#413 Your PC Soundcard is an Oscilloscope, a Signal Generator, and a Spectrum Analyzer (Arta, REW)

Oscilloscopes and signal generators are handy tools in our labs. Unfortunately, they are not cheap. What if you had such devices already and did not know?
All newer PCs have loudspeakers and a microphone. So they can create sound as well as record it. And usually in decent quality. Like oscilloscopes and signal generators! We only need a connection and software to create the desired waveforms and visualize the measured voltages. Fortunately, such software is available. And the best: We can use it free of charge!
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[Chiavaloni]

I use to work with sound cards as spectrum analyzer, since about 13 or 15 yrs ago, analysing engine knock sensor signals, while I tune the ignition advance time. Because the frequency of engine knock depends only on the piston bore diameter, and it's perfectly human audible, sound cards are perfect to use. And I can measure two channels at same time: engine phase and the knock sensor. So I can detect what's the real knock, in what cylinder(s) from some other noises like a bad adjusted valves, huge piston clearances and other engine noises. The other way is to use a simple audio amp and listen the signal generated by the sensor. It's obvious the hard way. Very hard.

[IoTT]

Nice video and brings up some memories of the past. Back in 1997 I used a PC sound card to decode the DCC track signal of my model railroad and display the commands that are coming along the track in real time. The DCC signal is a pulse width modulated square wave with a maximum bit rate of about 16kbps, so it was quite easy to decode with 44.kHz sampling. As interface I used a resistor in each wire to the track and two antiparallel diodes to limit the input voltage on the microphone input. Software was written in Borland Pascal for Windows, running on a 486 with Windows 3.1. Tempi passati ;-)

[uwezimmermann]

the "loss" of your low-pass filter only comes from the limited low input impedance of your sound card. You can easily check it by using a filter with 1 kΩ and 160 nF. A passive RC-filter is lossless in the passband if driving a high-impedance input.

[ChrisDreher]

Nicely done! I figured that this was possible back in the late 1990's but never found the time to explore using a sound card as an oscilloscope. It's great that other folks had the same idea but actually put in the time to bring it to reality.

[jthrush]

It is pretty easy to bypass the capacitor near the input or output jack on the soundcard to be able to input/output DC signals as well. I've done this both for using audio input as an oscilloscope, and for using the output as a signal generator for a laser galvanometer and it worked great for both.

[priyabratasadhukhan]

I use a similar software (soundcard oscilloscope), its very easy and gives real oscilloscope like interface. I also use two silicon diodes (one forward, one reverse biased) in parallel to the potentiometer on the input signal and ground wire to bypass any AC voltage greater than 700 mV. It saves the soundcard from any accidental over voltage when the potentiometer is not correctly set.

[robertcruz]

Yet another useful AND interesting video. Once again, you've saved me a week of research :-) Thank You!

[thorntontarr]

A deep dive into existing 'stuff' right under my nose; presented fully as always. Amazing what free software is 'out there' as you show. A very helpful video. I, of course, have a wonderful oscilloscope but didn't even think I had one in my PC. Very enlightening.

[reinholdu]

Nice one Andreas. If you learn something (which we may already know) it's (still) _your great way of presentation_ that makes it fun ... *Love That* 😘👍

[gdj]

I just remembered this one !

If the software has a audio analyser but you can't inject a sweeping signal .
Try a simple wight noise generator injected into the amp .
You will see the passband response on the analyser .

It has limited uses with RF also, tune for maximum noise or work from a good audio stage into the radio / unit / DUT .
Like passing a 100 khz square wave ( & overtones ) through a radio receiver .

Old tricks we used when all we had was time, a box of scrap, war surplus & brass screws !

[martin_mue]

My lab cat is very fascinated by todays presentation because of all those moving cursors :-)

[-bit]

This week ive learned about how SDR works with your dual channel sound card thanks for this video!

[PhG]

Excellent video and a very good introduction to sound cards and their benefits to signal processing. It's also a trip down memory lane... Many years ago (Pentium 3 and 4 era) I used a sound card to decode/encode tone signals in combination with radio equipment (CTCSS, SelCall tone sets like EEA, ZVEI I etc...). What a wonderfull time...

[CircsC]

White gloves and the tophat always make your videos feel special. It's like you're about to show us diamonds and artifacts. So classy!

Also thank you for this. I've needed a way to analyze signals without a scope.

[sdjhgfkshfswdfhskljh]

Easiest thing to experiment with - is to connect transparent diode to line input.
Now you will be able to receive IR signals from remote controls.
If you write corresponding software of course :)

[tonysfun]

Well done again Andreas! I was using something similar few years ago and not just on PC, but also using a tablet! It was working well, for what it is and mainly I had fun with it and so did my friends, for whom I made the cables for. Also old phones can be used to play with this kind of stuff, since the phone is old and not in use! I'm a Tracfone user so every year I get a new phone and my wife also, so at least 2 phones per year are dedicated for all kinds of projects, including Mooshimeter, Pokit Meter and few of my regular meters that have Bluetooth built in for remote measuring. Thank you again Andreas!

[-bit]

I love how the sweep test just randomly interferes with the talking 😂

[ThalassTKynn]

I actually did this years ago with my little netbook when I was putting a new stereo in my mum's car. I don't remember the programs I used but it was very handy to identify which wires went to which speakers.

[Iosens]

Thank you Andreas. And thank you for not following the "Make a stupid shocked face thumbnail" trend on You tube!

[jotapi]

Wonderful! That's going to be great stuff for experiments with my 12 yo in the workshop 👍