The rated voltage of ceramic capacitor is nothing to do with the voltage at which it actually breaks down and fails, it's to do with the voltage at which it retains its capacitance. If you could test the effect on capacitance as the dc bias increases, you'd find that it falls to a fraction of its rated value long before it's actually destroyed.
I had this theory regarding a 555 timer which uses a capacitor to determine frequency or duty cycle. There is a formula for output waveform of the 555 timer. Can the input voltage of a 555 timer be varied (while holding capacitance constant) in order to perform quick and easy capacitance measurements with regards to voltage (at least from 5-15 volts or whatever it is). Or will it exhibit nonlinear behavior because of other circuit properties?
Or of course if any one can suggest a IC that will work for the scenario that I have described it would be appreciated. I think a single chip solution without micro controller would be in everyone's best interest.
I have the same problem. I got 3 component drawers for free.
I had this theory regarding a 555 timer which uses a capacitor to determine frequency or duty cycle. There is a formula for output waveform of the 555 timer. Can the input voltage of a 555 timer be varied (while holding capacitance constant) in order to perform quick and easy capacitance measurements with regards to voltage (at least from 5-15 volts or whatever it is). Or will it exhibit nonlinear behavior because of other circuit properties?
Or of course if any one can suggest a IC that will work for the scenario that I have described it would be appreciated. I think a single chip solution without micro controller would be in everyone's best interest.
In one of my earlier posts I had mentioned a way to use a micro with a DAC, op-amp and ADC to determine the VC at least. It might need to be a boot-strapped op-amp with the higher voltages. A PWM controlled switch mode supply might be easier. My 1000v supply is just a PWM controlled high voltage transformer from some LCD back lighting with a high voltage bridge and high voltage caps. It does the job.
The theory was to charge to a fixed voltage and measure the amount lost at a constant current for an exact duraciton, then charge to the next higher voltage and repeat the process. As the capacitance falls off do to the VC the percentage of loss will increase. My other post might clarify this more.
https://www.eevblog.com/forum/chat/how-to-determine-the-voltage-rating-of-an-unknown-capacitor/msg184583/#msg184583
I'm just trying to think of the simplest solution with lowest part count and greatest availability for everyone.
I think it's worth revisiting what the voltage rating of a capacitor actually means.
With a ceramic, as we've discussed, it's primarily to do with the fall-off of capacitance with voltage. It's a limit imposed by the useful functional performance of the device. Exceed it and the part just doesn't do its job properly - and that's easily defined and measured.
With other types it's not so clear cut, though. Tantalums catch fire and go bang, so I'd be very wary indeed of trying to measure the rated voltage of one at all.
Other types may simply suffer a reduced lifetime at higher voltage, so you might find that a 10V cap works perfectly well at 20V for a while, but dies prematurely. A test instrument won't tell you that, unless you specifically set out to perform long-term reliability testing.
Personally I still think the cheapest, easiest way to get a capacitor of known value and rating for a project is to buy a new one from a reputable supplier - but I applaud the academic exercise nonethelsss.
I bought a Duoyi DY294 Semiconductor analyser a couple of years ago that also claims to provide the breakdown voltage of capacitors. I have never used it for such but suspect it works on the leakage across the dielectric as the voltage is ramped up to 200V I don't like causing a breakdown in a dielectric....it just seems the wrong thing to do somehow. I suppose if the capacitor is sacrificial and not for use it is of little consequence.
I have attached the DY294 manual
A review is here:
http://www.jestineyong.com/review-of-the-dy294-digital-transistor-tester-part-1/
http://www.jestineyong.com/review-of-the-dy294-digital-transistor-tester-part-2/
http://www.jestineyong.com/review-of-the-dy294-digital-transistor-tester-part-3/
For GBP30 delivered, it wasn't a bad buy.
Regards
Fraser
For many ceramic capacitors, the capacitance starts to fall off quite sharply as the dc bias is increased. Perhaps you could devise a circuit which measures capacitance with a gradually increasing dc bias on the cap under test until the capacitance falls by, say, 20%, or you chicken out - whichever happens first!