Bulk Flow Meter LB 442

No recalibration necessary

• Temperature fluctuations or other environmental factors have no effect on the measuring system
• Long term stability is guaranteed by automatic drift and source decay compensation
• High level of repeatability
• Easy testing of the measuring system by placing a standard absorber on the detector
• Low radiation activity through the use of highly sensitive scintillation counters
• Modest expenditure on cabling
• Simultaneous transmission of measurement data and supply voltage between the detector and the evaluation unit using a two-wire technique
• Immunity to interference
• Data transmission between the detector and the evaluation unit by ASK modulation (Amplitude Shift Keying)

Applications

• The chemical industry - eg. plastic granules, artificial fertilisers
• The paper and pulp industry - eg. wood chips, blocks of wood, wood pulp
• The mining industry - eg. coal, ore
• The mineral industry - eg. sand, gravel
• The foodstuff industry - eg. potatoes, potato chips, cornflakes

Operation The rod-shaped radiation source is specially designed for the application as regards loading, material and the conveyor system. The radiation source is installed in a lockable shielding mounted under the conveyor. The scintillation counter is installed on top of the conveyor and is in line with the radiation source. The intensity of the radiation received by the scintillation counter is a measure of the loading on the conveyor system. The evaluation unit calculates the mass flow rate based on the detector signal and the belt speed input from the tachometer. The choice of radiation source depends on the material loading: for high belt loading 60Co is used, for medium belt loading 137Cs is used, for low belt loading 241Am is used.

New detectors use a two-wire technique with interference-free data transmission using ASK modulation. The NaI crystal of the scintillation counter converts the absorbed radiation into photoflashes. The crystal is optically linked to a photo multiplier which, together with the detector electronics, converts the photoflashes into electrical pulses. The detector signal is transmitted to the evaluation unit by a two-wire circuit using ASK modulation. In this way, the entire system facilitates a high degree of interference-free operation. Scintillation counters have greater sensitivity than gas-filled ionisation chambers, therefore the required radiation activity can be reduced by a factor of ten. The NaI crystal detector affords high temperature stability and drift-free operation. The internal microprocessor controls the "intelligent" detector.