13
EDDYSENSOR Operating Manual
Filtering
There are three filters available. The application dictates which filter is
required.
The F1 (40 dB/decade) and F2 (20 dB/decade) filters for this module consist
of a variable low pass and high pass filter which combine to provide varia-
ble 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 has two optional speed ranges, 1 - 60 m/
min and 30 - 1000 m/min. (See the section
Filter settings for F3
below.)
No testing can be carried out while the filters are being set.
The filters F1 and F2 are set using the Gain switch on the front module
(see module diagrams on previous page). By pressing the Gain switch
continuously in the default Gain mode (for at least one second) and re-
leasing it again, the display first shows the high pass setting followed by
the low pass setting before returning to the gain setting. For each filter,
there are 20 filter settings available. The divisions correspond to approx. 8
steps per decade. The high pass setting and the low pass setting to-
gether form the required band pass filter. The settings required for a spe-
cific line speed are given in the following table. The filter settings, like the
gain, are permanently stored after being set up.
Filter settings for F1 and F2
Please note
