Lambda SR1, Operation Manual, Page: 148 / 317

SR1 Operation Manual 148
© 2014 Stanford Research Systems
The FFT2 Analyzer Panel
Because both the A and B inputs of the selected input domain are always used by the FFT2 analyzer
the Source selection for FFT only offers the choice of "Analog" or "Digital". The "Converter" and "Fs"
controls are common to all
analyzers . Like the FFT1 analyzer, the levels displayed on the FFT2 analyzer
panel are peak-based levels, not RMS levels. (Remember, the units the levels may be displayed in are
independent of the method of computation.) Because the FFT2 analyzer needs to take time to compute
FFTs, the continuous input data stream necessary to compute RMS levels is not be available. Likewise,
the fact that continuous data is unavailable means that the A-B phase computation, which also requires
continuous input data, is not available for the FFT2 analyzer. Frequency data is available for analog
inputs (which use a hardware-based frequency measurement technique) but not for digital audio inputs.
Bandwidth
The maximum bandwidth of the FFT is 1/2 of the sampling rate for the selected input source. To
instantly switch to full bandwidth, click the "Baseband" button. The "Zoom" feature of the FFT2 analyzer
allows selection of narrower bandwidths, in factor of 2 increments, as well. When the bandwidth is
decreased, the effective sampling rate is decreased and therefore the amount of time necessary to