phase meter

1 36 5V N1i...N4=IC1=74S00 phase meter This circuit can be used for accurate phase measurements up to 1 MHz. If all due care is taken during construc- tion, an accuracy of within 0.1° can be achieved for frequencies up to 100 kHz. Not bad! The two input signals, A and B, are fed to an RS flipflop consisting of NAND gates N1 . N4. As illus- trated in figure 2, this flipflop produces output pulses with a width that is directly proportional to the phase difference between the two input signals. Or, to be more precise, for any frequency the mark-space ratio (duty-cycle) is proportional to phase angle. Al, T1 and associated components are a current source; diodes D1 and D2 ensure that this current only flows to the integrator (A2) when the output from the RS flipflop is "high". This means that the integrator output will reflect the average value of the flipflop — its duty-cycle. The output from the integrator is smoothed (and inverted) by A3. The phase difference between the two inp...