AC Voltmeter [wattmeter]
Archiver
Posts: 46,084
Craig, do yourself a favor and go to http://www.analog.com
and look at the AD7750 product to frequency converter
data sheet. [noparse][[/noparse]PDF format download 16 pages].
This IC is cheap and was made specifically to be used in
electronic watt meters [noparse][[/noparse]small error over large current
range]. It handles power factor issues and gives a
pulse output proportionate to _real_ power in the
circuit. This pulse can be measured by the Basic Stamp!
Accurate power measurement with odd waveforms is not
trivial. A multiplier is required usually.
A simple analog circuit which accomplishes multiplication
is to vary pulse width with current and the pulse height
with voltage and then integrate the pulse output with
a capacitor and you'll get a reading of current x voltage
for one phase quadrant. In simple terms you can switch
the voltage you are trying to multiply with a pulse
width determined from the current - just a CMOS switch
can do this.
Another way this is done is with Hall effect devices
[noparse][[/noparse]OHIO Semitronics] where a magnetic field proportional
to voltage is put across a hall effect linear sensor
having a signal proportional to current running through it.
This gives a signal proportional to VxI out continuously.
[noparse][[/noparse]These are somewhat bulky and expensive modules].
Good luck...
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and look at the AD7750 product to frequency converter
data sheet. [noparse][[/noparse]PDF format download 16 pages].
This IC is cheap and was made specifically to be used in
electronic watt meters [noparse][[/noparse]small error over large current
range]. It handles power factor issues and gives a
pulse output proportionate to _real_ power in the
circuit. This pulse can be measured by the Basic Stamp!
Accurate power measurement with odd waveforms is not
trivial. A multiplier is required usually.
A simple analog circuit which accomplishes multiplication
is to vary pulse width with current and the pulse height
with voltage and then integrate the pulse output with
a capacitor and you'll get a reading of current x voltage
for one phase quadrant. In simple terms you can switch
the voltage you are trying to multiply with a pulse
width determined from the current - just a CMOS switch
can do this.
Another way this is done is with Hall effect devices
[noparse][[/noparse]OHIO Semitronics] where a magnetic field proportional
to voltage is put across a hall effect linear sensor
having a signal proportional to current running through it.
This gives a signal proportional to VxI out continuously.
[noparse][[/noparse]These are somewhat bulky and expensive modules].
Good luck...
________________________________________________________________
YOU'RE PAYING TOO MUCH FOR THE INTERNET!
Juno now offers FREE Internet Access!
Try it today - there's no risk! For your FREE software, visit:
http://dl.www.juno.com/get/tagj.
Comments
Gary
Original Message
From: "s premena" <premzee@j...>
To: <basicstamps@egroups.com>
Sent: Thursday, July 27, 2000 7:34 PM
Subject: [noparse][[/noparse]basicstamps] Re: AC Voltmeter [noparse][[/noparse]wattmeter]
> Craig, do yourself a favor and go to http://www.analog.com
> and look at the AD7750 product to frequency converter
> data sheet. [noparse][[/noparse]PDF format download 16 pages].
>
> This IC is cheap and was made specifically to be used in
> electronic watt meters [noparse][[/noparse]small error over large current
> range]. It handles power factor issues and gives a
> pulse output proportionate to _real_ power in the
> circuit. This pulse can be measured by the Basic Stamp!
>
> Accurate power measurement with odd waveforms is not
> trivial. A multiplier is required usually.
>
> A simple analog circuit which accomplishes multiplication
> is to vary pulse width with current and the pulse height
> with voltage and then integrate the pulse output with
> a capacitor and you'll get a reading of current x voltage
> for one phase quadrant. In simple terms you can switch
> the voltage you are trying to multiply with a pulse
> width determined from the current - just a CMOS switch
> can do this.
>
> Another way this is done is with Hall effect devices
> [noparse][[/noparse]OHIO Semitronics] where a magnetic field proportional
> to voltage is put across a hall effect linear sensor
> having a signal proportional to current running through it.
>
> This gives a signal proportional to VxI out continuously.
> [noparse][[/noparse]These are somewhat bulky and expensive modules].
>
> Good luck...
>
> ________________________________________________________________
> YOU'RE PAYING TOO MUCH FOR THE INTERNET!
> Juno now offers FREE Internet Access!
> Try it today - there's no risk! For your FREE software, visit:
> http://dl.www.juno.com/get/tagj.
>
>
>
Original Message
From: G. Shearer [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=eD1o6ULfGXPgibxOC-Y-W1Yo0dcH6W1o7RjW7uj_lO1Z-qqevwL5cu-tUOHvfq8wShst9inpC2qamItRmDuESA]g.shearer@v...[/url
Sent: Friday, July 28, 2000 9:16 AM
To: basicstamps@egroups.com
Subject: Re: [noparse][[/noparse]basicstamps] Re: AC Voltmeter [noparse][[/noparse]wattmeter]
Great Idea. Good Input.
Gary
Original Message
From: "s premena" <premzee@j...>
To: <basicstamps@egroups.com>
Sent: Thursday, July 27, 2000 7:34 PM
Subject: [noparse][[/noparse]basicstamps] Re: AC Voltmeter [noparse][[/noparse]wattmeter]
> Craig, do yourself a favor and go to http://www.analog.com
> and look at the AD7750 product to frequency converter
> data sheet. [noparse][[/noparse]PDF format download 16 pages].
>
> This IC is cheap and was made specifically to be used in
> electronic watt meters [noparse][[/noparse]small error over large current
> range]. It handles power factor issues and gives a
> pulse output proportionate to _real_ power in the
> circuit. This pulse can be measured by the Basic Stamp!
>
> Accurate power measurement with odd waveforms is not
> trivial. A multiplier is required usually.
>
> A simple analog circuit which accomplishes multiplication
> is to vary pulse width with current and the pulse height
> with voltage and then integrate the pulse output with
> a capacitor and you'll get a reading of current x voltage
> for one phase quadrant. In simple terms you can switch
> the voltage you are trying to multiply with a pulse
> width determined from the current - just a CMOS switch
> can do this.
>
> Another way this is done is with Hall effect devices
> [noparse][[/noparse]OHIO Semitronics] where a magnetic field proportional
> to voltage is put across a hall effect linear sensor
> having a signal proportional to current running through it.
>
> This gives a signal proportional to VxI out continuously.
> [noparse][[/noparse]These are somewhat bulky and expensive modules].
>
> Good luck...
>
> ________________________________________________________________
> YOU'RE PAYING TOO MUCH FOR THE INTERNET!
> Juno now offers FREE Internet Access!
> Try it today - there's no risk! For your FREE software, visit:
> http://dl.www.juno.com/get/tagj.
>
>
>