat evenly and then sense the temperature profile as it returns to ambient conditions.

You are right. Would it be easier to have a few seconds venting of the gas?

When we get down to it, there's a lot to be said for just weighing the bottle continuously. The installation for that would be pretty cheap and robust and could even work (low pass filtered) when the bottle was in a moving vehicle.