Quite some time ago a brief discussion of the problems of CISPR-11 was held on emc-pstc. A rumor held that certain problems were going to be fixed. I have examined EN 55011:1998 and found that most of the legacy problems still exist. (This is soley from the Group I point of view, bytheway.)
Fixed Problems: - For "equipment manufactured on a continuous or batch production basis" a single test sample is sufficient; current CISPR-11 requires statistical testing of five to 12 samples. Legacy Problems in Current and New Editions: - Class A explicity calls for 30 meter antenna distance. - Class B explicity calls for 10 meter antenna distance. - The antenna can be moved closer to overcome ambients, but clause 7.1.3 (1998) specifically states that the limit can not be corrected for the closer antenna position. CISPR-22 allows for such a correction. - In clause 7.1.3 (1998) the phrase "The highest recorded level of the electromagnetic radiation disturbance at each frequency shall be recorded." which consequently means (IMO) that every signal must be recorded at every frequency regardless of amplitude, a potentially time-consuming task. Besides, that statement repeats itself. New Problems or Potentials in 1998 Edition: - Extensive "safety and sensitive service bands" with specific emission limits (many measured at 10 meters only) are in Table 6, Annex E and F; they appear to apply to Group I equipment as well as Group II equipment. - Measurement methods for vertically travelling emissions (going straight up from the EUT) are under consideration (stated in Table 6) to protect avionics. - National authorities may require measurements to be made in situ and require the limits of Table 6 to be met to protect safety and senstitive service bands. Considering the remarkable new CISPR-22 conducted emission requirements for I/O lines, recently discussed on the list, it appears that CISPR-11 has at least one discernible advantage over CISPR-22 (not having it). But specifically granting local authorities the power to field-modify the emission requirements is, interesting? If this aspect is so important to a standard that covers a small fraction of the noise sources in operation, why isn't it also in CISPR-22? Regards, Eric Lifsey Compliance Engineer/Manager National Instruments --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
