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.
