Abstract: Power saving features are employed in a machine monitor to reduce electrical power consumption and increase the life of an electrical power source (such as a battery) which is used to power the monitor. The monitor includes a microcomputer having a high operating speed and a low operating speed. Power consumption is reduced by placing the microprocessor in a low-power sleep mode when full power capabilities of the microprocessor are not needed. Power consumption is further reduced by operating the microprocessor at the low operating speed when a high operating speed is not needed. The monitor also includes a communications port in electrical communication with the microcomputer for communicating with a peripheral device, and sensors for sensing machine characteristics such as speed, temperature, flux, or vibration.

Abstract: A programmable apparatus is used to determine the running speed of an ac induction motor based on vibration and flux measurements. A first analysis is performed on at least one of the vibration and flux signals according to a first criterion to determine candidate speeds and whether speed will be determined based on the first analysis or whether a second analysis is required. A second analysis is selectively performed if required by the first analysis. In the first analysis, vibration signals (for example) are transformed to the frequency domain, such as by Fast Fourier Transform, and vibration amplitude peaks contained in the resulting spectrum are analyzed to identify candidate peaks. If only one candidate peak is identified, the frequency at which the candidate peak occurs is used to determine motor running speed. If two or more candidate peaks are identified and the motor is a two-pole motor, the candidate peak having the maximum amplitude is used to determine running speed.