Lambda SR1, Operation Manual, Page: 261 / 317

SR1 Operation 261
© 2014 Stanford Research Systems
2.8.5 THD+N Panel
The THD+N Quick Measurment panel uses the Time Domain Detector to measure the THD+N (Total
Harmonic Distortion plus Noise) of the EUT. In free-run mode the measurement displays the
instantaneous THD+N of the EUT at a single frequency and amplitude, in addtion the source can be
swept over frequency and amplitude to yield the THD+N vs. frequency of the EUT for a range of input
amplitudes.
Cabling Configuration
The output of SR1's analog or digital generator is connected to the EUT's input. The output of the EUT is
connected to SR1's analog or digital inputs. The number of inputs and outputs and the connectors used
are specified in the
Setup Panel .
Generator Configuration
The output waveform is set to either Sine or Low Distortion Sine as specified in the panel. For THD+N
values below about -90 dB use the Low Distortion sine. For free-run operation the amplitude and
frequency of the generator is set to the frequency and level in the "start" column of the panel. For swept
operation the frequency is swept from the start to stop value for each amplitude value specified.
Analyzer Configuration
One or both analyzers (depending on the number of output channels specified in the Setup Panel ) are
configured as Time Domain Detectors . The upper and lower bandwdith limits are adjustable in the
"Analysis" section of the panel. The THD+N can either be displayed as the absolute amplitude of the
noise plus distortion, or the
Free Run Configuration
A barchart display is created for each output channel showing the instantaneous THD+N of the EUT.
Sweep Configuration
A graph will be created for each channel showing a graph of THD+N vs. Freq for the selected range of
amplitudess. Log spacing can be selected for both the frequency and amplitude sweeps. The settling
parameters of the THD+N measurement can be adjusted directly from the "Settling" tab of the panel.