Using the Distortion Meter and Spectrum Analyser for measuring signal distortion will give a definitive numerical value, but what does the distortion
look like? In the case of a sinusoidal waveform, is it clipping or crossover distortion for example. This needs to be known so one knows which part
of the circuit design needs closer inspection.
One can, as I often do, use a resistive network to sum an output signal to a reversed polarity input signal. However, it is a real pain adjusting the
two signals to balance to a null at the resistor centre point. Ah, you might say, use the differential inputs of the Oscilloscope to subtract the signals
and view the error. This has two gotchas. One being there is no variable Y gain on the Oscilloscope to finely null the two signals, the other problem
is there will more than likely a time/phase difference between the inputs, thus preventing complete cancellation.
For the above reasons, if the Distortion Analyser had an output which showed the residual signal upon which it’s distortion figure is measured,
I would be a very happy bunny.
Ooh, whilst I am here, if an NI MultiSim developer happens to have nothing to do for a day or two, could a variable gain be added the Y input attenuator
of the Oscilloscope? 🙂
Thanks,
Keith
Moved to CAR database: CAR 103295