NAME: Loofie Gutterman
CO.: Marvin Test Solutions
ROLE: Global producer of test equipment, software, and automated test solutions for the electronics industry
An industry veteran notes that test and measurement technology should keep pace with advancing embedded systems.
Why have attentions turned to embedded test trends and tools?
Embedded test and measurement (T&M) is a very important aspect of aerospace and defense. It helps aerospace firms and Department of Defense (DOD) organizations to reduce the footprint and cost of test by integrating test capabilities into the product itself. Embedded T&M can be implemented using different approaches but is typically integrated in the form of built-in-test (BIT) or built-in-self-test (BIST). BIT and BIST are typically achieved by including additional circuits and software code that combine to create internal loopbacks (wrap around) within the product and allows the testing of the product without the need for external test equipment. While this appears to be a straightforward approach, effective BIT requires in-depth analysis and careful design during the product’s development phase to ensure that the additional circuitry and code used by the BIT does not degrade the product’s reliability.
For most aircraft and vehicle systems, the use of BIT or BIST is sufficient and in many cases, eliminates the need for external test equipment. However, systems that interface with external devices (i.e., armament systems that need to interface with external weapons), may require a different approach. The reason is that even by incorporating loopback inside the product, there are many failure modes associated with the interconnect between the product and the external device. As an example, missile launchers need to interface with missiles and these could be live rounds (war shots) or practice/training missiles. Even with the best loopback design, it is highly likely that the connector interface between the launcher and missile may be damaged over time and such damage would not be detected by the BIT. In such cases, the designers will need to consider external loopbacks or external test equipment based on the complexity of the system. More complex systems are likely to require test equipment while simpler systems may be able to utilize an external wrap around connection strategy.
What advice can you offer for selecting or upgrading T&M systems?
Many of today’s aerospace systems were designed decades ago with a projected life cycle of 15 to 30 years. The test equipment deployed with these systems was most likely state-of-the-art at the time and it probably provided an effective test solution for those products based on the test technology available at that time. Over the years, these aerospace systems have undergone many upgrades and improvements but in most cases, the testers originally deployed with these systems remained unchanged (and therefore inadequate). These long product cycles create two major concerns for those organizations responsible for maintaining aerospace systems: obsolescence and test gap. Obsolescence dictates that testers be replaced or that the test capabilities be migrated to other testers even if the testers still provide good test coverage. The “Test Gap” is associated with the fact that the tester is no longer capable of testing the systems it was originally designed to test due to technological deficiencies resulting from upgrades to the products.
This problem is unique to aerospace and rarely exists in the commercial marketplace. In the commercial marketplace (semiconductor and consumer electronics as an example), the technology advances at such a rapid pace that as new products are being introduced, they require testers with new capabilities. As a result, these testers become obsolete every five to eight years and are being replaced frequently.
Test engineers and managers responsible for sustainment of aerospace systems need to review the testers they use and evaluate the following aspects:
- The projected end-of-life of the tester. This includes availability of subassemblies and components, feasibility of lifetime buys, long-term sustainment by the OEM or by other organizations, and any other aspect that may prevent on-going use of the tester
- The projected end-of-life of the system(s) supported by the tester. If shorter than the projected end-of-life of the tester then no action (or a different action) may be needed
- Potential test gaps. The inability of the tester to support current and future test requirements for the aerospace systems it supports
Based on the above evaluation above, the decision can be made regarding the path forward which may include:
- Tester upgrade or technology update
- Migration of the test capabilities to another, existing tester
- Development of a replacement tester
In all cases, current and future test requirements of the system(s) supported by the tester must be evaluated to ensure that the path forward will provide a long-term solution as opposed to a temporary “band aid.”