my colleague and me have hit a brick wall - and are hoping somebody can help us out here :)
Following scenario: We record some data using a computer with an NI card and some signal transducers. We need to record audio from a mic of an headset synchronously. First thought: Build a patch cabel for the headset. Measuring the mic signal to GND - no problem. However, the signal is offset by about 2.65V. My guess this is the necessary voltage for an electret microfone.
To get rid of the offset we then thought to measure the voltage between supply and mic signal. However the difference is 0 - a look with an oscilloscope confirmed that. Can anybody help explain, why supply as well as mic signal on a headset carry the signal information?