Signal processing electronic circuit diagram with zero adjustment and full scale function

　　Principle analysis:  The signal processing circuit with zero adjustment and full-scale adjustment functions is an AC voltage measuring head. IN+, IN-AC voltage terminals (no positive or negative); R1, R2, R3 are connected in series as current limiting resistors; TV is a voltage transformer, and VD1 is a voltage-stabilizing diode, which clamps the output voltage signal Vx to a safe range. Vx is led to the positive input terminal of the operational amplifier IC1A, and after being processed by IC1A, C2~C9, R6~R12, VD2, VD3, etc., the voltage is sent to IC1B, R18~R21 for shaping and output through RP2.

　　IC2, IC3, etc. constitute a reference voltage circuit.

　　Adjustment method: After the digital meter is connected to the working power supply, add 0V voltage (no electricity) to the IN+ and IN- terminals, adjust RP1 so that the digital meter head displays 000; then connect the 500V standard value, adjust RP2, and the digital meter head displays 500V to pass.

　　Tip: If three TVs are combined, they can form a three-phase voltage measuring head A, B, C. If TV is changed to TA (current transformer) and R1, R2, R3, R5 are removed and R4 is adjusted appropriately, it becomes a current measuring head. Three current measuring heads can form a digital three-phase electric meter.