Noob question for you

[paul1962]

Ok folks,

Let's talk electrolytic capacitors for a minute, which will probably be answered in seconds haha.

I have an out of circuit 47uF electrolytic that is marked up at 16W.V which is reading 90uF (way out of tolerance).

I'm assuming that it is actually 47uF at 16v ? or is this rated at 16W ? as I have never known any cap being marked up as 16W per volt before.
I thought it better to ask before I ended up getting it wrong. If it helps, this is in a pre amplifier circuit.

Could someone please clarify for me ?

Kind Regards

[Station X]

16W.V 16 Volts Working.

Capacitors never have their value expressed in watts. It's capacitance, voltage and ripple current.

[Ed_Dinning]

V W is volts working (16 volts)

If you are testing it with a DVM these can seriously mislead. They are good for volts, amps and ohms, but measuring inductors with iron cores, or caps that might be a bit leaky, forget it

Ed

[paul1962]

Originally Posted by Station X

16W.V 16 Volts Working.

Capacitors never have their value expressed in watts. It's capacitance, voltage and ripple current.

Thank you very much Station X You confirmed pretty much my thoughts. It just confused me seeing the W and V together .. very unusual.

Once again, Kind Regards to yourself and all the other great people on the forum

[Sideband]

Yes, WV is Working Voltage....simple as that!!

[paul1962]

Thank you very much for your input Ed and taking the time to reply

[winston_1]

Originally Posted by paul1962

I have an out of circuit 47uF electrolytic that is marked up at 16W.V which is reading 90uF (way out of tolerance).

Probably not. Many electrolytic capacitors have a tolerance rating of +100%.

[paul1962]

Originally Posted by Sideband

Yes, WV is Working Voltage....simple as that!!

Thanks Sideband and btw ... love your avatar message Rick is certainly out on his own on the keyboard

[Sideband]

Originally Posted by Ed_Dinning

If you are testing it with a DVM these can seriously mislead. They are good for volts, amps and ohms, but measuring inductors with iron cores, or caps that might be a bit leaky, forget it
Ed

Absolutely. Chances are if it's reading 90uF it's probably OK but you can't be sure using a DVM. It doesn't matter how good the DVM is either. You would be better off testing capacitors with one of the ESR meters from eBay. Search Peak Atlas ESR capacitance tester. They are not cheap but do a good job.

[Station X]

We don't know the application, but 16V wkg suggests it's a cathode bypass capacitor for the audio output valve of a receiver.

If it's electrically leaky it'll show up as incorrect cathode voltage, assuming the cathode resistor is OK.

[David G4EBT]

About £25.00 from several eBay suppliers will buy you MK-328 TR\LCR Transistor LCR Tester Semiconductor Device Analyzer, which won't just measure capacitance and ESR, but a whole lot of other things. It automatically recognised the component under test, only needs one key press, and auto shuts off after 20 secs.

Specification:

1. A key operation with automatic shutdown
2. Battery operation is possible since shutdown current is only about 20nA

3. Automatic detection of NPN and PNP bipolar transistors, N- and P-Channel MOSFETs, JFETs, diodes, double diodes, unidirectional thyristor and bidirectional thyristor.
4. Automatic detection of pin layout of the detected part.
5. Measuring the current amplification coefficient of the bipolar transistor and the voltage of base - emitter threshold
6. Darlington transistors can be identified by the threshold voltage of the high current amplification factor.
7. Detection the bipolar transistor and the protection diode of MOS
8. Measuring the Gate threshold voltage and Gate capacity value of MOSFETs.
9. Up to two Resistors are measured and shown values with up to four decimal digits in the right dimension. All symbols are displayed by the probe numbers of the Tester. So Potentiometer can also be measured. .
10. The resolution of the resistance measurement is 0.1Ω, can measure up to 50MΩ
11. One capacitor can be detected and measured. It is shown value with up to four decimal digits. The value can be from 30pF to 100mF. The resolution can be up to 1 pF
12. For capacitors with a capacity value above 2µF the Equivalent Serial Resistance is measured with a resolution of 0.01Ω and shown with two significant decimal digits
13. Up to two diodes are shown in correct order and by diode symbol. Additionally the forward voltages are shown.
14. LED is detected as diode; the forward voltage is much higher than normal. Two-in-one LEDs are also detected as two diodes.
15. If Reverse breakdown voltage is below 4.5 V Zener diode can be identified
16. Measurement of the capacity value of a single diode in reverse direction. Bipolar Transistors can also be analysed, if you connect the Base and only one of Collector or Emitter
17. Only one measurement is needed to find out the connections of a rectifier bridge.
18. Capacitors with value below 30pF are usually not be detected, but can be measured together with a parallel diode or a parallel capacitor with at least 30pF. In this case you must subtract the capacity value of the parallel connected part.
19. Can measure inductance resistance less than 2100Ω, the Measuring range is 0.01mH – 20H, but the accuracy is not very good. The measurement result is only shown with a single component connected.
20. Testing time is about two seconds, only capacity or inductance measurement can cause longer period.

Well worth considering.

You can use it with the three test leads supplied, or the plug-in 'ZIF' socket (Zero Insertion Force) which also comes with it.

Lots of youtube videos about it. EG:

https://www.youtube.com/watch?v=L7HrLqSRxgQ

[G.Castle]

Originally Posted by Sideband

Absolutely. Chances are if it's reading 90uF it's probably OK but you can't be sure using a DVM. It doesn't matter how good the DVM is either. You would be better off testing capacitors with one of the ESR meters from eBay. Search Peak Atlas ESR capacitance tester. They are not cheap but do a good job.

I'll second the Peak Atlas instruments, no not cheap, but service and backup for their gear is second to none. You pays your money and take your choice.

Not a shareholder, just a happy user

[Ed_Dinning]

Yes Peak Atlas is a good instrument to test caps. Other than that I would go for a component bridge, but they can be fiddly to operate.
As has been said, knowledge of voltage readings will also indicate faulty caps

Ed