a cadence sensor measures the speed at which the pedals are turning. It provides feedback to the electric motor, allowing it to adjust the level of assistance provided based on the rider's pedaling speed. Cadence sensors are generally less expensive than torque sensors, but they can provide a less natural riding experience. With cadence sensors, the motor output is based solely on the rider's pedaling speed, so the rider may experience a lag in assistance when starting from a standstill or when riding uphill.