Coincidental to all this micro-ohms and nanovolt talk, I've been doing
some severe large scale garage cleaning to thin stuff out. I found that
audio amplifier that I mentioned earlier, that is good for some LIA
reference driver applications. I also found my low-level measurement
notebooks, incl
Ed,
It is not sinusoidal AC. It is a DC voltage which is allowed to settle
before it is measured, It is then measured a few times to get an average.
The excitation current is then turned off to allow the resistors to cool
before the DC voltage is reversed and the process is continued. The key
facto
On 28 September 2017 at 19:17, ed breya wrote:
> Hmm. Alternating the direction of the current repeatedly and processing
> the results - sure seems like that is fundamentally an AC measurement too,
> despite using DC measurement equipment.
>
> Ed
I guess the point is current/voltage can be meas
Hmm. Alternating the direction of the current repeatedly and processing
the results - sure seems like that is fundamentally an AC measurement
too, despite using DC measurement equipment.
Ed
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Any technology that does not DC must have some other overriding redeeming
factors given the AC measurements are not nearly as accurate DC and AC
currents are just as inaccurate. Best bridges I have used take several
reading with half of them opposite polarity and average them together.
Sometimes ca
On 27 September 2017 at 22:22, ed breya wrote:
> I just noticed this discussion recently, so I'm late to the party, but
> that never stops me from adding my one-cent's worth.
>
> David, regardless of the aluminum and other material issues, I think your
> initial idea of using a lock-in analyzer i
I just noticed this discussion recently, so I'm late to the party, but
that never stops me from adding my one-cent's worth.
David, regardless of the aluminum and other material issues, I think
your initial idea of using a lock-in analyzer is definitely the way to
go. I'm very fond of LIAs, alt
I guess I would have to ask, "How do you know everything
was done 'right'?" The evidence you have stated makes a
pretty good case that it wasn't.
The neutral entering a sub panel at most has the same current
going through it as one of the line input leads, though in a
240V sub panel, load balanci
Aluminum...
Even with everything done right, with approved hardware, aluminum wiring
will tend to 'creep' (Aluminum mushing out of the way of the lug screw
or clamp.
Just recently I checked the main lugs on my 150A garage sub panel, and
sure enough the neutral lug was loose. This was about 8
7 3:54 AM
> To: Discussion of precise voltage measurement
> Subject: Re: [volt-nuts] Best way to measure micro Ohms
>
> Hi, just my $0.02 worth.
> I have some instrumentation amplifiers here also looked into low resistance
> connections for my other projects.
>
> If I recall
s-boun...@febo.com] On Behalf Of Andre
Sent: Wednesday, September 20, 2017 3:54 AM
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] Best way to measure micro Ohms
Hi, just my $0.02 worth.
I have some instrumentation amplifiers here also looked into low resistance
connections
: 19 September 2017 21:30
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] Best way to measure micro Ohms
David wrote:
> A practical problem is the tools available to me. The U-channel was
> machined by someone in my radio club, and the rest I made myself using
> not
David wrote:
A practical problem is the tools available to me. The U-channel was
machined by someone in my radio club, and the rest I made myself using
nothing more than a drill and hand tools. It would be nice to make more out
of one piece, but it would require better tools than I have readily
David wrote:
Thanks. You have confirmed what I was thinking - it is *probably* the
oxide causing the problem.
It's not a waveguide in the normal sense of the word, transmitting a TE or
TM wave down a hollow tube, but more like a coaxial line transmitting
something close(ish) to a TEM wave. Th
On 19 September 2017 at 20:32, Charles Steinmetz
wrote:
Looking at the pix, there appear to be lots of aluminum joints due to the
> "built-up" construction, maximizing the potential for the sort of troubles
> you are having. I would re-make the piece in brass, doing everything
> possible to use
On 18 September 2017 at 23:28, george wrote:
> The reason that DC is used commercially to measure resistance is simple,
> if you use AC you may well get the reactive component as well as the
> resistance coming into play.
>
That may not be an an issue with a dual-phase lock-in amplifier, as the
If this stuff is what I think it is, it does contain
a sand of sharp, probably aluminum oxide, abrasive.
The idea is when you bolt the connection together, the
abrasive will break through the aluminum oxide layer
on the conductors, and will mushroom out the aluminum as
the abrasive burrows in, mak
The reason that DC is used commercially to measure resistance is simple, if you
use AC you may well get the reactive component as well as the resistance coming
into play.
Such low resistance measurements commercially are normally only made on high
current power distribution networks as part of
Dave,
It looks like IET updated the design of the instrument with better
switching. If you download the manual from the IET website, they still show
the older model.
I wonder if the newer model incorporates a front switch that enables the
pulsed mode that was added by the owner on EEVBlog? I can't
On 18 September 2017 at 18:36, Todd Micallef wrote:
> Dave,
>
> Another meter is the Cambridge LOM-510A. I am not sure if it is in your
> budget but there has been a review made on EEVBlog. There is one currently
> on eBay with a current amplifier that I have never seen before today. It
> may be
Dave,
Another meter is the Cambridge LOM-510A. I am not sure if it is in your
budget but there has been a review made on EEVBlog. There is one currently
on eBay with a current amplifier that I have never seen before today. It
may be worth reviewing if it meets your needs.
Todd
On Mon, Sep 18, 20
David wrote:
Can anyone explain why commercial instruments use DC, despite that small DC
voltages will be developed by unwanted thermocouples? I would have thought
that using AC was a no-brainer no very low resistance measurements, but
commercial instruments don't use to use AC.
Difficulty
I use a Keithley 2182 and 6221 nano-ohm setup at work. It is a combination of a
reversing precision current source and a nanovoltmeter with embedded software
to manage the process. I can reliably measure into the 50 nano-ohm regime.The
surface chemistry of the metal joint is very important. Both
A DMM with good low resistance capability will have an "offset compensated
ohms" feature. A large current is used and then a small current is used.
The slope of the line formed by V-I points is the true resistance.
Measuring tiny DC voltages is easier than measuring tiny AC voltages. More
bandwidt
On 17 September 2017 at 21:58, Mitch Van Ochten <
mi...@vincentelectronics.com> wrote:
> The Keithley 2002 uses DC but automatically takes a reading of any offset
> voltage and subtracts it (offset compensation). Rated accuracy on the 20
> ohm range (2 years) is +/- 26 ppm, and with 10 averages i
On 17 September 2017 at 20:12, wrote:
> The question is what accuracy you need.
>
No a lot. I just want to find out if there's any voltage drops that are
significantly higher than I would expect. The unit makes an RF transmission
line, and the loss at RF is significantly higher than predicted by
-
From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of Dr. David
Kirkby (Kirkby Microwave Ltd)
Sent: Sunday, September 17, 2017 1:23 PM
To: Discussion of precise voltage measurement
Subject: [volt-nuts] Best way to measure micro Ohms
I want to measure the resistance between two bits of
19:23 Uhr
> Von: "Dr. David Kirkby (Kirkby Microwave Ltd)"
>
> An: "Discussion of precise voltage measurement"
> Betreff: [volt-nuts] Best way to measure micro Ohms
>
> I want to measure the resistance between two bits of aluminum. Each are 40
> x 30 mm a
In message
, "Dr.
David Kirkby (Kirkby Microwave Lt
d)" writes:
>I want to measure the resistance between two bits of aluminum. Each are 40
>x 30 mm across. One is 250 mm long, the other is 8 mm long.
The dominant factor in the resistance you want to measure is the pressure
on the cont
I want to measure the resistance between two bits of aluminum. Each are 40
x 30 mm across. One is 250 mm long, the other is 8 mm long. I'm wondering
is surface oxides are on the faces, so despite being held together with
bolts, the resistance is perhaps not as long as I would expect. There's
also a
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