GB1487829A - Dynamic weighing using differential filtering - Google Patents

Abstract

1487829 Dynamic weighing W & T AVERY Ltd 3 Sept 1975 [14 Sept 1974] 40161/74 Heading G1N(A) In a method of dynamic weighing a transducer signal containing an oscillatory component due to movement of the load is differentiated with respect to time, the signal and its differential are integrated over the weighing period T and the two integrates are then combined. In a modification the signal and/or differential are multiplied by single-valued functions f 1 (t), f 2 (t) respectively before integration the said functions having at least one maximum within the period T. The transducer signal converted into digital form is repeatedly sampled over a number of cycles of the oscillatory component i.e. N times during the period T, and the nth sample Sn, stored in store 10, is subtracted from the succeeding sample S n+1 in block 12. The sample and difference signals are multiplied by functions f 1 (t) and f2(t) respectively and the resulting signals are added by blocks, 22, 24 to the accumulated totals stored in blocks 26, 28. At the end of the period T the accumulated totals are added by block 30. To derive the static weight the resultant sum is averaged over the period T or T may be incorporated as an averaging factor in the functions f 1 (t), f 2 (t). Either or both functions f 1 , f 2 may be constant during the weighing period in which case corresponding circuit blocks 14 and 18 or 16 and 20 are omitted. The functions may alternatively be chosen to give high attenuation of components above a given frequency e.g. 2.5Hz. The value of f 1 (t) by which Sn is multiplied is given by f 1 (<SP>nT</SP>/N) and the value of f 2 (t) by which S n+1 -S n is multiplied is given by f 2 (<SP>mT</SP>/M). Second or higher order differentials may be used. In the case, for example, of a second differential a further store is provided to store S n+1 -S n and a further subtraction block provides the difference: (S n+2 - S n+1 ) - (S n+1 -S n ).