Abstract: A cooling system can include a two-stage compressor, a variable speed fan and a controller for continuously modulating cooling capacity of the system. The compressor can run in a loaded state and the fan can run at a first speed when a call for cooling calls for maximum system cooling capacity. The compressor can run in the loaded state and the fan speed can decrease to a second fan speed as the called for cooling capacity decreases. The compressor can run in an unloaded state and the fan speed can be increased. The compressor can run in the unloaded state and the fan speed can decrease to a third fan speed as the called for cooling capacity decreases.

Abstract: A cooling system can include a two-stage compressor, a variable speed fan and a controller for continuously modulating cooling capacity of the system. The compressor can run in a loaded state and the fan can run at a first speed when a call for cooling calls for maximum system cooling capacity. The compressor can run in the loaded state and the fan speed can decrease to a second fan speed as the called for cooling capacity decreases. The compressor can run in an unloaded state and the fan speed can be increased. The compressor can run in the unloaded state and the fan speed can decrease to a third fan speed as the called for cooling capacity decreases.

Abstract: A modular uninterruptible power supply is disclosed, which provides complete redundancy for all components required for UPS operation. Novel aspects of the invention include design of the modules and their interconnection and interoperability, as well as improved operation techniques applicable to UPS systems generally.

Abstract: A modular uninterruptible power supply is disclosed, which provides complete redundancy for all components required for UPS operation. Novel aspects of the invention include design of the modules and their interconnection and interoperability, as well as improved operation techniques applicable to UPS systems generally.

Abstract: A modular uninterruptible power supply is disclosed, which provides complete redundancy for all components required for UPS operation. Novel aspects of the invention include design of the modules and their interconnection and interoperability, as well as improved operation techniques applicable to UPS systems generally.

Abstract: A hand-held data collection and analyzing unit for collecting and analyzing vibration data induced by a rotating shaft including a processor that first converts the analog vibration signal into corresponding digital vibration samples. Thereafter, the processor provides in response to the digital vibration samples, corresponding output vibration samples in which samples within each set of output vibration samples are provided at a rate that varies as a function of variations in the speed of the rotating shaft. A digital processor then collects a time waveform record in response to a plurality of the output vibration samples, wherein the sample rate for the output vibration samples collected in the time waveform record varies as a function of variations in the speed of the rotating shaft.

Abstract: A modular uninterruptible power supply is disclosed, which provides complete redundancy for all components required for UPS operation. Novel aspects of the invention include design of the modules and their interconnection and interoperability, as well as improved operation techniques applicable to UPS systems generally.

Abstract: The polarized potential at the boundary between a submerged pipe and a medium is measured unaffected by the presence of a distributed IR drop in the medium due to an impressed current from a corrosion protection system. The voltage between the pipe and a reference electrode in the medium is measured when the protection system current is zero. This is accomplished with a sample-and-hold circuit controlled by a trigger signal derived from the input signal and having a variable phase for controlling the phase angle at which the sample is taken.