ODP: Digital Multimeters for Dummies

[Roman Sowa]

	-----Oryginalna wiadomość-----
	Od:	"inman at interpath.com"@interpath.com
[SMTP:"inman at interpath.com"@interpath.com]
	Wysłano:	7 listopada 1998 15:55
	Do:	synth-diy at mailhost.bpa.nl
	Temat:	Digital Multimeters for Dummies

> The Count:  The higher the count, the better because this is the number
> of samples used to calculate the measurement.  True or false?
> [Roman Sowa]  I'm not sure what you mean
> 
> True RMS:  True root mean square.  If it doesn't say true RMS, it is
> making measurements how?  Is this cheap alternative measurement
> system really that awful?
> [Roman Sowa]  it meaures mean value and shows it as it would
> be rms for sine wave. Other waveforms wil be measured with error
> It's not so awfull after all, but true rms might be usefull from time o
> time
> 
> Percent Accuracy:  What is completely unacceptable for high quality
> amateur work?
> [Roman Sowa]  I think 1%
> 
> Certificate of Calibration:  Do I need this
> [Roman Sowa]  True, you don't need it. the multimeter will loose
> accuracy with time after all, so you'd have to calibrate it every year
> a that's $$$. I don't care for such certificate
> 
> Autoranging vs. Manual Setting:  
> [Roman Sowa]  Autoranging is excellent for resistance measurements
> and most others. I like sometimes change to manual, and keep 20V range
> even when voltage drops near 0. Besides, with autoranging you can not
> destroy range switch (mine is crappy over the years). And it's nice
> to put DVM at 200mV range to 220AC outlet and see proper result.
> 
> Frequency:  Is this really a useful function on a handheld multimeter
> or I am a better off matching pitch using my Boss guitar tuner?  Or,
> is this function useful in a completely different way?
> [Roman Sowa]  they are always limited to few MHz which is nothing.
> And accuracy is in the crappiest area among counters.
> For tuning I use DDS signal generator
> 
> 3 1/2 Digit:  Does the half digit at the end mean that measurements
> are rounded to one decimal place?  I saw a Fluke with 3 3/4 digits.
> What does the 3/4 digit mean?
> [Roman Sowa]  3 1/2 is 1999 max display, 3 3/4 is 4999 display
> 
> 
> Two general questions...
> 
> Multimeters, even those with the same features (accuracy, functions, 
> etc...), seem to range wildly in price.  Are you paying for a real
> difference in quality or are you paying extra for a brand name
> that doesn't really mean anything?
> [Roman Sowa]  some brand names mean something, like long
> life accuracy, but I'm fine with mine almost no-name multimeters
> 
> Is it possible for a low cost multimeter to really be good at a large
> number of functions, from DC to AC, to transistor testing, to
> resistance, capacitance, and frequency?  Or, is it the case with
> multimeters that the do-it-all unit is a "jack of all trades and 
> master of none?"
> [Roman Sowa]  you'll have good all-in-one multimeter when
> you DIY it. But seriously, I've seen few of them.You must
> be lucky to get one, and it's in upper $$$ range.
> 
> 
> Thanks for the Advice,
> 
> Elliot
> "November:  Time to Start
> Being Nicer and Pull Up
> My 1998 Average"