Bosch Torque Sensor - Hows does it work ?

[JimmyBoy]

Just curious, having just serviced my Bosch Performance Line motor, does anybody know how the torque sensor work's (not what it does).
Are they strain gauges or piezo sensors.
The sensor has no moving parts and the transfer gear seems to press against a shaft with varying pressure dependant upon the pedal effort.

 

[Mikerb]

Most modern torque sensor system use a combination of a central rotating shaft held within a tight fitting outer ring that is magnetic. The rotating shaft causes a change in the magnetic field proportionate to the force applied to the shaft. The change in the magnetic field is measured by a FMG on the PCB which in turn regulates the electrical current applied...ie pedal assist.

 

[JimmyBoy]

This is what the torque sensor look like. There are no rotating parts.