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basics | What's the output voltage of full wave rect?
There are 8 messages in this thread.
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What's the output voltage of full wave rect? - DaveC - 2009-12-16 02:07:00
A full-wave rectified 32vac voltage without filtering or smoothing components. Just a bridge rectifier connected across a transformer 32v secondary (no center taps) without a load connected to the output of the bridge. What will my DMM read if it's in DCV mode when connected to this output? Thanks, Dave
Re: What's the output voltage of full wave rect? - Jasen Betts - 2009-12-16 05:44:00
On 2009-12-16, DaveC <i...@invalid.net> wrote: > A full-wave rectified 32vac voltage without filtering or smoothing > components. Just a bridge rectifier connected across a transformer 32v > secondary (no center taps) without a load connected to the output of the > bridge. > > What will my DMM read if it's in DCV mode when connected to this output? with no capacitors and a cheap average-reading DMM about 28V > Thanks, > Dave >
Re: What's the output voltage of full wave rect? - Phil Allison - 2009-12-16 08:59:00
"Jasen Betts"
DaveC
>
>> A full-wave rectified 32vac voltage without filtering or smoothing
>> components. Just a bridge rectifier connected across a transformer 32v
>> secondary (no center taps) without a load connected to the output of the
>> bridge.
>>
>> What will my DMM read if it's in DCV mode when connected to this output?
>
> with no capacitors and a cheap average-reading DMM about 28V
** So more expensive DMMs read *OTHER* than average values on their DC
volts ranges??
Do tell.
.... Phil
Re: What's the output voltage of full wave rect? - John Fields - 2009-12-16 09:45:00
On Thu, 17 Dec 2009 00:59:02 +1100, "Phil Allison" <p...@tpg.com.au> wrote: > >"Jasen Betts" > DaveC >> >>> A full-wave rectified 32vac voltage without filtering or smoothing >>> components. Just a bridge rectifier connected across a transformer 32v >>> secondary (no center taps) without a load connected to the output of the >>> bridge. >>> >>> What will my DMM read if it's in DCV mode when connected to this output? >> >> with no capacitors and a cheap average-reading DMM about 28V > > >** So more expensive DMMs read *OTHER* than average values on their DC >volts ranges?? > > Do tell. --- Funny! ;) news:1...@4ax.com JF
Re: What's the output voltage of full wave rect? - DaveC - 2009-12-16 11:17:00
> with no capacitors and a cheap average-reading DMM about 28V If a good "True RMS" DMM is used, will the reading be different? And can you help "teach me to fish" (show me the math)? Thanks, Dave
Re: What's the output voltage of full wave rect? - richard - 2009-12-16 13:24:00
DaveC wrote: > A full-wave rectified 32vac voltage without filtering or smoothing > components. Just a bridge rectifier connected across a transformer 32v > secondary (no center taps) without a load connected to the output of the > bridge. > > What will my DMM read if it's in DCV mode when connected to this output? > > Thanks, > Dave > 2*sqrt(2)*32/3.14159265=28.8101221484 Integral from 0 to pi of Sin(theta)/pi = Average voltage of Sin(theta) = 2/pi therefore 1/sqrt(2) rms -> 2/pi therefore 1 -> 2*sqrt(2)/pi therefore 32 -> 2*sqrt(2)*32/pi
Re: What's the output voltage of full wave rect? - John Larkin - 2009-12-16 22:34:00
On Thu, 17 Dec 2009 00:59:02 +1100, "Phil Allison" <p...@tpg.com.au> wrote: > >"Jasen Betts" > DaveC >> >>> A full-wave rectified 32vac voltage without filtering or smoothing >>> components. Just a bridge rectifier connected across a transformer 32v >>> secondary (no center taps) without a load connected to the output of the >>> bridge. >>> >>> What will my DMM read if it's in DCV mode when connected to this output? >> >> with no capacitors and a cheap average-reading DMM about 28V > > >** So more expensive DMMs read *OTHER* than average values on their DC >volts ranges?? > > Do tell. > Howzit going, Phil? A DC-coupled true RMS meter would read different from an averaging meter. But in real life, diode leakage and capacitance and transformer inter-winding capacitance would probably result in an unpredictable reading. John
Re: What's the output voltage of full wave rect? - Phil Allison - 2009-12-17 02:01:00
"John Larkin" > >>** So more expensive DMMs read *OTHER* than average values on their DC >>volts ranges?? >> >> Do tell. > > A DC-coupled true RMS meter would read different from an averaging > meter. ** Dogs bark and cat go meow. But a DC voltmeter is always average responding. > But in real life, diode leakage and capacitance and transformer > inter-winding capacitance would probably result in an unpredictable > reading. ** I have a 4.5 digit meter with true RMS AC ranges (200kHz BW) that can be DC coupled - a very handy feature. But one does not use it for the job the OP described without adding a load resistor, cos of the issues you mention. .... Phil