Foerster 6.453, Operating Instructions Manual

Page: 20 / 67

SENSORSYSTEM Ro 130
2.3 Construction DESCRIPTION
2-6
6.453 – 01/2006
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.
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 testing speed.
The following table shows these relationships and gives typical examples
for a practical selection:
Maximum testing speed Test head type
n = 1,500 rpm
n = 3,000 rpm
Number / Track
width TH / BS
Bright material
Fe - Nfe - Aust
rough rolled
Fe
Decreasing
sensitivity to short
flaws
0.25 m/s
0.5 m/s
2 TH / 2 x 2.5 mm 6.453.01-2311 6.453.03-2311
0.5 m/s
1.0 m/s
2 TH / 2 x 5.0 mm 6.453.01-2321 6.453.03-2321
1.0 m/s
2.0 m/s
2 TH / 2 x 10 mm 6.453.01-2331 6.453.03-2331
Tab. 2.1 Test head selection
Rotating disc with test heads
probe
Test
head