Airflow monitor: An effective approach to protecting assets and increasing safety in automated test equipment

Testing high power sophisticated avionics equipment requires accurate cooling airflow monitoring to protect the operator and expensive avionics equipment. This paper introduces an airflow monitor design that monitors cooling airflow, warns the operator when cooling airflow is below minimum requirements and automatically terminates testing prior to thermal failure. A method to accurately measure the cooling air flowing to a unit under test is critical to maintaining component reliability and reducing hazards associated with thermal runaway. Such a method has been designed and prototyped on the Navy's advanced Consolidated Automatic Support System (CASS). The airflow monitor incorporates a digital airflow sensor between the cooling air source and the unit under test. The digital airflow sensor accurately measures airflow and temperature and provides real-time feedback to the operator when low cooling air flow is realized. Further enhancements were made by designing the airflow monitor to shut down power to the unit under test when airflow does not meet minimum requirements. Customization is accomplished by setting simple resistor values which correspond to control settings, such as, minimum airflow required, minimum air temperature required, time delay before warning buzzer sounds, and time delay before unit under test shutdown. It has been demonstrated that with accurate monitoring and control of these variables, catastrophic thermal failure can be avoided and expensive avionics can be protected. Automated test equipment was originally conceived with the intent to maximize autonomy and take the burden off of skilled individuals troubleshooting a problem. A system that can not only monitor airflow, warn the operator of upcoming thermal danger and safely shutdown power to a unit under test on its own makes automated test equipment truly automatic. This paper illustrates one method to achieve such added reliability and system safety, with real examples demonstrating operational capabilities and cost savings. Description of the design concept, along with pictures and illustrations of working prototypes, provide a clear understanding of the importance of monitoring automated test equipment airflow.