I am currently making oscilloscope from my soundcard, which can measure the voltage of about 5V. What is the easiest way to know whether my scope works or not? I don't have access to low voltage AC sources. Can I use an electric motor/generator to generate some signal?
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1\$\begingroup\$ Since you're already using a sound card, can't you use that to generate some test waveforms? (-: \$\endgroup\$– Richard the SpacecatCommented Jul 15, 2019 at 9:24
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\$\begingroup\$ @RichardtheSpacecat Good idea. I haven't thought of that. Can I just connect the probes to three terminals of a TRS audio plug to see what happens? \$\endgroup\$– JethroCommented Jul 15, 2019 at 9:27
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\$\begingroup\$ I guess so, the tip and ring should have audio on them (that said, it'll probably be line-level, that is something around and up to 1Vrms (shush, pedants)). The sleeve should is most likely internally connected to the same ground as the line in's. For a quick test you needn't connect those and only poke at the tip/ring. That said, I don't know what monstrous circuitry you've devised for this, so I suppose you should know best. :D \$\endgroup\$– Richard the SpacecatCommented Jul 15, 2019 at 9:34
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3 Answers
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Either you use the output of the soundcard, or you plug in your smartphone as a frequency generator. If you use android, there is an app called "simple tone generator". You can use that to apply the frequencies you want to your osci.
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The easiest way is to touch the input with your finger. You'll see volts of mains hum if the input is a high impedance, less but still plenty to see if it's a lower input impedance.
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Use an audio signal source like a radio or a mp3 player. somethng that requires interaction to produce a signal (like a motor) may prove inconvenient.
but if all you have is a motor and some batteries put a resistor in series with the motor (about 1-10 ohms) and power the pair, scope the voltage across the resistor, there should be some ripples there that vary with the speed of the motor.
answered Jul 16, 2019 at 9:22