editor's blog
Subscribe Now

A Reverse Proof Mass?

This continues both the theme of “stuff at Sensors Expo” and non-traditional approaches to common sensors. Only this time, it’s the most ubiquitous of motion sensors, the accelerometer.

Most accelerometers use some sort of “proof mass,” a piece of silicon or metal or quartz or… whatever. Inertia makes the proof mass “move” in the opposite direction of acceleration, and you can measure that apparent movement.

Memsic (whose mag sensor we just looked at), does something different. The fundamental principle of inertia is still the same, but the proof mass, well, isn’t a mass. If you’ve ever carried a helium balloon in your car, you’ve seen the effect. (I haven’t, or I haven’t been perspicacious enough to notice and remember, so I’m taking their word for it.) When you accelerate your car, you’d expect the balloon to move backwards, just like those toys and stray French fries and the dog do.

But it doesn’t. It moves forwards. Why? Because the gas is lighter than the surrounding air (even compressed in a balloon), and the heavier air moves back, displacing the balloon forwards.

Memsic exploits this same behavior by heating gas in a cavity. They use nitrogen, although that’s not really critical. The point is that, by heating the middle of the chamber, you get this “ball” of warmer gas (I keep wanting to call it a “bolus” but I’m not sure if that word would apply). This heated mass is less dense – and hence lighter – than the gas on either side of it. So when the unit accelerates, it moves not back, like a normal proof mass would do, but forward, in the direction of acceleration. It’s like the proof mass is all the non-heated gas.

By putting temperature sensors at either end of the chamber, you can detect the approach and retreat of the heated gas and use that to signal acceleration.

The benefits of this are that you don’t get any of the messiness of a normal proof mass. There are no issues of shock, vibration, resonance, or stiction. Its calibration is more stable and it has better bias stability. The main drawbacks are that it’s not particularly responsive, so you can’t do high-G shock detection. And, of course, you need power for the heater, although they say it’s not that much – you could still use this in a phone.

The primary apps they’ve seen so far are for electronic stability control in cars and high-end inclinometers.

You can find out more on their website.

Leave a Reply

featured blogs
Sep 21, 2023
Wireless communication in workplace wearables protects and boosts the occupational safety and productivity of industrial workers and front-line teams....
Sep 21, 2023
Labforge is a Waterloo, Ontario-based company that designs, builds, and manufactures smart cameras used in industrial automation and defense applications. By bringing artificial intelligence (AI) into their vision systems with Cadence , they can automate tasks that are diffic...
Sep 21, 2023
At Qualcomm AI Research, we are working on applications of generative modelling to embodied AI and robotics, in order to enable more capabilities in robotics....
Sep 21, 2023
Not knowing all the stuff I don't know didn't come easy. I've had to read a lot of books to get where I am....
Sep 21, 2023
See how we're accelerating the multi-die system chip design flow with partner Samsung Foundry, making it easier to meet PPA and time-to-market goals.The post Samsung Foundry and Synopsys Accelerate Multi-Die System Design appeared first on Chip Design....

featured video

TDK PowerHap Piezo Actuators for Ideal Haptic Feedback

Sponsored by TDK

The PowerHap product line features high acceleration and large forces in a very compact design, coupled with a short response time. TDK’s piezo actuators also offers good sensing functionality by using the inverse piezo effect. Typical applications for the include automotive displays, smartphones and tablet.

Click here for more information about PowerHap Piezo Actuators

featured paper

Intel's Chiplet Leadership Delivers Industry-Leading Capabilities at an Accelerated Pace

Sponsored by Intel

We're proud of our long history of rapid innovation in #FPGA development. With the help of Intel's Embedded Multi-Die Interconnect Bridge (EMIB), we’ve been able to advance our FPGAs at breakneck speed. In this blog, Intel’s Deepali Trehan charts the incredible history of our chiplet technology advancement from 2011 to today, and the many advantages of Intel's programmable logic devices, including the flexibility to combine a variety of IP from different process nodes and foundries, quicker time-to-market for new technologies and the ability to build higher-capacity semiconductors

To learn more about chiplet architecture in Intel FPGA devices visit: https://intel.ly/47JKL5h

featured chalk talk

Electrical Connectors for Hermetically Sealed Applications
Many hermetic chambers today require electrical pathways to provide internal equipment with power, data or signals, or to receive data and signals from equipment within the chamber. In this episode of Chalk Talk, Amelia Dalton and Brad Taras from Cinch Connectivity Solutions explore the role that seals and connectors play in the performance of hermetic chambers. They examine the methodologies to determine hermetic seal leaks, the benefits of epoxy hermetic seals, and how Cinch Connectivity’s epoxy-based seals and hermetic connectors can add value to your next design.
Aug 22, 2023
3,995 views