Validation and testing of a MEMS piezoelectric permanent magnet current sensor with vibration canceling

• Current sensing with piezoelectric MEMS devices.
• Non-contact, non-invasive cantilever transducer.
• Cantilever beams with Niobium micro-magnets.
• Double cantilever system to cancel out other ambient vibrations.
• Results and measurements.

The work presented here documents the characterization and testing of a novel, proximity-based AC current sensor. By using a pair of cross-coupled MEMS piezoelectric cantilevers that have oppositely-oriented magnets on their free ends, a sensor has been created that needs no external power source and that measures AC current without the need for galvanic contact with, or fully encircling of, the current-carrying conductor. The resulting device is 11.2 mm long and has an output sensitivity of 5.8 mV/G at 6.8 mm from the center of the conductor. The sensor device has been characterized at frequencies of 60–200 Hz. Common-mode rejection ratio calculations demonstrate the effectiveness of the cancellation technique at frequencies other than those corresponding to the first resonant mode of the device.