Hi All, Jim has a good idea here. I have an experiment I use in presentations that shows the amount of an ESD current that couples onto a probe body (Fischer F-33-1) varies by about a factor of two depending how the lead is dressed as it passes through the probe, perpendicular through the center being the lowest.
Doug At 01:46 PM 6/21/99 -0400, Lacey,Scott wrote: > >In my opinion, letting the cable insulation touch the probe body is never a >good idea. I always try to "shim" the cable and probe in order to center the >cable within the probe opening. The trick is to keep the shims outside of >the probe. A good trick is to make a "V block" out of wood, with a deeper >center notch for the probe body. This insures good radial and axial >alignment (for consistency) and also prevents the probe body from touching >the ground plane. >Scott > > -----Original Message----- > From: Jim Eichner [SMTP:[email protected]] > Sent: Monday, June 21, 1999 1:10 PM > To: EMC-PSTC > Subject: RE: Current probe problem > > > In his write up of the problem, Doug writes > > "If possible, current probes should be positioned on the measured >cable > so as to minimize the potential between the cable and the current >probe > body. This usually means locating the probe near the ground/chassis >end > of a circuit." > > Following a tip from someone on this forum quite a while ago, I have > observed significant variation in the spectrum of noise along the >length > of a cable. I have started doing my cable current measurements by > sliding the probe over the length of the cable, with my spectrum > analyzer in max hold mode. I assume I get a "worst case sweep" by >doing > this, as I pick up the worst of everything at any position on the >cable. > > > Following Doug's advice above, or any instance of using a current >probe > in a single fixed position, could result in the probe being >positioned > right at a null for a frequency of interest, sending you on a wild >goose > chase looking for some other source. > > Does Doug or anyone else have similar experience or a better way to > overcome the problem? > > Regards, > > Jim Eichner > > Senior Regulatory Compliance Engineer > Statpower Technologies Corporation > [email protected] > http://www.statpower.com > Any opinions expressed are those of my invisible friend, who really > exists, but can only be seen by my dog. Honest. > > > > > > > > >--------- >This message is coming from the emc-pstc discussion list. >To cancel your subscription, send mail to [email protected] >with the single line: "unsubscribe emc-pstc" (without the >quotes). For help, send mail to [email protected], >[email protected], [email protected], or >[email protected] (the list administrators). > > > > --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
