Quick Capacitance Testing Help

[[email protected]]

Greetings. I need some quick help on this easy question. I am testing
capacitors in the power supply and other sections of an LCD monitor
using a RadioShack 42-Range DMM with capacitance testing functionality.
When I connect the leads to the electrolytic capacitors (polarity is
accounted for), all I get is a 0.F reading (in the µF range),
indicating overflow. This is the case when I test on other devices
too. Is my DMM damaged or what? Could it be the range of the DMM is
simply unable to accomidate for the capacitance? I don't personally
believe the latter is the case at all since no type of capacitor
registers anything with this test. If it is a problem with the
multimeter, what other tests can I do to see if the capacitor is good
or bad, or leaky, or whatever else it may be? Thanks a lot, I sure
appreciate it.

A learning, amateur electrician,
Brad G.

 

[Ralph Mowery]

Greetings. I need some quick help on this easy question. I am testing
capacitors in the power supply and other sections of an LCD monitor
using a RadioShack 42-Range DMM with capacitance testing functionality.
When I connect the leads to the electrolytic capacitors (polarity is
accounted for), all I get is a 0.F reading (in the µF range),
indicating overflow. This is the case when I test on other devices
too. Is my DMM damaged or what? Could it be the range of the DMM is
simply unable to accomidate for the capacitance? I don't personally
believe the latter is the case at all since no type of capacitor
registers anything with this test. If it is a problem with the
multimeter, what other tests can I do to see if the capacitor is good
or bad, or leaky, or whatever else it may be? Thanks a lot, I sure
appreciate it.

A learning, amateur electrician,
Brad G.

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Are you trying to test them in the circuit ? If so the meter usually will
not work. You will have to remove atleast one lead of the capacitor from
the circuit to test it. This is often the case of many components. If it
is a digital meter you may be able to test some components in the circuit,
but not usually the capacitors.

 

[[email protected]]

Greetings. I need some quick help on this easy question. I am testing
capacitors in the power supply and other sections of an LCD monitor
using a RadioShack 42-Range DMM with capacitance testing functionality.
When I connect the leads to the electrolytic capacitors (polarity is
accounted for), all I get is a 0.F reading (in the µF range),
indicating overflow. This is the case when I test on other devices
too. Is my DMM damaged or what? Could it be the range of the DMM is
simply unable to accomidate for the capacitance? I don't personally
believe the latter is the case at all since no type of capacitor
registers anything with this test. If it is a problem with the
multimeter, what other tests can I do to see if the capacitor is good
or bad, or leaky, or whatever else it may be? Thanks a lot, I sure
appreciate it.

A learning, amateur electrician,
Brad G.

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@

Are you trying to test them in the circuit ? If so the meter usually will
not work. You will have to remove atleast one lead of the capacitor from
the circuit to test it. This is often the case of many components. If it
is a digital meter you may be able to test some components in the circuit,
but not usually the capacitors.

Yeah, it's a digital meter. According to the manual, it's supposed to
be able to do in-circuit testing for capacitance. It grants that
you'll get a more accurate result if the capacitor is out of the
circuit, but right now I'm just aiming for getting a result at all.
Thanks once again

 

[Michael Black]

Yeah, it's a digital meter. According to the manual, it's supposed to
be able to do in-circuit testing for capacitance. It grants that
you'll get a more accurate result if the capacitor is out of the
circuit, but right now I'm just aiming for getting a result at all.
Thanks once again

If you're checking electrolytics, they may still hold a charge, which
may affect readings.

Keep in mind that the meter (unless it is out of the ordinary) is only
going to let you measure capacitance. And that will be affected by
the parallel components in the circuit. Maybe more important, many
capacitors will fail in other ways before their capacitance changes.
Especially electrolytics, where the failure often comes from rising
internal resistance, so they just can't do their job right. They
may show the proper value on the capacitance meter, but just can't
do the work. A different kind of meter, an esr meter, is used for
that sort of thing (and I gather is often the first thing used when
troubleshooting where time is money); it tests to make sure the
internal resistance of the capacitor has not gone up greatly.

Michael

 

[Michael A. Terrell]

Greetings. I need some quick help on this easy question. I am testing
capacitors in the power supply and other sections of an LCD monitor
using a RadioShack 42-Range DMM with capacitance testing functionality.
When I connect the leads to the electrolytic capacitors (polarity is
accounted for), all I get is a 0.F reading (in the µF range),
indicating overflow. This is the case when I test on other devices
too. Is my DMM damaged or what? Could it be the range of the DMM is
simply unable to accomidate for the capacitance? I don't personally
believe the latter is the case at all since no type of capacitor
registers anything with this test. If it is a problem with the
multimeter, what other tests can I do to see if the capacitor is good
or bad, or leaky, or whatever else it may be? Thanks a lot, I sure
appreciate it.

A learning, amateur electrician,
Brad G.

is a better place to ask for help
repairing something. Electrolytics need to be tested for ESR, which
takes different equipment..


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida