At first, there's no current flow, so the rate at which the integrator is charging is constant (zero). You start charging the integrator when the first contact is made, and wait until the rate of charge is constant. It seems to me that this will apply to both normally open, and normally closed cases. Further, it seems quite unimportant whether it is of a given value, so long as it is constant. There's a "gotcha" in this method, however, and that's that the bounce interval will consist of a number of small intervals during which the rate is essentially constant, and it is up to the integrator to "smooth" these steps into a slope. If you can detect the transition between the resulting slope to a constant level, you're home. The crux, therefore, is to select a time constant which will make it apparent that the charge rate is constant.

I'm curious about one thing, and that's the 0.2 ms value that was introduced in a previous post. I think that the last time I looked at reed relay spec's, the transition time, from open to closed, was on the order of 2 ms. The debounce time that was most frequently used, IIRC, was aobut 20 ms. Have reed relays improved that much in the last decade?