IEEE Transactions on Instrumentation and Measurement | 2021
Linearized Sigma–Delta-Based Direct Digital Converter for GMR Sensors
Abstract
A direct digital converter, based on the sigma–delta modulation principle, is proposed in this article for giant magnetoresistance (GMR) sensors. The proposed converter intelligently integrates the GMR sensors with an improved sigma–delta modulator and provides a linear digital indication of the input magnetic field. The digital output is obtained directly, without using any analog-to-digital converter modules. Some additional merits of the proposed interface are: 1) requirement of a single reference voltage; 2) easy-to-use facility to tune/enhance the overall sensitivity; 3) low conversion time etc. The modulator circuit is followed by a digital filter and decimation circuit, implemented in a microcontroller unit. This sigma–delta converter is validated extensively using simulation and emulation studies. The results from these studies corroborate well, and the maximum nonlinearity is found to be less than 0.12%. Finally, an experimental prototype is developed with a GMR sensor, and the functionality of the converter is tested for static and time-varying field inputs. The experimental nonlinearity of 0.69% shows the better performance of the proposed scheme with respect to other digital digitizer circuits present in the literature.