Exactly how does one of these work anyway? How do you measure the amount of liquid hydrogen in a bazillion gallon thermos jug? Couldn't they just go out and give it a good hard whack on the side of the tank and see if that fixes it?
Reminds me of a cartoon my biker buddy Butch drew up:
Two bikers, New Biker and Old Biker are talking and OB is introducing the members of the club.
NB, "Who's that ugly bald guy over there?" OB, "That's the guy we call 'CB'." NB, "CB. What, he was into those cheesy radios back in the early 80's?" OB, "Nah, it stands for 'Crispy Bob'. He used to check how much gas was in the tank by standing over the filler with a lit match and lookin down the hole."