distortion measurement

[sangbui_palpro]

Hi,

I have a question about distortion measurement with Labview and NI's Analog DAQ modules.  My concern is between the manual measurement technique and Labview's automated technique.  When using a manual distortion meter, the source and measurement functions are included in the same instrument.  In the automated technique, the source and measurement functions are in separate instruments and the software combines the individual instruments into a virtual distortion meter.  Is this virtual distortion meter equivalent to the manual technique?  Is it really reliable and accurate (since source and destination are different)?

Thanks.

Palpro

[johnsold]

It is not really a question of the source and measurement being in the same box. It is a question of the quality of the instruments. For either kind of system you need to get the answers to questions like these:

Is the distortion of the source much lower than the distortion of the device being tested? Are there non-distortion noise or spurious signals in the source output which will compromise the measurement? Is the dynamic range and noise floor of the measurement sytem good enough to give good results? Is the isolation between source and measurement good enough to avoid problems? How will you suppress the source signals to measure the distortion components?

Lynn