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Discussion in 'Electronic Basics' started by studio, Aug 17, 2004.

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  1. studio

    studio Guest

    Help!

    I'm trying to build something which will measure the force something like a
    hammer hits an object. So, for example, I hit this thing and it says 78.4
    PSI

    I'm not a technical person whatsoever so when I search on line, I'm getting
    all kinds of different stuff from industrial to engineered for space travel.

    I'm looking for something cheap that I can experiment with.

    And before the jokes come, I know I can get *that* in the binary groups.

    Please post questions, thanks in advance for your guidence.

    Studio
     
  2. studio

    studio Guest

    Thanks.

    I guess I was thinking like $100 USD.

    When I searched on "impulse measurment techniques" I am getting fairly
    technical things, research papers and such.

    Can you help me find a particular website?
     
  3. Jan Pompe

    Jan Pompe Guest

    If you are looking for sensors then industrial sites are the place to
    look but "something cheap" depends on your definition.

    What you are describing though is not just a sensor but a complete
    instrument. If you are a looking for something that measures the force
    with which an oboject is being hit you might refine your search to
    impulse measurment techniques.
     
  4. Jan Pompe

    Jan Pompe Guest

    If you are looking for sensors then industrial sites are the place to
    look but "something cheap" depends on your definition of cheap.

    What you are describing though is not justIf you are looking for sensors
    then industrial sites are the place to look but "something cheap"
    depends on your definition.

    What you are describing though is not just a sensor but a complete
    instrument. If you are a looking for something that measures the force
    with which an oboject is being hit you might refine your search to
    impulse measurment techniques. a sensor but a complete instrument. If
    you are a looking for something that measures the force with which an
    object is being hit you might refine your search to impulse measurement
    techniques.

    Finding something that will do the job without being destroyed could be
    a challenge an accelerometer attached to (or embedded in) an object of
    known mass might be a good start.



    Some sites:
    http://www.dytran.com/
    http://www.thomasregisterdirectory.com/load_cells/force_measuring_instruments_0031902_1.html
     
  5. Jan Pompe

    Jan Pompe Guest

    You are too quick for me I was in the process of modifying this when you
    responded.
     
  6. Bob Masta

    Bob Masta Guest

    If I understand you correctly, then you might consider
    putting an accelerometer on the hammer. That won't
    tell PSI because you won't know the contact area,
    but it may allow you to derive a useful number.

    What is it exactly you are trying to do?


    Bob Masta
    dqatechATdaqartaDOTcom

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    www.daqarta.com
     
  7. P.R.Brady

    P.R.Brady Guest

    Something simple like a pedulum bob and a scale to see how far it is
    displaced when hit?
    Phil
     
  8. andy

    andy Guest

    Analog Devices have integrated circuit MEMS accelerometers on their site.
    They use a mass and spring microengineered out of silicon to measure
    accelerations of up to about 50 g.

    Or you could put a sheet of rubber between two metal plates and measure
    the change in capacitance?
     
  9. dan

    dan Guest

    What's that Lassie? You say that studio fell down the old
    sci.electronics.basics mine and will die if we don't mount a rescue by
    Mon, 16 Aug 2004 21:49:58 -0400:

    I think what you want is a pressure transducer. They can be had from
    surplus stores. I think I saw them at C+H sales.

    That, plus a small hydraulic cylinder, will give you an analog signal
    proportional to the force applied to the piston rod of the hydraulic
    cylinder.

    The transducer works like the sending unit on your car's oil pressure
    gauge. You will need something to store/read the output if you need
    to see the results of a fast event like your hammer example. For
    slower events a DMM should be fine. You will need to test it with a
    known force, and you will need to chose a cylinder that has the proper
    bore(area) to create the PSI that the transducer is rated for.

    Good luck.
    Dan H.
     
  10. Wim Lewis

    Wim Lewis Guest

    I've never used 'em, but how about a strain gauge attached to the side
    of a rod with known (or measurable) elasticity? Like a nail maybe :)
    You could either integrate the output to get the total impulse delivered,
    or peak-detect it to get the maximum force.
     
  11. steamer

    steamer Guest

    --You might try posting this to rec.crafts.metalworking; there are
    quite a few folks up to strange stuff like this over there..
     
  12. onestone

    onestone Guest

    It depends what you are trying to do, and just how much force you expect
    to measure. Here are a frew ideas:_

    1. Load cell. A bit expensive to bash, but protect with a large plate.
    read the output faster than you would a load cell in, say a weighing
    scale. Analog Devices, and Maxim, among others have dedicated devices
    for converting and amplifying load cell signals.

    2. Known mass with accelerometer on surface of known coefficient of
    friction.

    3. piezo element, protected. measure the voltage spike.

    4. accelerometer in flexible lever, like the old school ruler twanging.

    5. as above with piezo

    6. Accelerometer on the object your bashing with. Know the mass of the
    object and the acceleration allows you to derive force.

    7. lever element arranged to electrically detect moment of contact with
    the object. A microswitch under neath, or laser beam, allows you to
    determine the force the lever was struck with, based upon the time it
    took from impact to switch operation.

    Cheers

    Al
     
  13. The resistance of the black foame used for shipping devices sensitive to
    electrostatics depends on pressure. A little bit from the last shipment
    of ICs is the cheapest sensor I know of.
     
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