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Hardware Technology

Harvard Professor Creates Paper Accelerometer 87

SuperSlacker64 writes "In an age where just about everything starts going digital, it's refreshing to see someone going back to our roots: paper. Well, sort of. Researchers at Harvard have created a cheap, dime-sized, paper-based accelerometer that they believe could be used in various ways, such as inexpensive medical testing. The device works because a carbon bridge stretches and changes resistivity as the device is accelerated." When they say "cheap," they mean it; the cost per device is estimated to be about four cents.
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Harvard Professor Creates Paper Accelerometer

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  • Re:Accuracy? (Score:5, Informative)

    by shaitand ( 626655 ) on Monday February 14, 2011 @06:47PM (#35204204) Journal

    I hath sinned. I read the article. *hangs head in shame* The paper counterparts are far less sensitive. Silicon sensors give about 80 micronewtons while the paper give 120 un.

  • Re:Accuracy? (Score:4, Informative)

    by MobileTatsu-NJG ( 946591 ) on Monday February 14, 2011 @07:12PM (#35204418)

    It says for use in medical testing equipment where I'm pretty sure one would want precision, no?

    Not every test, especially when aiming for low-cost, needs to reach Starfleet standards.

  • Missing parts... (Score:4, Informative)

    by Moof123 ( 1292134 ) on Monday February 14, 2011 @07:40PM (#35204668)

    Most accelerometers are not just a sense element.

    The Analog devices ones from a few years back included an onboard reference (to allow single supply operation), and an on board buffer amplifier with externally settable gain (i.e. integrated op-amp). The 4 cent sensor still requires precision op-amps, nulling trim pots, etc to get a usable sensor. Don't forget packaging to protect the element from kinks, moisture, etc.

    BUT, the most important thing about the accelerometers from Analog I used was they were laser trimmed for 0G, and used a very cool sense mechanism. The sensor was a micro-machined silicon mass on springs with a capacitive force/sense system that detects a perturbation of position by using a 1 MHz AC pump signal with a capacitive bridge and synchronous demodulation feedback. The mass is forced to be stationary by applying a DC electrical voltage on the capacitive sense plates, imparting a force 100% proportional to the applied DC voltage (i.e. purely LINEAR voltage to force relationship).

    So what? Their system keeps the mass centered, thus making micro-machined springs that hold the mass irrelevant to the output voltage. In other words the NON-LINEARITY of crap springs is servoed out, and the output voltage is not an open loop measurement with gain, but a true measure of the force being applied to the tiny little mass by the acceleration trying to be measured.

    Paper as a spring is not going to be repeatable from batch to batch, is subject to moisture, subject to fatigue, hysteresis, etc. Mad props for new uses of paper, but practical as a replacement for the devices it mocks it is not.

Money can't buy love, but it improves your bargaining position. -- Christopher Marlowe