Sensor Technologies: Cadence vs Torque sensors
Most road-legal e-bikes rely on sensors to determine when motor power is needed to assist your cycling.
There are two main types of e-bike sensor:
cadence sensors, which measure the rate of pedalling
torque sensors, which measure how hard you are pedalling.
As mentioned in our previous blog post on e-bike motor power, the type of sensors fitted to an e-bike is often overlooked in lieu of other 'more exciting' specifications like wattage or battery size.
However, the type of sensor fitted on an e-bike can have a huge effect on the riding experience.
Great for cheap e-bikes
Easy to fit and replace
Can feel jerky
Measures your pedalling effort for smoother power delivery
Extend battery range
More expensive investment
What do cadence sensors do?
The most widely available sensors for e-bikes are those which measure cadence, using data from the crankset to indicate when and how fast the pedals are moving. Many cheap e-bike conversion kits, especially those you fit yourself, use cadence sensors.
On a cadence-sensor e-bike, the motor will apply a specific amount of power depending on your pedalling speed, and depending on your selected pedal assist level (if your e-bike 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. This sometimes makes it feel a bit jerky or unexpected. 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. This often happens at traffic lights or if you need to suddenly move your pedal, and can throw cyclists temporarily off balance.
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.
Cadence sensor fitted-e-bikes 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.
For cyclists in hilly or varied terrain, torque sensors will provide a smoother ride and keep your battery lasting longer. They are usually a better long-term investment, as they keep you going for longer and you are not limited by the capabilities of cadence sensors.
With more sophisticated sensors coming with a higher price tag, it is something to consider when choosing e-bikes.
It is rare to find e-bikes with both 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 for your cycling.
We'd recommend you try out any e-bike before purchasing. Book a free test ride either in London or Cambridge where you can try out our range of bikes and explore the sensor technology and pedal assist on the beautiful country lanes and hills nearby.