Thermo Scientific Apex Service Manual page 108

Using the APEX Oscilloscope
8-6
Using the APEX Oscilloscope
Displayed are high-pass filtered X and R signals when a metal passes
thru the search head. X is larger indicating the metal's phase angle is
closer to 90 than zero degrees. (This signal is equivalent
approximately to a piece of ferrous metal about 1.0mm in diameter.)
Displayed below are high-pass filtered R and the Lo-pass signal. Note
the amplitude has lowered to 100 for better screen resolution.
It can be seen that the act of low-pass filtering does the following to
the signal: -
The top and bottom peaks are restored symmetrically about the
•
centerline i.e. they have equal magnitude – this can be important
for how we detect metal.
There is a delay between the high-pass R signal and the lo-pass
•
output.
Thermo Fisher Scientific
REC 4258 Rev C