Hello Rene, The CISPR14/EN55014 originally was intended for equipment without advanced electronics. The CISPR14 applies to household and similar equipment and was written in a time when people didn't feel the urge to implement computertechnology in devices like washing machines, coffee machines and such. One might consider the CISPR14/EN55014 to be somewhat outdated from a technical point of view. However, a washing machine running Windows(R)(TM) would still fall within the scope of the CISPR14/EN55014 instead of the scope of the more "modern" and, in this case, better suited EN55022/EN55011.
The CISPR14 is mainly intended for equipment which is/was based on electro-mechanical devices. A good example of these devices are gambling and pinball machines. The relay and mechanical switch technology from those days was not capable of producing emissions higher than a few hundred MHz. Since low frequency electromagnetical disturbances in these types of equipment were generated by the sparking of the switches and relays it was unlikely that these disturbances were emitted by the enclosure and were more likely to be emitted by an antenna of a rather large length, which would be the AC mains cord in most cases. The method of using the clamp measurement for measuring radiated power on an AC mains cord was intended to measure the harmonics and disturbances caused by low frequency EM energy, generated by electro-mechanical components. The scope of the CISPR22/EN55022 is ITE. This standard is written for equipment which is built around electronics in which relatively high frequencies are intentionally being generated. Although these relatively high frequencies may be emitted by cabling, cabinet radiation must then also be taken into account. Since there is an intentional generation of electromagnetic energy of a relatively high power and frequency, as compared to the traditional household equipment, the quality of the screening of the cabinet then also becomes very important. For instance, openings in a (metal) enclosure act like slot antennas in most cases. Some people thought that using the clamp measuring method on cabling of ITE equipment would give some confidence about compliance on an open area test site. However, it proved that this method could only be used as an indication if the cabling design was correct. For verifying if cabinet radiation was not a problem you would still have to perform an open area test site measurement. Performing only the clamp measurement is, or was, in many cases not sufficient to prove compliance with the CISPR22/EN55022. Therefore this method was never accepted as the proper method to prove compliance with this standard. Best regards, Pieter Robben Manager, location Niekerk of NMi Certin B.V. NB/CB for EMC, TTE, Radio and Low Voltage Dir. Tel: +31-594-505005 / 1-860-873-1454 (USA) Email: [email protected] / [email protected] (USA) At 99/02/13 11:12 PM, you wrote: >1. For a long time it was stated in CISPR22/EN55022 that some regulatory >agencies think that the clamp method is a good substitute for a OATS >measurement. But this method never was accepted for CISPR22/EN55022 and can >not be found in any other standard but CISPR14/EN55014. Why? >2. The clamp measures the HF power available on the wires going out of the >equipment. But is that all? Why do we have to put so much attention on the >enclosure seams of personal computers? Would you also put a clamp on the >enclosure seam? >3. Putting all wires together into one clamp is certainly not a good idea. >The HF-currents can add up, but as well can also cancel each other. >4.Look at a dipol antenna: In the middle a Balun (Power Source) Each side >one rod coming out. > Look at a personal computer: In the middle the computer, on each side a >wire acting as antenna coming out. > Do you think a absorber clamp can remodel that scenario? > >Regards > >Rene Charton
