Cadence or torque sensors tell an electric bike’s pedal-assist system (PAS) when to engage the motor and propel the e-bike forward. Although just about any combination of a cadence sensor, a torque sensor, or both will work, each sensor type can have an impact on an electric bike’s performance and ride. So what is the difference between a cadence sensor and a torque sensor on an electric bike? A common response in the bicycle manufacturing industry is that a cadence sensor determines if you are pedaling while a torque sensor measures how hard you are pedaling.‹ Go back to the blog
Pedal Assist Cadence SensorFor many cadence-based pedal assist systems, the electric bike’s motor is engaged when the rider begins to pedal forward. As an example, the EVELO Delta X has five available levels of pedal assist or PAS. At each of these levels, the motor will provide a prescribed amount of power in response to a signal from the cadence sensor. As the rider’s pedaling speed (cadence) increases the PAS will reduce the motor’s output. Put another way, the motor produces a set amount of power when the pedal revolutions are relatively slow — for example when the rider is first starting out — as the pedal cadence and momentum increase, the motor’s power is reduced from 100 percent of the given PAS-level output target to about 70 percent of that target. Here is a specific example, the Delta X electric bike will produce 1000 watts of peak power in PAS level five. It will output 1000 watts until the pedal cadence reaches a pre-defined threshold. At this point, the rider has built up momentum, and the motor reduces output to 700 watts. Later, if the rider downshifts to a high-speed, flat-ground gear and pedal cadence falls below the threshold, the motor will again produce 1000 watts of peak power (at PAS 5) to drive the Delta X forward.
A cadence sensor situated at the crank on an electric bike.One of the benefits of using a cadence sensor is the relatively light pressure needed to employ it. In fact, recreational riders or riders with tender knees may find a cadence-based PAS relatively more comfortable to ride. A cadence sensor does, however, require the rider to move the pedals at least a little before initially engaging the motor. For this reason, cadence-based pedal assist systems are coupled with a throttle in many cases. The rider can press the throttle to get the electric bike moving and then start pedaling to engage the PAS.