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I'm trying to make a simple microphone circuit using this microphone: http://www.cui.com/product/resource/cma-4544pf-w.pdf

I am connecting a 3V supply to a 2.2k Ohm resistor which then leads to terminal 1 of the microphone. I have terminal 2 of the microphone going to ground. I have terminal 1 of the microphone also connected to a 1uF DC blocking capacitor with the negative terminal of the capacitor being the terminal connected to the microphone.

I am then attempting to use a Tektronix DPO 4034 Oscilloscope to measure the output of the microphone by probing the positive side of the 1uF capacitor which has been left open.

When I do this, the oscilloscope is only showing the ambient static the probe is picking up. The signal on the oscilloscope does no change if the microphone has 3V power or not.

What can I do to be able to measure the output of the microphone?

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  • \$\begingroup\$ "I am connecting a 3V supply to a 2.2k Ohm res...", you can turn these words into a schematic. - "I am then attempting to use a Tektro.....", this should definitely be shown in a schematic. Some people measure current by putting it in parallel with what they are trying to measure. \$\endgroup\$ Dec 2, 2017 at 22:39

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To get something more than a couple of millivolts from the mic, you must have nearly deafening sound level at the mic. That means loud shouting from distance about five centimeters or less. Then you can get something like 100mV. If your oscilloscope can show 1mV/DIV then you can see something else than a blank horizontal line when one speaks using normal voice and the distance is 50cm. If you have normal 1 MegOhm oscilloscope input, it's no use to increase the capacitance from 1uF to 100uF.

If you need the available audio signal voltage from some weak sounds, you need a preamp. It unfortunately amplifies also the noise of mic's own electronics.

NOTE: This microphone is a low quality device. It's simply useless if you want to make low noise recordings of weak sounds such as non-shouting human speaking from several meters.

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  • \$\begingroup\$ If I were to wire the output of the microphone to a standard microphone jack and run it to my computer, could I use a program like audacity to record audio from the microphone? \$\endgroup\$
    – Zearia
    Dec 2, 2017 at 23:19
  • \$\begingroup\$ @Zearia. Yes if your soundcard records millivolt level signals. For example I have a soudcard that needs several hundreds of millivolts for full level input. For it this mic is useless without a preamp which has voltage gain at least say 30. Check, if your soundcard has an in-built mic preamp or level boost available. As I told, do not expect low noise when recording weak sounds. Speak from distances 0,5m or less can be ok. \$\endgroup\$
    – user136077
    Dec 2, 2017 at 23:28
  • \$\begingroup\$ Would it be possible to amplify the signal using an PNP 2N4403 BJT transistor? I happen to have one on hand. Would a simple common collector configuration work? \$\endgroup\$
    – Zearia
    Dec 2, 2017 at 23:32
  • \$\begingroup\$ @Zearia you can try common emmitter amplifier. Common collector amp do not provide voltage gain. an example: 78.media.tumblr.com/tumblr_lpmxdoQVUx1qf00w4.gif The component values probably aren't optimal. Even the voltage must be reverse because 2N4403 is PNP. Single transistor amp isn't low noise nor low distortion. \$\endgroup\$
    – user136077
    Dec 2, 2017 at 23:43

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