Capacitive height sensor

Discussion in 'The Projects Forum' started by cnc_freak, Oct 6, 2015.

  1. cnc_freak

    Thread Starter New Member

    Oct 6, 2015
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    Hello everybody.
    I'm trying to make a capacitive sensor to measure the distance of from sensor to a metal plate.
    I found an old schematic of an 13Mhz oscillator, but i cant found any information for the L1 transformer.
    Can anybody help me out here? At the "HF" connector is connected the sensor, which is a metal ring, like in the picture.
    Capacitance_sensors.jpg
    Any help will be appreciated.
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,969
    744
    It maybe one of the tuned IF coils found in fm radios, is there any other information about the circuit used, web site etc, going off the 470pf cap a resonance inductor at 13.56mhz, would be 290pico henrys, (0.290uH)
     
  3. cnc_freak

    Thread Starter New Member

    Oct 6, 2015
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    It must be something like that, but where can i find it, and what should i look for.
    I googled for HF transformer 13Mhz, and i looked also at digikey, they have a big selection of variable coils but i have no clue about the inductance i must look for. The only think i know that the in the parts list of the schematic it says HF coil 13Mhz. N02/98, nothing else.
    Im trying to find a picture of the complete board with all the parts on it, but i don't think this will help.
     
  4. cnc_freak

    Thread Starter New Member

    Oct 6, 2015
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    Here is the picture, i find it.
     
  5. cnc_freak

    Thread Starter New Member

    Oct 6, 2015
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    The board... DSCF1506.JPG
     
  6. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,969
    744
  7. cnc_freak

    Thread Starter New Member

    Oct 6, 2015
    5
    0
    Thank you very much for the reply.
    I managed to borrow the board and measure the inductance of the coil in question.
    I has a primary winding of approximately 150μΗ and a secondary of 12μΗ and no capacitor in.
    Here is a picture of the coil.
    The question is now, how can i reproduce this coil. Can i buy somewhere empty plastic reels ,with ferrite core to wind my own coils?
     
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