853. A Time-Sharing System for Real-Time Mass Properties Measurements

Paper

Abstract

A computer time-sharing system for real-time mass properties measurements is described. The system consists of a PDP-8/1 computer linked to up to four vertical balance machines and up to two moment-of-inertia/center-of-gravity machines. There is a teletype station near each machine in order to allow each operator to converse independently with the computer, plus a ‘master’ teletype station near the computer. A machine is controlled from its teletype keyboard, and test results are automatically typed on its teletype printer. When measurements are being made, the computer automatically acquires and processes data in real time, i.e., while the data are being generated. The teletypes operate in a time-sharing mode, i.e., an operator at one teletype station generally does not know that other stations are in use. A previous paper (Paper No. 738, 28th Annual SAWE Conference) gives a more detailed description of the vertical balance interface and digital signal processing. The present paper emphasizes the design and functioning of the computer time-sharing software, the design of multiple machine interfaces, and the operational characteristics of the system. It is shown that a small computer such as the PDP-8/1 can easily handle several machines ‘at the same time’ without producing noticeable delays, and further that the computer offers overall operational improvements which include faster and more efficient use of the mass properties machines.