Re: Comparison of laptop audio output and function generator

On Sep 27, 9:03 am, NoS...@xxxxxxxxxxx (Bob Masta) wrote:
On Wed, 26 Sep 2007 11:32:19 -0700, MRW <mr.whate...@xxxxxxxxx> wrote:
I am experimenting with an Instek oscilloscope. I have two sources.
One is an audio output from the laptop, and another one is a tone
output from a function generator.

This is a video of the laptop output:
http://video.google.com/videoplay?docid=-8413182111152350269&hl=en

This is video of the function generator output:
http://video.google.com/videoplay?docid=-3995690077431458348&hl=en

I just terminate the sources to a 1k-ohm resistor and put the
oscilloscope probes across the resistor.

Are laptop audio outputs really that "poppy" (intermittent signal
spikes)?

When I plug in a headphone to the output jack of the laptop, the tone
sounds clean. I was expecting to hear tiny pops.

If I were to take the laptop audio signal and re-route it to a
different circuit, how would I make the waveform "cleaner" like the
one from the function generator output?

I'm afraid that if I take the audio output of the laptop and connect
it to an amplifier, then the spikes will also get amplified and become
noticeable.

Sorry, I can't view your example (dial-up connection too slow!).
However, even the crappiest laptop chipset should not have
intermittent signal spikes. This sounds (no pun intended) like a
software problem. Is the software trying to generate a signal by
simply playing one cycle over and over?

You are welcome to download Daqarta for Windows and
use the built-in signal generator. If you still have problems,
(though I'm betting you won't) *then* you can blame the sound card.
The Daqarta generator is free to use forever... no need to
purchase if you don't need to monitor input signals.

A new version with lots of improvements and bug fixes is
going to be released Monday (I hope!), but if you can't
wait you can install the current version now and the new
one will install easily over it. One of the problems with the
current version is that many users say it immediately reports that the
trial period is expired, so you can't try the input functions.
That won't affect your using the function generator,
but it will prevent you from using the built-in auto-calibration
system to calibrate the sound card attenuators. You should
do that with the new version before the trial expires, and
the calibration will be retained.

Enjoy!

Bob Masta

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Signal Generator
Science with your sound card!


Hi Bob,

I'm actually using DAQARTA to generate the tones from the laptop. :-)
I'm using an older version, though.

I'll see if I can take a picture of the signal when I have access to
the oscilloscope again.

Thanks!

.

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