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The LB444 density meter is used for contactless, continuous measurement of liquids or bulk materials in pipes and vessels. It can be easily installed on existing pipelines without downtime. It works reliably and is unaffected by the colour, temperature, pressure or chemical properties of the product to be measured. Features include intrinsically-safe two wire connection to detectors, ASK signal modulation for interference suppression, and fieldbus compatibility.
Applications
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Measurement principle The gamma radiation emitted by a source is attenuated when it passes through matter. The degree of attenuation depends on the measuring path and product density. Given a constant length measuring path, radiation absorption is a function of the density of the material being measured.
Measuring arrangement A typical system arrangement is a source with shielding, a scintillation counter and an LB444 evaluation unit. Installation can be carried out without pipeline modification or production downtime. Both the shielding and the detector can be mounted on the outside of the pipe at various angles.
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If the pipe diameter is large enough to provide sufficient absorption, the measuring system can be fitted at an angle of 90° to the pipe axis. In the case of smaller pipe diameters, fitting can be made at an angle of 30° or 45° to achieve an adequate measuring path. |
| For more precise measurements with small pipe diameters, an s- or u- shaped measuring path is used. The radiometric measurement method affords a high level of operational safety and requires virtually no maintenance even in an adverse environment. |  |
Evaluation unit The LB 444 evaluation unit incorporates state of the art technology with a 32-bit processor for high speed and precision in even the most demanding applications.
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Radiation sources and shielding
All radioactive sources used for industrial applications are encapsulated in welded
stainless steel so that radioactive substance is kept separate and isolated from the
material being measured. In most cases, a 137Cs radiation source is used, although 60Co
and 241Am sources can be used for special measurement tasks. The shielding container
consists of a cast iron or stainless steel casing filled with lead and a lockable exit
channel for the radiation beam. Special shieldings are available for measurements in
vessels. Detector A scintillation counter with an NaI crystal is used as a detector. Photoflashes are produced in the crystal when radiation is absorbed. The number of flashes is proportional to the intensity of the radiation field. The crystal is optically linked to a photoelectric multiplier which, together with the electronics, converts the photoflashes into electrical impulses. Compared to other detectors, eg. ionisation chambers, the advantages are obvious: high sensitivity to gamma radiation, low source activities, temperature stability and practically unlimited service life. The compact shape of the crystal allows it to be easily shielded against fluctuations in ambient radiation which could otherwise influence the measurement. The signals are transmitted to the evaluation unit using a two wire technique with ASK modulation to ensure the suppression of interference. |
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Calibration A user friendly calibration program makes correct operation easier. Special product characteristics and the conditions at the measuring site are automatically taken into consideration. During startup, a single calibration point is sufficient. For very precise calibration, up to 10 measurement points can be used. Should temperature fluctuations occur, the temperature compensation sets the unit of measurement with regard to a reference temperature. The contactless radiometric measurement method demonstrates high long-term stability and hence is essentially maintenance free.
Application Notes
Engineering data To prepare our
quotation we require the following application data:
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Click here for LB 444 technical data
for more information, email
SE Asia and Australasia: industrial@berthold.com.au
North America: usinfo@berthold.com.au
Europe: euroinfo@berthold.com.au
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