Electronic thermostat

Abstract

An electronic thermostat for controlling multiple temperature altering apparatus of an animal enclosure or the like employs a linear sensor comprised of an elongate black body, tubular probe containing a semiconductor active element of a current source which produces a sensor current that varies linearly with changes in temperature. A voltage divider to produce a plurality of temperature sensor signals which are used to produce primary of override actuation signals. The set temperature signal is selectable between two set point limits which are selectively variable to calibrate different scales. A plurality of detectors respectively compare the plurality of sensor signals with a common set temperature reference signal to produce a plurality of detection signals at a plurality of preselected temperatures associated therewith. The preselected temperatures at which a first heat control detection signal is produced is different from the preselected temperature of which the first cool control detection signal is produced, so that a dead zone between cycles is created. Primary detectors in both the cooling and heating stages cause actuation of associated cooling and heating apparatus, respectively, only if the detection signal is maintained for a preselected time period to prevent shortcycling. Override detectors, on the other hand, cause actuation of the same apparatus within a shorter override time period if the temperature associated therewith is achieved before actuation in response to the primary detector.