-1
\$\begingroup\$

Ceramic capacitors are not marked with any kind of code that we can identify their model. Think that we have a batch of capacitors (lots of nearly identical capacitors) with unknown ratings. We can obviously use LRC meter to measure a capacitor's capacity. How can we verify or identify its voltage rating?

One solution I can think of is applying the alleged voltage or each possible voltages for ceramic capacitors in the market for a given(?) period of time, then measure its capacity again. If capacity is decreased, we can defer that the capacitor is burned and the capacitor's voltage rating is the voltage that we applied before last one.

Is there any better solution for that? If not, how much time is enough for a reliable voltage rating testing?

\$\endgroup\$

closed as unclear what you're asking by Elliot Alderson, RoyC, Oleg Mazurov, hacktastical, Axeman Aug 23 at 13:34

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • \$\begingroup\$ Your question is not consistent with your comment to @Umar. In your comment you said you want to verify your suppliers, which suggests that you do have a voltage rating for the parts and you want to verify this specification. In your question you said the parts had "unknown ratings" which is a much different problem. \$\endgroup\$ – Elliot Alderson Aug 19 at 11:23
  • \$\begingroup\$ @ElliotAlderson Not necessarily. I stated that "applying the alleged (rated) voltage" in my question, or each available voltage rating one by one in order to test an unknown capacitor's voltage rating. Overall, what is the difference? If you can verify a capacitor voltage rating, then you can identify by trial and error approach too. \$\endgroup\$ – ceremcem Aug 19 at 11:37
  • 2
    \$\begingroup\$ Verifying a specification is a pass/fail test that is easy to perform. Measuring the voltage rating is much more difficult to do, particularly if you have no idea what that voltage rating should be. \$\endgroup\$ – Elliot Alderson Aug 19 at 11:43
  • \$\begingroup\$ There are just a few options of capacitor ratings for ceramic capacitors in the market, AFAIK: 16V, 25V, 50V, 100V. That's not seem to be hard to try each one. I'm not talking about measuring if the capacitor rating is 18V or 19V. \$\endgroup\$ – ceremcem Aug 20 at 3:56
2
\$\begingroup\$

The voltage rating is tied up to the lifetime of the capacitor, so doing a short test will not give definitive answers immediately, which is unfortunate for you.

However I would play with the DC-bias characteristic. When applying a DC voltage across the capacitor to capacitance value will drop significantly. Especially DC-bias close to the voltage rating.

I recommend that you look at Murata's SimSurf online portal. Here you can input a DC-bias for a given capacitor and see how much the capacitance drops. Then try and compare with your test values, from DC Power supply and LCR-meter.

\$\endgroup\$
0
\$\begingroup\$

Summary:

  • it is really not possible to guarantee the characteristics of the capacitor merely by testing only a few random samples from the unknown batch.
  • If these parts are going into a design in to the field, I would never advise to do that.

Capacitor voltage ratings are not highly controlled parameters. So it is difficult to gauge the voltage rating of all the capacitors just by testing.

For example: this was quoted by one of the reputed capacitor supplier. When we order a capacitor with 5 V rating, the capacitor supplied to us can be 5V rated one, or 10 V, or 16V or even 25 V. It depends on their production line and distribution line. Sometimes 5V rating capacitor doesn't even be produced separately but will be listed as 5V(and delivered at slightly lower price) just because there is a competitive part outside with same rating.

How much time is enough?

Really depends on your application life time. Normally, endurance testing (HALT - Highly Accelerated Life Rest) can be done to test the life time of the capacitors. Ceramic capacitor keep their charge well up to high temperature (100 degree C or more) and hence I think the test would be difficult!!)

I believe you are not planning to test all of them. Best bet is to buy new ones with part number, unless this is not going to a product to the field.


From Murata, there is one simple description for the measurement of life time for the Ceramic capacitors in the below link enter image description here https://www.murata.com/en-eu/support/faqs/products/capacitor/mlcc/qlty/0010


Below is a quick comparison of DC bias characteristics of four capacitors of different voltage rating but of same value, same package and same temperature tolerance and same accuracy.

GCM188L81H104KA57,DC0V,25degC ---> 50 V DC GCH188R71E104KE01,DC0V,25degC ---> 25 V DC GCJ188R72A104KA01,DC0V,25degC ---> 100 V DC GCJ188R71E104KA12,DC0V,25degC ---> 25 V DC

enter image description here enter image description here

I would never try to attempt to gauge the voltage rating only from the DC bias characteristics. it is simply not defined but I believe it will follow some what the higher voltage rating curves only based on my past experience.

\$\endgroup\$
  • \$\begingroup\$ "I believe you are not planning to test all of them": I'm planning to test only some random samples. I want to double check my suppliers regardless of their trustworthiness. \$\endgroup\$ – ceremcem Aug 19 at 8:13

Not the answer you're looking for? Browse other questions tagged or ask your own question.