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From: rww@esl.UUCP (Richard W. Webb)
Newsgroups: sci.electronics
Subject: Accelerometers on a chip
Keywords: accelerometers, chips, seismology
Message-ID: <740@esl.UUCP>
Date: 1 Aug 88 22:05:49 GMT
Reply-To: rww@esl.UUCP (Richard W. Webb)
Organization: ESL, Inc., Sunnyvale, CA.
Lines: 35

Hello Electronics experts,
	I remember reading recently (in the last 3 months) about a design
    of a small chip based accelerometer.  The principle was that of a
    variable capacitor, where the movable plate was actually a piece
    of deposited metal that overhung another metal well.

                     ^
                     | Acceleration causes bending of the metal overhang.
                     v
   \__________    __________________________/
    XXXXXXXXXX\___________________XXXXXXXXXX
    XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

    The amount of acceleration is detected as a change in the capacitance
    between the plates of the air gap as the metal overhang bends.  The
    degree of bending is slight, but the device can be made more sensitive
    by making the length of the overhang larger.  Fast response is not a
    vital factor for our application either, as the sampling rates are
    at most 100 Hz.

	Some of my friends and myself are interested in producing small
    scale seismographs to monitor earthquakes in the California area.
    We currently have two (2) classical mechanical seismographs.  But
    now we are looking into the possibility of using single chip
    accelerometers as the sensing elements in a network of seismographs.

	Any references to actual sensors like these, articles about such
    sensors, or any other related types of sensors would be greatly
    appreciated.

	Thanks,
-- 
Richard W. Webb                           ecvax!decwrl!borealis!\
ESL Inc.  MS/302                                 sdcsvax!seismo!- ames!esl!rww
495 Java Drive           (408) 738-2888 x5729     ucbcad!ucbvax!/     /
Sunnyvale, CA  94088     SMAIL: rww@esl.ESL.COM         ihnp4!lll-lcc!