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Summary of Data Logger Responses

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  • Summary of Data Logger Responses

    Dear Colleagues,

    This message includes a summary of responses to a question I posted in May,
    regarding data logging devices for pressure measurements. Thank you to all
    who responded.

    Frank L Buczek, Jr, PhD
    Director, Motion Analysis Laboratory
    Shriners Hospitals for Children
    1645 West 8th Street, Erie, PA 16505, USA
    (814) 875-8805 voice, (814) 875-8756 facsimile
    ************************************************** ********************

    Design specifications and pricing for Pressure Sensing Transducers and
    associated data recording device.
    -- commercially available preferred
    -- custom fabrication considered

    We want to assess compliance for the use of a plastic body jacket in the
    treatment of scoliosis; recommended usage will be 23 hours ON, 1 hour OFF,
    with exceptions from time to time.

    -- Pressure sensing will be needed only for on/off states, rather than the
    measurement of actual pressure values.

    -- Pressure sensors should NOT be adversely affected by temperature (i.e.,
    an instrumented body jacket left in a hot automobile should not record wear
    compliance during this time period.)

    -- Two pressure sensors are anticipated, mounted flush with the interior
    surface of the body jacket, most likely adjacent to the lateral rib cage on
    each side of the body.

    -- The data recorder should be of low profile (less than 3/8 inches), and
    preferably of flexible or somewhat concave construction. It should be
    capable of sampling the sensors once each hour, and storing the information
    for a six month duration, although other sampling rates and durations will
    be considered. The power requirements for the device should be met with an
    integral power supply, such that the entire data recorder and power supply
    are no larger than 6 in x 4 in x 3/8 in. The smaller, the better.

    -- The sensors and data recorder will be fabricated into a body jacket by
    an orthotist.

    -- The recorder should be capable of downloading to an IBM compatible
    personal computer; we expect this to occur once every six months (see

    ************************************************** ********************
    RESPONSES (Edited for brevity by FB)

    Have you considered using force sensing resistors (FSR)? A FSR is an
    electronic element whose resistance varies with the pressure applied to the
    element. It is a 0.3 mm thick laminated polymer construct. They come in
    various sizes and are distributed by Interlink electronics, California,
    (805) 484-1331 , fax (805) 484-8989.

    Kenton R. Kaufman, Ph.D., P.E.
    Associate Professor of Bioengineering
    Co-Director, Biomechanics Laboratory
    128 Guggenheim
    Mayo Clinic
    200 First Street SW
    Rochester, MN 55905
    Phone: (507) 284-2262
    FAX: (507) 284-5392
    ************************************************** ********************
    Try and call Dr. Avanish Patwardan. He can be reached either at Loyola
    School of Medicine, IL. or at the Rehabilitation Research And
    Development Center, VA Hines Hospital, Hines IL.

    He has done considerable work developing sensors to do similar things.

    Ted Morris
    Senior Project Engineer V: 612-626-2561
    MVS/Prosolvia F: 612-626-0679
    ************************************************** ********************
    We sell tactile pressure transducers. Check out our site at
    to see if this is what you are seeking.

    Jeffrey Stark
    Sensor Products Inc.
    ************************************************** ********************
    Saw your post and thought I'd pass on some ideas. If you're looking for a
    very reliable and relatively inexpensive data logger that is quite small
    and virtually indestructible, you should check out the HOBO and Tattletale
    by Onset computer.

    I used these for an ambulatory monitor about 8 years ago, and found them
    excellent, easy to program, and quite reliable. .....Temperature stability
    is a concern for the contact sensors. I've used
    Force Sensing Resistors (FSR, Interlink) for years for footswitches, and
    they are reasonably reliable, but I don't have any experience with them in
    a chronic application. What you might want to do instead is use an
    infrared proximity sensor that would trigger when the body jacket is worn
    and so the body is in close contact with the plastic. I'd use at least 2
    sensing sites, probably 3, to reduce the chance that they could be

    Interlink is at:

    IR Proximity sensors:

    James Carollo, Ph.D., P.E.
    Senior Research Scientist
    Mobility Research and Assessment Laboratory
    The University of Texas
    Southwestern Medical Center at Dallas
    9705 Harry Hines Blvd., Suite 105
    Dallas, TX USA 75208 (214) 351-2041
    ************************************************** ********************
    We do have a product which may be of interest to you. The recorder will
    accept one or two sensors in the size of a matchbox recording at 50 Hz for
    hours. A notebook computer will be required for reading the data and the
    calibration file......

    Susan Diekrager
    Executive Vice President
    novel electronics inc.
    964 Grand Avenue
    St. Paul, MN 55105
    tel. 612.221.0505
    fax 612.221.0404
    ************************************************** ********************
    I am an electrical engineer working at the institute of
    Biomedical Engineering at the University of New Brunswick, and
    have considerable experience in such instrumentation tasks.

    One of our particular research projects involved the monitoring of
    EMG, foot load and knee angle bending during normal working
    activities of nurses. ...The fabricated system collected data for up to 4
    and then downloaded the information to a PC computer via a standard
    RS232 link.

    For your application, we could borrow the foot sensing circuitry
    developed for the "nurse" study and the data download
    software. However, to extend the data collection period to 6
    months and drop the sampling rate, a re-design of the
    processor section of our instrumentation would be necessary. As
    absolute pressure information is not required this would be
    relatively simple as no analog-to-digital converter would be
    required. My concept at this stage is that every hour a
    micro-power timer would "wake up" the processor, which would take
    look at the force sensors to see if the subject was wearing the cast
    and store the result (YES or NO) in non-volatile memory. This memory could
    approximately 16000 YES/NO decisions. If you sample at 30 minute
    intervals this translates into approximately 330 days.

    Dennis F. Lovely.
    Research Professor Tel: (506) 453 4966
    Institute of Biomedical Engineering Fax: (506) 453 4827
    University of New Brunswick Internet:
    PO Box 4400, FREDERICTON,
    NB, E3B 5A3
    ************************************************** ********************

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