Date: Tue, 17 Aug 2004 18:43:18 -0700

Author: "Chuck"

Subject: RE: aha! Pasco power amplifier problem solved


Actually, RMS voltmeters have been the exception rather than the rule. As
you point out usually only available in the higher end units. This was true
in the analog versions as well. When buying a meter it is more common to
have that feature offered as electronics have matured.


-----Original Message-----
[] On Behalf Of Steve Wonnell
Sent: Tuesday, August 17, 2004 8:04 AM
Cc: Steve Wonnell
Subject: RE: aha! pasco power amplifier problem solved

Hi Chuck,

Could you elaborate on this? All the digital voltmeters that I've used
recently measure the RMS voltage or something close to it. The exceptions
are those that specifically have a setting for measuring the peak voltage.
It's been a while since I've used an analog meter but I seem to recall
that those also measured the RMS voltage.

For example, Fluke's higher-end voltmeters are guaranteed to measure the
"true RMS" voltage; their low-end voltmeters don't have such a guarantee
but presumably they measure an approximation of this RMS voltage.

Thanks for the tip about the ARRL handbook; I wasn't aware of it.

Steve W.

On Mon, 16 Aug 2004, Chuck wrote:

> Date: Mon, 16 Aug 2004 19:46:52 -0700
> From: Chuck
> Reply-To:
> To:
> Subject: RE: aha! pasco power amplifier problem solved
> More bad news, Most voltmeters read avg or peak volts, not RMS... Most
> libraries have a book called "The ARRL Handbook". It is one of the best
> books to familiarize someone with electronics. If I remember right, it
> Chapter 3 or there about where the practical basics start.
> cheers,
> chuck...
> -----Original Message-----
> From:
> [] On Behalf Of cablem
> Sent: Monday, August 16, 2004 7:43 AM
> To:
> Cc: Keith Bonin
> Subject: aha! pasco power amplifier problem solved
> Remember about 6 months ago, there was some discussion about why the
> pasco power amplifier was putting out twice what some of us thought it
> should? It ends up being a definition of amplitude. I had been defining
> amplitude as peak-to-trough amplitude. The PASCO software/hardware
> defines it as midpoint to highest OR lowest point . So, when the pasco
> power amp (and also new 750 interfaces with the power amp built in) puts
> out a wave with an amplitude of 2, I read it as 4.
> So, its a matter of definition. Technically, +A is supposed to be
> midpoint to peak, -A is supposed to the midpoint to trough. So, I've
> learned something! Go me! Now, I just have to remember that ac
> voltmeters read rms values (2V pasco = 1.4V on voltmeter).
> Chele
> --
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Machele Cable
> Lab Manager
> Physics Dept.
> Wake Forest University
> Winston-Salem, NC 27109
> Phone: 336-758-5532
> Fax: 336-758-6142
> "Foxtrot", 7/1/2004:
> "3...2...1...Lift off!"
> "I think the payload was too top heavy."
> "Maybe we shouldn't try launching Barbies."
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Steven K. Wonnell
Physics and Astronomy Department E-Mail:
Johns Hopkins University Phone: (410) 516-4696, 516-5468
3400 N. Charles Street Fax: (410) 516-7239
Baltimore, MD 21218-2686 Office: 478 Bloomberg

From Wed Aug 18 11:44:06 2004