Main Display - Virtual Reference Mode - Ametek 7280 Instruction Manual

Chapter 5, FRONT PANEL OPERATION

5.4.02 Main Display - Virtual Reference Mode

5-56
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
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 5-34.
Figure 5-36, Main Display - Virtual Reference Mode
In virtual reference mode, the instrument operates exactly as in single reference
mode, with the following exceptions:-
The Main Display always shows the annotation "Virtual Reference Mode" in the
bottom right-hand section of the display as a warning to the user that this mode is
being used.
Although the upper three display positions can be reconfigured to display magnitude
and/or phase information, neither of these is relevant since there is no reference
signal to which the phase can be related, and the magnitude equals the X channel
output. Similarly, controls affecting the instrument's reference phase, such as Ref
control to adjust the