In double-feeding detection, high levels of noise are generated, reducing the S/N ratio. How can this noise be reduced?
Wrap copper film 0.2-0.3mm in thickness around the sensor and connect the film to the GND of the circuit.
Alternatively, increase the peak-to-peak voltage of the drive signal within the tolerable range to raise transmission sound pressure.
Increasing the number of drive waves may destabilize oscillation and disturb sound waves, resulting in lower sensitivity. Avoid driving the sensor with 6 or more pulses.