How to tell amount of propane in tanks ?

[hamm2018]

I use this system:
Mopeka TankCheck LPG Tank Check Dual Sensor with Monitor Kit

it can read the level of your tanks from hundreds of miles away with the phone app. It is about $90.00 and does a good job.

I removed the auto change over because having 1 empty tank and having a full tank is better then having 2 empty tanks at 3 in the morning. (just my thoughts)