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  • frequencyThis sound frequency meter circuit is simple to build and can be constructed in a portable format. In can measure frequencies with a minimum level of 10 mVrms and a maximum frequency of up to 100kHz. It can be powered by penlight batteries since its standby current is 4 mA. The input is protected from high voltage levels up to 250 Vac.

    IC1 4518 is wired to give a hysteresis of only 18mV so that its sensitivity is enough for the whole frequency range. The output of IC1 is directly connected to the counter IC1a which divides the signal by 2 and the following three counters divide by 10. In any of the measurement range with this frequency meter, 50 Hz is the point where the meter will have full deflection. The signal from S2 is used to trigger the monostable multivibrator. The monotime of this circuit is set to one-half of the frequency range – 10ms.

    The tester is very sensitive that the power line frequency will be displayed when the input is touched by a finger. The sound frequency meter circuit can be calibrated using the power line frequency. While touching the input with a finger, adjust P1 slowly until the correct frequency is displayed.

    Frequency meter circuit diagram

    sound frequency meter circuit diagram

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    7 Responses to "Sound Frequency Meter Circuit"

    1. Bishwajit says: on March 22, 2011 at 12:20 pm

      plz clear me about the ic1A, ic1b, etc.

    2. hananie joee says: on September 6, 2011 at 8:51 am

      component’s list please..and also clear me about ic1A,ic1B and other unclear components….thanks.

    3. Russell Clift says: on February 17, 2012 at 8:52 am

      A1 and A2 are a single chip, a dual comparator. Do not use a generic opamp use a comparator, meaning do not sub out this part. IC3 is a 555 timer, preferably a cmos type. IC1 and 2 are both Dual BCD counters. Not hard to figure out.

    4. udit singhal says: on March 14, 2012 at 12:28 pm

      how can we measure the audio frequency

    5. Hasnain says: on May 30, 2012 at 3:18 pm

      Kindly tell the details of input signal..

    6. udit singhal says: on May 30, 2012 at 7:16 pm

      we want to measure the audio in hertz i.e its frequency as we measure the audio intensity in db

    7. Rui Figueiredo says: on February 15, 2015 at 9:22 pm

      Interesting and easy however IC3 have note reference, I guess it´s a f to V converter but the market is full of such IC’s.
      Many thanks if you clarify

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