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Pistons and microprocessors

  1. Jun 9, 2014 #1
    So in an insulin pump there is a cartridge that holds 200 mL of insulin, this is broken into 200 "units" of insulin (i would use metric but i can't seem to find the proper metric prefix for 1x10^-5). The piston is controlled by a microprocessor and gives these very small "units" of insulin, the smallest it can give is .05 of one of the "units" my question is how hard is it to get a piston to move that exactly?
  2. jcsd
  3. Jun 9, 2014 #2
    not that hard if you use a stepper motor with a screw drive setup.
  4. Jun 9, 2014 #3


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    Staff: Mentor

    Or even a microstepper motor with the screw drive... :biggrin:
  5. Jun 11, 2014 #4


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    Science Advisor

    There is no SI prefix for 1x10^–5. It is 10x10^–6 = 10 u.
    If a 200 mL cartridge holds 200 “units” then each unit is 1 mL.

    0.05 mL is an interesting volume. It is the approximate volume of one drop of water.
    If you use a common eye dropper, 20 drops = 1 mL.

    Intravenous drips are regulated by counting drops.
    Different profile drippers have different drop volumes. Standards are 10, 15, 20 or 60 drops per mL.

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