TMM sensor unit
The TMM4 sensor is the newest development of IDbike, and can be used for measuring the crank torque if the cyclist. Because of the high precision this sensor can be applied in electric bicycles as well in power measurement systems.
At this time the production runs smoothly, sensors are on stock.
The TMM4 sensor consists of a plastic housing, which holds a printed circuit board (pcb) , a magnet, a ball and a bias spring.
The sensor is mounted on the drop out and measures the deflection of the drop out that is caused by the chain force.
The sensor is connected to the control unit with a 3 wired cable. The sensor can be hardwired or can be connected with a little connector.
The pcb houses the Hall sensor element, which is sensitive to the position of the magnet.
The stainless steel ball is inserted in the housing to guarantee an optimal contact between the drop out sensor plate and the plastic housing, the bias spring makes sure that the ball is pressed securely against the drop out.
The printed circuit is protected against moisture, salt and dust, by a special coating
Specification (optional between brackets)
| Supply voltage: |
5 (3 V) |
| Output voltage: | 1 V- 4 V ( 0.6V - 2.4V) |
| Measuring range sensor: |
0,3 mm |
| Max. allowable displacement plastic sensor housing: |
± 1 mm |
| Max. allowable displacement drop out plate: | 0.3 mm (depending on Al alloy) |
| Sensitivity TMM sensor: | approx 10 mV/μm ± 10% |
| Allowable range ZTV (zero torque value): | 2 V ( 0.6 V ) |
| Temperature influence: | < 1 mV/ ºC |
| Electrical disturbance: | < 10 mV |
| Effect of moisture: | < 10 mV |
| Operational temperature: | -10 - 40 ºC |
| Storage temperature: | -25 - 60 ºC |
| Life expectance: | 10 year |
Application example: Pedal force sensor in pedal assist electric bicycle
TMM sensor measures the chain force and thus also the pedal torque of the cyclist. The chain force causes a small deflection in the special drop out. This deflection of maximal 0.1 mm is sensed by al small hall element.
Application in frame drop out of bicycle
Next to measuring forces, the sensor eventually also can be used for measuring small displacements.
