© PCE Instruments
26
Eng
li
s
h
8. "
FILTER" - Filter type: Averaging, Differential, Low-pass, High-
pass, Bandpass;
Filters setup is carried out for the channel Frequency 1 and
Frequency 2.
Averaging Filter
Switching on of the averaging filter "Avrg" sets a number of points N
to be averaged from 2 to 127 points with a step of 1, 10, 100 points.
Can be used when working with high gains and scales to reduce
noise signal by smoothing it.
Differential Filter
Switching on of a differential filter “Diff” activates its settings, where L
– filter depth, set in the range from 2 to 127 units with a step of 1, 10,
100.
Low-Pass Filter
Switching on of a low-pass filter activates the field for setting up the
frequency LF from 1 to 4000 Hz with a step of 1, 10, 100, 1000 Hz.
The frequencies from 0 Hz to the set value of Hz are allowed.
The low-pass filter is used to reduce the noise respectively high-
frequency non-essential signal components by displaying only those
signals whose alternating frequency is lower (i. e. slower) than the
frequency of the selected low-pass filter. Since electronic noise is
usually caused by high- frequency signals, the noise on the screen is
lower, if the frequency of the low-pass filter is set low, too.
The low-pass filter is used for static applications (usually with hand-
held probes).
It is important that the low-pass filter is not too low, because defect
signals are not displayed anymore, if you move the probe across the
crack at a speed that is too high with regards to the filter frequency.
If for example you move the probe very slowly across the crack, then
the dot slowly tracks the full defect signal at a low-pass frequency of
10 Hz. If, one the other hand, you move the probe across the crack
more quickly at the same low-pass frequency, you will see only a
small amplitude on the screen. This happens because the frequency
of the signals is now too high for the low-pass filter frequency you
selected.
If, however, you increase the low-pass filter frequency, the full
amplitude of the defect signal is displayed, i. e. the higher the test
speed the higher the frequency of the low-pass filter to be selected.
Since differential probes generate a dual signal that changes more
quickly than that of an absolute probe at the same speed, you
