Propane tank monitor

I also use one tank at a time without making use of the auto-switch over feature. I like the door knob cover idea on the tank valve you're drawing from. We boon-dock frequently and I do the bathroom scale thing when I want to know EXACTLY how much propane remains in the partially used 30# tank (working with the tank's empty weight stamped on the tank and plus 4.2 #'s per gal actual remaining propane). That way I can determine clearly if I think it'd be worth the bother or necessary to top-off the partial tank at a convenient refill stop along the way. We also carry an extra 20# tank for portable grill, lantern, heater, etc.