[SI-LIST] : Re: Diff probes for tdr.

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From: Ken Taylor (kentaylor.usa@gte.net)
Date: Thu Oct 19 2000 - 18:30:34 PDT


John Fisher's solution below is a very good one that I have used
extensively. Although a little clumsy mechanically (you will want to use a
probe positioner, hold the probe at about 45 degrees to get the tips and the
ground to contact, keep the tips and ground path VERY short like 2 mm or so)
they give great results. One more thing, however: If the probe impedance
doesn't match your DUT impedance, you will get reflections etc. and you
won't be able to see anything close in to the contact point. To solve that,
match the impedances as closely as possible, keep the probe (semi rigid
stuff) more than, say, 6" long, and then all the mismatch will be at the
flexible cable/probe connection, and you can keep it out of the way of your
measurements. These probes work well for 17 pS Tr.
One last thing, these things were whipped up for customers by friendly Tek
AEs, and weren't part numbered for sale. (How can you charge $5000 for these
things? Can't, so they don't sell them!) The real Tek (and Agilent) probes
looked nice, are definitely nicer mechanically, but can't hold a light to
these "do it yourself" probes.

Regards, Ken.

Ken Taylor
Polar Instruments, Portland, OR, USA.
ken.taylor@polarinstruments.com

John said
<<We have built these using equal length sections of semi rigid coax with
sma's at one end. The semi rigid copper outer shield is soldered together
approx. every 3 &quot;.&nbsp; Prepare the ends by careful cutting of the
shield with an exacto knife,&nbsp; than solder the center conductors to
the launch point vias or pads. Tektronix shipped some of&nbsp; these to
us as accessories when we bought their IPA-510 a few years ago.&nbsp; I
might be able to find a tek part number but someone like Micro-Coax could
make some for you or find an off the shelf semi rigid assembly with sma's
on both ends and then just cut it in half. Be carful not to bend it too
much and kink it.&nbsp; These can also make nice 50 Ohm 10x passive
probes with the addition of a series 450 resistor at the end.<br> >>

----- Original Message -----
From: "si-list-digest" <owner-si-list@silab.eng.sun.com>
To: <si-list-digest@silab.eng.sun.com>
Sent: Thursday, October 19, 2000 5:00 PM
Subject: si-list-digest V1 #286

>
> si-list-digest Thursday, October 19 2000 Volume 01 : Number
286
>
>
>
> In this issue:
>
> 1.) [SI-LIST] : High Frequency Seminar
> "chasgra" <chasgra@email.msn.com>
>
> 2.) [SI-LIST] : SI - Salary Survey
> sainath nimmagadda <nescafe@dacafe.com>
>
> 3.) [SI-LIST] : Differential TDR probes
> "zanella, fabrizio" <zanella_fabrizio@emc.com>
>
> 4.) Re: [SI-LIST] : Differential TDR probes
> "Ritesh Kapahi" <rkapahi@idt.com>
>
> 5.) Re: [SI-LIST] : Differential TDR probes
> Salvador_Aguinaga@3com.com
>
> 6.) RE: [SI-LIST] : Differential TDR probes
> "Daniel, Erik S." <Daniel.Erik@mayo.edu>
>
> 7.) Re: [SI-LIST] : Differential TDR probes
> John Fisher <jmfisher@cisco.com>
>
>
> ----------------------------------------------------------------------
>
> Date: Wed, 18 Oct 2000 18:30:58 -0700
> From: "chasgra" <chasgra@email.msn.com>
> Subject: [SI-LIST] : High Frequency Seminar
>
> This is a multi-part message in MIME format.
>
> - ------=_NextPart_000_000C_01C03931.8EE7A3A0
> Content-Type: text/plain;
> charset="iso-8859-1"
> Content-Transfer-Encoding: quoted-printable
>
> Rocky Mountain Chapter EMC Society presents:
>
> High Frequency Measurements and Noise in Electronic Circuits
> - - one day demonstration based seminar.
>
> An informative and entertaining multimedia seminar for digital and =
> analog designers as well as test engineering and EMC personnel.=20
>
> by Douglas C. Smith=20
>
> Author of High Frequency Measurements and Noise in Electronic Circuits=20
>
> An Unusual Seminar - Sign up here.
>
> This seminar is unique. Demonstrations on real circuits are used to =
> illustrate most of the concepts being taught unlike most seminars which =
> are taught through the use of vu-graphs as the main medium. About 70% of =
> class time is spent in demonstrations. Complicated math is avoided. This =
> format makes the seminar more interesting to the students and helps them =
> to achieve a deeper understanding of the material covered. Many students =
> have said that this was the best technical seminar they ever attended!=20
>
>
>
> When: Dec 1 2000
>
> If you are interested then goto our weblink: =
> http://www.ewh.ieee.org/r5/denver/rockymountainemc
>
> Look for the Dec 1 meeting link and sign up!!
>
> Charles Grasso
> Vice Chair RMCEMCS
>
>
> - ------=_NextPart_000_000C_01C03931.8EE7A3A0
> Content-Type: text/html;
> charset="iso-8859-1"
> Content-Transfer-Encoding: quoted-printable
>
> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
> <HTML><HEAD>
> <META content=3D"text/html; charset=3Dwindows-1252" =
> http-equiv=3DContent-Type>
> <META content=3D"MSHTML 5.00.2919.6307" name=3DGENERATOR></HEAD>
> <BODY bgColor=3D#ffffff>
> <DIV><FONT size=3D2>
> <P align=3Dcenter><A name=3DTitle><FONT size=3D6>Rocky Mountain Chapter =
> EMC=20
> Society</FONT></A><FONT size=3D6> presents:</FONT></P>
> <P align=3Dcenter><FONT color=3D#0000ff face=3DArial size=3D6><B>High =
> Frequency=20
> Measurements and Noise</B></FONT> <FONT color=3D#0000ff face=3DArial =
> size=3D6><B>in=20
> Electronic Circuits<BR></B></FONT><FONT color=3D#0000ff face=3DArial =
> size=3D5><B>- one=20
> day demonstration based seminar.</B></FONT></P>
> <P align=3Dcenter><FONT size=3D5><I>An informative and </I></FONT><FONT=20
> color=3D#ff0000 size=3D5><B><I><U>entertaining</U></I></B></FONT><FONT =
> size=3D5><I>=20
> multimedia seminar for digital and analog designers as well as test =
> engineering=20
> and EMC personnel.</I></FONT> </P>
> <P align=3Dcenter><FONT face=3DArial size=3D4><B>by </B></FONT><A=20
> href=3D"http://www.ewh.ieee.org/r5/denver/rockymountainemc/1dayemc.htm#Ab=
> out The Instructor"><FONT=20
> face=3DArial size=3D4><B>Douglas C. Smith</B></FONT></A> </P>
> <P align=3Dcenter><FONT size=3D4>Author of <I>High Frequency =
> Measurements and Noise=20
> in Electronic Circuits</I></FONT> </P>
> <P align=3Dcenter><A=20
> href=3D"http://www.ewh.ieee.org/r5/denver/rockymountainemc/seminarsignup.=
> htm"><FONT=20
> size=3D5><B><U>An Unusual Seminar - Sign up here.</U></B></FONT></A></P>
> <P align=3Dleft>This seminar is unique. Demonstrations on real circuits =
> are used=20
> to illustrate most of the concepts being taught unlike most seminars =
> which are=20
> taught through the use of vu-graphs as the main medium. About 70% of =
> class time=20
> is spent in demonstrations. Complicated math is avoided. This format =
> makes the=20
> seminar more interesting to the students and helps them to achieve a =
> deeper=20
> understanding of the material covered. Many students have said that this =
> was the=20
> <I>best</I> technical seminar they ever attended! </P>
> <P align=3Dleft>&nbsp;</P>
> <P align=3Dleft>When: Dec 1 2000</P>
> <P align=3Dleft>If you are interested then goto our weblink: <A=20
> href=3D"http://www.ewh.ieee.org/r5/denver/rockymountainemc">http://www.ew=
> h.ieee.org/r5/denver/rockymountainemc</A></P>
> <P align=3Dleft>Look for the Dec 1 meeting link and sign up!!</P>
> <P align=3Dleft>Charles Grasso<BR>Vice Chair=20
> RMCEMCS</P></FONT></DIV></BODY></HTML>
>
> - ------=_NextPart_000_000C_01C03931.8EE7A3A0--
>
>
>
> **** To unsubscribe from si-list or si-list-digest: send e-mail to
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> ------------------------------
>
> Date: Thu, 19 Oct 2000 11:44:46 -0800
> From: sainath nimmagadda <nescafe@dacafe.com>
> Subject: [SI-LIST] : SI - Salary Survey
>
> Hi SI folks:
>
> I understand that with growing complexity in multimedia technology, SI
> positions are getting increasingly challenging (we see "PhD preferred"
> in ads)and hopefully lucrative too. We often find salary surveys for
> mainstream folks such as IT professionals. I am just curious if there is
> some kind of salary survey for SI folks too. I am sure that helps us SI
> folks have an idea where we stand in this dynamic market.
>
> Best,
>
> SN
> _____________________________________________________________
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>
> ------------------------------
>
> Date: Thu, 19 Oct 2000 15:44:15 -0400
> From: "zanella, fabrizio" <zanella_fabrizio@emc.com>
> Subject: [SI-LIST] : Differential TDR probes
>
> We're having problems getting a good high frequency launch when probing pc
> boards and cable differential pairs when taking TDR measurements.Has
anyone
> found good differential TDR probes which allow you to measure very closely
> spaced points on pc boards or cables?
>
> Thanks and regards,
> Fabrizio Zanella
> Hardware Engineering
> EMC Corporation
> fzanella@emc.com
>
>
> **** To unsubscribe from si-list or si-list-digest: send e-mail to
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>
> ------------------------------
>
> Date: Thu, 19 Oct 2000 14:12:22 -0700
> From: "Ritesh Kapahi" <rkapahi@idt.com>
> Subject: Re: [SI-LIST] : Differential TDR probes
>
> Agilent has got some micro probe which is an accessory for their high
> bandwidth scope 86100 and differential TDR module 54754A . It usually has
a
> long lead times (3-4 months)
> Bye
> Kaps
>
> - ----- Original Message -----
> From: zanella, fabrizio <zanella_fabrizio@emc.com>
> To: SI List (E-mail) <si-list@silab.eng.sun.com>
> Sent: Thursday, October 19, 2000 12:44 PM
> Subject: [SI-LIST] : Differential TDR probes
>
>
> > We're having problems getting a good high frequency launch when probing
pc
> > boards and cable differential pairs when taking TDR measurements.Has
> anyone
> > found good differential TDR probes which allow you to measure very
closely
> > spaced points on pc boards or cables?
> >
> > Thanks and regards,
> > Fabrizio Zanella
> > Hardware Engineering
> > EMC Corporation
> > fzanella@emc.com
> >
> >
> > **** To unsubscribe from si-list or si-list-digest: send e-mail to
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> > ****
> >
> >
>
>
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>
> ------------------------------
>
> Date: Thu, 19 Oct 2000 16:39:38 -0500
> From: Salvador_Aguinaga@3com.com
> Subject: Re: [SI-LIST] : Differential TDR probes
>
> Kaps,
>
> Have you comfirmed that the TDR Module 54754A works with their new 86100A
main
> frame?
> They (their sales guys) tell me that it will not be ready until Dec 00.
>
> Thanks,
> - -- Sal
>
>
>
>
> "Ritesh Kapahi" <rkapahi@idt.com> on 10/19/2000 04:12:22 PM
>
> Please respond to "Ritesh Kapahi" <rkapahi@idt.com>
>
> Sent by: "Ritesh Kapahi" <rkapahi@idt.com>
>
>
> To: "zanella, fabrizio" <zanella_fabrizio@emc.com>, "SI List
> cc: (Salvador Aguinaga/MW/US/3Com)
> Subject: Re: [SI-LIST] : Differential TDR probes
>
>
>
> Agilent has got some micro probe which is an accessory for their high
> bandwidth scope 86100 and differential TDR module 54754A . It usually has
a
> long lead times (3-4 months)
> Bye
> Kaps
>
> - ----- Original Message -----
> From: zanella, fabrizio <zanella_fabrizio@emc.com>
> To: SI List (E-mail) <si-list@silab.eng.sun.com>
> Sent: Thursday, October 19, 2000 12:44 PM
> Subject: [SI-LIST] : Differential TDR probes
>
>
> > We're having problems getting a good high frequency launch when probing
pc
> > boards and cable differential pairs when taking TDR measurements.Has
> anyone
> > found good differential TDR probes which allow you to measure very
closely
> > spaced points on pc boards or cables?
> >
> > Thanks and regards,
> > Fabrizio Zanella
> > Hardware Engineering
> > EMC Corporation
> > fzanella@emc.com
> >
> >
> > **** To unsubscribe from si-list or si-list-digest: send e-mail to
> > majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE
> > si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
> > si-list archives are accessible at http://www.qsl.net/wb6tpu
> > ****
> >
> >
>
>
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>
>
>
>
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>
> ------------------------------
>
> Date: Thu, 19 Oct 2000 17:26:16 -0500
> From: "Daniel, Erik S." <Daniel.Erik@mayo.edu>
> Subject: RE: [SI-LIST] : Differential TDR probes
>
> Fabrizio-
>
> A couple things we have used with some success for diff TDR on PC boards
and
> chip packages:
>
> 1. GGB Picoprobe Model 10
> - --------------------------
> These are micro-coax probes with needle-like tips connected at the end.
> They are pretty cheap, and there are a wide variety of options (different
> needle tip lengths, widths, materials, ...). We have used two
ground-signal
> style probes soldered together to form a GSSG style differential probe.
The
> needles are flexible and can be bent to accommodate different board
> geometries (although bending the needles too much definitely degrades the
> launch). There are some technical drawbacks to these, but they have come
in
> handy for troubleshooting.
>
> 2. GGB Picoprobe Model 40A Dual probes
> - ---------------------------------------
> These are very good microwave probes (with an advertised 40 GHz bandwidth)
> that you can buy in GSSG or GSGSG styles in a variety of pitches. They
are
> fairly expensive, the lead times are long for custom orders, and I would
not
> recommend trying to bend these(!) to accommodate different geometries, but
> they are electrically very good.
>
> There are a number of other similar microwave probes we have used in
various
> special cases, but I think I have used these two options the most.
>
> - Erik
>
> ==================================================================
> Erik Daniel, Ph.D. Mayo Foundation
> Voice: (507) 284-1634 Guggenheim 1011B
> Fax: (507) 284-9171 200 First Street SW
> E-mail: daniel.erik@mayo.edu Rochester, MN 55905
> ==================================================================
>
>
> > -----Original Message-----
> > From: zanella, fabrizio [mailto:zanella_fabrizio@emc.com]
> > Sent: Thursday, October 19, 2000 2:44 PM
> > To: SI List (E-mail)
> > Subject: [SI-LIST] : Differential TDR probes
> >
> >
> > We're having problems getting a good high frequency launch
> > when probing pc
> > boards and cable differential pairs when taking TDR
> > measurements.Has anyone
> > found good differential TDR probes which allow you to measure
> > very closely
> > spaced points on pc boards or cables?
> >
> > Thanks and regards,
> > Fabrizio Zanella
> > Hardware Engineering
> > EMC Corporation
> > fzanella@emc.com
> >
> >
> > **** To unsubscribe from si-list or si-list-digest: send e-mail to
> > majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE
> > si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
> > si-list archives are accessible at http://www.qsl.net/wb6tpu
> > ****
> >
>
> **** To unsubscribe from si-list or si-list-digest: send e-mail to
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>
> ------------------------------
>
> Date: Thu, 19 Oct 2000 15:38:44 -0700
> From: John Fisher <jmfisher@cisco.com>
> Subject: Re: [SI-LIST] : Differential TDR probes
>
> <html>
> <font size=3>Fabrizio,<br>
> <br>
> We have built these using equal length sections of semi rigid coax with
> sma's at one end. The semi rigid copper outer shield is soldered together
> approx. every 3 &quot;.&nbsp; Prepare the ends by careful cutting of the
> shield with an exacto knife,&nbsp; than solder the center conductors to
> the launch point vias or pads. Tektronix shipped some of&nbsp; these to
> us as accessories when we bought their IPA-510 a few years ago.&nbsp; I
> might be able to find a tek part number but someone like Micro-Coax could
> make some for you or find an off the shelf semi rigid assembly with sma's
> on both ends and then just cut it in half. Be carful not to bend it too
> much and kink it.&nbsp; These can also make nice 50 Ohm 10x passive
> probes with the addition of a series 450 resistor at the end.<br>
> <br>
> Regards<br>
> <br>
> John<br>
> <br>
> At 03:44 PM 10/19/00 -0400, you wrote:<br>
> <blockquote type=cite cite>We're having problems getting a good high
> frequency launch when probing pc<br>
> boards and cable differential pairs when taking TDR measurements.Has
> anyone<br>
> found good differential TDR probes which allow you to measure very
> closely<br>
> spaced points on pc boards or cables?<br>
> <br>
> Thanks and regards,<br>
> Fabrizio Zanella<br>
> Hardware Engineering<br>
> EMC Corporation<br>
> fzanella@emc.com<br>
> <br>
> <br>
> **** To unsubscribe from si-list or si-list-digest: send e-mail to<br>
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eudora="autourl">http://www.qsl.net/wb6tpu><br>
> ****</font></blockquote><br>
>
<div>*********************************************************************</
div>
> <div>John M. Fisher -- Cisco Systems&nbsp; --
jmfisher@cisco.com</div>
> <div>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 170 W. Tasman Dr., Bldg G, San Jose
> CA 95134-1706</div>
>
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sp;&nbsp;&nbsp;&nbsp;</x-tab>&nbsp;
> \/</div>
> <div>Manager Signal Integrity, Enterprise Line of Business</div>
> <div>408-527-9186,&nbsp; Page 408-308-5501, Fax 408-526-5504,&nbsp;
> N6PFN</div>
> *********************************************************************
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>
>
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> ------------------------------
>
> End of si-list-digest V1 #286
> *****************************
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