Economic MEMS based 3-axis water proof accelerometer for dynamic geo-engineering applications

Accelerometers are one of the most used sensors for monitoring dynamically sensitive systems either in field or in laboratory scale experiments. One of the key requirements in dynamic geo-engineering application is that these sensors should be water proof or water insensitive. Traditional accelerometers used in practice are based on piezoelectric/piezoresistive technology and are generally water sensitive. They are also one-axis (can measure one dimensional acceleration), big in size and expensive (typical minimum price is 300 USD/axis). These accelerometers are adapted in dynamic geo-engineering applications dealing with saturated soils by sealing the junction of the cables and the accelerometer by appropriate sealants. In this paper, the development of an inexpensive (circa 10 USD/axis), light weight, three-axis (can measure three dimensional accelerations) Micro Electro Mechanical Systems (MEMS) based accelerometers and their application to geo-engineering problems is presented. The sensor is based on ADXL 335 chip and can be made water proof. Performance of 3-axis MEMS accelerometer is presented along with the methodology to make it water proof.