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Thanks]]> Thu, 28 Aug 2008 11:32:12 -0700 http://www.8051projects.net/forum-t12150.html http://www.8051projects.net/forum-t12150.html there are two methods to measure the AC voltage:
1. the first method is the simple method of rectifying the AC volatge and converting it to a equivalent DC voltage. this method is simple but has the limitation that it would sense the peak voltage of the AC signal. So once calibrated the voltmeter would be accurate as long as the AC signal retains its waveform. But the problem would arise if the waveform is clipped/clamped or distorted e.g. if u are measuring the output from a triac controlled output.
2. the second method is to directly sense the ac voltage levels at specific sampling intervals (faster than the line frequency) and calculate the true RMS (root mean square) value of the AC voltage.
this requires quite a bit of processing /coding.

note that in both the cases u require to first scale the AC voltage down to the level
acceptable by ur ADC.
first decide on which method u plan to use and then design the circuit accordingly.
If u go for the first method , use a precision full wave recitfier to convert the scaled voltage to DC.
For the second method u may get some idea on interfacing AC power line from the datasheet of
CS5460A which is an energy meter IC used for measuring line voltages and current.
good luck.:)
]]> contact@nospam.com (Ajay Bhargav) Thu, 28 Aug 2008 20:28:47 -0700 http://www.8051projects.net/forum-t12150.html