Re: Onto a new learning curve…CD ignition

[legendre]

quote FrankR:

quote legendre:

quote FrankR:

Gotta tell you though, you could actually cobble up your own DVA Adapter. I did. Very crude though, but it shows how little is actually in the real deal.

I can’t image there’s a whole lot needed.. it’s just a peak hold circuit. A fast, high-voltage diode, a small value low-leakage cap..? What else is in there?

Why can’t a standard DVM with peak-hold feature be used?

ETA: I just found a discussion on another site. Apparently, I was correct – nothing more than a cap & diode in there. For some reason, the builder also used a 1M resistor in parallel with the cap – I have no idea why. All that would do is cause the “held” reading to fall off to zero more quickly. He also used a 2.2uF @ 450V electrolytic cap – I’d have tried more like 0.22uF – 1.0uF first (in a low-loss film type) before venturing into electrolytic territory.

I believe the resistor is to bleed down the capacitor after you finish with it. To make ready for the next test and so it isn’t sitting there like a rattlesnake ready to bite you.

It would certainly have that effect, but I’d also think it would tend to cause the reading to fall-off more quickly than desired.. before it can be read, and so forth. Basic math, T=RC etc.

And it’s not like just crossing the leads won’t eliminate any remaining charge. If I built one, I’d leave off the drain resistor.. but I’m still not convinced that a general-purpose meter with a peak-hold function wouldn’t suffice. Maybe I should set up a simulation, and take some data,,? =)