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Chapter 5, FRONT PANEL OPERATION
figure 5-45.
Manual Setup
If the semi-automatic setup method does not work because the signal requires a time
constant longer than 100 ms then the initial search can be performed manually. This
can be done using the controls on the right-hand side of the display, and the Start
Frequency control on the left-hand side.
The controls operate as follows:-
TIME CONSTANT
This control sets the instrument's output time constant.
SENSITIVITY
This control should be set so that the amplitude of the expected signal will be at least
50% of full-scale. For example, if the signal is expected to be about 10 µV then set
the full-scale sensitivity to be either 5 µV or 10 µV.
NOTE: If the full-scale sensitivity is set so that the signal is less than 50% full-
scale then it will not be found.
START FREQUENCY
Once the Time Constant and Sensitivity Controls have been set to suitable values,
the Start Frequency control should be slowly adjusted from below the expected
signal frequency, until the Magnitude display reads in excess of 50%. The easiest
way to do this is by using the active cursor control to place a cursor under an
appropriate digit of the Start Frequency display and then using the
control to
adjust the frequency.
MAGNITUDE
This displays the present signal magnitude as a percentage of the set full-scale
sensitivity.
VIRTUAL LOCK
When the instrument's internal oscillator and full-scale sensitivity are set so that the
signal is measured as 50% of full-scale or greater, then pressing this key enters the
virtual reference mode, and the Main Display - Virtual Reference Mode appears, as
shown in figure 5-44.
5-57
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