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This application note describes a simple method for
measuring parameters from the AC power line.
Parameters such as zero crossing, frequency, and
relative phase can be measured. This method is useful
for measurements on 50, 60, and 400 Hz power
systems with voltages up to several hundred volts. The
method requires only one external component, a
resistor, and is more reliable than previously published
methods using capacitors or bulky, expensive
transformers.
AN521
Interfacing to AC Power Lines
FIGURE 1: PIC16C5X SERIES INPUT
Author: Doug Cox PROTECTION CIRCUIT ON I/O
Microchip Technology Inc.
PINS
VDD
INTRODUCTION
This application note describes a simple method for P
measuring parameters from the AC power line.
Parameters such as zero crossing, frequency, and

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