Winfield,
You still have an HP4194, don't you?
Try doing a sweep of capacitance and ESR from 60 Hz to 1 MHz of some caps from a defective mother board. I visited my local computer repair guy and he gave me a couple of defective boards destined for recycling.
Especially sweep some of the really small, high capacity, low voltage caps. I saw some unusual characteristics with the physically small caps.
Some of the ones I tried had self-resonance at 100 kHz.
Since lots of single-chip uPs include decent adc's these days, why not just digitize the voltage drop across the cap? One could then note the cap charging slope and untangle it from the true esr. And measure capacitance, for free.
John
buck)
Sure,however I think the sensitivity of the typical 10 bit ADC in a cheap micro is about an order of magntitude too low, so you need a preamp anyway.
Thanks, I'll try that if I can find a certifiably-bad cap. I have five different kinds of large impedance-measuring instruments that can measure milli-ohm esr, some in circuit. But the appeal of the little esr meter is its small size.
buck)
That's about right, but it's still going to be simpler than most of the goofy and truly terrible "esr" meters we've seen here lately.
You may as well measure leakage and dielectric absorption while you're at it; code is cheap.
John
Do you want some failed caps with high ESR? I can send you plenty. :(
I can even test them on the original design DSE meter and mark the ESR on each for you.
Hey, that would be great! Here's my address.
Winfield Hill 617-497-4670 Rowland Institute at Harvard
100 Edwin H. Land Blvd Cambridge, MA 02142-1297
I'll try to get them out, first of the week. I have a plastic gallon bottle that's about half full, right now. I think I still have some larger FP mount electrolytics that were rated for 60 Hz use. I'll have to go to the post office to pick up some flat rate boxs.
All you're going to get is a bunch of this crap:
Granted they are amateurish junk, but your designs and ideas are so
*ugly* they are borderline grotesque. When you have something artful to suggest that will be the day....
You don't approve of my products? Show us some of yours.
John
As they say, I don't have to be a chef to know the food stinks...
Show us something you've designed.
John
Then by your reasoning, you should be able to gauge the relative stinkness of your own cooking?
Gee Fred, is there anything you DO like about electronics?
Maybe its not the food, but the diner?
You show us an esr meter that doesn't require a VMX crate.
I suggest we have an esr-meter design contest. However, to make it usenet friendly, and accessible to the readers, all entries must be made in ASCII drawings, annotated with text.
Okay, you're on!
Eh? No real engineers need apply ?:-)
...Jim Thompson
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