Now tried. Damage to the office not too bad (trying for 'knock-for-knock'). It works okay, I suppose, but not bowled over with performance. Is fine down to about 0.3/0.4m, then jumps to zero and becomes erratic. Suspect the latter is due to poor discrimination, or ringing of the transducer (is now down to 1 or 2ms after the transmitted pulse that the echo is received).

I don't know about you, but I can detect a gap down to a foot or so from the other car, without help. What I really need is something that reads down to an inch! We have serious parking problems in the UK...

I will now take the plunge and drill 22mm holes in my car bumper and try for real. Perhaps I should look at a minicam solution?

Dave