Jun 16, 2014

What is a technology company?

posted by Dick Selwood

Am I being picky or over-sensitive? A recent report talks about how Europe has produced 30 technology companies worth more than $1bn. They include "Clothing retailer Asos, games studio King Digital, property portfolio Zoopla and music service Spotify." Are these technology companies? Zoopla's core business is pulling together into a single web site, property listings from a wide range of sources. They do have other service for the estate agents whose properties they advertise and there is serious technology underlying this, but if you look at their job ads, of the 15 on the site today, only two are for technologists (Perl and Python developers). The rest are for people involved in the business of getting more ads onto their site and more users to the site.

Again Asos, which claims to be the most visited fashion and beauty website in the world, is in rag trade- it exists to sell clothes. Again serious underlying technology, but that is not the point.

Europe does have technology companies, ARM and Imagination, Infineon, STMicroelectronics are companies who create technology. So are companies who build systems using their products, such as Thales.

All financial organisations use massive amounts of technology: high frequency trading- a technology for gaming the markets that is under a great deal of critical scrutiny but somehow seems to be unstoppable - exploits mind staggering technologies, but even retail banking would be  impossible without technology, yet these companies are not labelled as technology companies.

Confusing companies who use technology to deliver a product or service with companies who create technology seems dangerous. When the dotcom bubble burst it was companies using technologies who were the problem, but the companies who create technology were equally hammered by the stock markets.

Since there is nothing we can do about it, I suppose I should just ignore it all and keep my fingers crossed that when this bubble bursts, real technology companies survive.

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Jun 12, 2014

Sensor or Switch?

posted by Bryon Moyer

Honeywell recently released a new AMR (anisotropic magneto-resistive) sensor. We looked at this basic technology some time back, but there was another aspect of the release that confused me: the sensor was compared to a reed switch. And, at first glance, I don’t see a switch (=actuator) and a sensor as being the same thing.

For those of you steeped in this technology, what follows may seem rather basic and even obvious. But if you’re new to the space, then there’s some room to untangle some concepts that can be easily conflated.

Part of the issue has to do with being precise with terms that might be confused. If I think sloppily, I end up confusing a reed switch with a reed relay. What’s the difference? Well, a reed switch is simply a two-lead component. The switch connects the leads, presumably completing some circuit. That switch is actuated by a magnetic field (either to open or close it). That field is applied externally; exactly how depends on the application. Critically, there’s no magnetic component built into the switch.

So, in a way, the reed switch is a magnetic field detector. When the field exceeds a threshold, the reed moves, and you can think of this as a crude digital magnetic field sensor.

Now, if you include a magnetic coil along with the reed switch, adding two new leads, now you have a reed relay. This is much more of an actuator than a sensor, since it creates its own magnetic field. So switch and relay confusion can create sensor and actuator confusion.

Now let’s look at the AMR sensor schematic from the data sheet. From the outside, it may look just like a Hall Effect sensor, another sensor based on magnetic phenomena. (The field directions are apparently different, but I won’t dwell on that.)

Figure.png

 

On the left is the detector circuit. Because this constantly draws power, it must do so exceedingly sparingly. The original application for this (more on that in a moment) required no more than 500 nA; Honeywell has a couple of devices, one at 310 nA, the other at 360 nA. They claim this to be more than an order of magnitude more miserly than the lowest-power Hall Effect device, with greater sensitivity.

Once it detects the field, it flips the flop and the output value changes. Now… this output looks something like a beefy CMOS output, not like a wire in a reed switch. And if it drives a CMOS input, then this will simply look like a digital indicator with no DC load current. But if the output drives something that pulls current, then the pull-up (or the pull-down) acts as a switch that makes or breaks that circuit. In this way it more resembles a reed switch.

Here’s one other possible source of significant confusion: this is not like the magnetometer you may have in your phone. Your phone mag, like most sensors, provides continuous readings of the ambient magnetic environment. The phone can go in and interrogate the value at any time. By contrast, this AMR sensor is digital: either on or off. You can’t go in and measure the actual field. So it’s unlike many other sensors out there. That on/off characteristic is what makes it appear to be a switch – and contributes to the sensor/switch confusion.

So if you think of a reed switch as a switch that can be used as a sensor, then here you have a mag sensor that can be used as a switch.

By the way, that application I alluded to above? Apparently people were trying to monkey with electric meters using magnets to disrupt the metering. So AMR sensors (it takes two of them) are used to detect such anomalous magnets. Obviously, being in a meter, they have access to power, but it’s the power someone else is paying for, so it has to be tiny so as to be undetectable on their bill.

You can read more about Honeywell’s part in their release.

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Jun 10, 2014

Accelerometer Fingerprints

posted by Bryon Moyer

An interesting paper was published earlier this year by a team from University of Illinois at Urbana-Champaign, University of South Carolina, and Zhejiang University. In short, it says that the accelerometer in your phone could give you away even if you’ve locked all your privacy settings down tight.

The idea is based on the fact that each accelerometer is unique at the lowest level, having minor but detectable differences in waveform or harmonic content. To the extent that the characteristic resonance of an accelerometer can identify it uniquely (or nearly so), it acts as a signature.

This means that an app can “record” a phone’s accelerometer and then store it in the cloud for future reference. Some other app can also sample the accelerometer and send the sample to the Cloud, where a search engine can match the signature and identify the phone. (This is the way music is identified these days, so there is clearly precedent that the search aspect is doable.)

“Unique” may actually be an overstatement from a purely scientific standpoint. As they point out, they haven’t done enough of a statistical sample to prove uniqueness over the many millions of phones out there, and they don’t have some theoretical model to suggest uniqueness. But they measured 36 different time- and frequency-domain features in 80 accelerometers, 25 phones, and 2 tablets and came away pretty convinced that there is something to pay attention to here.

They discuss the possibility of “scrubbing” the measurements by adding white noise or filtering, but each of the things they tried was either ineffective or too effective (that is, it affected how an application operated).

To me, it seems like there’s an abstraction problem here. A phone has a raw accelerometer followed by a conditioning circuit and a digitizer. Eventually a value is placed in a register for retrieval by an application. In a perfect world, all distortions and anomalies would be “filtered” out by the conditioning and the digitization so that what lands in the register has been purged of errors – making all accelerometers look alike. That’s a pretty high bar to set, but you’d think that, even if not perfect, it would at least get rid of enough noise to make a uniqueness determination infeasible.

Then again, as they point out, (a) it took 36 features to get uniqueness, and (b) if you couldn’t quite get there using just the accelerometer, you could also bring the gyro (et al) into the picture – effectively adding more features to the signature. So any policy of “cleanup” prior to registering the final value would have to be applicable (and actually applied) strategically across a number of sensors. In other words, some fortuitous solution related to how accelerometers are built would be insufficient, since it couldn’t be used on a gyro as well.

The only other obvious solution would be policy-based. You could restrict low-level access, but that would rule out apps needing high precision readings. The OS could flag apps that need low-level access and ask permission, although presenting that request to a non-technical phone user could be a challenge. And the OS would have to actually check the program code to see if it does low-level access; relying on declarations wouldn’t work since the concern here is specifically about sneakware, whose authors are not likely to volunteer what they’re about.

I’m curious about your thoughts on this. Are there other solutions? Is this much ado about nothing? You can read much more detail in the original paper, and then share your reactions.

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