Electric cooker control unit has control panel with ultrasonic pulses and receiver detecting characteristic frequency vibration modification by presence of finger

摘要

An electric cooker control unit (11) has a removable conducting opaque control panel (15) with piezoelectric ultrasonic transmitter (20) and receivers (22) with pulses close to the characteristic frequency of the surface and a processor (24) comparing radiated and reflected signals detecting change due to the effect on surface vibration of a finger (17).