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medical sensor

Former Member

hello,

 

im working on fetal movement sensor. what kind of sensor is the most suitable to use for better accuracy?

any idea and suggestion? please share with me. thank you

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  • 0

    Hi Diana,

    Piezo-electric sensors based on polyvinylidene-flouride (PVDF) films are about the most sensitive sensors available for measuring motion. PZT sensors are another pretty sensitive Piezo-electric sensor technology - often called Piezo benders - used in little buzzers. Ultrasound imagers use a variation on the Piezo-electric sensors. A third technology that might work is any kind of sensitive microphone - they can usually also sense motion, but motions also produce sounds. I'm sure you have discovered the movement of the mother is far greater than the movement of the fetus, so much signal processing may be needed to distinguish which movements are from the fetus. If you use multiple sensors, it is possible to determine the location of the source movement due to the propagation time of the signal. You can try to capture time of arrival of each movement, which requires each sensor to recognize the signals that are from the same initiating motion.

    For PVDF transducers you can check out the various Piezo film elements from Measurement Specialties.

    For Piezo benders you can check out Pui Audio, Cui Inc and Murata Electronics.

    Doug

  • 0 in reply to dougw

    Thank you very much mr @douglas wong. i am really interested to know more in piezo-electric sensors based on polyvinylidene-flouride (PVDF) films. can you help me in finding the specific type and model of sensor to use for my project?. i am also need to prepared the circuit for the sensor. if you have any material or link to the information really hope you can share it with me and i am really appreciate it. actually i planned to place about 4 to 6 sensors for better accuracy as you also know that its difficult to placed only one sensor as per fetal move around in the mom's belly. thank you for your time sir.

  • 0 in reply to Former Member

    Hi Diana,

     

    element14 sells rigid piezo elements from Multicomp and Murata - here is one that has wires attached:

    MCFT-27T-4.2AL-127 - MULTICOMP MCFT-27T-4.2AL-127 - PIEZO ELEMENT | Newark element14 Canada

     

    This is a typical pvdf film sensor:

    http://www.meas-spec.com/product/t_product.aspx?id=2478#

    https://www.sparkfun.com/products/9196

     

    You can use either a high impedance voltage amplifier or a charge amplifier to monitor the output signals - most often a charge amplifier is used for piezo sensors.

    Here are some documents on how to monitor the output signals from piezo electric sensors:

    http://resenv.media.mit.edu/classes/MAS836/Readings/MSI-techman.pdf

    http://www.ti.com/lit/an/sloa033a/sloa033a.pdf

     

    Doug

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