Hi Gert, As far as I know, most of test labs think more than 1 meter is a reasonable length of cable in the real life. They don't use at least 3 meters. But I agree with what you said about low frequency emission.
Regards, Barry Ma ------------- Original Text From: "Ing. Gert Gremmen" <[email protected]>, on 5/14/98 12:48 AM: hello Jim, group, I suppose that your goal in immunity testing is to show that the equipment continues to function, therefore i believe you should add loopback systems at least showing that the communication really takes place. Further more, in order to optimize emissions you should at least connect a reasonable amount of cable (standard printer length) or at least 3 meters (1/4 lambda) to make sure that anything low frequent will emit. (from an emc-technical point of view) Generally speaking, i should say that you cannot use loopback connectors unless you replace them by "dummies" that provide you with information about the protocol quality. I want to refer to f.a. EN 55022 saying that one should optimize emissions by varying cable lengths, orientation and path. I do not believe that they included the no-cable option :<)). Regards, Gert Gremmen == Ce-test, Qualified testing == Consultants in EMC, Electrical safety and Telecommunication Compliance tests for European standards and ce-marking Member of NEC/IEC voting committee for EMC. Our Web presence: http://www.cetest.nl List of current harmonized standards http://www.cetest.nl/emc-harm.htm 15 great tips for the EMC-designer http://www.cetest.nl/features01.htm Support the International Red Cross Million 2000 Lottery: http://www.pluslotto.com/default.asp?urlref=3300008136443 -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Jim To Sent: woensdag 13 mei 1998 23:40 To: [email protected] Subject: Loop back or peripherals for EMI testing Hello EMI colleagues, It is a general practice among us to select peripherals (printers, monitors, etc.) that do not contribute noise to the EUT during testing. Once these peripherals are found, they are used as basis for testing with different EUT's. My question is this: Is it legal to substitute peripherals with loop-back connectors, such as in the case of serial, parallel, and Ethernet ports? If the answer is no, please direct me to a clause or paragraph of either the CFR or CISPR standard for my future reference. Many thanks for your reply. Jim To Force Computers, Inc. Tel: 408-369-6213 Email: [email protected]
