Replacing obsolete instrumentation — Lessons learned

Overcoming test-equipment obsolescence is paramount in military and aerospace applications where test systems are supporting equipment with a service life of more than 20 years. However, replacing one or more obsolete instruments in a test system can have major consequences for the deployed Test Program Set (TPS). An emulation strategy can help you incorporate new test instruments to migrate from obsolete instruments. The major challenge is to manage the replacement ideally without changes to the existing TPS. This paper discusses the various aspects related to replacement of obsolete instruments. When instrument models are replaced, new versions are not necessarily compatible with the previous version, either in terms of functionality or remote control commands. The requirement of having minimal or no changes to the TPS generates high challenges for vendors of instruments - the emulation of obsolete instrumentation to achieve backwards compatibility includes code compatibility as well as true functional and behavioural compatibility. Modern instruments have integrated emulation capabilities. The paper describes in detail the requirements, challenges and “lessons learned” through implementing the emulation in complex instruments like network analyzers and spectrum analyzers. In detail the emulation capabilities of modern spectrum analyzers are discussed, for example how to handle different mixer levels, analog vs. digital resolution bandwidth filters, swept frequency spans vs. digital FFTs to achieve behavioural compatibility. Further migration strategies and steps which are required to successfully handle the replacement are discussed. Finally, an overview on measures and strategies to mitigate obsolescence problems for new designed test systems based on layered software structures, on VISA, IVI drivers and technologies like LXI, concludes the paper.