The HOBO Motor On/Off data logger records motor on and off conditions within an AC magnetic field with its internal sensor, or mechanical dry contact closures from external sensing devices. This data logger is ideal for tracking the usage & runtimes of motors, pumps, compressors, and other equipment. The HOBO UX90-004 Motor On/Off Data Logger is available in a standard 128 KB memory model (UX90-004) capable of 84,650 measurements and an expanded 512KB memory version (UX90-004M) capable of over 346,795 measurements.