A Microcontroller-Based Compact Device for Measuring Weak Magnetic Fields

Measurement of the weak magnetic field has frequent applications in magnetic compass, flexible electronics, position sensing, and human–computer interaction (HCI). Some available devices can measure these magnetic fields but also have limitations such as expensive cost, complex hardware, large size, low range, and less accuracy. This research has developed a low-cost, compact microcontroller-based magnetic field meter for measuring weak magnetic fields. The device incorporates an anisotropic magnetoresistive (AMR) sensing module, a microcontroller, and an organic light-emitting diode (OLED) display. The change in resistance due to variation in the magnetic field is detected using an AMR sensor and is translated into digital data with the help of a suitable signal conditioning unit and analog-to-digital converter (ADC), all included in the HMC5883L module. The data received by the microcontroller is displayed on the OLED display. The developed device was calibrated using a Helmholtz coil, and its comparison was made with two different magnetometers for measuring weak magnetic fields. The device displayed an accuracy of less than ±1.5% and a resolution of
$0.073 ~\mu \text{T}$
for a measurement range of
$\pm 800 ~\mu \text{T}$
. The parameters like sensitivity, linearity, repeatability, and hysteresis for the developed device were also determined to identify its performance. The designed compact device can become a cost-effective means for accurately measuring weak magnetic fields in industrial and laboratory applications.