Zero price oscilloscope using the computer's sound device

[ayeaye]

I had to try it better but, i'm too lazy. So i tried this saving in xoscope, with microphone only. It looks like that what is on the screen at the moment, can be stored into "memories", like from menu   channel -> store -> mem c . Then when saving into a file, that file is quite simple. It starts with some information about the sampling rate, etc.

But what follows, are just columns of numbers, looks like one for every channel, and "memory". It looks like that it has 45 samples per screen, not clear why 45, 50 did make sense, but it seems to have 45. So there are 45 rows, in each several numbers ("columns") separated by tabs. Numbers are integers, all appeared to be less than 100, not sure how many vertically.

Anyway, this is a very easy format, no problem to read it with python, to do calculations. Instead of the rather cryptic way how it does calculations using perl. I have not tried it yet, but, selecting a channel that is not used, and pressing $, enables to calculate a trace for that channel. It has functions for perl for that, like a perl script can be called by $, to do calculations. There is some example of such script. And this script most likely also enables to write some output to terminal, such as power. So calculations can be done in that way, but as i said it's rather cryptic. But then calculations can also be easily done by reading the saved file with a python script. So no matter what way, calculations can be done.

It looks like $ enables to enter a perl expression, and  cannel -> math -> external command  enables to run a perl script. Who tries it out may write here how to do it.

So, how much i figure so far. operl.in is the perl script (filter) that is run when entering a function, that may be an expression, with $. External command could be the same, a user script instead of operl.in. To that external script, the samples of the channels 1 and 2 are given in an input stream number 3, calculated samples are written into the standard output stream. The function is supplied in the environment variable FUNC, as a string. As the standard output stream is taken, it is possible to write to terminal by writing to the standard error stream, or write to a file. And there is nothing more to it. Thus, these scripts can also be written in python instead of perl.

Just to give you some idea.

[ayeaye]

If you want to make it adjustable, replace the 100 ohm resistors with 100 ohm trimmers or potentiometers, as below. Then though the the resistances of the trimmers have to be measured every time after adjusting, to calculate the voltages.

About these, two opposite diodes in parallel, this can be used for protection, but then there has to be a low pass filter before, to filter out short voltage spikes, otherwise these are useless for protection. And in several widely known circuits there is no such filter at all. With that filter, it should protect well, but 1 volt or such is still a too high voltage for the microphone input, there still has to be some 100:1 voltage divider after such diodes.

The voltage on the microphone input is very low, usually maybe some 5 mV.