Magneto-Electric Rotation Detector

Change in duty ratio (speed-dependent)
When a magnetic material moves through a magnetic field, eddy currents are generated on its surface, and these eddy currents produce a magnetic field (green arrow). This magnetic field interferes with the magnetic field generated by the magnetoresistive sensor, resulting in a change in midpoint voltage.

The direction of the eddy currents changes depending on the direction of the moving magnetic material.
Additionally, since the eddy currents increase in proportion to the speed, as the rotational speed increases, the change in midpoint voltage also becomes larger.

Change in duty ratio (temperature dependence)
Magnetoresistive elements have temperature dependence. Since the MP-9810/MP-9830 uses two magnetoresistive elements, the midpoint voltage changes due to slight differences in temperature characteristics between the elements.

The change in midpoint voltage of the output
The signal amplitude obtained from the magnetic resistance sensor is small, on the order of several tens of mV, so after amplification, it is shaped into a waveform to become the final signal. Since the change in midpoint voltage is also amplified, if the midpoint voltage changes due to temperature variations or an increase in rotational speed, it may result in changes in the duty cycle of the final output signal or the disappearance of the square wave output.