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Gamma radiation emitted from a shielded source travels through the vessel at the set height to a detector. When product level enters the beam path, the radiation is significantly weakened or totally bloked so that the amount of gamma at the detector suddenly drops. This change in counts per second at the detector results in the detector switching a relay or a sudden change in the 4-20 mA output. When used as a low level switch, the detector normally sees no counts from the source, and triggers the relay or changes the 4-20 mA output when level drops below the source and it suddenly sees many counts from the source.
Temperature, pressure, dust, colour, and chemical properties of the product have no influence on the outcome of the measurement. Consequently this results in the high reliability and low maintenance of the radiometric measurement systems, even under harsh operating and environmental conditions.
Our highly sensitive detectors achieve a better measuring effect and operate with remarkably low source activities. Depending on the application the source activity can be reduced by up to 80%.
The patented method for detector stabilisation ensures a consistent measurement performance, reliably compensating temperature and aging effects. If these go unnoticed and are not compensated, they can cause considerable loss in production yields and product quality suffers.
Cosmic radiation control also makes it possible to keep the required source activity very low. Only Berthold can offer a SIL 2/3 detector certified for either high or low level switching, the LB480.
The LB 480 SpeedStar version detector is used when very fast process changes must be monitored. The SpeedStar feature ensures extremely fast response times in the millisecond range. This feature is used when monitoring steel plate edge in order to straighten the cut edges while the plate is being transported on a roller conveyor, or to position glowing and scorching steel blocks. It is also used to detect over or under-filled liquid containers, e.g. gas tanks, while they are being conveyed.
With this function, weld tests will no longer cause false low level signals. The counts per second of gamma received at the detector is monitored, and when there is a sudden jump above the counts seen from the source, the measured value is frozen until the external radiation influence is over. A digital output signals the detection of interfering radiation. All our level measurements are equipped with XIP.
Berthold has published the whitepaper “Radiometric Measurements – Accuracy, repeatability and errors”, wherein the radiometric measurements are explained and how your process can be performed with highest accuracy and reproducibility and the error sources can be minimized. The paper explains the nature and causes of these errors, and identifies solutions where these errors can be suppressed through the application of „best practices“ and proper design.
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