4
EDDYSENSOR Operating Manual
Filtering
There are three filters available for the EDDYSENSOR. The application
dictates which filter is required.
The F1 and F2 filters for this module consist of a variable low pass and high
pass filter which combine to provide variable band pass filters. Because the
coils and their sensing widths are known we can calculate the filter range
in speed as this is more appropriate in practice than Hz. The filters can be
set very close to the testing speed – however, defects which occur outside
this speed range are damped or suppressed. In applications where the test
piece is brought up to its final speed over a longer time period, the filter has
to be set relatively wide in order not to damp or suppress signals which
occur in the acceleration phase.
F3 is a fixed bandwidth filter that can be switched between the two speed
ranges, 1 - 60 m/min and 30 - 1000 m/min.
The filters are selected by turning the hex switches on the printed circuit
board of the front module (see diagrams below and on next page).
The only switch active for filter F3 is HPL as shown in the diagram below.
There are two positions of HPL that can be selected according to the line
speed:
HPL = 0 for the speed range 1 - 60 m/min
HPL = 1 for the speed range 30 - 1000 m/min.
Filter setting
F3 filter
PCB
Side view of the printed
circuit board (PCB)
Front panel
These switches are not
used for the F3 filter
For 1 - 60 m/min, set HPL=0
For 30 - 1000 m/min, set HPL=1