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  • #1

    Testing data

    I had time today to check each coil, results of the test.
    20 CM diameter coil
    L= 307uh
    R= 1.44 ohms
    F= 321 KHZ
    Wire type = Litz
    Winding type = spiral,solenoid

    25.5 CM diameter coil
    L= 315 uh
    R=1.43 ohms
    F= 339 KHZ
    Wire type = speaker wire #28 gauge
    Winding type = spiral,solenoid

    30Cm diameter coil
    L= 306uh
    R= 2.23 ohms
    F= 327 KHZ
    Wire type = Litz
    Winding type = spiral, solenoid

    20.5CM diameter coil
    L=245uh
    R= 1.9 ohms
    F=131 KHZ
    Wire type = Litz
    Winding type modified basket weave

    All coils have card stock top an bottom sprayed with MG Chemicals =Total ground carbon conductive coating , all shields are connected to (-) ground side of coils.
    Have a great weel best to all Jim, I will calculate "Q" later when I have time.
    Tags: None
  • #2
    From those self resonant frequencies the capacitance is quite high.
    I calculate the C for your four coils as:
    801pF
    700pF
    775pF
    6030pF

    For a comparison the last Mono 10.25" (26cm dia) coil I built:
    24 turns, #26 PTFE bunch wound.
    398uH, 2.5 Ohm, 17pF
    Fo = 1.933MHz
    R damping = 1500 Ohm
    First sample delay <8usec.
    Not sure of coil's 'Q'

    Comment

    • #3
      Originally posted by James View Post
      I had time today to check each coil, results of the test.
      20 CM diameter coil
      L= 307uh
      R= 1.44 ohms
      F= 321 KHZ
      Wire type = Litz
      Winding type = spiral,solenoid

      25.5 CM diameter coil
      L= 315 uh
      R=1.43 ohms
      F= 339 KHZ
      Wire type = speaker wire #28 gauge
      Winding type = spiral,solenoid

      30Cm diameter coil
      L= 306uh
      R= 2.23 ohms
      F= 327 KHZ
      Wire type = Litz
      Winding type = spiral, solenoid

      20.5CM diameter coil
      L=245uh
      R= 1.9 ohms
      F=131 KHZ
      Wire type = Litz
      Winding type modified basket weave

      All coils have card stock top an bottom sprayed with MG Chemicals =Total ground carbon conductive coating , all shields are connected to (-) ground side of coils.
      Have a great weel best to all Jim, I will calculate "Q" later when I have time.
      How did you measure SRF ?

      Comment

      • #4
        Something seems odd about capacitances of those coils. They are way to high.

        Comment

        • #5
          There is a setup for this testing, maybe you know about it already. http://www.geotech1.com/forums/showt...lf+capacitance

          Comment

          • #6
            I did not measure the capacitance of the coils, that was comment from another gentleman. I really don't understand what "SRF" means ? Thank you 6666 for the site to measure capacitance. Best to all Jim

            Comment

            • #7
              SRF = Self Resonant Frequency

              Comment

              • #8
                I found my frequencies were wrong, 100kohm series resistor with the function generator was a 100 ohm. Miss marked resistor, 20.5 CM coil=95.0khz,30CM coil=107.7khz,25.5 coil=95.5khz, and 20CM coil=89.3khz. I will recalculate the "Q"s later. Best to all Jim

                Comment

                • #9
                  I did test the Q of the 4 coils, 20CM q=13.59, 25.5CM=11.25, 30CM=15.35, and 20.5CM=18.12. I did the ringing test for the "Q", also I did the math formula calculations, they both are very close. I have 1 more coil to build an test when the materials arrive. Best to all Jim

                  Comment

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