Hi Ken and the group,
Thanks for the information. The common mode current was in the 100 MHz
region and WAY over what would be enough to exceed just about any
limits of radiation, and this was on the power cord (and therefore any
other leads to some extent).
Doug
Ken Javor wrote:
> I have seen the same kind of thing, but I believe there is a simple
> explanation. The input leads must meet CE102, but the output leads need only
> meet RE102, so they shield the output leads running to a dummy load in a
> control chamber. The fact that the customer can't shield the leads is
> another problem for another day. This doesn't happen when equipment is
> procured by an integrator and designed per the integrator's definition, but
> it is common with off-the-shelf gear.
>
>
>
> for a son 3/26/03 1:38 AM, Doug Smith at d...@emcesd.com wrote:
>
>
>>Hi All,
>>
>>Just wanted to put my 2 cents worth in. The same thing may be
>>happening in Mil-spec testing. Recently, I was at a client's site for
>>a purpose unrelated to this story.
>>
>>I noticed interference to the measurement I was trying to make on a
>>piece of equipment. The equipment had enough common mode current on
>>its leads to fail emissions, even though it was turned off! There was
>>a military battery charger for small batteries on their bench so I
>>connected my current probe to its power cord and noticed enough common
>>mode current to cause a 30 dB+ failure of emissions over a broad
>>frequency range. I would suppose the battery charger had been tested
>>to mil-specs. If so there is a problem here, even accounting for the
>>repeatability problems in mil-spec testing.
>>
>>Doug
>>
>>Grasso, Charles wrote:
>>
>>>Hi Derek - Go Reds!!
>>>
>>>This is not a surprise to me. I have railed at much length a couple
>>>of years ago as to the latest FCC changes to the emissions
>>>qualification. I am sure you are familiar with it so I won't
>>>belabour the point. Fundementally the FCC PC emissions procedure
>>>has rendered the EMC discipline almost irrelevent. The new procedures
>>>coupled with the lack of enfocement makes it difficult to justify
>>>the increased costs of EMC design & test. It also makes the
>>>whole measurement uncertainty push ridiculous. After all
>>>if the procedures allow for prodcut that 20dB out of spec why
>>>bother with a couple of dB of error??
>>>
>>>Lets give the emissions standards some teeth or eliminate it
>>>all together.
>>>
>>>.......
--
___ _ Doug Smith
\ / ) P.O. Box 1457
========= Los Gatos, CA 95031-1457
_ / \ / \ _ TEL/FAX: 408-356-4186/358-3799
/ /\ \ ] / /\ \ Mobile: 408-858-4528
| q-----( ) | o | Email: d...@dsmith.org
\ _ / ] \ _ / Website: http://www.dsmith.org
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