need recommendation for digital multimeter

[Gary Peek]

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.

 

[[email protected]]

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.

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.

 

[speff]

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.

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. ;-)

 

[Gary Peek]

Handheld or benchtop? either
You need to measure high voltages/currents? no
Need or want frills ... not needed
Want RMS measurement? not needed
Need absolute accuracy? preferable
Budget range?

< 400? is that reasonable?

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

 

[John Larkin]

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. ;-)

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

 

[Phil Allison]

<[email protected]>

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

 

[Gary Peek]

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

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.

 

[mike]

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.

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

 

[Phil Allison]

"mike"

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.

** 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

 

[Chuck]

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. ;-)

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

 

[Gary Peek]

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.

Always good advice, and I have thought about that, thank you.

 

[mike]

"mike"


** 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.

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.

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.

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

 

[Phil Allison]

"mike"

Let me be less tactful...

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

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

** 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.

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.

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

YOU have failed to think the issue through.



** 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