Capacitive MEMS accelerometer for condition monitoring
1. Introduction
Predictive maintenance (PdM) is a key component of the smart industry that involves monitoring equipment during operation to detect early warning signs of potential failures. PdM is largely based on condition monitoring (CM) through the analysis of vibration, which is the most common method to detect imbalance, misalignment, and other anomalies in machinery. Traditional vibration sensing instruments are based on piezoelectric technology, but capacitive MEMS technology is gaining popularity in this field for various reasons involving flexibility and cost, and the fact that MEMS sensors are closing the gap to piezoelectric sensors in terms of bandwidth and dynamic range. This paper describes the signal processing technique used during standard equipment operation to extract many of the parameters used for diagnosis and PdM, directly from an accelerometer integrated into a smart node. We also include a comparison between a triaxial digital ST capacitive MEMS sensor accelerometer (IIS2DH) and a conventional triaxial piezoelectric accelerometer.
2. Why use MEMS sensors instead of piezoelectric sensors?
Traditional vibration sensing instruments are based on piezoelectric technology, but capacitive MEMS technology is gaining popularity in this field for various reasons:
- fast recovery after high shock,
- frequency response includes DC and is stable over time,
- good stability over time and across temperatures,
- digital output: easy wiring and no need for external ADC or other signal conditioning circuits,
- integrated self-test,
- embedded functionality,
- low power, small size, low weight,
- cost-effective.