Use only the phase meter of three chips ----- Phasemeter

Keywords: a circuit diagram of the phase meter, the phase meter circuit Only three phase meter a chip simple and efficient low frequency phase meter circuitry, the IC requires only three, absolute precision and resolution better than 0. 5 ° to the full 360 °. This is three chips: a CMOS D flip-flop, a CMOS Schmitt inverters and a bipolar comparator quadrilateral (see FIG.). And a comparator U1B, U1D portions constituting respective input zero-crossing detector. For protection purposes, the four diodes comparator inverting input terminal to ground potential clamped to ± 1 forward voltage drop of the diode within. 74HC14 Schmitt inverter U2A and U2B part, act as a buffer. Load resistors R3 and R4 connected to the input of the buffer, and the driving of the dual flip-flop U3A U3B. U3A as a configuration set-reset flip-flop, the set input of U2A rising from the buffer (from the edge of the input "A"), and a reset input from the flip-flop U3B. U2D, U2F and U3B constitute a single narrow pulse flipflop U3A is reset by the rising edge of U2B from the buffer (from the edge of the input of "B"). U2C buffered output of U3A. R5-7 and capacitor C1 form a voltage divider and a low pass filter integrator, and that the scale of the filtered output U2C. U2C output is a positive pulse, is proportional to the difference between the pulse width and the two negative input of the circuit zero-cross point, so that the average voltage across C1 is proportional to the phase difference between the two input terminals. Comparator U1C and 2N2222 transistor (Q1) section constitute a unity gain amplifier, the voltage of C1 and the buffer supplied with a low output impedance. C2 helps U1C linear region, Rq then establish a control pole. A calibration circuit, and a first portion of the opening turned off, and a second portion closed, supplying a low frequency 50-1000Hz 1Vp-p square wave, simultaneously applied to two input terminals. A digital voltmeter indirectly monitor the output of the output lead and ground. R7 is then adjusted so that the voltage reading is 1.800V. After the adjustment, the switch circuit returns to normal. Scale digital voltmeter, this time has been calibrated to indicate the phase difference between the two inputs of this circuit, the scaling factor of 0.01%. Measurement accuracy, 50 - 1000 Hz, is better than 0.2 ° when a square wave 1Vp-p; at 3Vrms (rms) sinewave, which accuracy better than 0.5 °.

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