Well, if the peanut gallery is joining in...
At my previous employer, we made equipment that didn't intentionally
radiate. However, it was test and measurement equipment.
So, back in 1996, we used to test to EN 55011 (The EN version of CISPR
11). EN 55011 classified equipment as Doug describes. We were Group 1,
Class A because we didn't intentionally radiate; and we weren't meant for
a domestic environment. EN 55011 set the equipment classifications and
the pass/fail test limits...however, it referred to CISPR 16 for the
test/measurement methods. This is in agreement with Doug's take.
Then, EN 61326-1 (The EN version of IEC-1326-1) came along, and we started
to use that. If I recall correctly, the original (1997) version of EN
61326-1 had its own equipment classifications for emissions (A and B for
Industrial and Residential respectively) and its own pass fail limits for
emissions. So, all it needed was a reference to CISPR 16 for the
emissions test method. I believe that this is also in agreement with
Doug's take where he considers EN 61326-1 and EN 55011 and their IEC/CISPR
equivalents as limit setting documents; while CISPR 16 is a how to test
document.
If you compare the limits of EN 61326-1 to EN 55011 (back in 1997) you
would find that the Class A radiated emissions limits were 10dB higher in
61326-1; but the antenna was moved up to 10m from 30m...which would
"theoretically" give about the same limit because the E field strength
>from the DUT should rise by a factor of 3 (roughly 10dB) if you moved the
antenna 3 times closer.
In my mind, I always thought that the emissions limits in EN 61326-1 were
set to be similar, if not the same as EN 55011. The main difference
between the two was that EN 61326-1 also covered immunity requirements
while creating even finer immunity classifications for test and
measurement equipment ("continuous" vs "discontinuous" operation and
"monitored" vs "unmonitored" operation, "battery powered", "handheld"...)
EN 61326-1:1997 also had the debatable exception for harmonics and flicker
for Class A devices. It specifically called out harmonics and flicker
requirements for Class B devices, while omitting them from the Class A
device requirements. (If anyone cares to search the archives; you'll find
a huge debate on this back in 1997/1998.)
Many people have used EN 55011 and EN 61326-1 almost interchangeably for
emissions limits. However EN 61326-1 is more complete for equipment that
fits its scope because of the fine points that I highlight above. I also
agree with Doug and Derek in that, references to CISPR 11 and/or EN 55011
in EN 61326-1 probably aren't typos.
Chris Maxwell, M.Sc
Electrical Engineer
Critical Imaging LLC
> From the peanut gallery:
>
> CISPR 11 Classifies ISM Equipment into different categories:
> Group 1 & 2 and Class A & B
>
> FROM CISPR 11 (with comments):
> Group 1 ISM equipment: group 1 contains all ISM equipment in which there
> is
> intentionally
> generated and/or used conductively coupled radio-frequency energy which is
> necessary for the
> internal functioning of the equipment itself.
> (Translate this to mean internal clocks and compare it to the definition
> of
> Digital Devices used be the FCC.)
>
> Group 2 ISM equipment: group 2 contains all ISM equipment in which
> radio-frequency energy is
> intentionally generated and/or used in the form of electromagnetic
> radiation
> for the treatment of
> material, and EDM and arc welding equipment.
> (The devices that transmit RF energy intentionally into the environment
> for
> industrial purposes)
>
> Excluded from the testing requirements and limits of this standard are
> components and
> subassemblies not intended to perform any stand-alone ISM function.
>
> Class A equipment is equipment suitable for use in all establishments
> other
> than domestic and
> those directly connected to a low voltage power supply network which
> supplies buildings used
> for domestic purposes.
> (This seems very straight forward and I believe is the same wording as
> found
> in CISPR 22 and 47 CFR Part 15)
> NOTE 1 Operation of equipment which does not meet the class A limits but
> does not result in unacceptable
> degradation of radio services may be sanctioned on a case-by-case basis by
> the competent national authority.
> NOTE 2 Although class A limits have been derived for industrial and
> commercial establishments, administrations
> may allow, with whatever additional measures are necessary, the
> installation
> and use of class A ISM equipment in a
> domestic establishment or in an establishment connected directly to
> domestic
> electricity power supplies.
> (I get a chuckle out of NOTE 2)
>
> Class B equipment is equipment suitable for use in domestic establishments
> and in
> establishments directly connected to a low voltage power supply network
> which supplies
> buildings used for domestic purposes.
> -----
>
> I'm in agreement with Derek and think that it isn't a 61326 typo, but a
> correct clarification. If I want to do more research on a measurement
> technique or equipment I pick up CISPR 16. For a particular test method
> for
> a specific type of product, CISPR 11 or 22 or 14, etc. A vast majority of
> the products that I see are Group 1 Class A devices per the definitions
> above. I would call most "Electrical equipment for measurement, control
> and
> laboratory use" scientific devices falling under ISM.
>
> Regards,
> Doug
>
>
-
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