Roland R4000 Manual page 24

System description
The following example shows a signal level of 0,47V and a noise level of 0,2 V:
Noise level = 0,2 V
Fig. 5: Details of dB-value
Thus a signal-to-noise ratio of 2.35 (0.47 V/0.2 V) results, which equals 7.4 dB.
So the detection grade threshold for class "good" has been reached. This tube will not be sorted
out.
2.6.1 Effect of weld seam width on detecting capability
This example makes it easy to understand what would happen if the weld seam width was
reduced. With a 50% width the noise level would rise considerably, since the intersective point then
rises with the signal.
Here the signal-to-noise ratio would be below 2. Thus the detection grade threshold for class
"good" could no longer be reached – the tube would be sorted out (when class "good" is set).
The smaller the weld seam width is chosen, the harder it is to reach the detection grade threshold
for class "good".
But the setting of the weld seam width also affects the positioning accuracy.
A signal peak being almost as large could very well represent the real weld seam and could thus
be undetected as weld seam. But if the weld seam zone becomes decreased, the possibility
increases that this signal (which is almost as large) will fall into the noise zone. If this happens, the
detection grade threshold will no longer be exceeded – the tube will be sorted-out.
Thus the possibility of incorrect positioning will be reduced.
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ROLAND ELECTRONIC GmbH · Otto-Maurer-Str. 17 · DE 75210 Keltern · Phone +49 (0)7236-9392-0 · Fax +49 (0)7236-9392-33
Weld Seam Detection System R4000 SND40
for Tubes, Cans and Drums
Weld seam width (-)
Rule: small weld seam – high positioning accuracy.
This coheres with the fact that the likelihood of having similar peaks to those
of a weld in this area decreases.
Summary: High detection reliability when:
− Detection grade threshold "good", "extra" or "ultra"
− Weld seam width "as small as possible"
Manual
Weld seam width (+)
B0059001 / Rev. 2.3