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I recently soldered an electret mic. I have never soldered before. How do I check whether I have damaged the electret mic? If it was a speaker I could have done continuity check but for a mic I don't know. I measured the resistance it comes somewhere around 1.7Kohm. If I blow into mic ,it comes to 2Kohm. Is this how we check it?

enter image description here

I made a pre-amplifier circuit. It's not working. I am not sure whether it is the problem with the mic or the circuit.

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  • \$\begingroup\$ 2MOhm seems too much. What the datasheet says? \$\endgroup\$
    – user76844
    Commented May 13, 2016 at 19:02
  • \$\begingroup\$ It doesn't come with a datasheet \$\endgroup\$
    – Sreeraj Chundayil
    Commented May 13, 2016 at 19:06
  • \$\begingroup\$ Hard to believe it's alive. What is your amplifier circuit? \$\endgroup\$
    – user76844
    Commented May 13, 2016 at 19:06
  • \$\begingroup\$ sorry- there is a typo, it's 2KOhm. \$\endgroup\$
    – Sreeraj Chundayil
    Commented May 13, 2016 at 19:09
  • \$\begingroup\$ Then it's just fine, the circuit is bad. \$\endgroup\$
    – user76844
    Commented May 13, 2016 at 19:10

1 Answer 1

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Electret mics have a built-in FET as an "amplifier" which requires power.

  • get a power supply, say 5V
  • connect GND to the - of the mic
  • connect 5V to a 22k resistor, the other side of the resistor goes to the mic
  • connect your oscilloscope between GND and the + pin of the mic
  • start whistling, alter two frequencies
  • change input sensitivity on the scope, you shall see a signal in millivolts range
  • and you will see nice sine waves as you're whistling.

Basically this is what you do (without the output capacitor, which cuts the DC power from the output):

http://i0.wp.com/www.scienceprog.com/wp-content/uploads/2014/01/Electret_condenser_microphone_schematic.jpg?resize=300%2C208

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