AC main voltage measurement

[cheetha]

- use a higher order low-pass filter. You would need to learn a bit about active filters.

can u plz suggest a circuit??

and

- average the measurement in the digital domain, ultimately over multiples of the mains period. 100 ms averaging time is used by most multimeters, works both for 50 and 60 Hz.

how many values are required and after how much interval the values must be taken??

thanks



plz hlep

 

[Venkadesh_M]

can u plz suggest a circuit??

and



how many values are required and after how much interval the values must be taken??

thanks



plz hlep

take your ripple's period (that is main frequency * 2) take 10 samples inside the period and average it....

 

[cheetha]

take your ripple's period (that is main frequency * 2) take 10 samples inside the period and average it....

the average value is ALSO varying.....

plz suggest a circuit that can filter noise and ripples efficiently and completely.........

 

[Venkadesh_M]

if you need very accurate and without ripples means put a transformer and a bridge rectifier that will be very stable and no ripples... and you wont need a opamp circuit...

 

[cheetha]

if you need very accurate and without ripples means put a transformer and a bridge rectifier that will be very stable and no ripples... and you wont need a opamp circuit...

i have placed bridge rectifier at ac mains and use voltage divider of 1M and 10k to drop the voltages at the output i have used voltage follwer opamp circuit. at the output of voltage follower i have placed 10k resistor in series and capacitor in parallel of 10uf. i have set the oscilloscope to ac input and placed the probe after the resistor at capacitor terminal there are ripples of 100mV p-p with no specific waveform....

plz help

 

[Venkadesh_M]

You are doing something wrong i think, post your circuit....

 

[cheetha]

You are doing something wrong i think, post your circuit....

here is attached image and file of sensing circuit



View attachment Draft3.rar

plz help its too urgent

 

[Venkadesh_M]

put a 220nf cap before 1 meg after rectifier (Caution high voltage capacitor). put a diode before the feedback (precision rectifier). connect a 22k parallel to 100uf...

 

[cheetha]

put a 220nf cap before 1 meg after rectifier (Caution high voltage capacitor). put a diode before the feedback (precision rectifier). connect a 22k parallel to 100uf...

it didnt worked as no any waveform was available after adding capacitor....
it worked in simulation but not in real hardware...

 

[Venkadesh_M]

it didnt worked as no any waveform was available after adding capacitor....
it worked in simulation but not in real hardware...

Then you did some thing different from simulation....

 

[cheetha]

Then you did some thing different from simulation....

no nothing different......
really i became sick of this
i also tried to measure ac by dropping it by voltage divider then i increased its level to 2.5V ..... in this case i am able to take samples after 0.444 ms (in proteus) and for 50 hz wave the time for one cycle would be 20ms and no of samples would be 45....
so i take each adc value divide it by 100 and added to previous values (in first cycle initial value is kept zero) i added upto 100 values for the average ....and displayed the measured value on 7 segment ....
still the values are unstable...........................
can any one can suggest code or algorithm that can solve my problem
thankssss

 

[Venkadesh_M]

no one can help you without your project file....

 

[cheetha]

no one can help you without your project file....

project file???

 

[Venkadesh_M]

proteus file with program