[sdiy] Multimeter Quest

[Happy Harry]

Hi John

(inline)


>From: John Potter <JPotter at IT.RJF.com>
>To: "'synth-diy at dropmix.xs4all.nl'" <synth-diy at dropmix.xs4all.nl>
>Subject: [sdiy] Multimeter Quest
>Date: Thu, 6 Sep 2001 11:13:51 -0400
>
> > Hello All -
> >
> > Believe it or not I actually spent several hours searching through the
> > list archives and reading specs/features on different multimeters the
> > other evening.  I've got a couple quick questions.
> >
> > How important is the ability to do transistor hfe testing?  Will my
> > synth-diy life suck without this.

No... it will not SUCK.  Hfe testing can be done with a simple
jig you can build yourself... and you can use pairs that are well
matched by design like the 2SC1583, etc...

(now BBD's... suck!)

  I saw some conflicting statements in
> > the archives regarding this topic.


> >
> > I'm having some trouble tracking a DMM w/ the other features that I'm
> > concerned with as well as this feature.  If I through out the HFE 
>testing
> > my options seem to open up greatly.  Other features I'm concerned with
> > outside of standard IVR measurements are hold, auto/manual ranging, cap,
> > diode, high accuracy, and cost < $130US or so.
> >
> > True RMS measurements?  Many of the archive notes I found seemed to
> > indicate it wasn't all it was cracked up to be but, to me, it kind of
> > seems contrary to logic to get a highly accurate DMM and then do
> > measuments using a method that will introduce error.  I guess as long as
> > you've got a sinusoidal output you could just measure that but what
> > happens when you've only got saw, tri, square?  How about if you're
> > measuring something like the voltage output from an Envelope?

True RMS may well be overrated for your application... its really not
too interesting to measure the "area under the curve" of a weird waveform 
(saw, tri, etc.)  This is where a scope is a better tool, usually you want 
to see peak levels, offsets, etc... the meter is not
well suited to this application.

Measuring the "envelope" is for a scope also... what would it mean if you 
DID measure the envelope anyway ???  Some meters have a bar graph
at the bottom of the display which might be of some (little) use.
> >
> > As far as "Hold" goes - does it usually Hold at the peak measurement or
> > just hold whenever you remove the probes?  I guess I'm asking if you 
>need
> > something w/ Min/Max/Avg for that?

Hold is not useful IMHO... it is intended for a service tech who may
not be able to look at the probes and the meter at the same time...usually 
because he will fall off the catwalk and plummet 20 feet down into the heart 
of a robotic assembly line. (yikes)

DIY is not so physically demanding. I do not ever use hold... I don't
trust the the time I touched the probes at was a good or valid sample.
OMHO.... (only my humble opinion)
> >
> > For what it's worth, I've been primarily looking at Fluke and Extech - 
>and
> > B+K a little bit.

I've been happy with my Fluke 77, I won it in as a doorprize at a trade show 
about 15 years ago. When they said "and the winner of the Fluke meter is 
Harry..." I remember saying "Thank you GOD!" quite loudly. The Fluke rep was 
quite amused. Other prizes were a TV (yeah..
soap opera... no thanks!) and a hair dryer... not too useful in my case.

It might be nice to have a capacitor reading function if it is no extra 
trouble.  I would not bother with frequency measurement but
some folk might... probably not enough resolution to do any good.

I'd look for a meter that can measure a wide range of current... down
to some microamps would be excellent... but at least under a millamp
is a must. AC and DC current is good also.

H^) harry

> >
> > Thanks much - I'm sure I'll have a couple more related questions over 
>the
> > next couple days.
> >
> > JP
> >
> >


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