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This paper is based on the author's recent experience with the development of computer software for a dual unit tensile acceptance test station controlled by two minicomputers in a graphite production facility. Specific examples from that experience are used as illustrations in a more general discussion. Major items that must be considered in the design, development, and implementation of a real-time software system are control, operator, and equipment interfaces, data acquisition and analysis, and software verification and change control.
In addition to actual movement of the test machine crosshead, control aspects include consideration of methods to determine the condition of the machine by way of calibration and load rate checks, and control of the specimen testing sequence. Operator and machine interfaces should be designed in such a way that the operator does not feel impeded in the performance of his work by the computer. Control panels should indicate the progress of the computer during testing so that the operator does not panic during computer delays.
The software must be designed to have a high probability of acquiring all of the digitized stress-strain points without placing a disproportionate load on the computing system. Data analysis programs should be designed to compute values for comparison with acceptance specifications and to assist in analyzing unusual data. Orderly verification of the software by an outside person provides added insurance that the final system will perform the activities specified in the original program specifications. Any changes to verified software should be fully documented, authorized, and, if required, reverified before implementation.
This paper describes how the general requirements outlined above were implemented in a production testing system.
computers, computer programming, materials testing, data acquisition, automation
Research specialist, Re-entry Systems Materials Engineering, Lockheed Missiles and Space Co., Sunnyvale, Calif.