Bias voltage correction of HMC1022 AMR sensor

The design of magnetic electronic compass is introduced. Using Honeywell Anisotropic Magneto Resistance (ARM) sensor HMC1022, novel magnetic electronic compass has been developed. Despite rigorous testing has been done after produced, small resistance error still exists in, which result in bias voltage. Bias voltage amplified has a great influence on the measurement of geomagnetic field (weak magnetic signal). Using parallel resistance to correct bias voltage of HMC1022, the detailed steps of parallel resistance derived from experimental data are described. Complete compensation for residual bias voltage caused by selection limitation on resistor is achieved by using microprocessor digital subtraction. The applicability of parallel resistance calculation methods was demonstrated. The experiment shows that error can be limited to between -0.2 and +0.2. So the magnetic electronic compass can reach to the high accuracy.