Piezoelectric sensors use a piezo element (usually a disk like the ones found in musical pickups) mounted on the printer in such a way that the mechanical force of touching the bed with the nozzle causes the disk to flex, which generates a signal. That signal gets filtered and conditioned and is sent to the Printer’s controller as if it was any other endstop.
This style of sensor usually has one drawback, however, which is that it’s electrical filtering circuit needs to be calibrated to a specific state that changes depending on the printer it’s installed on. Conditions like temperature, or differing input voltage can cause a piezo sensor’s calibration to get skewed.
The Pyr0-Piezo, on the other hand, can account for these variances. It has an onboard microcontroller (a tiny CPU) that constantly monitors the circuit and makes on-the-fly adjustments to ensure the filtration circuit remains stable and ready to probe at all times. Hence, the calibration of this sensor, while still necessary, is completely automated.