Digital Techniques to Test Analog Systems

Advances in digital techniques and microcircuitry packaging make it possible to economically upgrade the manual test set into efficient semiautomatic or fully automatic test equipment. The ability to provide functions as discrete building blocks further allows the application of digital techniques to checkout of analog systans at the flight line or launch pad. This concept can provide the customer with a reduction of development cost, time, spare parts, and training and, at the same time, permit the potential of updating the equipment as new and improved modules become available. It is quite conceivable that the customer may, in time, modify the function of a test set by field modification kits. A useful method of implementing these requirements has been achieved in the semiautomatic AN/ASM-237 Bomb Computer Test Set by supplying an operator with preprogrammed switch-selected test points which call up the proper stimulus inputs and display digital quantitative test values and messages, while providing the proper interconnections to the system under test. The AN/ASM-237 has been specifically programed to test the Bomb Computer Set CP-805/ASQ- 91 used in the F-4D Phantom aircraft. This airborne computer is an all-analog device having inputs from cockpit controls, radar, and inertial navigation systems. A thin film program is used and is programmed to permit 90 self-tests or malfunction tests to be interrogated and test values displayed for each of the 45 normal tests, giving a total capacity of 4050 tests.