The Prevalence of Traditional Geophones in Geotechnical Monitoring
Solenoid geophones have been the industry’s default technology for construction vibration monitoring for decades, without significant consideration or innovation in alternative solutions. At frequencies within ISEE standards of 2Hz – 250Hz, solenoid geophones can give acceptable results. But below that? Studies have found that errors in PPV values for 10Hz geophones can range from -40% to +30%. Why is this important? Because the natural frequencies of many large structures — like buildings and bridges — as well as certain soil profiles, often fall within the lower frequency range. Low frequency is the range where the largest risk for structural damage occurs.
Unlike geophones, MEMS accelerometers not only reliably perform better than solenoid geophones at frequencies below 2Hz – they perform better above 125Hz as well.
These charts, generated from testing conducted by an independent, third-party lab, compare the MEMS technology used by the Inzwa Veva III vibration monitor to a solenoid geophone-based vibration monitor against the ISEE standard. The geophone-based device performed as the manufacturer advertised and as any field practitioner would expect, and was consistent with the manufacturer’s calibration report. While both sensing technologies proved up to standard within the middle range of frequencies, there remains a glaring difference in at the lower and upper ranges, where MEMS technology proves its superior performance.
At 1.5Hz, the geophone-based sensor had approximately 2dB lower response than the 40g MEMS sensor. At 1Hz, that performance gap grew to approximately 8dB – 60% lower than the MEMS sensor.
At frequency levels above 125 Hz, differences as high as 24% were recorded between the different technologies, with the MEMS sensor producing more accurate readings. Also note that beyond the ISEE’s upper limit of 250Hz, the MEMS technology continued to perform better than the geophone-based sensor.
The Future of MEMS Technology
MEMS-based accelerometers not only perform well within the ISEE standard, they provide SUPERIOR performance for vibration monitoring at frequencies below 2Hz and above 125Hz. MEMS technology for construction vibration monitoring is here to stay.
MEMS technology is redefining modern technology. It’s leading to improved performance and innovative applications across diverse industries including:
- Automotive: MEMS devices are found in airbag deployment systems, tire pressure monitoring, electronic stability control, and inertial navigation systems.
- Biomedical: MEMS enables advancements in drug delivery systems, lab-on-a-chip devices, implantable sensors, and microfluidic devices.
- Consumer Electronics: MEMS accelerometers and gyroscopes are used in smartphones, microphones, and MEMS-based pico-projectors.
- Aerospace and Defense: MEMS devices contribute to navigation systems, unmanned aerial vehicles (UAVs), and satellite systems.
Learn More about MEMS Technology
See Vibration Monitoring Research: MEMS Accelerometers in Blast-Induced Shock and Vibration Monitoring, presented at the 2023 ISEE National Conference.
See Whitepaper: The Use of MEMS Accelerometers in Construction Vibration Monitoring, by Gerald Verbeek, MsC.
