Low-cost vibration sensor for condition-based monitoring manufactured from polyurethane foam

Ubiquitous vibration sensing forms a core requirement of Internet of Things (IoT) applications in condition-based monitoring (CbM). Such sensors can enable cost savings by identifying incipient failures in industrial machinery and, thereby, optimized maintenance schedule planning. Conventional piezoelectric and microelectromechanical systems (MEMS)-based vibration sensors developed for such applications cost upwards of tens and hundreds of dollars, limiting the scale of their deployment. In this article, we present an extremely inexpensive vibration sensor prepared with commercially available polyurethane foam that is commonly used for packaging of fragile goods. We present a process to coat the pores of the foam with conductive carbon ink to impart piezo-resistive properties to the material. A proof of concept realization of vibration sensor with 80-Hz sensing bandwidth is presented, along with experimental data demonstrating classification of vibration signals for different machine operating conditions. The spectral content of the measured vibration signal shows good agreement with spectral content of the audio recordings of corresponding acoustic measurements.