Measurement of the frequency of the grid voltage is done by first measuring the time between two successive foot of the mountain, as Figure 2. At the time of the grid voltage moves up above 2.5 V, a timer is run in normal mode. And when the value of grid voltage moves up on the 2.5 V anymore, timer 1 is stopped. Timer 1 run during Δt1.
Figure 2
Timer 1 is 16-bit timers. This timer is operated with prescaler = 8. Time for counting one digit is tT1 = 0.723 microsecond. The result of count is 16 bit hexadecimal value stored in a register TCNT1 that formed by pairing 8-bit registers TCNT1H and TCNT1L.
For 50 Hz input signal, the counting result is 6C00h. To avoid detection of the harmonic frequency, the frequency restricted from 35 Hz to 70 Hz. So that, the valid value of TCNT1 is from 9A49h until 4D24h. Maximum error of this counting is 0.004%.
The Need for Phase Difference Measuring Instrument
Measure the Frequency of Grid Voltage rather than Measure the Frequency of Current
Voltage and Current Converter
The Signal Conditioning
The use of the microcontroller ADC
Phase Difference Measurement
Output Display Format
For 50 Hz input signal, the counting result is 6C00h. To avoid detection of the harmonic frequency, the frequency restricted from 35 Hz to 70 Hz. So that, the valid value of TCNT1 is from 9A49h until 4D24h. Maximum error of this counting is 0.004%.
The Need for Phase Difference Measuring Instrument
Measure the Frequency of Grid Voltage rather than Measure the Frequency of Current
Voltage and Current Converter
The Signal Conditioning
The use of the microcontroller ADC
Phase Difference Measurement
Output Display Format
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