I want to mount a gyro sensor on a Wheel to determine the angular Speed of it. (More specific, for clinical trials we want to measure the speed of wheelchairs and wheeled walkers by fixing a sensor to the wheels).
Does the gyroscope sensor need to be mounted in the center of the wheel or can it also be mounted off-center?
Will there be noise or any other Forces affecting the measured data if it is not fixated to the middle (axis) of the turning object?
To obtain the most accurate measurement, the gyroscope sensor should be mounted as close as possible to the centre of the wheel, which is the axis of rotation. Mounting the sensor at the axis of rotation will eliminate any noise or forces due to the wheel’s rotation, and the measurement will only reflect the angular speed of the wheel.
To determine the angular speed of a wheel, use shaft encoder or magnetic sensor with rotation counter, like used on bicycles.
Gyros drift, are noisy, need to be calibrated, and must be connected to an MCU by wires, so they seem to be a very poor choice for your application.