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precision rectifier for such high voltages ?? I doubt whether that is adviced.
basic resitor dividers should do your job.. if its processed with a mico,then probably you can calibrate in the s/w,
garg29,
Whether the 2nd method is practical depends on the required accuracy. At 50V, the error due to a 0.7V diode drop would be approximately [.7/(50 X 1.414)] X 100 = 1%. At 500V it would be 0.1%. I'm assuming that the filter will charge up to the peak value of the input, and that the input is sinusoidal.
Regards,
Kral
Aside from the accuracy issues, remember that 500V is hazardous. It will be subject to many safety regulations. If you cannot use a transformer at the input, you will have to protect the user (and yourself as well as your equipment) somehow.
You will also find that there may be PCB leakage effects at high voltages that will add to your inaccuracies. Add guard bands around the high voltage areas to minimize this. (I am assuming that you will be making a PCB.)
Thanks Kral & antedeluvian for replying. My signal will be sinusoidal but in practical conditions there would be offcourse lot of noise. Will that make a problem? (I'm weak in analog electronics!)
This is really a very loaded question. It depends on the source of the noise and its frequency and amplitude amongst other things. If the noise is at the source, then it would be reduced in the same ratio as the orginal signal, remaining at the same percentage of the signal.
Your first course should be to to try and reduce the noise at the source. Techniques include shielding and decoupling capacitors if that is possible.
Assuming that you are using a resistive divider and that the frequency of the noise is signicantly higher than your signal frequency it is simple and cheap enough to add a capacitor across the second resistor to ground. This will create an RC network (with the larger resistor) and you should choose the cutoff frequency to be above the frequency of your source signal.
If you use a "precision rectifier" there is quite likely some filtering already in the circuit and you can add filter circuits with the remaining op-amps.
You should also apply filtering to the A/D signal in software. Keep in mind that you may also need an anti aliasing filter depending on the source frequency and the sampling rate.
My personal preference would still be to use an input transformer.
Hi Garg ,,,
Surely there is a need for u to provide a precision Rectifier . Because .. Any high voltage could be brought into the lower level with the normal Voltage Divider. But the Voltage divider Output cannot be measured as it is .. and it need to n\be rectified inorder to give it to an ADC .
In rectification process , the Output Voltage you could measure is the Peak Voltage . If the Voltage input provided to u is a Chopped or controlled AC , Then the Change in Voltage could not be identified by your hardware.
I don't think rectification is needed. Think of the A class amplifier. Bias ADC at a quiescent level and apply the divided voltage via a decoupling condenser.
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