What are 6.5 Digit Multimeters Good For?

Fri Mar 12, 2010 8:50 am   

On Thu, 11 Mar 2010 19:11:54 -0800, D from BC <myrealaddress_at_comic.com>
wrote:



But have no clue as to why.

Fri Mar 12, 2010 8:55 am   

On Thu, 11 Mar 2010 18:53:32 -0800, D from BC <myrealaddress_at_comic.com>
wrote:



Try Keithley

http://www.keithley.com/products/dcac/dmm/highper


http://www.keithley.com/products/dcac/sensitive/lowvoltage/?mn=2182A

Fri Mar 12, 2010 8:56 am   

On Thu, 11 Mar 2010 23:25:31 -0600, Jim Yanik <jyanik_at_abuse.gov> wrote:


Which is why Keithley is better.

Agilent is good, don't get me wrong.

Don't be a LarkinTard. Instead of a lard ass, he is a Tardass.

Fri Mar 12, 2010 8:57 am   

On Thu, 11 Mar 2010 20:29:08 -0600, "mook johnson" <mook_at_mook.net> wrote:


by most.

Fri Mar 12, 2010 8:59 am   

On Thu, 11 Mar 2010 20:38:15 -0600, AZ Nomad
<aznomad.3_at_PremoveOBthisOX.COM> wrote:



Damn! The little bastard actually said something quite intelligent!

I am impressed... really.

Fri Mar 12, 2010 9:05 am   

In article <kisjp5h1mmb1du7r5b37m07g8dcdbfq6ja_at_4ax.com>,
OneBigLever_at_InfiniteSeries.Org says...

That wasn't worth reading.

Fri Mar 12, 2010 9:10 am   

In article <kisjp5h1mmb1du7r5b37m07g8dcdbfq6ja_at_4ax.com>,
OneBigLever_at_InfiniteSeries.Org says...

Want to explain it for me?

Fri Mar 12, 2010 10:02 am   

On Fri, 12 Mar 2010 00:05:48 -0800, D from BC <myrealaddress_at_comic.com>
wrote:


The one millivolt, or the lack of a clue?

Fri Mar 12, 2010 10:57 am   

Jon Kirwan a écrit :

If only that...

--
Thanks,
Fred.

Fri Mar 12, 2010 11:18 am   

D from BC wrote:

Depends what you are doing. In the 80's the kit I worked on used a bank
of up to 8 Solartron 7060 DVMs to measure signals to ppm accuracy. Most
people settled for 4 or 6 and there was an option to have just one DVM
and multiplex the signals. We changed from Solartrons to the first high
precision ADCs that were able to achieve the required precision in the
early 90's, but a few 7060s (and their improved replacements) were
needed for test and calibration. The new kit had to be provably better
than the 7060 on the bench before the punters would even consider it.

These days high precision DVMs tend to be used mostly to calibrate, test
and correct the linearity, drift of secondary measurement devices and
sensors. I can't imagine anyone building high precision DVMs into
commercial kit today but I could be wrong. We stopped doing it in the
early 90's.

I can't remember the chip number but I think it was an AD part with dual
slope integration and almost ppm accuracy out of the box. I did the
calibration software to correct systematic errors and linearise it for
our application. Obtaining true linearity is harder than it sounds.

Integration periods had to be local mains synchronous and the linearity
had to be spot on for the intended application to work at all. Users
were looking for reproducible 4-5 figure accuracy on the ratio of feeble
ion beam signals from Faraday detectors. Dating moon rocks and similar.


Things where you need excellent long term stability and linearity with
genuine 6 digit accuracy after signals are averaged for long enough.

Regards,
Martin Brown

Fri Mar 12, 2010 1:23 pm   

On Thu, 11 Mar 2010 17:56:35 -0800, the renowned D from BC
<myrealaddress_at_comic.com> wrote:


If you're developing precise instruments, you would prefer to have
test equipment that has higher (preferably MUCH higher) performance
than the devices you are developing. Say you have designed a 0.1% or
0.01% current source for a sensor and want to confirm how much it
drifts with temperature within 1%.

It's not as easy when you approach or pass the limits of what has been
done (or what you can afford to buy/rent/borrow) and you have figure
out how the heck to test it.

I don't see how a meter like that would be all that useful if you were
only developing digital, audio or RF though.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff_at_interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

Fri Mar 12, 2010 1:30 pm   

On a sunny day (Thu, 11 Mar 2010 17:56:35 -0800) it happened D from BC
<myrealaddress_at_comic.com> wrote in <MPG.26033f321480b139896e5_at_209.197.12.12>:


They are not needed, all you need is a 5 Euro multimeter,
and in extreme cases a precise reference.
That means if you use one of those reference chips, you borrow
the very accurate multimeter for a day, measure your reference chip,
write it down, and use that to calibrate your cheap multimeter,
or o compute it's real value,
Saved: 1000$

Of course there are exceptions,
but in places where that counts they usually have a lot of ++++expensive stuff anyways.
Usually places where nothing really useful is done, like in CERN, or ITER, or LIGO,
etc.

Fri Mar 12, 2010 4:10 pm   

On 3/11/2010 9:38 PM, AZ Nomad wrote:

A knat is the KDE version?

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net

Fri Mar 12, 2010 4:21 pm   

On Fri, 12 Mar 2010 10:10:31 -0500, Phil Hobbs
<pcdhSpamMeSenseless_at_electrooptical.net> wrote:


Ahh...clever. that brought a smile. Thanks!

--
Rich Webb Norfolk, VA

Fri Mar 12, 2010 4:26 pm   

D from BC schrieb:


Hello,

if you carefully read the specifications of some 8.5 Digit multimeter,
you will find out that you get the full performance only up to one day
after calibration, at 20 +- 1 °C and only when measuring DC voltages
between 1 and 10 V. ;-)

Bye