Understanding synthetic instruments

Synthetic instrumentation (the concept of using a common set of hardware for many test applications) is starting to see implementation in military test applications. The potential gain comes from reducing the risk of test-equipment obsolescence by implementing test functions in software rather than in measurement-specific instruments.

• Class A: Modular/loosely coupled open architecture. A “spin your own” architecture based on modular instruments (ADCs, DACs, and up/downconverters) where test engineers develop their own measurement functions such as rise time, fall time, and frequency entirely in software. This implementation is the most flexible but requires the most effort.
• Class B: Integrated synthetic instruments. Here, a manufacturer purchases a test system’s hardware and the software that implements measurement functions. A test engineer then develops tests by stringing together measurements. Class B requires less investment in software development than the modular approach, with some limitations.
• Class C: Application-specific synthetic instruments. This implementation results in measurements specifically tailored for a specific device under test, but it limits flexibility should a new device require testing.

Granieri and Lowdermilk claim that using synthetic instruments “increases measurement speed and testing efficiency” because synthetic instrumentation “is primarily a signal based stimulus & measurement paradigm.” They go on to argue that a signal-based method can process a data set faster than a traditional instrumentation setup can and that use of synthetic instrumentation fosters test and measurement interoperability and can reduce training costs. 
 
 

Synthetic instruments use signal conditioners, up/downconverters, and ADCs to convert incoming signals to digital for processing, while DACs convert processed digital signals back to analog.