Thermo Scientific Apex Service Manual page 110

Using the APEX Oscilloscope
Metal has passed thru the aperture and the final part of the signal (to
the left of the vertical dotted-line) is about to overwrite the older data
on the right hand side of the vertical dotted line. In other words, the
dotted line indicates both the beginning of the signal and the end of the
signal. It is important to show this so that signal analysis mistakes are
not made.
Next is the use of the trigger facility. Go to the Config screen and set it
up like below: -
The important point to note is that channel 1 and 2 are set as previous
when looking at the delay and symmetry restoration of the low pass
filter, the time base is back to 2 seconds and the trigger source is set to
detection.
Now press ENTER to return to the scope display. What you'll see is
this:
Note the trigger information contained in the lower right block.
Previously it said "FREE" meaning the scope traces were free-running
and cycling continuously. Now it indicates that it is waiting for a
metal-detection. Pass a piece of metal thru the search head and you
will see trigger information registering the detection and then
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Using the APEX Oscilloscope Thermo Fisher Scientific
REC 4258 Rev C