Design, Development, Fabrication and Testing of Meso-Scale Accelerometers Using Capacitive and Hall Effect Sensing

Abstract

We designed, developed, fabricated, and tested two models using different transduction techniques, materials, and fabrication methods. A single-axis, single-mass spring-steel accelerometer using Wire-Cut EDM for DACM and Hall-Effect for transduction. Dual-axis Dual-mass accelerometer made with thermoplastic polyurethane (TPU) and capacitive sensing. 3-D printed model uses TPU and capacitive sensing, while wire-cut model uses Spring-Steel and Hall-Effect. A micro machined accelerometer's precision and high resonance frequency are tradeoffs. We overcome the Hall Effect sensor's low sensitivity by attaching a displacement-amplifying compliant mechanism (DaCM) to the accelerometer's proof-mass to increase displacement and sensitivity without affecting its natural frequency. Hall Effect sensor measures DaCM output displacement. The accelerator's voltage change is calibrated. The 3D-printed casing protects the accelerators. To prove the benefits of DaCM, we modified two designs and incorporated DaCM within the same footprint, increasing displacement by 60% and resonance frequency. 3-D Printing has been reported a lot in Meso-Scale sensor journals. This trend has been rising since the pandemic, due to the shortage of Silicon-based micro sensors and the sophisticated fabrication of MEMS-based sensors. TPU's low stiffness and moderate density made it a good choice for our sensor's springs and mass. The model has a dynamic range of 0g-2g and a resolution comparable to MEMS accelerometers in the same range. This model uses capacitive sensing because of its superior resolution and sensitivity. The 3-D-printed model is attached to the evaluation board.