Hi,

Is it possible to test capacitors reliably without a capacitance
meter?


Marky P.

"Marky P" wrote in message
...
Hi,

Is it possible to test capacitors reliably without a capacitance
meter?

If you want to test capacitors reliably you need an ESR (Effective series
resistance) meter, not a capacitance one.

Otherwise testing by substitution is your best bet.

David.

"David Looser"
"Marky P"

Is it possible to test capacitors reliably without a capacitance
meter?

If you want to test capacitors reliably you need an ESR (Effective series
resistance) meter, not a capacitance one.


** That only applies to electrolytic caps - plus the name is "equivalent
series resistance".

Plus an ESR meter will NOT find electro caps that have excessive leakage,
de-polarised or even become short circuit.

Capacitance meters are basically only handy when you have caps with no
markings, ambiguous markings or an unknown colour code.


...... Phil

"Phil Allison" wrote in message
...

"David Looser"
"Marky P"

Is it possible to test capacitors reliably without a capacitance
meter?

If you want to test capacitors reliably you need an ESR (Effective series
resistance) meter, not a capacitance one.


** That only applies to electrolytic caps -

True, but with modern equipment the vast majority of faulty capacitors are
electrolytics. Of course if he was talking about pre-1960 equipment then
leaky paper capacitors are almost a given.

plus the name is "equivalent series resistance".

Both terms are used. In this context they are equivalent because they
effectively mean the same thing.

Plus an ESR meter will NOT find electro caps that have excessive
leakage, de-polarised or even become short circuit.

Agreed, but these faults are readily apparent with normal testing methods.

Capacitance meters are basically only handy when you have caps with no
markings, ambiguous markings or an unknown colour code.

Agreed.

David.

"David Looser the Brain Dead Lying **** "


Is it possible to test capacitors reliably without a capacitance
meter?

If you want to test capacitors reliably you need an ESR (Effective
series resistance) meter, not a capacitance one.


** That only applies to electrolytic caps -

True, but with modern equipment the vast majority of faulty capacitors...


** So ****ing what ?

The OP never alluded to what sort of caps he wanted to test.

So your assumption is 100% FALSE !!!!!!!!



plus the name is "equivalent series resistance".

Both terms are used.


** Complete ********.


Plus an ESR meter will NOT find electro caps that have excessive
leakage, de-polarised or even become short circuit.

Agreed,


** So your assertion above is a 100% total pile of CRAP.

Just like you - sunshine.




...... Phil

Phil Allison wrote:

True, but with modern equipment the vast majority of faulty capacitors...
** So ****ing what ?
The OP never alluded to what sort of caps he wanted to test.
So your assumption is 100% FALSE !!!!!!!!

You know, when I see an outburst like this I always imagine the poster
sat at the computer wearing his underwear and a straight jacket, typing
by picking up a pencil in his teeth and dribbling everywhere.

Either that or wearing a dress like the character "Anne" in the popular
British comedy "Little Britain".

--
Squirrel Solutions Ltd Tel: (01453) 845735
http://www.squirrelsolutions.co.uk/ Fax: (01453) 843773

Registered in England: 05877408

David Looser wrote:

"Marky P" wrote in message
...
Hi,

Is it possible to test capacitors reliably without a capacitance
meter?

If you want to test capacitors reliably you need an ESR (Effective series
resistance) meter, not a capacitance one.

Otherwise testing by substitution is your best bet.

David.


Its possible measure the value of capacitance using a low Rout signal
generator feeding a potentiometer in series with the capacitor with one
lead grounded. A volt meter is used to measure signal voltage across the
C. Set the signal gene at 10.0V sine wave at some chosen F. Alter the
value of the series resistance until you see 7.07Vrms appear across the
capacitor.
Disconnect the pot without altering its resistance, then measure its
resistance accurately.

C in uF then can be calculated = 159,000 / ( R in ohms x frequency ) so
say you had R = 5,000 ohms, and F = 1.0kHz, then C = .0318uF .

You could also have an air cored inductor of known inductance, and
parallel the C with the L, and feed it with a signal from a 10k
resistance from the sig gene. Using an osciloscope, tune the gene F for
the highest peak in resonance, known as Fo. Record Fo.

C in uF = 25.351 x 1,000,000 / F in Hz squared x L in milliHenrys.

Eg, if L = 100mH, F = 1kHz = 1,000 Hz, C = 0.251uF.

There are other ways using an old fashioned bridge.

ESR is measured in other ways, but it seems the OP wanted to know how to
work out the C value without a C meter.

Many cheap DVMs now sold measures C very well.

But they don't always measure L very well, espcially iron cored items
with variable L value at different F and V applied.

Patrick Turner.

"Patrick Turner" wrote in message
...



ESR is measured in other ways, but it seems the OP wanted to know how to
work out the C value without a C meter.

Does it? the OP talked about "testing" a capacitor, not "measuring" it; that
sounds to me more like someone who wanted to know whether a capacitor was
faulty.

Since the OP has remained silent since his first post what he actually
wanted remains a mystery.

David.

On Wed, 1 Oct 2008 10:42:53 +0100, "David Looser"
wrote:

"Patrick Turner" wrote in message
...



ESR is measured in other ways, but it seems the OP wanted to know how to
work out the C value without a C meter.

Does it? the OP talked about "testing" a capacitor, not "measuring" it; that
sounds to me more like someone who wanted to know whether a capacitor was
faulty.

Since the OP has remained silent since his first post what he actually
wanted remains a mystery.

David.

Very sorry! I forgot made this post (someone over at alt.digital.tv
remined me). I want to test for faulty caps. It's in a power supply
unit in a 1980's professional multi-track tape recorder

Marky P.

"Marky P" wrote in message
...
On Wed, 1 Oct 2008 10:42:53 +0100, "David Looser"
wrote:


Since the OP has remained silent since his first post what he actually
wanted remains a mystery.

David.

Very sorry! I forgot made this post (someone over at alt.digital.tv
remined me). I want to test for faulty caps. It's in a power supply
unit in a 1980's professional multi-track tape recorder


Faulty capacitors in power supplies usually make themselves apparent by such
problems as low voltage or excessive ripple on one or more of the output
lines, or rather more obviously by leaking electrolyte, bulging seals etc.
In view of the age of this unit your best bet is probably simply to replace
any suspect capacitors rather than bothering to try and test them.

David.