Die ontwikkelikng van 'n meetinstrument om die transiente van roterende masjiene te meet

Abstract

Transducers are needed to detect defects in rotational machines . If a potential defect is detected in time , without dismantling the machine , repairs could be carried out when the maintenance facilities are available with minimum loss in production . Analysis of the speed and acceleration parameters are used to predict the existence of defects in a machine . This project in volved the development and utilisation of a comprehensive set of software in conjunction with a high resolution measuring instrument , which have the ability to measure both the speed and acceleration parameters of rotational machines . The measuring instrument hardware consists of the following : • Shaft encoder : A high resolution incremental shaft encoder is used to determine the tor_g..u e of the rotat-ing shaft . The output pulse of the shaft encoder is processed within the encoder to minimise the generation of noise . • Signal proces;.. ing unit : The speed of the machine is obtained from the signal processing unit with the aid of analogue techniques , by converting the output pulses of the shaft encoder to a corresponding voltage . By differentiation of the speed signal , the instantaneous acceleration of the machine is obtained . The output of the instrument is digitized by an analogue-to-digital converter card before the signal is processed by a computer. The software developed for the measuring instrument displays a menu, showing the options to be carried out to ensure the correct sampling of the speed and acceleration of the motor . The sampled data is shown graphically on the computer screen before it is saved for processing . Correct operation of the measuring instrument has been verified by practical evaluation . A number of tests in this regard have been carried out and satisfactory results were achieved. Particular knowledge regarding the following has been obtained: • Transient characteristics of rotational machines . • Format, construction and use of transducers.