Using Audacity as an Oscilloscope

[djsfantasi]

Tony Stewart
Tony mentioned that Audacity on a PC could be used as an oscilloscope. I was wondering how you physically connected the probes to the PC.

Let's say for an example I want to probe a 5VDC (supplied by 9VDC) circuit; probe an Arduino Mega with an audio shield specifically?

This is a specific example that I have. But I'd like to generally know how to connect the two.

 

[Nigel Goodwin]

Tony Stewart
Tony mentioned that Audacity on a PC could be used as an oscilloscope. I was wondering how you physically connected the probes to the PC.

Let's say for an example I want to probe a 5VDC (supplied by 9VDC) circuit; probe an Arduino Mega with an audio shield specifically?

You most probably don't, as the sound card inputs are AC coupled - so no DC measurements.

 

[alec_t]

Because the PC sound card is used, only AC signals in the ~20Hz-20kHz range are measurable directly. Their amplitude must be at or below line level.
However, to monitor (slowly varying) DC you could use a voltage-to-frequency converter to drive the sound card.

 

[djsfantasi]

Great information guys.

I was going ask again about connecting 9VDC to a sound (1V) input. Then the import of alec_t's post hit me! I'll look into that interface a Googlic-ious search

 

[Tony Stewart]

make your own probe with 10:1 divider R ratio using an audio extension cable and stereo Jack.
Measure input resistance on AUX channel to choose series R. Some are DC connected.
If not , shunt with suitable Rp and add series R's for 10:1. Calibrate with 5V

e.g. 10K shunt 90k series for both channels. up to 100k, 900k

Change Windows Recording source to AUX enabled and Mic OFF