The time constant is obviously milliseconds, not nanoseconds. Electronics doesn't necessarily involve calculus and number theory, but it does require arithmetic.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
You might do an ASCII code analysis of the "u" character in the jpeg file, and give us your expert opinion as to whether it's actually a "p".
Get a life!
-- John Larkin Highland Technology, Inc lunatic fringe electronics
That is the most detailed circuit drawing and annotation to NOT "read anything" that possibly has ever existed.
The waveform as-is is just a waveform; voltage VS time. No capacitance axis. One must interpret it to deduce the capacitance; that interpretation is 47uF.
ESR vs frequency is strange too. But at $40 per joule it's a tad pricey... like 100x the cost of an electrolytic.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
Master writing!
-- Bill Sloman, Sydney
It is 47u the same way my daughter would have written
47u - almost illegibly. (I seriously wonder how anybody could have assessed her exam scripts. I blame keyboards.)While there's no problem with that for the originator, it is a problem if other people need to understand it.
But my handwriting is pretty crappy now :)
My incorrect assumption was inductance in the resistor, but if this is significant then capacitance meters should have different test voltages.
Any good LRC bridge will at least allow you to superimpose an external bias voltage on a capacitor (or a bias current on an inductor). The latter is even more important, wot.
--sp
-- Best regards, Spehro Pefhany Amazon link for AoE 3rd Edition: http://tinyurl.com/ntrpwu8
It isn't for nothing that many types of capacitors have wider tolerances than other components. Most times for smoothing a PSU line you don't care provided that it is more than some minimum amount and capable of handling the ripple current without premature failure.
(some dodgy PC motherboard PSU capacitors notably fail this way)
Real electronic components are always a little bit imperfect. Some more so than others.
-- Regards, Martin Brown
After 20+ posts the question has not been adressed. Why is the charging phase not an e- function but the discharge is?
Werner Dahn
Neither the rise nor the fall is exponential. In this kind of high-K capacitor, C is changing continuously as a function of V, so the curves are distorted. And there's a lot of dielectric absorption, which makes things even mushier.
I'm using these caps as the filters on the output of a bunch of synchronous buck switching supplies. I don't expect a lot of ripple voltage, but the average DC voltage, on various switchers, will change the actual capacitance values, by amounts like 4:1 down from the specified capacitance.
These caps become useless at higher voltages not because they short out, but because the capacitance becomes so small. There are uses for this capacitive nonlinearity, like high-voltage shock lines and RF tuning.
I thought the waveform might be interesting, and it was easy to set up, so I posted it. It became a silly uproar amongst people who are more concerned about penmanship than electronics.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
They can look at the jpeg file name.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
It is a nice and quick way to actually see and to some extent measure the effect. Might be worthy of a mention in the next AoE. If the measurement is done with a low charge current and a hi-res meter plus a computer (Labjack, for example) the measurement could be quite precise.
Thinking about an Excel + VBA app. That reveals I am part of the boomer generation. But I did use the word "app".
-- Regards, Joerg http://www.analogconsultants.com/
Classic c-bridges used low-voltage sine waves. Our Boonton 72s use 100 mV RMS, and one version used 10 mV, to avoid linearities in semiconductor junctions. The Boontons have a rear-panel connector that allows a DC bias to be superimposed on the cap under test. The Boontons are fabulous instruments, cheap on ebay, but would be useless to measure my 47 uF cap.
Cheap c-meters, like in cheap DVMs, charge a cap and measure the time it takes to get to some voltage. They often report nonsense.
The value of a capacitor, like an inductor, can vary a lot depending on the measurement frequency and drive amplitude.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
Extracting a full circuit model, including nonlinearity and DA, might be a PHD thesis project.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
Here's an integrator/Schmitt trigger tri wave generator made with an X7R cap:
(It's the acquisition aid for a super stable etalon-locked diode laser for downhole applications (Allan variance about 1E-10 at 100,000 seconds). Not bad for something that had to fit in a 2-inch cased hole. Pity the start-up went under. (The founder had the most spectacular mid-life crisis in living memory.) :(
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Or you could write it more legibly!
Sigh!
DA should be in the low single-digits for a decent MLCC. That leaves extracting the nonlinearity which doesn't seem too onerous a job if the resolution in the ADC is 12 bits or better. Usually one does not need to know the result to a high degree of precision, just the rough percentage of capacitance loss over a given voltage range.
Of course, this also opens up nice low-frequency variable filter and VCO applications.
-- Regards, Joerg http://www.analogconsultants.com/
Nice! I never saw one that extreme but so far haven't used high-density X7R capacitors in them.
Hopefully not a health crisis. I lost one long-time client to pancreatic cancer. Fast, the president/CEO had only a few weeks. His wife did the right thing, didn't make any major decisions for a year and then sold the company. I have a lot of respect for her remaining this level-headed after such a sad event. We still exchange Christmas cards.
-- Regards, Joerg http://www.analogconsultants.com/
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