Foerster 6.461.21, Руководство по эксплуатации

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SENSOR SYSTEM Ro 35 L
2.3 Construction DESCRIPTION
2-6
6.461.21 - 2008/06
2.3.1 Test Heads
The test heads are both the heart of the sensor system and its most criti-
cal components.
They consist of an eddy-current probe with field, measuring and clear-
ance windings which are installed in a precise mechanical holder and are
connected by means of a highly flexible special cable with a connection
plug.
Due to high centrifugal forces (acceleration up to 4,500 g!) and the rough
environmental conditions at the testing location, the probes are protected
by a ceramic armor, nevertheless replacement of probes is possible.
As already mentioned in the ‘Mode of operation’ section, there is a
mathematical relationship between the number and track width of the test
heads, the rotational speed and the test speed.
The following table shows these relationships and gives typical examples
for a practical selection:
Maximum test speed
[m/s]
Decreasing
sensitivity to short
flaws
Track width BS
[mm]
Test head type
0.75
1.5
2.5
6.461.21-2025
1.5
3.0
5.0
6.461.21-2050
n = 4,500 rpm
n = 9,000 rpm
Tab. 2.1 Test head selection
Rotating disc with test heads
Probe
Test
head