Stanford Research Systems DS345, Manual

Page: 37 / 139

Modulation and Sweeps
2-21
Marker Center and Span
The markers may also be set by the center frequency and span (width) of the
marked region. Pressing [SHIFT][MRK CF] and [SHIFT][MRK SPAN] respec-
tively sets the center frequency and span. The center frequency may have
any value from 1
µ
Hz to 30.2 MHz range. The span may be any value such
that the marker frequencies are greater than zero and less than or equal to
30.2 MHz. If the span is positive the marker start position will be below the
stop position, while if the span is negative the marker start position will be
greater than the stop position. If the MODIFY keys are used to change the
span- pressing [MODIFY UP] will double the span, and pressing [MODIFY
DOWN] will divide the span in half. When the center frequency is changed
the span is held constant, while changing the span holds the center frequen-
cy constant. If the center frequency or span is changed such that the marker
frequencies are out of the allowed range an error will be displayed.
Marker to Span
Pressing [SHIFT][MRK=SPAN] sets the positions of the markers to the ex-
tremes of the sweep span. The marker start frequency will be set to the
sweep start frequency, and the marker stop frequency will be set to the
sweep stop frequency. This function is useful for finding the markers when
setting up a sweep.
Span to Marker
Press [SHIFT][SPAN=MRK] to set the sweep span to the marker positions.
Now the sweep start frequency will be set to the marker start frequency, and
the sweep stop frequency will be set to the marker stop frequency. This func-
tion can be used to "zoom in" on a marked section of the sweep. If this func-
tion sets the sweep frequencies to a value not allowed for the selected wave-
form, an error will be generated and the sweep disabled.
SWEEP OUTPUT
The rear-panel SWEEP output is a 0–10 V analog output that ramps linearly
during a sweep. The output voltage is 0V at the sweep start frequency, and
10V at the sweep stop frequency (during TRIANGLE sweeps the SWEEP
output will go from 0V to 10V to 0V). This output may be used to drive a chart
recorder or x-y oscilloscope.
BLANK/LIFT OUTPUT
This is a TTL compatible output that is low during the upsweep of a sweep
and high during the during the downsweep or sweep reset. This output may
be used to blank the retrace of an x-y oscilloscope, or lift the pen on a chart
recorder.
0V
10V
Sweep Output
Blank/Lift Output
RAMP and SINGLE Sweep
0V
10V
Sweep Output
Blank/Lift Output
TRIANGLE Sweep
Figure 2: Auxilliary output waveforms
during different types of sweeps.