Hi Xing,
Find my comments below marked with ***.
Your email stated:
>Our test lab receive a CB TEST REPORT FOR NATIONAL RECOGNIZATION,
>the EUT is a class II ac adapter having a bridging capacitor (4700pF)across
>the reinforced
insulation
>The touch current measured by CB is 0.17mA(4700pF declared)
>but the value we measure is 0.28mA(4700pF)
>which one is correct ?
*** To answer your question, you/we will need to know the applied voltage and
frequency across that
capacitor. On the surface, it does appear that the CB and your lab measured
this parameter under
different conditions. Also, was this single capacitor the only component that
was bridging the
reinforced barrier during the CB's test?
>it depend on test equipment?
*** Possibly.
>How to judge
*** This can easily be calculated. The measured results should be very close to
the calculated
results. For instance:
@120V 60Hz, I = 0.213 mA
@220V 50Hz, I = 0.325 mA
@240V 50Hz, I = 0.354 mA
@264V 50Hz, I = 0.390 mA
>How to obtain accurate result?
*** Use good quality instruments (I'm sure that you are) with suitable
measurement resolution.
I hope this will assist you in approaching a satisfactory resolution to your
problem.
Comments anyone?
Best regards,
Ron Pickard
[email protected]
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