eBike Sensor Technology: the difference between Cadence and Torque sensors
What sensors do eBikes use?
Lots of eBikes rely on sensors to determine when motor power is needed to assist your cycling.
There are two main types of eBike sensor - cadence sensors, which measure the rate of pedalling, and torque sensors, which measure how hard you are pedalling.
As mentioned in our blog post last week on motor power, the type of sensors fitted to an eBike is often overlooked in lieu of other 'more exciting' specifications like wattage or battery size. However, the type of sensor fitted on an eBike can have a drastic effect on the riding experience.
Cadence Sensors - What are they? What do they do?
The most widely available sensors for eBikes are those which measure cadence, using data from the crankset to indicate when and how fast the pedals are moving.
On a cadence-sensor eBike, the motor will apply a specific amount of power depending on your pedalling speed, and depending on your selected pedal assist level (if your eBike is fitted with a control).
Cheap, easy to fit and replace, the problem with cadence sensors is that their responsive power delivery is not always reliable, kicking in at times it is not really needed. For example, when riding downhill, the motor will apply unnecessary power if you are pedalling slowly.
In other instances, only a little bit of pedal movement can give a big surge of motor power when a high assist level is selected, so cadence sensors tend to feel a bit jerker. Additionally, if you have a low assist level selected when tackling a steep climb, you'll likely have to turn up the assist level manually, as a cadence sensor is not fully responsive to your increased efforts.
That said, cadence sensor fitted-eBikes are less expensive, and you can pick up a good one for under £1,000.
The Benefits of Torque Sensors
The other type of sensor, which measures torque, determines the force of rotation applied to the crank set.
Torque sensors give a better indicator of user effort than cadence sensors and so can vary the motor's responsive power delivery more dynamically. For example, in the hill climb situation, the user would not need to turn up the assist level as the torque sensor would sense you were pedalling harder and tell the motor to accordingly apply more power.
This intuitive response creates the sensation that you are riding a normal bike, so if you enjoy the feeling of cycling, it is likely you will prefer the more natural input provided by a torque sensor. Torque sensors also tend to extend battery range, as they only deliver as much power as needed - whereas cadence systems will often expend battery needlessly.
With more sophisticated sensors coming with a higher price tag, it is something to consider when choosing eBikes. Indeed, it is quite rare to have an eBike with a torque sensor and a hub-drive motor, but ARCC Bikes has achieved this with the ARCC Intelligent Drive Pod, which provides a smooth and progressive power delivery.