Chart recording apparatus

Abstract

Chart recording apparatus for use with industrial instrumentation systems and the like, and comprising memory means to maintain a signal level for long time periods without drift. An input signal level is translated into the positioning of a pen, through the use of an actuator motor controlled by the input signal and a position feedback signal. A friction device is coupled to the pen to hold it in any given position, thereby to serve as a memory for the input signal level. The friction device comprises a thin vane-like element which is secured to the movable member and disposed in the air-gap of a permanent magnet. The air-gap also includes a mass of tiny magnetizable particles which, under the influence of the magnetic field, engage the surfaces of the vane-like element to develop a frictional restraining force. This frictional restraint has the characteristic of being relatively low upon initial movement away from a start point, and thereafter increasing progressively to a plateau level, thereby providing superior dynamic performance particularly in a servo positioning system. A plurality of such controllers can be operated in a time-shared mode, with the memory device of each non-activated recorder holding its pen fixed in position to prevent drift.

Dependencies are inferred from the claim text.