Hi Amund, This type of tests needs an intelligent approach. The 3 seconds dwell time may be too long, or may be simply too short. Carrying out the test as you describe may lead to both excessive test times AND insufficient testing although be it according to the standard.
In advance of testing you will need to investigate 2 parameters: - at what frequency ANY susceptibility can be expected and found (this by selecting arbitrary steps and dwell times manually and possibly increased test levels)) - what is the time to find out if any susceptibility occurs (reaction time of equipment) and if you may find a way of detecting immunity problems both fast and possibly automated (test software ?) Of course , looking at the circuit diagram will give you clues about the probability of immunity problems, and how they will manifest themselves. Following those investigations you will have a pretty good idea of the properties of your equipment regarding this test, and you will be able to comfortably select and adapted frequency step and dwell time. Experience has showed that immunity problems in general behave like wideband (2-20 Mhz wide) networks. Probably you will need to find out the frequency where the problems maximize manually. About the difference in modulation frequency I have an interesting example. One day I tested a potentiometer equipped system where the electronics lacked immunity in measuring the potentiometer output voltage. This voltage was conditioned using a bad designed opamp circuit. However, after the opamp, the signal was sampled with a 1 Khz rate by a microprocessor system. I found out that due to the slowness of the full system (partly mechanic) no immunity was found BUT when the modulation frequency approached exactly 1 Khz. Within 3-4 hz band of this frequency the mechanics started moving in a frequency equal to the difference of modulation and sample frequency. Other frequencies where averaged out by both microprocessor software and mechanics mass. So watch out for pitfalls like this, and carefully decide how to detect susceptibility properties. Conclusions: A fully automated measurement according to the standards will almost certainly fail to detect some if not all problems if not assisted by (how happy we are) skilled EMC engineers. Gert Gremmen ce-test, qualified testing -----Original Message----- From: [email protected] [mailto:[email protected]]On Behalf Of [email protected] Sent: Friday, June 14, 2002 8:29 AM To: [email protected] Subject: IEC/EN61000-4-6 - time consuming test Hi all, This is about the Conducted RF immunity standard IEC/EN61000-4-6. Facts: This test shall be conducted to all power lines (AC and DC) and signal lines. The test level is usually 3V or 10V, depending on the type of product. Modulation is 80% AM and 1kHz sine. The frequency range is mainly 0.15-80MHz with frequency step of 1% and a dwell time of 3 seconds. To run a 0.15-80MHz sweep takes approximate 32 minutes (3 sec and 633 frequency steps). If you have a system/product with 10 lines connected, then you have to run the test for 320 minutes = 6 hours. Well, that is maybe not that time consuming, but if you also have to fulfil other test requirements as 400Hz AM modulation and 1Hz pulse modulation, then the total effective test time will be 18 hours. Discussion: When testing a fire alarm product for EU (CE mark) and marine marked (Wheel mark), you have to do all three modulations, 80% AM 1 kHz / 400Hz and 1 Hz pulse. The AM are pretty close in frequency, but equipment can behave different depending running 1kHz or 400Hz (someone says so..). The 1Hz pulse modulation is quite different from the AM. We had hoped to decrease the test time and wonder if we could arrange the tests another way. Could it be possible to run only 400Hz AM and 1Hz pulse with increased amplitude (maybe 16V), and thereafter argue that the equipment will pass 1 kHz@ 10V ? If so, then the test duration wound have been decreased by 33%. Time is money, in fact ... Question: Do you have any suggestions how to "modify" or combine the sweeps, in order to avoid three complete sweeps pr line? Best regards Amund Westin Oslo, NORWAY ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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