Sensing in a Jerky World

Ehsan Vatankhah – e.vatankhah@utexas.edu

The University of Texas at Austin, Austin, TX, 78712, United States

Popular version of 1pSA8 – Magnetostrictive-based Jerk Sensor: experimental characterization and analytical estimation of sensitivity
Presented at the 188th ASA Meeting
Read the abstract at https://eppro01.ativ.me/appinfo.php?page=IntHtml&project=ASAICA25&id=3864493&server=eppro01.ativ.me

–The research described in this Acoustics Lay Language Paper may not have yet been peer reviewed–

Researchers at the University of Texas at Austin have developed and tested a new type of accelerometer-a device that measures motion-using a special material called Terfenol-D. This work explores how magnetostrictive materials, which change their magnetic properties when stressed, can be used to sense movement in a simple and reliable way.

How the Sensor Works
The sensor uses a rod of Terfenol-D, a material known for its strong magnetostrictive effect. When the rod is subjected to acceleration (movement), it experiences stress that changes its magnetic state. This change generates a small voltage in a coil wrapped around the rod, which can be measured as an electrical signal. The design uses permanent magnets to provide a steady magnetic field, ensuring the sensor responds in a predictable, linear way.

Key Features and Findings

• Sensitive to Jerk: Unlike most motion sensors that respond to acceleration or velocity, this sensor naturally responds to “jerk,” which is the rate of change of acceleration. This means its sensitivity increases with frequency up to its first resonance, making its performance in terms of signal to noise ratio to excel as frequency increases.
• Low Output Impedance: The sensor produces signals that can be easily transmitted over long cables without losing strength, unlike some traditional accelerometers that require extra electronics to preserve signal strength.
• No External Power Needed: The sensor generates its own signal from motion, so it does not require an active power supply for operation, making it suitable for remote or hard-to-reach locations. The design avoids complex parts, which could make it easier and less expensive to manufacture.

Testing and Performance
The team tested the sensor using two methods: vibrating it with a piezoelectric device and striking a plate with a specialized hammer. In both cases, the sensor’s output matched well with predictions from computer models and theoretical calculations. The sensor demonstrated a low noise floor (the smallest signal it can reliably detect), comparing favorably with commercial accelerometers.

Measurement setup using automatic modal hammer for vibrating the sensor.

Potential Applications

• Seismic and Underwater Sensing: The sensor’s design is promising for applications such as seismic monitoring or underwater acoustic sensing, where devices may need to operate for long periods without maintenance or external power.
• Large-Scale Sensor Networks: Its simplicity and self-powered operation make it a good candidate for use in networks of sensors spread over wide areas, such as for environmental monitoring.

Next Steps
The researchers plan to further develop this technology for underwater use, where measuring motion accurately is essential for applications like underwater navigation or monitoring ocean conditions.

Funding
This research was supported by the Office of Naval Research.

Contact
For more information, contact Ehsan Vatankhah at the Chandra Family Department of Electrical and Computer Engineering, University of Texas at Austin.