Signal Generator Noise

[Testman]

Signal Generator Noise

When viewing a sine wave output from the signal generator on a separate dedicated o-scope I notice a significant amount of high frequency noise imposed on the waveform. I also notice that the spectrum analyzer displays peaks at non harmonic frequencies of the signal generator output e.g. 1.5 KHz for a 1 KHz output. I don't see either of these results if I input a signal to my sound card from a separate signal generator. I am using the default THD settings. Are these findings anomalous? Can you suggest a cause and/or solution?

bonfis
Post at 12-6-2012 10:36

Yes, it is anomalous. It looks like a sound card hardware problem. Have you tried the software on another sound card?

virtins
Post at 22-6-2012 00:03

Just did today. Results are identical. Both sound cards show the same noise riding the sine wave. One card is an external EMU 0202 USB and the other a Turtle Beach PCI card. If its a hardware problem it's not in the sound card.

bonfis
Post at 4-7-2012 22:35

Another two possible causes of noise could be (1) the connection cable (2) How you connect the ground lead?
virtins
Post at 10-7-2012 09:31

The connection cables have been switch without any change in the noise. The scope connects directly to sound card output via a direct or X10 probe. No difference noted between the X10 and X1 probe settings. The probe ground connects to the sound card output cable shield.

bonfis
Post at 4-8-2012 08:31

[brian_mk]

This appears a similar issue to the problem I recently reported under 'Soundcard Spurious Signals'.
In my case, the spurious frequency peaks for a 1kHz input signal are not the same.

My results were similar on two different PCs with two different sound cards (one PCI, the other USB).
I also found changing cable and earthing arrangements made no difference.

Was this problem ever resolved?

[VirtinsTech]

Could you please post a screenshot showing the problem?