editor's blog
Subscribe Now

Another Magnetic Measurement

One of the fun things about the MEMS and sensors space is that there are often many ways of skinning the many proverbial cats. Magnetometers are one example.

When Bosch Sensortec introduced its BMC050 6-axis sensor last year, they made particular note of their FlipCore technology for detecting the strength of the earth’s (or any local) magnetic field. Detailed information, however, wasn’t readily available.

At the recent MEMS Executive Congress, I was able to talk with Bosch Sensortec’s Marcellino Gemelli to get the next level of understanding. And, in principle, it’s surprisingly straightforward. It simply relies on the familiar equation V=L di/dt.

They essentially build a transformer. One coil has a magnetic material in it, and they run a current through the coil; the secondary coil acts as the detector. The trick is that they periodically reverse the current through the primary coil. At the point where they reverse the current, you get a voltage spike in the secondary coil.

But the timing of that spike relates to the entire magnetic field, not just the one created by the primary. That includes the earth’s magnetic field (as well as any local “anomalies”). If the device is facing East/West, then the contribution from the earth’s field is orthogonal and has no impact; it has maximal impact if the device is facing North/South. The amount of that component delays (or advances) the voltage spike with respect to the time when the current in the primary coil was changed.

By measuring this phase shift in the output pulse train, they determine the heading of the device.

Of course, there are details with respect to calibration, and it has to be done in three axes, so the reality is somewhat more complicated than the theory, but they appear to have tamed it; they’re in production. With a 1000 microtesla field (which, I guess, would be 1 millitesla), they claim roughly 0.5 degree angular resolution.

The device itself combines the magnetometer with an accelerometer, which is essential for providing the tilt compensation necessary for an eCompass. You get acceleration data out of it as an additional bonus.

Leave a Reply

featured blogs
Jan 15, 2021
I recently saw (what appears at first glance to be) a simple puzzle involving triangles. But is finding the solution going to be trickier than I think?...
Jan 15, 2021
It's Martin Luther King Day on Monday. Cadence is off. Breakfast Bytes will not appear. And, as is traditional, I go completely off-topic the day before a break. In the past, a lot of novelty in... [[ Click on the title to access the full blog on the Cadence Community s...
Jan 14, 2021
Learn how electronic design automation (EDA) tools & silicon-proven IP enable today's most influential smart tech, including ADAS, 5G, IoT, and Cloud services. The post 5 Key Innovations that Are Making Everything Smarter appeared first on From Silicon To Software....
Jan 13, 2021
Testing is the final step of any manufacturing process, and arguably the most important, and yet it can often be overlooked.  Releasing a poorly tested product onto the market has destroyed more than one reputation for quality, and this is even more important in an age when ...

featured paper

Overcoming Signal Integrity Challenges of 112G Connections on PCB

Sponsored by Cadence Design Systems

One big challenge with 112G SerDes is handling signal integrity (SI) issues. By the time the signal winds its way from the transmitter on one chip to packages, across traces on PCBs, through connectors or cables, and arrives at the receiver, the signal is very distorted, making it a challenge to recover the clock and data-bits of the information being transferred. Learn how to handle SI issues and ensure that data is faithfully transmitted with a very low bit error rate (BER).

Click here to download the whitepaper

Featured Chalk Talk

Protecting Circuitry with eFuse IC

Sponsored by Mouser Electronics and Toshiba

Conventional fuses are rapidly becoming dinosaurs in our electronic systems. Finally, there is circuit protection technology that doesn’t rely on disposable parts and molten metal. In this episode of Chalk Talk, Amelia Dalton chats with Jake Canon of Toshiba about eFuse - a smart solution that will get rid of those old-school fuses once and for all.

Click here for more information about Toshiba efuses