Control and alarm system for freezer case temperature

A system for controlling the temperature of a refrigeration compartment and for indicating an alarm temperature condition of said refrigeration compartment, for use with a refrigeration system operatively controlling the temperature of said compartment, said refrigeration system including a thermodynamic fluid circulation system having a heat radiator positioned in thermal relation with said compartment and also having a controllable fluid control valve within said fluid circulation system for varying the flow of thermodynamic fluid to said heat radiator to operatively control the thermal effect of said evaporator radiator within said compartment, said system comprising:

• sensor means thermally coupled with said compartment for sensing the actual temperature within said compartment and for creating an analog electrical sensor signal related to the actual temperature sensed;
• analog to digital converter means electrically connected with said sensor means to receive the sensor signal, said analog to digital converter means operatively converting the sensor signal into a digital compartment temperature signal;
• a first temperature selector means selectively operable for establishing a first digital limit signal representative of an upper limit temperature of a range of desired temperatures within which the temperature of said compartment is normally to be regulated;
• a second temperature selector means selectively operable for establishing a second digital limit signal representative of the lower limit temperature of the range of desired temperatures within which the temperature of said compartment is normally to be regulated;
• a third temperature selector means selectively operable for establishing a digital alarm limit signal representative of a predetermined alarm condition temperature outside of the range of desired temperatures at which an alarm condition is to be signalled;
• first multiplexer means operatively connected to receive the compartment temperature signal and the first limit signal from said converter means and said first temperature selector means, respectively, and operative to supply both the compartment temperature and first limit signals when enabled;
• second multiplexer means operatively connected to receive the compartment temperature signal and the second limit signal from said converter means and said second temperature selector means, respectively, and operative to supply both the compartment temperature and second limit signals when enabled;
• third multiplexer means operatively connected to receive the compartment temperature signal and the alarm limit signal from said converter means and said third temperature selector means, respectively, and operative to supply both the compartment temperature and alarm limit signals when enabled;
• enabling means connected with said first, second and third multiplexer means for operatively enabling said first, second and third multiplexer means in sequence;
• alarm means operatively connected for control by said computer means, said alarm means indicating an alarm condition when energized;
• and
• computer means operatively connected to control said first, second and third multiplexer means and said converter means, said computer means operatively controlling said multiplexers to supply the signals from each of said multiplexers to said computer means when said each multiplexer means is enabled, said computer means operatively utilizing the compartment temperature signal and the first and second limit signals and said alarm limit signal to determine if the compartment temperature falls within or without of the range of desired temperatures, said computer means further operatively supplying a refrigeration control signal to said fluid control valve of said refrigeration system to regulate said fluid control valve in a predetermined manner to create a desired thermal effect within said compartment to urge the compartment temperature within the desired range of temperatures, said computer means further operatively determining if said compartment temperature reaches the alarm condition temperature, and said computer means further operatively delivering an alarm control signal to said alarm means to energize said alarm means upon determining that the compartment temperature has reached the alarm condition temperature.