Hi, All I want to measure the ESD induced noise on the power and ground planes. First thing I need to make sure is that the probe itself did not cause any inaccuracy. Two different type of probes were used: 1.) high impedance single ended FET probe. Signal pin solder to power side of decoupling cap, and ground pin soldered to ground side of cap. 2.) high impedance differential FET probe. '+' pin solder to cap power, and '-' side solder to cap ground. I calibrated method 1 with a same size cap soldered on probe pins, but the cap was not mounted on the board. Probe was placed on the same point as real measurement. Are those two methods are valid way to measure the ESD noise? The results from two methods had some differences. Method 1 measured bigger noise. The noise switching with 1 - 2 ns period and ~ 10 V swing in the beginning, then decay to zero in about 100 ns. Method 2 had similar period and 6 - 7 V swing, then decay to zero. But it had a wide pulse (50 + ns) after the high frequency switching noise. I don't know how to interpret the data. Thanks! Jinhua Chen EMC Corp. ------------------------------------------------------------------ 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 FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org 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