I posted a couple of half-baked ESR meter schematics. A couple of people riffed on them constructively.
Or poor players. I'd think the idea of brainstorming in public would appeal to some people, like a trapeze act without a net. Looks like I was wrong.
John
OK, I'll stand while these guys dance around the problem.
John
noting that 10 mA into 1 mohm is 10 microvolts, still pencil-free.
If it's all AC coupled, it could be protected from reasonable hazards and do batteries, too.
If the frequency could be swept, it could analyze power supply output impedances, too. Nice for stability analysies.
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.
If I had the time to play with this stuff, I would be trying to design a proper VNA with 12 term correction that will go up to >3GHz, that seems not to have been done yet in the homebrew world.
Chris
That's a nice juicy signal to work with.
Best regards, Spehro Pefhany
-- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
A really robust design might allow you to check the ESR of the line voltage caps in an operating SMPS, though I'm not sure I'd want to go that far.
Best regards, Spehro Pefhany
-- "it\'s the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
Win, thank you for your concern. They are treating symptoms, not the real problem. Thanks to Congress the VA is not allowed to treat it. My doctor (at least the current one) agrees that my teeth all have to come out. I have had a problem with low level infections most of my life. This infection is in my jawbone, at the roots of my teeth.
Under a law passed by congress, teeth are NOT a medical issue. Well, at least for Veterans. Period. End of story. Don't you even think about asking us again! OTOH, these same morons can got into any military medical facility at any time they want, and get free dental care. They don't need appointments, and can cut in front of any soldier's health care, unless they are surgery.
There are three very small groups of Veterans that are granted dental care:
1: Just discharged from active duty, and no care was available where you were stationed. 2: You were being treated when you were discharged. They will continue care for a brief period. 3: Homeless for over 60 days.The VA will do the work if you can pay their price in advance, or sign papers to allow it to be deducted from your disability pension. Their rate is higher than some private practices. If I let them do the work, I would be homeless.
I had oral surgery to remove a hollow stump that was cutting my tongue a few months ago, thanks to some friends that got together and raised the money. The oral surgeon that did the work refuses to pull the nine remaining teeth because he can't see any reason for them to cause pain. He said it was just the nerves in the jaw bone being affected by the one infected tooth. He was wrong. Not that it matters, because there is no way I can afford the $250 per tooth, for nine teeth. That is over 20% of my income for the year.
The County health office refused to help, because "We only treat women and children's dental problems.". (Plus all of the illegal aliens.) They didn't want to give me any help at all, because "Oh, you know that the Federal government takes care of everything for you vets, and we have to help all these unmarried women (and their illegitimate kids)!".
The state dental college in Gainsville is no help. Their prices aren't that great, its a several hour trip, and they play a daily lottery to see who gets treated that day.
As the infection level changes, it affects the blood sugar and pressure, and causes more or less swelling in my legs. While I was on antibiotics to prepare for the oral surgery the swelling went completely down, and all the pressure sores dried up in under 48 hours. I had to stop taking all my medications, but my blood sugar and pressure were almost normal without them. The constant pain and numbness in my left hand and arm was barely noticeable. My vision was the sharpest it had been in years.
In spite of all this, the VA isn't allowed to do what's needed. They spent more on additional medications last year than it would have cost to do the dental work. About $6,000 more.
-- Service to my country? Been there, Done that, and I\'ve got my DD214 to prove it. Member of DAV #85. Michael A. Terrell Central Florida
Sno-o-o-ort! But it'll use a uP ;-)
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
America: Land of the Free, Because of the Brave
(snip)
But.... But.... This project is unmanaged and totally voluntary. It's worse than a Standards meeting. Axes to grind notwithstanding. Under the circumstances, I thought it was moving along somewhat. Lots of latitude is needed unless some rules are formed for handling contributions.
I'm learning a bunch and have only one contribution. It is that posts that argue against designing the device should be considered TOTALLY out of order. It appears to me to be a project for those who "can do" and want to do. All others can remain (or start to be) silent.
Whoever suggested the project did a brilliant thing.
Golly gee, Ferddie! Just where would I find this support group for "Congress is practicing medicine, on me?" and has no damn idea what they're doing?
Why don't YOU abandon usenet and join a support group for "I only think I'm superior to everything else in the known universe"?
-- Service to my country? Been there, Done that, and I've got my DD214 to prove it. Member of DAV #85. Michael A. Terrell Central Florida
Yes, of course -- required.
Yes. Since I've got gain and synchronous detection, 10uV should be fine. I'm planning using a 199.9mV FS Datel panel meter (low power), so for a 2-ohm range, with 1 mill-ohm resolution, a G=10 instrumentation amplifier will be OK (an extra x1.414 for RMS will be squeezed in someplace). G=100 would provide 0.1m resolution, but there'll probably be a fair amount of noise and drift, etc., anyway.
Initially I had considered 100mA drive, but that'd be hard on the battery, and worst-case capacitor-discharge current would be 10x higher. Course, we could add a depletion-mode limiter, as you suggested...
Mine won't. They require code.
I like that one, John. Now how about the IN amp? Maybe the AD8220, but I'd like more common-mode range.
One concern will be inductive coupling in the 4 leads going out to the DUT; that could easily bash a lot more than 10 uV into the sense circuit. If it can really do values like a milliohm, the leads will have to be done right, too.
What's the sinewave source? Are you going to trim the phase of the drive into the phase-sensitive detector? To get good capacitance rejection, the phase will have to be spot-on.
John
If you're working at a fixed 100 KHz, how about using a transformer? You'd get absurd common-mode range and some decent voltage gain for free. Maybe even tuned, with a trimmer cap that fine-tweaks the system phase alignment.
John
Michael,
I'm sure you'd disagree with him about a lot of things, but if you have the opportunity, you'd probably enjoy watching Michael Moore's latest film, "Sicko." He has various cases similar to yours in there -- folks like 9/11 rescue workers who were *volunteer* EMTs, and as such there was no one interested in patching them up after, e.g., burning their lungs out digging through the debris of the twin towers. Sadly, it appears as though you'd be getting better care right now if you were a Canadian, Englishman, or possibly even a Cuban rather than a U.S. Citizen.
Hey, if we come up with a decent ESR meter design, perhaps you could assemble & sell them and make enough money on the side to cover some of your medical needs.
This wouldn't work for you, but there's a Michigan? woman in Sicko who just crosses the border into Canada and gets medical treatment there by listing a friend of hers as her common law husband.
---Joel
no, I assumed you werent stupid enough to actually do that, and would of course include some R, as John D. pointed out. Merely illustrating how to move the switch out of the measurement path, to achieve the same objective.
Cheers Terry
[snip]
It's not just VA. Medicare doesn't cover dental either. My wife had over $12K of dental surgery last year due to (what you seem to have) a tooth infection that got into the jawbone.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
America: Land of the Free, Because of the Brave
I'm not. Did you also expect all the lurkers out there to understand, as well? I've seen people stupid enough to wire a power switch across a device to turn it off by shorting it out, then complaining that they were being sold defective power transformers, because they kept burning them up.
At least put a smiley with bad ideas like that to give them a clue. I've smelled enough burnt insulation from people who don't grasp the basics.
-- Service to my country? Been there, Done that, and I've got my DD214 to prove it. Member of DAV #85. Michael A. Terrell Central Florida
That is still a lot more signal than the noise on the input of an op- amp or a 100K resistor.
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