Lambda SR1, Руководство по эксплуатации, Страница: 77 / 317

SR1 Operation 77
© 2014 Stanford Research Systems
Input Configuration: Coupling
DC DC coupling of the analog inputs.
AC AC coupling of the analog inputs with ~1.7 Hz corner frequency.
To the left of the controls for each channel is the visual level indicator for that channel. The blue led
glows when the input level is below approximately half-scale. The green led glows when the input level is
between half scale and full scale, and the red led glows when the input exceeds full scale. If the red led
glows continuously then the signal either exceeds the input range of the instrument, or in the case of no
autoranging, the range needs to be manually adjusted. Note that the input level indicators are also
displayed at the bottom of SR1's main window so that they are visible even when the Analog Inputs
Panel is not displayed.
ChA ChB
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Analog Level Indicators
When a potentially damaging high voltage is detected at the input SR1 automatically switches the input
range to the largest possible value (160 Vrms) and removes any termination resistors selected by the
user in order to protect the instrument. If this occurs, the input voltage range will be shown in red as
shown below:
Remove the input and reset the range manually to restore normal operation.
Hi-Res Converter Sampling Rate Selection
The second tab of the Analog Input Panel contains a single control to select the sampling rate of the Hi-
Resolution ADC. SR1's analyzers use two different high-quality audio ADC's— the 16-bit "high-
bandwidth" converter operating at a fixed sampling rate of 512 kHz, and the 24-bit "high-resolution"
converter which can operate at a variety of sampling rates
Analog Inputs: Hi-Resolution Converter Sampling Rate
128 kHz The converter runs at a fixed 128 kHz sampling rate.
64 kHz The converter runs at a fixed 64 kHz sampling rate.
Digital OSR The converter runs at the Digital Audio Output Sampling rate that is set in the
Digital I/O panel.
Digital OSRx2 The converter runs at twice the Digital Audio Output Sampling rate that is set in
the
Digital I/O panel.
The last two settings are useful for making cross-domain measurements of D/A converters using FFT
Chirp or Multitone signals where the stimulus is generated in the digital domain but the measured signal
is in the analog domain. Using Digital OSR or Digital OSRx2 as the converter sample rate maintains
synchronicity between the generator and the analyzer.