[sdiy] How could I have missed a frequency counter in my own lab!

[Magnus Danielson]

From: Scott Gravenhorst <music.maker at gte.net>
Subject: [sdiy] How could I have missed a frequency counter in my own lab!
Date: Mon, 19 Nov 2001 10:27:38

> Yesterday while fiddling with my 4069 VCO stuff, I
> just noticed a button on my Fluke 8060a DMM that says
> 'Hz'...  !!!!  I've had this thing for YEARS.  I had
> just finished measuring the freq of the VCO with my 
> O'scope at 200 Hz, so I decided to try it.  It read 205.
> Not bad at all.  
> 
> I no longer have the manual for this DMM, do any of you 
> know what the range of accuracy is for this meter?

Just from experience, it will probably beat your scope by a
digit. Most scopes are such a lousy frequency counters, even expensive
onces. A little noise and jitter and the scope goes into greater
uncertainties.

Fluke's are kind of OK for most audio, but I have a trusty old HP
counter under a rubidium clock, which just gives me way more digits
than I usually care about, since it is more overkill than I care to
explain.

Go with the Fluke and let the scope take care of waveforms instead.
If you want to get sligthly better readings out of a scope one should
use a delayed view on a scope and measure the delay until reachning
the same level. If you do this on the digital scopes, you run against
the internal crystal oscillator, and that is usually more than
adequate accurate, so you could get a digit or two more than the
normal views "Freq Measure" feature which just gives a estimate, not a
real measure. I use that to see the neighborhood. If I get 3 digits
out of what I expected I lift an eyebrow, I don't trust them for more
than 2 digits usually.

Cheers,
Magnus