Hello Inge,
I would certainly be interested in that paper.
Best Regards,
Joe Russeau
----- Original Message -----
From: "Hernefjord Ingemar" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, December 03, 2007 7:10 AM
Subject: Re: [TN] SV: [TN] SV: [TN] SV: [TN] Low Noise Coaxial Cable
Question
Well, well, this story never ends.
1. the vacuum cables are in practice waveguides more than cables. Not
suitable for SIR. Forget them.
2. My pA meter had an ordinary RG-58 PTFE cable for 0-100 VDC. The
instrument maker says nothing about need of anything better.
3. Diel professor not available.
After this, I contacted my friend with SIR as specialty. He gave me an
article written by NN, who is said to be one of the best in the SIR game.
That author wrote e.g. this:
" Discuss SIR standards....an impossible task, as there are forty
standards, most of them being contradictory (!), sometimes even within a
single standard (!!)."
Whos was this daring author with the sharp pen? I can give you a thread :
Cyprus. He-he.
Anyway, I can copy the 7 page, very informative, article and send it to
anyone interested. Cables are discussed also in the paper.
/Inge
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Hfjord
Sent: den 30 november 2007 22:19
To: [log in to unmask]
Subject: [TN] SV: [TN] SV: [TN] SV: [TN] Low Noise Coaxial Cable Question
We use vacuum 'filled' cables, or rather flexible metal tubes, for obtaining
best possible S/N ratio. I'll check with the guys if these 'cables' are
suitable for your purpose. However, they cost a lot, typically 1,000
USD/meter. I'll also check what kind of cable there is for my own Keithley
pico ampere meter. I noted in their manual, the importance of having as
short as possible cable, constant room environment, and that the job is more
about calibrating than measuring. One of my friends is a SIR specialist.
I'll check if he has something to add. Another is professor on a uni with
dielectricum as specialty. (he never understands my questions despite his
grade..or I'm too stupid to understand his replies) /Inge
-----Ursprungligt meddelande-----
Från: TechNet [mailto:[log in to unmask]] För Joe Russeau
Skickat: den 30 november 2007 20:41
Till: [log in to unmask]
Ämne: Re: [TN] SV: [TN] SV: [TN] Low Noise Coaxial Cable Question
Doug,
You quote Joe just fine. I should've been a little more detailed in my
original posting. I automatically assumed that it would boil down to the
materials making up low noise coaxial cable as opposed to standard coaxial
cable. Silly me, I should have known better. As always, I appreciate your
inputs and those of the other TechNet Gurus.
Joe Russeau
----- Original Message -----
From: "Douglas O. Pauls" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, November 30, 2007 2:28 PM
Subject: Re: [TN] SV: [TN] SV: [TN] Low Noise Coaxial Cable Question
Obviously Joe quotes Joe better than I quote Joe.
So, yeah, what he said..........
Man, am I glad it is Friday.........
Doug Pauls
Joe Russeau <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
11/30/2007 01:22 PM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
Joe Russeau <[log in to unmask]>
To
[log in to unmask]
cc
Subject
Re: [TN] SV: [TN] SV: [TN] Low Noise Coaxial Cable Question
Hello Seth and Inge,
Seth thank you for that very educational response.
Basically, I am researching all of the different SIR test equipment
available. I'm looking into purchasing a newer system (By-the way, this
is
not an invite to SIR equipment manufacturers to bombard me with product
literature). Anyway, one of the groups I have been speaking with
recommended
using their low noise coaxial cables. I asked how they classified the
cable
as low-noise. They responded that they pull the cable taught, drop a
weight
on it and measure the resulting charge. If no charge, then it is
considered
low noise. What I had hoped for with asking my question and the question
to
TechNet, was to find out what materials were best for low-noise coaxial
cables. I have been contacting different cable manufacturers, who claim
to
have low-noise cable, to try and determine if the materials sets are
consistent from manufacturer to the next. I figured that would allow me to
find the cabling and perhaps make the cables myself. What I have found is
that each cable manufacturer uses different materials for their low-noise
cable. So, now I'm back to square one. So perhaps I should ask the
question this way. If you were in the process of measuring low currents,
as
is done in an SIR test, and you were looking into coaxial cables as the
transfer vehicle from the DUT to the measurement equipment, what materials
would you prefer in the cables to give the best data integrity?
Best Regards,
Joe Russeau
----- Original Message -----
From: "Hfjord" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, November 30, 2007 1:27 PM
Subject: [TN] SV: [TN] SV: [TN] Low Noise Coaxial Cable Question
Exellent! However, Joe has still not told us WHAT he wants to do with the
cable. I doubt he is on a level, that dielectric intrinsic noise will play
a
role. Few test engineers work with such problems. If he isn't a Nobel
Prize
aspirant of some kind. I suggest someone finds remedy against Tinnitus.
He/she will get the prize, I'm sure. And the inventor will create a lot of
noise...he-he
/Inge
-----Ursprungligt meddelande-----
Från: TechNet [mailto:[log in to unmask]] För Seth Goodman
Skickat: den 30 november 2007 18:55
Till: [log in to unmask]
Ämne: Re: [TN] SV: [TN] Low Noise Coaxial Cable Question
Joe,
Some of what has been mentioned is really part of other cable
specifications and has nothing to do with noise created in the cable
itself. For instance, penetration of electromagnetic fields inside a
cable shield is often described by the manufacturer's specification for
shielding effectiveness. To the extent that the cable has in imperfect
coaxial shield, it can convert ambient electric or magnetic fields into
a loop voltage or flowing current. If external fields are the source of
your problem, you want cable with high shielding effectiveness as
opposed to low-noise cable. For electric fields, improving the shield
means thicker braid, finer wire in the braid, better conductivity of
braid wire and plating, more than one braid and/or a foil shield. For
magnetic fields, a shielded twisted pair may do better.
The traditional electronic noise sources, which are Johnson (thermal)
noise, shot noise and a group of unrelated mechanisms that produce 1/f
noise, do not produce appreciable noise in cables. When cable
manufacturers list a cable as low-noise, they usually mean triboelectric
noise. If the connected circuit puts a dc potential on the cable, then
mechanical flexing can change the capacitance between conductors, which
will cause current to flow in the external circuit. The triboelectric
and capacitance change with motion can together be called microphonics,
as they are both motion-related. Another source or noise in
high-voltage cables is leakage.
Regards,
Seth Goodman
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