Paul, What I have done in the past is that I have tied the plane to my sampling scope, I have looked at the noise using the noise itself as the trigger. When you start increasing the threshold of your trigger in either direction you will start getting rid of the noise which have less amplitude at certain frequencies and as you keep on increasing the threshold you will see that you will be left with some waveforms that will be your dominant noise. The 66 MHz that you are talking about might be in there. You can measure the amplitude from there. Khalid -----Original Message----- From: pgregory [mailto:pgregory@xxxxxxxxxx] Sent: Thursday, August 29, 2002 1:46 PM To: 'si-list@xxxxxxxxxxxxx' Subject: [SI-LIST] Measuring Power and Ground Plane Noise How does one properly measure power plane or ground plane noise? I have a case where I believe there is 66 MHz noise on the planes. I want to know how much noise is on each plane. Both measurements require a reference point that you must assume to be stable, or perhaps that is considered stable by the measurement. So I measure across a decoupling capacitor and that shows some noise on the power plane. But how do I get a good measurement of the ground noise? And if there is noise on the ground plane, how do I get that noise out of the power plane measurement? Thanks for any help. - Paul ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu