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I want to measure for ex a battery 0.7V dc using a program like Visual Analyser/Soundtrack Oscilloscope/jDTF/Scope/xoscope. I connect the negative pole of the battery to sleeve and the pozitive to ring enter image description here

But I dont see any changes on soundtrack oscilloscope. I tested it with microphone on the same plug in and it was respondign to my voice, but when I plug in the dc voltage nothing is changed, there is only noise. Do you know what am I doing wrong?

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    \$\begingroup\$ Audio is AC, dc is blocked. You need to ac couple the signal. Have you looked up the recommended circuits for that software? \$\endgroup\$ – Passerby Feb 20 '16 at 17:32
  • \$\begingroup\$ PC mic inputs are often on stereo sockets, so you have and, left and right. Secondly, the mic input my well be AC coupled, so you won't see any signal from DC source. Thirdly 0.7V is too high for mic level, but OK for line level input ( also usually stereo and AC coupled). \$\endgroup\$ – user1582568 Feb 20 '16 at 17:34
  • \$\begingroup\$ I know the max volt is 5V to not damage the audio card \$\endgroup\$ – Jim Feb 20 '16 at 17:37
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    \$\begingroup\$ Do you understand the previous comments? There is a series capacitor on the input to your soundcard. You can not measure DC. \$\endgroup\$ – Transistor Feb 20 '16 at 17:43
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    \$\begingroup\$ What everyone is telling you is that there IS a capacitor inside the PC. You will not be able to measure DC on the PC audio channels. \$\endgroup\$ – mkeith Feb 20 '16 at 20:08
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There are differences, you can't get DC into a sound card as everybody is telling you. Hopefully you can see the differences here. Oscilloscope probes also have a much better bandwidth than a 3.5mm cable. The oscilloscope also has an "amplifier" to gain the signal.

schematic

simulate this circuit – Schematic created using CircuitLab

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