[SI-LIST] Re: How to measure voltage drop on plane
- From: ronald miller <ron@xxxxxxxxxxx>
- To: zhang_kun@xxxxxxxxxx
- Date: Mon, 19 Jul 2004 17:11:19 -0700
A practical method for measuring this is using the Tektronix
differential probes. Some are good
up to 2 Ghz and some up to over 3 Ghz. Single ended probes do not make
it because of the internal
ground currents in the oscilloscope. These probes cancel out most of
the common mode noise so
you get a good measurement .
Place one probe pin on ground and the other on the point to be measured,
and as has been
said, close together.
Hopefully they will come up with a differential probe to 10 Ghz soon.
ron miller
zhangkun 29902 wrote:
>Dear Ray
>
>In Paul's paper "Modeling Electromagnetic Interference Properties of Printed
>Circuit Boards", he proposed how to measure the voltage drop on the ground
>net. I think this method is not suitable for the complex PCB.
>
>At one time, we are check one PCB with Intel. The engineer said that "the
>noise on the ground" was too large. I ask them how to measure "the noise on
>the ground". There is no answer.
>
>Is the voltage drop on the ground plane useful?
>
>Best Regards
>
>Zhangkun
>2004.7.20
>
>----- Original Message -----
>From: Ray Anderson <reanderson@xxxxxxxxxxxxx>
>Date: Monday, July 19, 2004 11:54 pm
>Subject: [SI-LIST] Re: How to measure voltage drop on plane
>
>
>
>>Zhangkun-
>>
>>The measurement of power/ground noise is a differential
>>measurement
>>(even if you use a single-ended probe) of the power voltage (Vdd)
>>with
>>respect to the associated ground voltage (Gnd).
>>
>>When making these sort of measurements you need to measure Vdd
>>with
>>respect Gnd at the same XY spatial location for the measurement to
>>make
>>sense. (i.e. vertically coincident). If you measure Vdd with
>>respect to
>>Gnd where the Gnd node is physically offset some significant
>>distance
>>(wrt lambda) then the measurement just doesn't make sense.
>>
>>If the Gnd measurement point is offset from the Vdd measurement
>>point by
>>only a small fraction of an inch instead exactly coincident with
>>the
>>measured Vdd location that is probably an acceptably small error,
>>however if the offset is on the order of inches or more then the
>>measured voltage doesn't make sense. Why? Because you are
>>measuring
>>voltages 'across time' where the time is the time-of-flight from
>>the Gnd
>>node coincident with the Vdd node (which you should be using as a
>>reference) to the Gnd node which is distant (which you should NOT
>>be
>>using as a reference). Measurements of voltage across time are
>>undefined, at least with respect to the measurement of
>>power/ground
>>noise which you propose.
>>
>>-Ray Anderson
>>
>>
>>
>>Zhangkun wrote:
>>
>>
>>
>>>Dear all
>>>The power ground noise at one location is easy to measure. How to
>>>
>>>
>>measure voltage drop on plane at different location? Is it
>>impossible? There is one method proposed by C. R. Paul. However,
>>the structure of Paul's is too simple.
>>
>>
>>>Best Regards
>>>
>>>Zhangkun
>>>2004.7.19
>>>
>>>
>>>
>>>
>>>
>>.
>>
>>------------------------------------------------------------------
>>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
>>
>>
>>
>>
>>
>
>------------------------------------------------------------------
>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
>
>
>
>
>
------------------------------------------------------------------
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
Other related posts:
