BERTHOLD TECHNOLOGIES LB 444, Operating Manual

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04/03
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LB 444
63
8.2 Radiating Interference Detection
Select the function Radiating interference ( Parameter menu, page 19) to suppress inter-
fering radiation (e.g. weld seam testing).
Caution:
When this function is on (Radiating Interference <ON>), the automatic switchover of the
time constant (function
Rapid switchover ) is always off.
When turning this function on, you have to define a
Sigma value which defines a window
for the measuring signal. If the detector signal suddenly exceeds this threshold,
• the measurement stops
• the error message “ Interference Radiation” appears on the display.
The measured value and the current outputs are held on the last value.
Reset the error message and start the measurement via the keyboard by confirming the
error message with < enter >; then start the measurement with < run > or externally via
the digital input.
Note:
Enter n > 5 to rule out false alarms with sufficient statistical safety. The mathematical
correlation shows that the distance from the alarm threshold is dependent upon the re-
spective mean pulse rate I
m
.
For calculation it holds: Sigma =
I s /
Example:
Count rate I
m
= 300 cps, n = 6
I
S
= I
m
+ n *
m
I
I
S
= 300 + 6 *
300
= 404 cps
Thus, an alarm is signaled as soon as I
S
exceeds the value of 404 cps.
Note:
Due to the dynamic behavior of radiating interfering detection, a quick increase of the
pulse rate due to operative factors (e.g. very fast emptying of the vessel or major short-
term density changes caused by stirrers) may be interpreted as interfering radiation.
For example, opening the active beam channel on the shielding can also cause a quick
increase of the pulse rate. You have to reset the alarm that is then triggered, or better,
do not enable radiating interfering detection at first. Enable radiating interfering detec-
tion only after calibration has been performed.