What is a cadence sensor on an electric bike?

A cadence sensor on an electric bike is a device that measures the speed at which the rider is pedaling. It is typically mounted on the crank arm or the bicycle frame. The sensor detects each rotation of the pedals and sends a signal to the bike's motor to provide the appropriate level of assistance based on the rider's cadence. This allows for a smoother and more efficient pedal-assist experience. Some electric bikes also use cadence sensors to adjust the power output based on the selected pedal assist level, giving riders control over the level of assistance they want while riding.