With respect to 'alarm systems' - EN 50130-4 is the applicable technical standard. However, 50130-4 refers to the IEC 1000/EN61000 series specs, 'but with modifications'.
Let's take for instance the 1000-4-5 Surge spec that Amund referenced. In EN 50130-4, the following is stated: "The test apparatus and procedure shall be as described in IEC 1000-4-5 with the following modifications and clarifications taken into account:" Then there are two paragraphs - one for Mains and one for I/O lines. With regard to the length of cables in the I/O lines: "The length of the signal lines between the EUT and to coupling/decoupling network(s) shall be less than/equal to 2m, " But the sentence continues with a clarification if there is screened cables: "however, if it is specified that certain signal lines must only be connected with screened cables, the in these cases the transients shall be applied to the screen of a 20m length of screened cable as show in figure 3." (Figure 3 is titled : "Typical arrangement for coupling onto screened signal lines". It shows the test set-up with a 20m dimension between the EUT and the coupling/decoupling network). I guess they made that pretty clear in THAT standard. While a 'typical' installation of my product does not use screened cables of such lengths, I do make such a length available for the test. Hope this helps. John A. Juhasz GE Interlogix Fiber Options Div. Bohemia, NY -----Original Message----- From: [email protected] [mailto:[email protected]] Sent: Thursday, October 31, 2002 1:05 PM To: [email protected] Subject: RE: Surge - injection point on screened cable This is a good example of an inarticulate clause in a standard. One sentence in clause 7.5 reads "Normally, the maximum length of the specified shielded cable shall be used. But the following sentence reads "With respect to the frequency spectrum of the surge 20 m length of the specified shielded cable shall be used in non-inductively bundled configuration for physical reasons." Duh! What they heck are they trying to say in that last sentence? Are we expected to use the maximum length cable specified for the application but no longer than 20 m? That's seems to be what is being said in a convoluted way. Richard Woods Sensormatic Electronics Tyco International -----Original Message----- From: [email protected] [mailto:[email protected]] Sent: Thursday, October 31, 2002 10:48 AM To: [email protected] Subject: Surge - injection point on screened cable According to IEC/EN 61000-4-5, the surge pulse shall be injected onto a screened cable 20 meters from the DUT. We have a fire alarm system with 20 detectors connected on the same screened cable, 1.5 meters between each detector. We have been told from the local test lab that we have to add a 20m cable between each detector in order to surge test each detector. I'm sure our local cable distributor like that idea ... , but do we really have to do this ? Why is this 20 meters cable needed ? Is it to induce the surge pulse from the screen into the cable lines? The 20 detectors make a total cable distance of 30 meters and the screen is continuous. Is it possible to insert a pulse in the beginning of the cable and test all detectors simultaneous ? Regards Amund ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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