Tradeoffs in synthetic instrument design and application

There are efforts underway within industry to develop synthetic instrumentation (SI) as a complement to traditional monolithic instrumentation designs. This provides flexibility in the selection of SI components to match the performance level required and to also overcome obsolescence issues. The synthetic instrument concept is attractive because signal processing and generation can be handled by platform independent software routines. The capability of an instrument can be changed or extended by simply down loading a new program or upgrading a driver. Common programming standards such as IVI can simplify transitioning to replacement hardware and software when obsolescence becomes an issue. With the explosion in personal computer development, processing power has become an inexpensive commodity. A/D and D/A converters are becoming commodities as well, with increasing speed and resolution every year. Signal conditioning remains a custom element as it usually must be tailored for specific applications. Leveraging COTS hardware and software can reduce cost and shorten system development times. As with any new concept, application of synthetic instrument raises issues that must be considered. Synthetic instruments impact overall test system architecture. The impact depends on the complexity of synthetic instrument function and where the signal processing functionality (software) is located. Emulation of legacy instrumentation is another issue. Since the SI measurement processes used are typically different from the legacy instrument, the synthetic instrument may not perfectly emulate the legacy device. For military test systems where longevity and user maintainability are prime requirements, the logistics tail must be considered. Development cycles for military test equipment are long by commercial standards. The world of COTS changes rapidly and it is not uncommon for COTS technology to be obsolete before the system is fielded. Another concern is environmental standards. Military systems typically have stringent requirements for shock, vibration, temperature, humidity, EMI/EMC, and other environmental requirements that commercial systems are not required to meet. This paper examines some of these issues related to synthetic instrumentation. As always with engineering, there is no perfect answer, there are only tradeoffs to be optimized.