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Thermostat with means for disabling PID control

  • US 4,991,770 A
  • Filed: 03/27/1990
  • Issued: 02/12/1991
  • Est. Priority Date: 03/27/1990
  • Status: Expired due to Fees
First Claim
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1. A thermostat for minimizing deviation from a first preselected temperature during a temperature recovery period wherein a plant is used to change the temperature of a space, comprising:

  • a memory adapted to receive, store and output first and second preselected temperatures and a new second preselected temperature;

    a PID controller connected with said memory;

    a means for disabling a PID controller connected with said PID controller and said memory, said means for disabling being adapted to disable said PID controller and lock on the plant during the temperature recovery period until a second preselected temperature is reached;

    a comparator in communication with said memory, said comparator being adapted to generate an error signal which is equal to the difference between a current room temperature and said first preselected temperature when said current room temperature first reaches said second preselected temperature and then reaches a maximum difference from said second preselected temperature;

    a means for modifying said second preselected temperature connected to said comparator, said means for modifying being adapted to subtract said error signal from said second preselected temperature to create a new second preselected temperature for use in a next temperature recovery period.

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