Lambda SR1, Operation Manual, Page: 26 / 317

SR1 Operation Manual 26
© 2014 Stanford Research Systems
Select Analog THD Ratio A by double-clicking it. We're now ready to set up the graph to display our
sweep.
Return to Page 2 of the page control. In the trace listing panel at the bottom of the graph unclick the
Power Spectrum trace that we were looking at previously. Now use the "Plus" button at the top of the
display to add another trace to graph. This time open the "Sweep" node and select "THD Ratio A".
Select a log X-axis (to match the log sweep we just specified, and select dB as the Y-axis units with the
unit entry controls. Select a Y axis range from -95 to -10 dB. Now start the sweep by pressing the
"Sweep" button on the front panel. After a few seconds you'll see the results of the sweep:
This, of course, is exactly what we expect. At an amplitude of 100 uVrms, the THD+N is simply 20*log
(100 uV/1V) = -80 dB. At the other of the sweep the the THD+N is 20*log( .1V / 1V) = -20 dB.
This quick example only scratches the surface of SR1's capabilities, but should give you a feeling for
how the instrument operates.