Synthetic instrument

A synthetic instrument is a term in metrology (test and measurement science). A Synthetic Instrument is software that runs on a Synthetic Measurement System to perform a specific , analysis, or measurement function. A Synthetic Measurement System (SMS) is a common, general purpose, physical hardware platform that is intended to perform many kinds of synthesis, analysis, or measurement functions using Synthetic Instruments.

Typically the generic SMS hardware is dual cascade of three subsystems: digital processing and control, A/D or D/A conversion (codec), and signal conditioning. One cascade is for stimulus, one for response. Sandwiched between them is the device under test (DUT) that is being measured.

A synthetic instrument is the opposite of the retronym natural instrument. Although the word “synthetic” in the phrase synthetic instrument might seem to imply that synthetic instruments are synthesizers: that they only do synthesis; this is incorrect. The instrument itself is being synthesized; nothing is implied about what the instrument does. A synthetic instrument might indeed be a synthesizer, but it could just as easily be an analyzer, or some hybrid of the two.

Synthetic instruments are implemented on generic hardware, i.e., generic meaning that the underlying hardware is not explicitly designed to perform the particular measurement. This is probably the most salient characteristic of a synthetic instrument. Measurement specificity is encapsulated totally in software. The hardware does not define the measurement.

An analogy to this relationship between specific measurement hardware versus generic hardware with its function totally defined in software is the relationship between specific digital circuits and a general purpose CPU. A specific digital circuit can be designed and hardwired with digital logic parts to perform a specific calculation. Alternatively, a microprocessor (or, better yet, a gate array) could be used to perform the same calculation using appropriate software. One case is specific, the other generic, with the specificity encapsulated in software.

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