Re: Where are all the ESR meters?

On Mon, 23 Jul 2007 21:29:45 +0100, Chris Jones
<lugnut808@xxxxxxxxxxxxxxxx> wrote:

John Larkin wrote:

On Sun, 22 Jul 2007 15:57:37 GMT, Fred Bloggs <nospam@xxxxxxxxxx>
wrote:



Jim Thompson wrote:
On Sun, 22 Jul 2007 04:24:21 -0700, Winfield <winfieldhill@xxxxxxxxx>
wrote:


Jim Thompson wrote:

Winfield wrote:


I'll post mine, when I get enough energy to transcribe
it from my paper scratchings, calculations and notes.
Remember, it must be four terminal, and handle high DC
voltages when probing in-circuit storage capacitors.

How high is "high"?

Perhaps a better question is, how big is big?

Several designs we've been considering have a
pair of diodes to discharge the test capacitor
and limit the circuit voltages, but I've heard
these can fail with large, charged capacitors.

I think the issue isn't necessarily how high
the voltage (tube amplifiers get to hundreds
of volts), or how high the current delivered,
but how much energy is going to be dissipated
in the protection components that discharge
the guilty capacitor.

I'd say the answer is, the size of two fists.
I think we're talking about ~ 100J of energy.
Isn't that more than enough to blow out a
common glass diode and/or a 1/4-watt resistor?


Should be enough to crank you over a few times ;-)

...Jim Thompson

WH is stalling... input protection has little to do with a basic
measurement architecture. I had no idea this little project would be so
difficult for everyone:-)


Interesting that for a proposed "group design", hardly anybody is
willing to make a first step. The psychology of group design is
fascinating, and it turns out that an audience is a huge inhibition;
people tend to not expose ideas if they fear they are imperfect, and
might give some nit-picker grounds for public criticism.

Brainstorming is delicate because people are fragile. At my place, we
scribble goofy ideas on a whiteboard, do a lot of stupid stuff (don't
distinguish between circuit-as-proposal and circuit-as-joke), argue
and laugh a lot, and sometimes come up with brilliance, with no way to
tell who gets the credit. Some people just can't play at this game.

John

Look, I already have a perfectly good ESR meter that I built from a kit
designed by Bob Parker. You can talk to him about it, he is on
aus.electronics and is helpful. I don't feel the need to reinvent the
wheel, especially because it is a good wheel. It would be very hard to
design an ESR meter that would be of more use in practical situations.

A quick look at the schematic and writeup suggests that it can't
untangle ESR from capacitance at low C values. The "good esr versus
capacitance" chart screened on the front confirms.

Besides, this is sci.electronics.design, not sci.electronics.copy.

John

.

Relevant Pages

  • Re: Where are all the ESR meters?
    ... voltages when probing in-circuit storage capacitors. ... The psychology of group design is ... determining ESR then it goes. ...
    (sci.electronics.design)
  • Re: Where are all the ESR meters?
    ... John Larkin wrote: ... voltages when probing in-circuit storage capacitors. ... Interesting that for a proposed "group design", ...
    (sci.electronics.design)
  • Re: Where are all the ESR meters?
    ... Jim Thompson wrote: ... voltages when probing in-circuit storage capacitors. ... Interesting that for a proposed "group design", ... I already have a perfectly good ESR meter that I built from a kit ...
    (sci.electronics.design)
  • Re: Where are all the ESR meters?
    ... Jim Thompson wrote: ... voltages when probing in-circuit storage capacitors. ... Interesting that for a proposed "group design", ...
    (sci.electronics.design)
  • Re: Where are all the ESR meters?
    ... voltages when probing in-circuit storage capacitors. ... The key is to produce the simplest possible design that measures ESR, if something else comes free along with that without introducing one iota more of complexity then fine, but if it requires one speck of dedicated hardware not useful for determining ESR then it goes. ...
    (sci.electronics.design)
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