Abstract: A method of determining the condition of a battery which backs up a real-time clock (RTC) when a main power supply fails or is disconnected, in a system which includes a controller having a volatile random access memory (VRAM) and a non-volatile random access memory (NVRAM). The method includes the steps of periodically storing the time value of the RTC in NVRAM, and periodically writing a predetermined data pattern in VRAM, while the main power supply adequately powers the real time clock. The method then includes the steps of detecting a power-down condition of the main power supply, and terminating the recording and writing steps when the detecting step detects power-down. Return of main power, or power-up, is then detected, with the data pattern stored in VRAM then being compared with the predetermined data pattern.

Abstract: A method of adding asynchronous logging of data relative to events into a time based data logger which stores operator initiated headers in a data array, as well as synchronously storing data relative to variables of a transport refrigeration unit at predetermined constant time intervals. The operator associated headers include a preamble having a predetermined number of data bytes which include a header designator and a digital code which identifies the specific type of header being entered. An event header is provided having a preamble which includes the same number of data bytes as the preamble of the operator associated headers, for each type of event to be asynchronously stored in the data array. The header designator associated with the operator associated headers is inserted into the preamble of each of the event headers. A digital code is provided which identifies each event header, and the digital code is inserted into the preamble of each of the event headers.

Abstract: Methods and apparatus for converting a refrigeration unit having a manually controlled thermostat to remote operation via a data logger, without replacing the manually controlled thermostat. A set point temperature selector associated with the thermostat is fixed at a predetermined value, and a resistance temperature detector (RTD), which is normally connected to a temperature input of the thermostat, is disconnected. A set point temperature for a space conditioned by the refrigeration unit is selected via the data logger. The data logger monitors the temperature of the conditioned space, compares the temperature of the conditioned space with the set point temperature selected via the data logger, and determines an operating mode for the refrigeration unit which will cause the temperature of the conditioned space to be maintained in a predetermined range relative to the set point temperature selected via the data logger.