[sdiy] RE: Volt-a-meter

[Ben Riggs]

I knew your meter whips my meter before you even said it. I *only* have a 4
1/4 digit fluke handheld, which I know is a great indicator, but there is no
traceability of its measurement (I've never had it calibrated, can't really
justify the cost atm).

During the daytime I work in a NATA accredited electrical test laboratory
(as a tech, not an engineer), which is why I never believe anyone when they
claim to be accurate without quoting traceability and uncertaintity of their
measurement. One of the things that we hammer is never believe what the
meter is telling you unless we can traceably prove the whole system. Even at
6 1/2 digits there are a lot more things that can influence the
uncertaintity of the measurement than the accuracy of the meter.

If I ever required an accurate meter, I got access to a couple of agilent
3458A DMMs, which are NATA traceably calibrated, but a bitch to use if you
want minimize your uncertaintity at 8 1/2 digits.

http://www.home.agilent.com/USeng/nav/-536897931.536881781/pd.html

b.

-----Original Message-----
From: Paul Schreiber [mailto:synth1 at airmail.net] 
Sent: Sunday, 9 October 2005 2:18 PM
To: Ben Riggs; 'synthDIY'
Subject: Volt-a-meter

> so whose meter is accurate? Whose method of measuring voltage is most
> accurate?
>
> I believe you that your MIDI->CV converter AND your meter is stable and
> predictable at that precision, but absolutely spot-on accurate, I'm not
too
> sure of.

Well, what meter do you have? This is a HP34401A, which has been calibrated
to 6 
1/2 digits of accuracy.
The calibration standard used is accurate to 8 1/2 digits. It was done on a 
Fluke 5520A, here is the link:

http://us.fluke.com/usen/products/5520A.htm?catalog_name=FlukeUnitedStates&C
ategory=PMELE(FlukeProducts)

If you don't understand metrology, there is lots of info on the web. You may
run 
accross the term "NBS traceable",
Google on that and learn some more. My point is: there is such a thing as a 
"voltage standard", and my meter can
whip your meter :)

And THIS meter kicks *everyone's* meter out the window:

http://us.fluke.com/usen/products/8508A.htm?catalog_name=FlukeUnitedStates&C
ategory=CALMM(FlukeProducts)

>
> My question to the group is, at what level of precision do we (in sdiy)
stop
> caring about accuracy? ie. if my meter says 1.0001 Vdc, and yours says
> 0.9999 Vdc do we really care which one of us is more accurate?

The average $50 DVM is fine for the vast majority of synthDIY work. But if
the 
object of the project is to produce a *reference standard* MIDI-CV
converter, 
then I want 6 1/2 digits. But that's just me :)

Paul S.