Dead-time simulator for industrial process control apparatus

Claim 1

A DEAD-TIME SIMULATOR COMPRISING, IN COMBINATION, FIRST AND SECOND SIGNAL-RESPONSIVE MEANS CONNECTED IN SERIES SUCH THAT THE OUTPUT OF SAID FIRST SIGNAL-RESPONSIVE MEANS IS APPLIED TO AN INPUT TO SAID SECOND SIGNAL-RESPONSIVE MEANS; ONE OF SAID SIGNAL-RESPONSIVE MEANS COMPRISING PHASE-SHIFTING MEANS HAVING MEANS TO DEVELOP AN OUTPUT SIGNAL (1) IN PHASE WITH ITS INPUT SIGNAL AT ZERO FREQUENCY, (2) SHIFTED IN PHASE 90* WITH RESPECT TO ITS INPUT SIGNAL AT SOME INTERMEDIATE FREQUENCY, AND (3) SHIFTED IN PHASE AN AMOUNT APPROACHING 180* AT HIGH FREQUENCIES RELATIVE TO SAID INTERMEDIATE FREQUENCY, WHEREBY SAID PHASE-SHIFTING MEANS PRODUCES, IN RESPONSE TO A STEP INPUT SIGNAL, AN OUTPUT WHICH INITIALLY IS INVERTED WITH RESPECT TO THE SENSE OF THE INPUT STEP BUT WHICH GRADUALLY AND OVER A RELATIVELY LONG PERIOD OF TIME CHANGES TO A SIGNAL HAVING THE SAME SENSE AS THE ORIGINAL STEP INPUT; THE OTHER OF SAID SIGNAL-RESPONSIVE MEANS COMPRISING INTEGRATING MEANS ARRANGED TO DEVELOP AN OUTPUT SIGNAL CORRESPONDING TO THE TIME INTEGRAL OF THE SIGNAL APPLIED TO THE INPUT THEREOF.