WEIGHING A NUMBER OF OBJECTS IN SUCCESSION

摘要

The present invention provides an apparatus for sensing displacement at relatively low frequencies, comprising a linear variable differential transformer comprising a core which moves in accordance with said displacement, a primary winding, and two matched secondary windings in series; means for energizing the primary winding with a signal which varies cyclically; means for deriving from the output across the secondary windings a signal representative of said displacement which has a principal ripple component derived from the energizing signal; means for filtering said representative signal whereby said ripple component is reduced; and means for taking successive samples from the filtered signal always on the same point in the principal ripple component cycle, which samples are representative of said displacement.