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A Non-MEMS Magnetometer

We’ve spent a lot of time talking about MEMS in these pages, but not all sensors are MEMS. At Semicon West, I got to talk to Becky Oh of PNI Sensors. They make geomagnetic sensors with noise characteristics around 30 times better than Hall-effect sensors, as she tells it. But they’re not MEMS sensors.

They use a material whose permeability changes with the magnetic field. They wrap this material in a coil and then put the resulting variable inductor in an RLC tank and use the oscillation frequency as an indicator of the magnetic field.

Of course, like all sensors, they need software. They include low-level code that corrects for local magnetic anomalies, although, on its own, the sensor needs some movement to calibrate itself. Combined with a gyro and accelerometer, they can distinguish between an external field change and actual movement of the sensor.

Given the discussions we’ve had on sensors being different from each other, making universal fusion harder, her perspective was that the data returned by sensors are generally quite similar: it’s the APIs that tend to vary. And, of course, software uses APIs, not data directly, so those calls end up masking the similarities between sensors.

Given the size of their sensors (not huge, but not MEMS), they’re not looking to sell into phones. They have background in military, navigation, and virtual reality applications; they’re looking to grow further into games and TV controllers. These are somewhat more forgiving than some of their earlier markets in that they are, more or less, pointing applications, and absolute heading isn’t critical for those apps in the way it is for navigation apps.

They’re building a new fab in Santa Rosa, CA. It seems to be part of a trend to bring manufacturing back to the US – as long as the manufacturing line itself doesn’t require hiring any real people. The key to these fabs is automation: everything is done by computer. There is a need for a hundred or so well-trained people that can work (and repair) the equipment, which is less than would have been used in the past or overseas, but more than would be in the US if they remained overseas.

Even though they aren’t MEMS, they’re joining the MEMS Industry Group, since there’s a lot of commonality with the ecosystem and other players there. And it appears that the Group will let them in…

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