Monitoring GAS Levels
Truma LevelControl
Uses Ultrasound to measure the volume of GAS in the tank, this information is relayed to an app on your phone.
Mopeka Pro
Also uses Ultrasound to measure the volume of GAS in the tank, and again relays to an app on your phone. These are about half the price of the Truma ones, but you MUST buy and fit something to stand the tank off the base. In the UK the base of the tank is level with the stand ring so you need to prop the tank up so you don't crush these.
UK Base Stand for above sensor
Note: Using the base stand above requires you to cut/break the supports from the frame and then screw+glue each of the three sections down. Its not hard and works well. If you find a UK 11/13kg Propane bottle stand that just works out of the box, LET US KNOW? Pretty much everything you can get on Amazon/eBay are for USA size tanks.