SOFTWARE FOR DESIGN OF ANALOG INDICATING TYPE OF ELECTRICAL INSTRUMENTS

Abstract

Although with the advent of digital electronics, digital indicating instruments have become very widely used, still the importance of analog indicating type of electrical instruments cannot be ignored. They shall continue. to be an integral part of electrical measurement systems,. There are a wide variety of analog indicating type of electrical instruments like moving Iron, moving coil, thermal, electrostatic and induction types based on different principles. A precise and a generalised design procedure for all the instruments is very difficult to achieve, because the accurate design of these instruments is largely dependent on the practical experience and empirical formulations. Still the permanent magnet moving coil instruments lend themselves to a fairly accurate design. In the present work a user-Interactive software for the complete design of permanent magnet moving coil instruments_ (ammeters and voltmeters) has been prepared. All the three operating systems of the instrument i.e. the deflecting system, the controlling system and the damping system have been designed. All the aspects of mechanical & electrical design have been dealt with in detail. In mechanical design, the design of pivot andjewel assembly is of utmost importance as the friction at this Junction greatly influences the quality of the instrument. The slightest amount of mishandling can cause damage to the delicate mountings in the Instrument. Hence a feature that gives the maximum distance of safe drop and the equivalent static load of Impact has been incorporated. Finally the various performance parameters like the figure of merit, accuracy, time period of movement, overshoot, power consumption at full scale deflection etc. have been calculated. The complete design is in S.I. system of units. The software has been developed in FORTRANN-77 and successfully tested on the PC-AT.