5
3.4 Exam/Plot
The EXAM/PLOT key toggles between two modes of operation. In the plot mode, the
screen is periodically updated with the results of a new measurement. The exam mode
freezes the display, and adds a frequency cursor. The cursor shifts left or right by pressing
the FREQ arrow keys. The plot data values under the cursor are displayed numerically on
the left edge of the graph. Holding the FREQ key will gradually accelerate the cursor
movement, while individual FREQ key presses move the cursor in single pixel steps.
When the VIA Bravo MRI calibrates itself, it sweeps a bandwidth that is twice a large as
the display. This will allow you to do panning operations in the exam mode without triggering
a new calibration cycle. This expanded calibration width improves operator convenience
when panning, especially when using the cable null feature. To avoid excessive calibration
cycles, only press the FREQ key while in exam mode, pressing the FREQ key in the plot
mode forces a new calibration.
If you press the ENTER key during exam mode, the cursor will pop back to the original
center frequency position. When you press the EXAM/PLOT key, the cursor position
determines the new center frequency, and you will be back in plot mode.
If you pan far enough, you will notice that the graph truncates. The truncation occurs at
the edge of the calibrated frequencies. If you wish to remove the truncation, you must force a
new calibration cycle. One way to do this is to just enter a new center frequency (paragraph
3.1). Other ways to force a calibration cycle are to press the FREQ or WIDTH arrow keys
while in the plot mode (paragraphs 3.2 or 3.3).
EXAMPLE: Once you press the EXAM/PLOT key, the cursor comes up. Press the
FREQ down key until the cursor reaches the far left of the screen. Hitting EXAM/PLOT again
brings the unit back to PLOT mode with the new center frequency without recalibrating.
You can now hit EXAM/PLOT again and continue moving the cursor to the left.
3.5 Power On
The unit is powered up by pressing the ON key. Be sure that there are batteries installed
or the power pack is connected. The unit is configured with the settings that were in effect
when the OFF key was last pressed. If you ever want to start the VIA Bravo MRI with factory
preset values, hold the ENTER key while you power up the unit.
3.6 Power Off
To turn off the unit, press the OFF key. The settings (center freq, sweep width etc.) are
automatically saved to memory prior to turning off. These values will be recalled the next tine
you power on. If you power down by merely unplugging the power pack (not a good idea!),
the present settings will not be saved.
3.7 F1 Help Screen
The help screen displays an abbreviated overview of the function keys. This can be used
to figure out which menu something is located in without having to explore through the
menus.
Summary of Contents for VIA Bravo MRI
Page 1: ...MRI Network Analyzer MRI Network Analyzer 100KHz to 70 MHz ...
Page 42: ...38 NOTES ...
Page 43: ...39 NOTES ...
