T&T: 12 volt Charging options

[Bob Peterson]

If I believe correctly that this thread started out by mentioning a Trace
inverter, most of the older Trace models have their own display built right
in that will read peak-to-peak readings directly without any other meter.  I
know my U2512SB model does.

Bob Peterson
"Lopaka Nane"
47' Lien Hwa CPMY
San Francisco 

-----Original Message-----
From: trawlers-and-trawlering-bounces@lists.samurai.com
[mailto:trawlers-and-trawlering-bounces@lists.samurai.com] On Behalf Of
Peter Bennett
Sent: Tuesday, May 29, 2007 8:37 PM
To: Gil Johnson; trawlers-and-trawlering@lists.samurai.com
Subject: Re: T&T: 12 volt Charging options

Tuesday, May 29, 2007, 5:43:15 PM, Gil wrote:

GJ> Peter, right you are on RMS.  So, with the exception of an o'scope 
GJ> how would you read the actual p-p voltage?

doesn't everyone have a 'scope?  :-)

Cheap meters may actually read peak voltage, but be calibrated to read RMS,
assuming they're measuring a sine wave.  Better meters are described as
"True RMS Reading" and will display the actual RMS voltage, regardless of
the waveform.

GJ> Gil

GJ> ----- Original Message ----
GJ> From: Peter Bennett <peterbb4@interchange.ubc.ca>
GJ> To: Gil Johnson <dogtrawler@yahoo.com>; 
GJ> trawlers-and-trawlering@lists.samurai.com
GJ> Sent: Tuesday, May 29, 2007 8:36:54 PM
GJ> Subject: Re: T&T: 12 volt Charging options


GJ> Tuesday, May 29, 2007, 3:52:28 PM, Gil wrote:

GJ>> Jeff, I'm confused.  110VAC is 110-120VAC, meaning that it's peak 
GJ>> to peak voltage is 110.  Use any AC voltmeter and you'll likely 
GJ>> read something between 110 and 125 VAC.  If they are suggesting a 
GJ>> different method of measuring the voltage, it would be helpful to 
GJ>> understand.  Not having that point of reference would make it 
GJ>> impossible to troubleshoot a suspected voltage problem.

GJ> No.  AC voltage is normally specified as the RMS (Root mean square) 
GJ> value.  AC of a given RMS voltage will produce the same power as DC 
GJ> of the same voltage.

GJ> The peak voltage of a sine wave is 1.4 times the RMS value - hence 
GJ> 120VAC RMS has a peak voltage of 168 volts.  Peak-to-peak voltage is
GJ> 2.8 times the RMS value.

GJ> From some previous comments (Arilds?), apparently some generators 
GJ> produce a distorted waveform, with flattened (and therefore lower
GJ> voltage) peaks.

GJ>> "In order to meet its ratings, 164 peak volts are required. A 
GJ>> battery charger uses only the top portion of the input sinewave.
GJ>> Therefore, small variations in peak voltage results in large 
GJ>> variations in the amount of the waveform that the charger has to 
GJ>> work with. Standard public power of 117V has a peak voltage of 
GJ>> 164V."

GJ>> Gil





-- 
Peter Bennett, VE7CEI    Vancouver, B.C., Canada
Lien Hwa 28 (AKA Polaris 30) "Sea Spray"