Patent ID: 7180054

Claim:
A method for error-blanking and -compensation of interference signals originating from gammagraphy in a radiometric measuring system, wherein a process variable L (t) is determined by means of a radioactive radiator and a detector, which method comprises the steps of: determining the change ΔLm=Lm (ti) −Lm (ti+1) for two, arbitrary per se, time t i and t i+1 , between two radiometric, measured values Lm (ti) and Lm (ti+1) registered by the detector at these times and, by means of a predetermined, calculative relationship ΔLm=f(ΔP 1 ), comparing said change with a change ΔP 1 =P 1(ti+1-τ) of a first, non-radiometrically measured process parameter, registered in the corresponding time interval; assuming that no interference of the radiometric measuring system is present in case the change ΔLm=Lm (ti) −Lm (ti+1) of the radiometric, measured value Lm (i) corresponds to a previous change ΔP 1 =P 1(ti-τ) −P 1(ti+1-τ) of the first, non-radiometrically measured process parameter in the corresponding time interval and to the calculative relationship ΔLm=f(ΔP 1 ), wherein, from the last-measured, radiometric, measured value Lm (n+1) , the associated process variable L (ti+1) is determined and issued onto a bus connected with a process control system, without an additional signal indicating an interference; and assuming that an interference of the radiometric system is present in case the change ΔLm=Lm (ti) −Lm (ti+1) of the radiometric, measured value Lm (i) does not correspond to a previous change ΔP 1 =P 1(ti-τ) −P 1(ti+1-τ) of the first, non-radiometrically measured process parameter P 1 =P 1(t-τ) in the corresponding time interval and to the calculative relationship ΔLm=f(ΔP 1 ), wherein: based on the previous change ΔP 1 =P 1(ti-τ) −P 1(ti+1-τ) of the first process parameter P 1 , a radiometric measurement Lc (t+1) is calculated, by means of the recorded, calculative relationship ΔLm=f(ΔP 1 ), for the time t i+1 ; from the calculated, radiometric measurement Lc (ti+1) , the associated process variable L (ti+1) is determined and issued onto the bus connected with the process control system, together with an additional, interference-indicating signal; and in a subsequent recording, at a time t i+2 , of the change ΔP 1 =P 1(ti+1-τ) −P 1(ti+2-τ) of the first, non-radiometrically measured, process parameter and of the measuring of the radiometric, measured value Lm (ti+2) , the latter is used together with the calculated radiometric measurement Lc (ti+1) to determine the change ΔLm=Lc (ti+1) −Lm (ti+2) and this is referenced for determining whether an interference of the radiometric measuring system is still present.