Lcr-t4

[Nazarych]

Hi friends! Tell me, what table to use for measuring ESR Capacitor? The Device - LCR-T4!
Sorry for mistakes!

[mariushm]

Re: Lcr-t4

There is no right table to use.

The tables you find on the Internet are just approximations, basically they tell you that for a large number of series of capacitors of a certain capacitance range and voltage rating, you should expect ESR value to be less than the amount listed.

There are older series of capacitors which have ESR much higher than new series of capacitors with same capacitance and voltage rating, so you can't go just by the number in the table.

For example, an older Nichicon PM series 33uF 35v should have an ESR of 0.49 ohm or lower while a newer Panasonic FM 33uF 35v should have an ESR of 0.3 ohm or less... which is pretty big difference, but both are good values.

If your table says expect 0.5 ohm or less and your Nichicon PM capacitor shows 0.55-0.6 ohm on the esr meter, technically I would still consider it good enough (because it's probably quite old and as they age capacitors degrade a bit)

On the other hand, if I use this chart below and test a Nichicon PM capacitor and it shows 1 ohm, it would be bad because I expected around 0.5 ohm and I got twice that. Yet the table says anything below 1.2 ohm is fine, which obviously isn't - 1.2 ohm may be fine for some older general purpose capacitors but not for newer series :



The best thing to do would be to search for the capacitor series you test, download the datasheet and compare your readings with the values in the datasheet.
Once you do a bunch of measurements you sort of get an idea of what capacitors would measure and you won't need tables anymore.

[Nazarych]

Re: Lcr-t4

I found the datasheet Nichicon, but can not find ESR. Can you tell? Maybe I did not understand until the end!
https://cdn.badcaps-static.com/pdfs/...d50db6d4ae.pdf

[mariushm]

Re: Lcr-t4

At high frequencies (let's say 50kHz or higher), the ESR of electrolytic capacitors is pretty much equal to impedance. It's within a few percent of the actual ESR value, it's basically so close that you don't care.

So you can look in the datasheet at the Impedance section, at the 20 C / 100 kHz column. You don't care about measurements done at negative temperatures, as your circuit is unlikely to be running at -10c or negative temperatures.

For the 33uF 35v capacitor, you look in that datasheet on page 5 and you have there 33uF , 35v, 6.3 x 11 mm , 0.49 ohm impedance at 20c / 100 kHz and 225mA ripple current at 105 c/ 10kHz..200kHz
That's the most important things you need to know when replacing capacitor with another one... impedance should be as close as possible or a bit lower than the original capacitors, and the ripple current should be very close or higher.

So less impedance is ok, but much lower impedance can be bad for circuits.
Less ripple current can be bad, capacitors can be damaged. Higher ripple current is OK.

The cheap ESR meters don't measure the actual ESR value anyway, they measure something close to what ESR would be, just like the impedance column is something very close to ESR.

Proper ESR meters cost from about 80$ and up (you would look for LCR meters with ESR measurement capability at 100kHz).

[Nazarych]

Re: Lcr-t4

1. In the last table dont have all values, including impedants. Where to get impedants for 160-450v?
2. How to measure the ripple current?
3. Is it enough to measure Lcr-t4?
4. What is the deviation of normal capacity capacitor, so it can be used?(For example: 1000uF)

Sorry to ask many questions)

[stj]

Re: Lcr-t4

you cant test ripple without very expensive equipment

[Nazarych]

Re: Lcr-t4

It is very bad! The second question is exhausted.

[mariushm]

Re: Lcr-t4

For large capacitors, the impedance is usually small, below 1-2 ohm.

Anyway, high voltage capacitors (200v+) are not usually used in circuit at high frequencies. At most they're subjected to pulses of power coming from the Active Power Factor Correction circuitry, but they're not as "stressed" as the low voltage capacitors on the secondary side of a DC-DC converter.

Also, keep in mind that cheap ESR meters like LCR-T4 may not be able to accurately measure the ESR of such large capacitors, such cheap tools are "optimized" for capacitors rated for lower voltages and high capacitance.

I 'm not sure I understand what you mean by deviation of normal capacity.

Electrolytic capacitors should be the value listed on label +/- 20% (the default). The modern fabrication technologies make it possible to get capacitors within +/- 5% of the value desired.

When capacitors go bad, sometimes the actual capacitance can increase (you should still replace those capacitors though)

ps. if you don't know, that's what the letter M you see on lots of capacitors is for, the +/- 20% tolerance.

EIA Tolerance Capacitor Marking Code
Letter Tolerance
Z +80%, -20% - this is used with electrolytic capacitors where the minimum value is the major issue.
M ±20%
K ±10%
J ±5%
G ±2%
F ±1%
D ±0.5%
C ±0.25%
B ±0.1%

A lot of other codes commonly used, you can find here: http://www.radio-electronics.com/inf...r-markings.php

[Nazarych]

Re: Lcr-t4

I 'm not sure what understand what you mean by "When capacitors go bad".


Suppose I have a capacitor 450v, 100uF(M): 120-80uF, 0-2 Om - Working,
120+ or 80-uF, 2+Om - not work?
I understood correctly?

[Nazarych]

Re: Lcr-t4

I 'm not sure what understand what you mean by "-20% - this is used with electrolytic capacitors where the minimum value is the major issue."

[stj]

Re: Lcr-t4

+-20% of the uF over it's rated temperature range.
(caps look better when warm!)

[mariushm]

Re: Lcr-t4

The capacitors have from the factory a capacitance value that's within -20% and +20% of the actual value. If the value is outside that range, the capacitor is probably faulty/bad.

So for example, if you buy 100 capacitors which say on them 100uF 450v, it would be perfectly acceptable to measure anything between 80uF and 120uF. In real world however, the large majority of them should be closer to 100uF.

Just out of curiosity, I have here in front of me a box with about 50 100uF 25v Panasonic FM capacitors and i'm going to pick random ones and list the capacitance:

96.25
95.37
96.38
98.24
96.12
96.85
96.25
97.14
95.81
96.83

So as you can see the manufacturing process is so refined that even though the tolerance is +/-20%, they're pretty much in the +/- 5% range. The capacitance may be affected a bit by ambient temperature, my room right now is probably around 20c.

With this particular series and manufacturer (Panasonic), knowing that they're usually pretty close to the value printed on them, I'd be a bit concerned if I pull one out of a circuit and I measure it and read for example 85uF ... while "legally" the capacitor could be between 80uF and 120uF , I know that the large majority of capacitors in this series should be within 95 .. 105 uF so a 85uF capacitor would worry me a bit.

I 'm not sure what understand what you mean by "-20% - this is used with electrolytic capacitors where the minimum value is the major issue."

There are particular types of capacitors which can be fabricated to have large capacitance but have some drawbacks compared to regular capacitors like large variation with temperature or with voltage or other things.
Those capacitors are sold as a value, but may the actual value may be as low as -20% ... and up to 80% more than normal printed capacitance.
You could use such capacitors for example for a camera flash - you don't care how much energy you store in the capacitor, as long as it's at least a certain amount of energy.

// measured using a Uni-T ut61e multimeter, which is a 22000 count meter with +/-3% accuracy when it comes to measuring capacitors.

[Nazarych]

Re: Lcr-t4

To summarize:
1. The main indicators of the capacitor are capacitance, ESR and ripple current.
In some datasheet No ESC, I can use impedance.
For measure ripple current Need expensive device!

2. The caps look near capacity have meant tolerance capacity through temperature.
Better if it will be close to normal.

3. For 160-450v Impedance(ESR) is 1-2 Om.

I understood correctly?

[Nazarych]

Re: Lcr-t4

Thank you for answering!