OK, OK, just kidding! [

]

In simple terms (which are all I understand anyway), the HUP states that:

dp.dx >= h

i.e. the uncertainty in momentum (delta p) times the uncertainty in position (delta x) must always be (at least) as big as Planck's constant (h).

(Incidentally, in simple terms, this can also be written as: dv.dx >= h/m - i.e. divide both sides of the previous equation by the mass, m, so the momentum turns into velocity, giving: error in velocity times error in position is at least h divided by the mass).

But h is VERY small: 6 x 10^-34 Joules seconds.

When you say you know the position of a particle hitting a detector, you don't really mean that you know with ABSOLUTE PRECISE accuracy where it is. What you mean is that you know it to within an accuracy of, maybe, 0.000000000001 metres. And you know the momentum to an accuracy of, maybe, 0.000000001 kg-metres-per-second. So then dp.dx is the product of these two numbers, i.e. 10^-12 * 10^-9 = 10^-21, which is greater than h, so the HUP still holds.

The HUP is more useful in theoretical considerations.

For example, another version of the equation is: dE.dt >= h - i.e. uncertainty in energy times uncertainty in time is at least h. If you apply this to a vacuum, it means (apparently, in very simplistic terms) that for any small region of space, you can't be sure that there's absolutely never any energy in that space. (For a small period of time dt, you can't have E=0, there must be some fluctuation in E, dE, to ensure that dE.dt >= h.) Hence virtual pairs of particles and antiparticles popping into and out of existence for (incredibly small) periods of time.

I don't know if this is helping or not (you probably know all this already). Have I missed the point in your question?

P.S. One link I've found re: the HUP which I think is moderately interesting is as follow:

http://www.physlink.com/Education/AskExperts/ae689.cfm(It's from that other physics forum I don't like much - but occasionally it's useful.)