🚀 go-pugleaf

In article <BzwHA7.6y@zoo.toronto.edu>, henry@zoo.toronto.edu (Henry Spencer)
 writes:
> In article <2B3582F9.18867@news.service.uci.edu> gkwan@balboa.eng.uci.edu (Greg Kwan) writes:
>>1. Get the best DMM you can--it's the most important test instrument.
>>I have a Fluke 77 and have been very happy with it, but would probably
>>go for an 87 or 79 now. You'll probably use the freq. counter since
>>it's a pain to fire up the scope just to measure a frequency...
> 
> Note, though, that any frequency measurement using something other than
> a scope relies heavily on assumptions about waveform.  When I first got
> my current scope, I hoked up a little audio-frequency square-wave generator
> with a 555 as an independent test signal.  I was a bit surprised to find
> that my frequency counter read twice what the scope showed me.  
> [...] There is no substitute for seeing exactly what's happening.

I'll second this, and LOUDLY, too.  

It appalls me to see frequency counters (and instruments like DMMs that include
counters) that have no trigger level control, no input coupling selector (AC or
DC), no edge selector (rising or falling).  You wouldn't buy a triggered-sweep
scope without such controls; of what possible use is a counter without them? 

I've seen many of these idiot-box counters (Star-Tek, Optronics, etc.) misread
a pure sinewave at audio line level.... they may be good for "transmitter
sniffing", where the input is at very low level, but I doubt they're good for
much else. 

Anyone who trusts one of these counters without checking the waveform on a
scope, if only to get in the right ballpark, is being as foolish as the person
who thinks that a digital watch must be accurate simply because it isn't
analog.  

> -- 
> "God willing... we shall return."       | Henry Spencer @ U of Toronto Zoology
>        -Gene Cernan, the Moon, Dec 1972 |  henry@zoo.toronto.edu  utzoo!henry

"God" was willing -- none of the relevant physical laws or principles of
chemistry have changed that I know of, so the the hardware designed in the
sixties ought to work just fine today. It was Senator Proxmire who wasn't
willing. 

	--- Jamie Hanrahan, Kernel Mode Consulting, San Diego CA
Internet:  jeh@cmkrnl.com, hanrahan@eisner.decus.org, or jeh@crash.cts.com
Uucp:  ...{crash,eisner,uunet}!cmkrnl!jeh