need recommendation for digital multimeter

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I'm needing to update the accuracy of my voltage measurements.

Looking for recommendations for a 4 1/2 digit or better
multimeter, specifically, would like to measure down to the
1000th of a volt as accurately as possible, including my
5 volt and 10 volt measurements.

I've done a lot of looking around, but the specs on these things
vary considerably. Some practical advice would be appreciated.

Re: need recommendation for digital multimeter
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I like the Thurlby-Thandar multimeters. The 1906 - which I've used in
two different jobs - offers more than you ask for at a very reasonable
price, including four terminal resistance measurements and the
facility to log 100 successive measurements into local memory.

Their 1604 - at half the price - does pretty much exactly what you ask
for.

http://www.tti-test.com/products-tti/precision/digital-multimeters.htm

Clive Sinclair was involved when Thurlby-Thandar started up, but they
managed to stop him messing up their quality control fairly early on,
and they do seem to have managed to take advantage of Clive's genius
for finding really cheap ways of doing things, without getting stuck
with his compulsion to make the product too cheap to be reliable.

--
Bill Sloman, Nijmegen


Re: need recommendation for digital multimeter


I like the Thurlby-Thandar multimeters. The 1906 - which I've used in
two different jobs - offers more than you ask for at a very reasonable
price, including four terminal resistance measurements and the
facility to log 100 successive measurements into local memory.

Their 1604 - at half the price - does pretty much exactly what you ask
for.

http://www.tti-test.com/products-tti/precision/digital-multimeters.htm


**  I owned a  TTI 1604 briefly, before returning it to the supplier (
Farnell ) as it has serious bugs.

A second sample demonstrated exactly the same bugs, so they were designed
in.

The bugs were in the auto-ranging and all the ohms ranges - which could and
did give completely erroneous readings.

6800 ohms reading 3940 is not good  !!!!

Many of the bugs derive form the makers trying to get 4.5 digit resolution
from a DMM chip that is not speced for that job.



.......   Phil






Re: need recommendation for digital multimeter
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Seems to be a nice meter but Phil A. expressed some concerns
in another post. Also, Saelig seems to be their only US
distributor, and quoted 6 weeks, $519.

So I'm still looking. Thanks.

Re: need recommendation for digital multimeter
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Consider carefully what you'll be measuring.

I was elated to pick up a 5.5 digit HP voltmeter for free
at a garage sale.

Took it home, hooked it up to a battery.  Was very cool
to see 1.31V to 5.5 digits.

But when I tried to use it for real measurements, I got
3 digits of reading and 2.5 digits of noise.  I put it in the
attic.  Only time I drag it down is when I need to measure
the voltage drop across an inch of wire.

To get any use out of a high-res voltmeter, you need a VERY
controlled environment.  But I'm sure you already know that.
mike


--
Return address is VALID!

Re: need recommendation for digital multimeter

"mike"
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** There is a low pas filter in line with the input of a DMM when set to
read DC volts, generally set to give 3 dB attenuation at about 20 Hz with
a -6 dB /octave slope above that.

PLUS, nearly all DMMs have the sampling rate set so a whole number of cycles
of the AC supply frequency are included in each reading -  means any
residual 50 or 60 Hz ( plus harmonics ) will not affect the DC reading.

Sometimes a meter with sampling time set for use in a 60 Hz country winds up
in a 50 Hz one and vice versa.



......   Phil












Re: need recommendation for digital multimeter
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Let me be less tactful...
Most people, including (maybe especially) very smart engineers
who graduated at the top
of their class, don't think things through.  They take a quick look at
(part of) the problem, count the digits, go buy one without considering
the further implications of their choice and spend a LOT of time trying
to make the rest of the system live up to that expectation.

My intention was to expose
this issue without making any accusations.  Many problems can be better
addressed with less brute force.
Anything that requires 5.5 digits of repeatable measurement is gonna
be a nightmare.  Sometimes, you gotta do it.  But avoid at all costs.


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That's really great IFF line (related) noise is what is corrupting your
reading.

There surely are applications that require high resolution.  My
statement was that I found the extra two digits of noise less useful
than the bench space taken up by the meter.

And we haven't even started talking about all the issues that
affect accuracy.

mike
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--
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Re: need recommendation for digital multimeter

"mike"
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**  Go ahead  -  make my day  ......


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**  Which is very often the case.

And since noise above 20 Hz is attenuated that only leaves very low
frequency noise as a possible culprit.



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**  But there is no need for ANY such noise to be there.

   YOU have failed to think the issue through.


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**  Betcha this one is you  *whole*  problem.

 And if it ain't, then just add your own, external LP filter until the noise
causing end digit jitter is gone.




........   Phil






Re: need recommendation for digital multimeter
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Handheld or benchtop?
You need to measure high voltages/currents?
Need or want frills such as capacitance, hFE, temperature, frequency?
Want RMS measurement?
Need absolute accuracy? Or just resolution/linearity?
Budget range? < $10? < $100? < $1,000? < $10,000?

This is a nice one in the highest bracket:  ;-)
http://www.home.agilent.com/agilent/product.jspx?nid=-536902435.536881781.00&cc=AW&lc=eng

Kind of nice to see my 10uA current sources reading 10.0024233 uA
without adjustment. ;-)



Re: need recommendation for digital multimeter
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either
no
not needed
not needed
preferable
< 400? is that reasonable?

Good questions, I didn't know I would get so much detail
from y'all, thank you.

Re: need recommendation for digital multimeter

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Yikes, what does a beast like that cost?

Any idea how it works?

That last digit is 0.1 pA, about 600,000 electrons per second.

John


Re: need recommendation for digital multimeter

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If you need that level of accuracy, give some thought to how you plan
to calibrate from time to time, and the cost of doing so. Precision is
much less costly than absolute  accuracy and sometimes  is more
useful.

Chuck

-

Re: need recommendation for digital multimeter
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Always good advice, and I have thought about that, thank you.

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