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Re: Xylophone Magnetometer



This rather old (4yrs+) archival URL has a thumbnail on the X magnetometer
from that vantage point. The sense/drive oscillates at the resonant frequency:
the magnetic disturbances it was intended to detect were apparently
associated with onboard transients. etc.

Brian W

<http://www.earth.nasa.gov/nra/archive/nra98oes12/apendixg.htm>

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* MEMS-BASED XYLOPHONE MAGNETOMETER

MEMS-based xylophone magnetometer uses an alternating current to drive a micro-machined bar at its resonant frequency. The magnitude of the bars deflection is based on the Lorentz force produced by the current and magnetic field, which is detected optically. This device can measure local magnetic field gradients as well as spacecraft magnetic interference. This MEMS magnetometer has a linear response. By altering the drive current, the sensitivity can range from nT to T. Its dynamic range far exceeds the fluxgate magnetometer, is much smaller, and uses much less power. Piezoresistive, magnetorestrictive magnetometers, and tunnel-based magnetometers have mT to µT sensitivities. The mass of the device is 10 g, it consumes 200 mW and requires < 1 cm3.

For EO3, it is proposed to mount the magnetometer on the periphery of the spacecraft where it can sense magnetic fields in the 1 to 25 nT range. This will allow the demonstration of the sensitivity of the magnetometer to both the space environment and to the magnetic fields produced by the spacecraft itself. The readiness has been demonstrated by the successful operation of a breadboard and will be demonstrated by a brassboard version to be flown on APEX sounding rocket in Jan 1999. The MEMS version with optical sensing will be ready by late 2000.
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At 09:40 AM 8/1/2003 -0700, you wrote:
On Thursday, Jul 31, 2003, at 22:35 US/Pacific, Brian Whatcott wrote:

> I notice an unfamiliar form of magnetometer is
> coming from the nanomachine shops: the xylophone magnetometer.
> A current through a mechanically resonant bar results in a
> deflection due the Lorentz force in the presence of a magnetic field.
> The mechanical Q of the device provides a useful sensitivity
> enhancement. Thought to have uses in sensing stray fields at close
> quarters, say in noise reduction measures for outboard
> magnetometers aboard spacecraft.
>
> Brian Whatcott Altus OK Eureka!

Interesting; I never heard about this. My guess
is that the instrument is for measuring amplitudes
of sinusoidally changing fields. Is this correct?
Ludwik Kowalski


Brian Whatcott Altus OK Eureka!