In message <[email protected]>, dated Mon, 9 Feb 2009, Grace Lin <[email protected]> writes:
>I have learned from members that ANSI C63.4 and CISPR 16-1-2 are the >calibration standards for LISN for my daily measurement. I have one of >my two LISNs ship out last week to an accredited calibration lab. I >wonder if I need to ship out the other one for calibration since the >second one is used for support equipment. I would strongly advise it. I have found strange differences in results with two apparently good LISNs. This may be why the CISPR 16-1-2 requirements have been made more detailed over the past few years. > Is it sufficient that I verify it in-house? If yes, I would need your >help with calibration. It's always worth knowing how to do it. > >I study A.8 of CISPR 16-1-2 Edition 1.2 and Annex E of ANSI C63.4-2003 >this morning. Here are my questions: > >1. The title of A.8 is "Measurement of the voltage division factor of >an artificial mains V-network". What does "voltage division factor"? >Does it mean insertion loss? Not exactly; it's the ratio of input voltage, at the connector supplying mains power to the EUT to output voltage at the connector for the measuring receiver. Differences in the impedances at these points are not taken into account, so the ratio is not 'insertion loss' as normally defined. A.8 was written by someone who knew the subject very well, so well that it can be very difficult for others to understand. And the requirement for voltage division factor is 'hidden' in the caption of Figure 4.10. >2. Is the adapter, mentioned in Figure A.6a, Figure A.6b of CISPR >16-1-2 and Figure E.1(a) of ANSI C63.4, commercially available? I don't know: I've made mine myself. >If not, is there any guidelines to make it (type of connectors, size >and length of wires/cables, etc.)? I think there is no need to be extremely meticulous about this. Whatever mains connector you use, it is not matched to 50 ohms or anything else, but it is electrically 'short' (compared with a wavelength) even at 30 MHz, so it has little effect. Just keep all connections short and rigid (movement of connections can impair repeatability). >Should I take a pin from a power plug and solder one end to a SMA >receptacle? No. The connections in Figure A6a are **coaxial cables**, so that isn't a single connection to L1 but a coaxial connection to L1 and ground. >If yes, is there any preference for the type of the receptacle (cable >jack, panel jack, bulkhead, etc. >http://www.amphenolrf.com/Products/CatalogPages/sma_catalog.pdf)? Just keep the wires short and rigid, if the connection is not coax. I have, for example, mounted two BNC connectors (L1/ground and N/ground) directly on a metal plate attached to the cover of a UK 13 A plug. I also have a single BNC connected by a short (100 mm)50 ohm coax to a 13 A plug. Inside the plug is a network of five 82 ohm resistors. One goes >from each power pin to the ground pin. The other three are connected as a delta, one apex to each power pin, and the third to the incoming coax inner. The outer of the coax goes to ground, of course. This gives an input impedance close to 50 ohms, and 30 ohms between power pins and >from each power pin to ground (network alone; no generator connected). The insertion loss is 11.2 dB. I don't remember whether someone told me about this arrangement or whether I invented it. With this device, you can look at both outputs of the LISN at once, if the switching allows you access to both outputs simultaneously (as, in my opinion, it should) for direct comparison purposes. >3. How do I terminate the mains port? The LISN, Solar 9252-50-R-24-N >(same as 9252-50-R-24-BNC except with N connector) comes with a >permanent attached power cord. Should I pick up a receptable (no wire >attached) and connect 50 ohms resistor to L and N respectively, and >connect the other end of the resistors to ground reference? That's all you can do without modifying the LISN. You could cut the cable short, fit an in-line IEC 320 free socket to it and use an IEC 320 mains lead in future. Then you would have a terminator consisting of an IEC 320 plug with two parallel pairs of 100 ohm resistors inside, power pins to ground. >4. Is there any requirement (VSWR etc.) for the 50 ohms terminator? Any commercial terminator is most unlikely to have a poor VSWR up to 30 MHz. Even a 51 ohm metal film resistor inside a BNC plug is likely to be OK. >5. Is 10 dB pads needed? Figure A.6a and Figure A.6b of CISPR 16-1-2 >show them. The NOTE from Figure E.1(b) states "Attenuator pads not >used with network analyzer. The pads are there to prevent errors due to mismatched impedances. Your set-up and LISN may or may not need them. You can only tell by measuring with and without to see if the results differ. >6. Figure A.6a and Figure A.6b of CISPR 16-1-2 show two ports of >network analyzer are used. Figure E.1(b) shows three ports of network >analyzer are used. The vector network analyzer I have access to comes >with four ports >(http://www.home.agilent.com/agilent/product.jspx?cc=US&lc=eng&pageMode= >OV&pid=810708&ct=PRODUCT&id=810708). The calibration kit available is >3.5mm >(http://www.home.agilent.com/agilent/product.jspx?cc=US&lc=eng&pageMode= >OV&pid=1000003542%3Aepsg%3Apro&ct=PRODUCT&id=1000003542%3Aepsg%3Apro). >How many ports do I need to connect to (port 1&2, or port 1&2&3)? You only need to use one output port and one input port. > I start using a VNA two weeks ago and is not familiar with it. As a >matter of fact, I used a demo VNA (only two ports >http://www.us.anritsu.com/products/37000D-Series_Lightning-Family-of-mic >roW-VNAs--Value-Line_ARSPG_ARQQSidZ643.aspx) to calibrate cable loss. I suggest you try to fix a training session with Agilent. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk Things can always get better. But that's not the only option. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
