Abstract: A system is provided for dynamically detecting and providing an electronic output representative of changes in the position of a fuel injection element in an internal combustion engine. The system includes an electronic circuit having a sensor for sensing a change in a magnetic field external to the circuit, and providing an output representative of the change. Circuit elements are electronically coupled with the output of the sensor for providing an output indicating the presence of the magnetic field change. A nulling circuit is provided for nulling the electronic circuit responsive to the sensor output, to thereby compensate for ambient magnetic fields, temperature and process variations. Exceptionally low current circuit characteristics are achieved in an integrated circuit configuration and geometry having very low junction leakage characteristics.