Confused dude, and by orders of magnitude, dude

[Terry Michaels]

Message text written by Bill Layer
>Hi Terry, All,

Something came to mind.

>As a mental reminder, the time constant for a one meg resistor connected
to
>a one uF capacitor is one second, frequency is 1/6 Hz.

With respect to T=R*C, isn't this the time required for the cap to reach a
certain percentage of the rail, like 60% or somesuch? If memory serves,
there is a different and slightly more complex formula for a 'full'
charge...

Or was I sleeping that day?

<

Hi Bill:

That was an approximation of course, one meg, one uF and one second are
easy to remember.  The precise definition is the time required for charge
on the cap to reach 63.2% of the source voltage.  Full charge can never be
exactly arrived at, theoretically it is infinite, althought the difference
eventually gets to the point where it is unmeasureable.  There is a formula
to approximate it, I don't remember it though.

Terry