Hello all,

this might be a bit off topic, however is there a (easy or not) way to
tell the working voltage of a ceramic disc capacitor? I have tons of
these surplus or saved capacitors but often the working voltage is
marked when equal or higher than 1 kV. When I have to reuse a capacitor
in a high but not so high voltage circuit (let's say 200 Vdc) I never
know how to find the correct size or how to measure the insulation
voltage of the capacitor.
Fortunately film capacitor have a clear marking :-)
Best regards

Francesco IS0FKQ

In article . com,
wrote:

this might be a bit off topic, however is there a (easy or not) way to
tell the working voltage of a ceramic disc capacitor? I have tons of
these surplus or saved capacitors but often the working voltage is
marked when equal or higher than 1 kV. When I have to reuse a capacitor
in a high but not so high voltage circuit (let's say 200 Vdc) I never
know how to find the correct size or how to measure the insulation
voltage of the capacitor.

Francesco-

A problem with determining a capacitor's voltage, is that the test can
be destructive. Once the insulation resistance has broken down, the
capacitor is most likely no longer unusable.

For ceramic capacitors, you can take a chance and apply twice the
expected working voltage and verify there is no leakage after the
initial charging has occurred. Some capacitor testers have a capability
to do this test.

Fred
K4DII

"Fred McKenzie" wrote in message
...
In article . com,
wrote:

this might be a bit off topic, however is there a (easy or not) way to
tell the working voltage of a ceramic disc capacitor? I have tons of
these surplus or saved capacitors but often the working voltage is
marked when equal or higher than 1 kV. When I have to reuse a capacitor
in a high but not so high voltage circuit (let's say 200 Vdc) I never
know how to find the correct size or how to measure the insulation
voltage of the capacitor.

Francesco-

A problem with determining a capacitor's voltage, is that the test can
be destructive. Once the insulation resistance has broken down, the
capacitor is most likely no longer unusable.

For ceramic capacitors, you can take a chance and apply twice the
expected working voltage and verify there is no leakage after the
initial charging has occurred. Some capacitor testers have a capability
to do this test.

Dielectric stress tests should be run for a long period of time, if you
really want to be sure.

If the OP has lots of capacitors and the ability to safely test at high
voltages, then destructive testing is an option. One determines the failure
voltage and then extrapolates the safe working voltage from that (more than
one unit must be failed, to be reasonably sure).

High-capacity ceramics might be safe at 50 dcwv, or so. Moderate capacity
ceramics are probably OK at 100 to 200.

wrote:

Hello all,

this might be a bit off topic, however is there a (easy or not) way to
tell the working voltage of a ceramic disc capacitor? I have tons of
these surplus or saved capacitors but often the working voltage is
marked when equal or higher than 1 kV. When I have to reuse a capacitor
in a high but not so high voltage circuit (let's say 200 Vdc) I never
know how to find the correct size or how to measure the insulation
voltage of the capacitor.
Fortunately film capacitor have a clear marking :-)
Best regards

Francesco IS0FKQ

my first q is to check that youre familiar with the voltage codes used
on ceramics. V rating is indicated by one letter or number. If so, and
theyre unmarked for some reason, do you have many of each type? If so,
testing a few to destruction would be a workable way to get some
ratings. Cant think of any other options, unless perchance you remember
the operating V of what they were taken off.


NT

ha scritto:

wrote:

Hello all,

this might be a bit off topic, however is there a (easy or not) way to
tell the working voltage of a ceramic disc capacitor? I have tons of
these surplus or saved capacitors but often the working voltage is
marked when equal or higher than 1 kV. When I have to reuse a capacitor
in a high but not so high voltage circuit (let's say 200 Vdc) I never
know how to find the correct size or how to measure the insulation
voltage of the capacitor.
Fortunately film capacitor have a clear marking :-)
Best regards

Francesco IS0FKQ

my first q is to check that youre familiar with the voltage codes used
on ceramics. V rating is indicated by one letter or number. If so, and

I'm not sure about these codes, often on ceramics I see only 3 numbers
and one letter and I assume the one letter is the tolerance code (M, Z
often).
Other have someting like 103P with an E on top and 82 lower in the
disc.
Others have YY on top and usual capacity code on a lower line.
In short the answer is no, I haven't been able to find good references
about all markings, so if anyone has good sources for learning these
codes please share them!
As for the destructive test, yes, it's an option, so if other else
fails, I'll test them this way.

Thanks!

Francesco IS0FKQ

Capacitor Voltage Rating codes:

1 = 100V
3 = 25V
4 = 4v
5 = 50V
6 = 6.3V
8 = 400V
9 = 5v -- ?
9 = 300V -- ?
* = 75V
A = 1000V
C = 600V/630V
E = 150V
F = 63V
G = 2000V
H = 3000V
J = 4000V
K = 5000V
S = 1500V
V = 250V
W = 2500V
X = 350V
Y = 16V
Z = 10V


Dielectric codes:

A = NP0(C0G)
C = X7R
D = X5R
F = X8R
G = Y5V
U = U Series
W = X6S
Z = X7S


Tolerance codes:

B = ±.10 pF
C = ±.25 pF
D = ±.50 pF
F = ±1% (/= 10 pF)
G = ±2% (/= 10 pF)
J = ±5%
K = ±10%
M = ±20%
Z = +80%, -20%
P = +100%, -0%


NT