Re: [SI-LIST] : Measuring Ground Noise

John Fisher (jmfisher@cisco.com)
Wed, 24 Jun 1998 08:51:52 -0700

To measure noise on Vdd I reference my probe to a nearby ground via.

John

At 06:58 PM 6/23/98 -0700, Dima Smolyansky wrote:
>Agreed on all points. What follows, however, is that you can measure
>localized noise on your ground plane - you just need to figure out what
>your reference point will be.
>
>Thanks,
>
>-Dima Smolyansky
>
>
>----------
>> From: Larry Smith <ldsmith@lisboa.Eng.Sun.COM>
>> To: si-list@silab.Eng.Sun.COM; markn@rccorp.com
>> Subject: Re: [SI-LIST] : Measuring Ground Noise
>> Date: Tuesday, June 23, 1998 8:14 AM
>>
>>
>>
>> > Can anybody suggest a good way of measuring Noise on GND around
>> > devices?
>> >
>> > Thanks,
>> > Mark Nass
>>
>> Measure Gnd noise with respect to Vdd... At signal integrity
>> frequencies, there is no such thing as an ideal reference point. All
>> signals and noises are differential (something with respect to
>> something else). A high bandwidth single ended probe with short (1/4
>> inch, if possible) leads for both Vdd and ground will work well. You
>> can measure Vdd WRT Gnd as well as any signal WRT ground. This is
>> excactly what a device located at that position will see and respond
>> to.
>>
>> regards,
>> Larry D Smith
>> Sun Microsystems
>>
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