Abstract: A microprocessor based device which monitors the operation of a compressor in a refrigeration system and automatically shuts the compressor down if a monitored condition is abnormal. Sensors in the refrigeration system sense conditions such as refrigerant pressure and temperature, superheat, oil pressure and motor current draw. If a sensed condition is outside of a safety range and remains there for a time out period, an alarm condition is indicated and the device generates a alarm signal and shuts down the compressor. A detachable display module includes a keypad for carrying out field programming and a LCD screen for displaying the refrigerant conditions and programming prompts and commands. A rest button permits resetting twice before a service call is required.

Abstract: A temperature sensor which is flush mounted on a wall of a room in which the temperature is sensed. A mounting plate secured to the wall has a cavity in its face which receives an aluminum sensor plate and an insulating block which thermally insulates the sensor plate from the mounting plate. A temperature sensing integrated circuit contacts the back side of the sensor plate and has electrical leads which extend to the back side of a printed circuit board mounted in a pocket on the back side of the mounting plate. The integrated circuit acts as a current source having its output signal enhanced by active solid state circuit components mounted on the back side of the circuit board where their heat is dissipated by conduction through the mounting plate and wall and by convection and radiation into the wall cavity to avoid affecting the sensor plate. The circuitry allows active factory calibration and eliminates adverse effects on the signal caused by background environmental noise.