Abstract: Devices and methods for microprocessor supervision in a special purpose computer system are provided. One illustrative embodiment includes a first watchdog timer internal to the microprocessor and a second watchdog timer external to the microprocessor. In some cases, the internal watchdog timer may be initiated prior to or during the operating system startup and the external watchdog timer may be initiated after the operating system is up and running. The internal watchdog timer may have a relatively longer timer duration than the external watchdog timer, but is not required in all embodiments. In some embodiments, the internal watchdog timer may monitor the microprocessor's startup sequence and the internal watchdog timer and/or external watchdog timer may monitor the microprocessor when the operating system is up and running. If the microprocessor faults at any time during startup or while the operating system is up and running, the internal and/or external watchdog timer may trigger a microprocessor reset.

Abstract: Devices and methods for microprocessor supervision in a special purpose computer system are provided. One illustrative embodiment includes a first watchdog timer internal to the microprocessor and a second watchdog timer external to the microprocessor. In some cases, the internal watchdog timer may be initiated prior to or during the operating system startup and the external watchdog timer may be initiated after the operating system is up and running. The internal watchdog timer may have a relatively longer timer duration than the external watchdog timer, but is not required in all embodiments. In some embodiments, the internal watchdog timer may monitor the microprocessor's startup sequence and the internal watchdog timer and/or external watchdog timer may monitor the microprocessor when the operating system is up and running. If the microprocessor faults at any time during startup or while the operating system is up and running, the internal and/or external watchdog timer may trigger a microprocessor reset.

Abstract: A method of controlling a refrigeration case of a refrigeration system including the steps of locating an expansion valve of a refrigeration case, moving the expansion valve of the refrigeration case out of a predetermined position, sampling temperature readings from an evaporator coil of a refrigeration case, calculating an adaptive proportional-integral-differential (PID) of the temperature of the evaporator coil for the refrigeration case, and moving the expansion valve to a second position closer to the predetermined position based on the calculated proportional-integral-differential until the temperature of the evaporator coil for the refrigeration case is within a predetermined temperature range.

Abstract: A method of controlling a plurality of commonly piped compressors for a refrigeration system having a plurality of refrigeration cases including the steps of sensing a suction pressure of the refrigeration system, determining whether the sensed suction pressure is within a predetermined pressure range, and turning compressors ON or OFF in stages until the suction pressure is within the predetermined pressure range. The method also includes the steps of sensing a case temperature for each of the refrigeration cases if the sensed suction pressure is within the predetermined pressure range and determining whether the sensed case temperature is within a predetermined temperature range.

Abstract: A pair of thermistors are mounted in a tube which diverts a minor portion of the air flowing through a duct of an HVAC system. One thermistor is heated by a feedback control system to maintain a substantially constant temperature differential between the thermistors. A signal representing the flow velocity is detected by detecting the power which is applied to the heating body to maintain the constant differential. That power represents the thermo power being carried away from the heated body. The temperature of the unheated thermistor is also detected. The signals are converted to digital form and applied to a computer for computing the flow rate in the ducts.