WEIGHING SCALE WITH VALIDATING REFERENCE CHANNEL

摘要

An electronic scale for weighing an article includes a weighing channel with a sensor such as load cell 12 for providing an output indicative of the instantaneous weight of the article, and a reference channel with a reference sensor 22 for providing an output A indicative of instantaneous vibrations affecting the output of the weighing channel; the two channels include respective matched low pass filters 16, 26. The scale circuitry also provides a signal B indicative of the long term average of the reference channel's output via a filter 28. Comparator unit 30 compares the average signal B with the reference channel's output A and provides a validation signal when the reference channel's output does not differ by more than a threshold amount from the average signal. The validation signal is used by microprocessor 20 to indicate the absence of spurious vibrations and that the output of the weighing channel is valid. The threshold amount is preferably a percentage of the signal B. In an alternative embodiment (Figs. 4, 5 not shown), the filter 28 and comparator 30 are omitted and the microprocessor 20 makes a comparison of the instantaneous output of the reference channel filter 26 with the average value of that output to derive the validation signal. IMAGE