Re: [CAD_CAM_EDM_DRO] Re: EDM GENERATORS

David G. LeVine wrote:

> At 12:20 PM 8/7/2007, you wrote:
>
>>it does seem that one should have a test for short before each pulse,
>>if that can be added to the circuit.
>
>
> Putting a small voltage limited current into the work (e.g. 1 mA and
> 0.6 Volts) after a short delay (to allow the channel to decay) should
> either result in zero volts (short) or 0.6 Volts (depending on the
> voltage limit.) The circuitry is pretty simple, but the devil is in
> the details -- protecting the comparator from the HV spikes.

Actually, I don't think you need any additional power source.
What you do is measure the voltage, say, one microsecond after
turning on the power sources. If it is still zero, the work has
shorted to the electrode. If it goes up to a high voltage for
at least a few microseconds before the dielectric breaks down,
then that is OK.

Jon