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?
Best Answer
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.