Transitioning Nodal Array Approach Readout Circuits from Simulation to Hardware: An Experimental Study

This study explores the transition of the Nodal Array Approach (NAA) readout circuit from simulation to hardware implementation, where its accuracy and practicality for pressure sensor applications are assessed. The Nodal Array Approach (NAA) circuit was tested using known resistors (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{5 1 0} k \Omega$</tex> to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$16 \mathrm{M} \Omega$</tex>) in place of FlexiForce sensors to simulate varying pressure conditions. Voltage measurements were conducted across three switch configurations using analog switches, and data were collected via the Nucleo F401RE microcontroller and CoolTerm software. The NAA algorithm then calculated resistance values through nodal analysis, and the results were compared with actual values to evaluate accuracy and error performance. Experimental results indicate that high accuracy is achieved by the NAA system for resistance values between 510 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{k} \Omega$</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1 \mathrm{M} \Omega$</tex>, with errors consistently remaining below 1.5%. In typical resistance vs. force behavior for force sensors, higher resistance corresponds to lighter applied force or no force at all, meaning minimal or no pressure is applied to the sensor. However, for higher resistances (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{8. 2 ~ M} \boldsymbol{\Omega}$</tex> to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{1 6 ~ M} \boldsymbol{\Omega}$</tex>), significant deviations are observed, with errors exceeding 16% in some configurations. Based on this experiment, it can be concluded that greater accuracy is achieved when all sensors are in contact, compared to cases where only some sensors are activated. When certain sensors are not in contact, higher percentage errors are experienced by the system, compromising data integrity. Therefore, this method is more suitable for an application with all sensors consistently engaged, rather than others application, where sensor engagement varies due to uneven pressure distribution.