Pen recorder control circuit - switches off when paper is absent or damaged using control signal derived from pen to drum resistance

摘要

A circuit for controlling, esp. interrupting, a printer placing measurement data on paper when the paper is damaged or has run out has a rapid response. The control signal is derived from the electrical resistance between the printer printing element and the paper support. The paper drive is interrupted for a min. time following a given delay after the control factor has reached a defined level indicating the absense of paper. If a thermal print element is used the heating power is also interrupted. The paper drive interruption delay time varies with the paper speed. The output of a control voltage comparator drives the pen drive and heater via a flip-flop and OR-gate and the paper drive via a further flip-flop and AND gate.