Re: Re TDC DC

[P3D John W Roberts <roberts@xxxxxxxxxxxxxxxxx>]

>Date: Tue, 15 Jul 1997 03:51:41 -0500
>From: P3D Peter Homer <P.J.Homer@xxxxxxxxxxxxxxxxx>
>Subject: Re TDC DC

>This is perhaps a little of topic 

Don't think so.

>A lecturer at work has told me about a student I have not
>met yet who wishes to demonstrate and measure this surge. So far I have not
>come across a method to do this so have been trying to devise one of my own
>without success . I cannot display it on a oscilloscope for instance...

Do you mean you haven't figured out how to do it, or that you tried an
experiment that should have shown a surge on the oscilloscope, and nothing
appeared? (Or that you don't have an oscilloscope? :-)

I would think that putting a low-resistance (say 0.5-10 ohm) power resistor
in series with the light bulbs, putting the leads of the oscilloscope across
the resistor (taking care to avoid problems with scope ground), setting the 
gain so that the normal "on" current is easily perceptible, then switching
on the circuit would show whether there's a momentary current surge.

Of course an analog storage scope or a digital scope would be best for this
type of measurement, but even with an analog non-storage scope, if you set it
to auto-trigger and very slow sweep, you ought to at least see how high the
dot bounces.

John R


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