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arup
Joined: 06 Sep 2004
Posts: 34
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 17 Dec 2005 7:50 Idea of measuring RMS voltage and current using MCU ADC |
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Dear sir,
I have a project which needs to measure Supply Voltage and Current.I want to measure them using only MCu adc (ST7 with 10 bit ADC and 6 analog i/p channel).Could anybody help me ??I want a tested circuit and also want the design idea/steps to develope this firmware to measure voltage and current rms value.I believe supply input voltage is always RMS if it is not mentioned.so i don't have to take voltage sample ,square ,take average and take root of it.Or do I??Pls correct me if i am wrong.
pls note the max voltage and current for the system to measure are 260 V and 30 A respectively.And I know how to configure the adc for this particular MCU
Thanks,
arup
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smxx
Joined: 18 Aug 2005
Posts: 188
Helped: 8
Location: iran(ahwaz)
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18 Dec 2005 8:02 Re: Idea of measuring RMS voltage and current using MCU ADC |
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hi
Analoge Device have some Ic that give a signal and give rms value in output (analog output).
for sine wave ,if you have 2 sample with 90 angle(y(Θ)and y(Θ+90))
you can calculate peek of signal
Ym˛=y(Θ)˛+y(Θ+90)˛ Yrms=Ym/√2
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amrstaha
Joined: 29 Aug 2005
Posts: 141
Helped: 6
Location: Egypt
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19 Dec 2005 17:58 Re: Idea of measuring RMS voltage and current using MCU ADC |
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You will have to sample the voltage (or current) signal at a fixed rate if the signal is not sinusoidal. The sampling frequency should be as high as possible to accurate results. After taking n samples you can caculate the RMS from
frms=√(Σ(sample(i)^2)/n) where i=1 to n
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arup
Joined: 06 Sep 2004
Posts: 34
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20 Dec 2005 9:31 Re: Idea of measuring RMS voltage and current using MCU ADC |
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yes, The i/p supply wave form is sinusoidal.Max analog signal to the ADC pin is 5V .If any body is having the ckt pls post here.
thanks,
arup
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narender_aec_eee
Joined: 02 Jan 2006
Posts: 3
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02 Jan 2006 9:37 Idea of measuring RMS voltage and current using MCU ADC |
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| hi can anyone upload a circuit which can measure ac voltage using parallel port or microcontroler and adc.
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sam_manchali
Joined: 14 Jun 2003
Posts: 105
Helped: 3
Location: sharjah
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02 Jan 2006 10:22 Re: Idea of measuring RMS voltage and current using MCU ADC |
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hi,
check out this link , it may be helpful...
http://www.atmel.com/dyn/resources/prod_documents/doc2566.pdf
regards
sam
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auto_mitch
Joined: 14 Oct 2004
Posts: 212
Helped: 20
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02 Jan 2006 10:44 Re: Idea of measuring RMS voltage and current using MCU ADC |
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Check out this link
http://www.zilog.com/docs/z8encorexp/appnotes/an0216.pdf
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