metrology Metrology is the scientific study of measurement. It establishes a common understanding of units, crucial in linking human activities. Modern metrology has its roots in the French Revolution's political motivation to standardise units in Fran ...

(test and measurement science), a synthetic instrument is

software Software is a set of computer programs and associated documentation and data. This is in contrast to hardware, from which the system is built and which actually performs the work. At the lowest programming level, executable code consists ...

that performs a specific

synthesis Synthesis or synthesize may refer to: Science Chemistry and biochemistry *Chemical synthesis, the execution of chemical reactions to form a more complex molecule from chemical precursors ** Organic synthesis, the chemical synthesis of organ ...

analysis Analysis ( : analyses) is the process of breaking a complex topic or substance into smaller parts in order to gain a better understanding of it. The technique has been applied in the study of mathematics and logic since before Aristotle (38 ...

, or

measurement Measurement is the quantification of attributes of an object or event, which can be used to compare with other objects or events. In other words, measurement is a process of determining how large or small a physical quantity is as compared ...

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 Digital data, in information theory and information systems, is information represented as a string of discrete symbols each of which can take on one of only a finite number of values from some alphabet, such as letters or digits. An example is ...

and control,

analog-to-digital In electronics, an analog-to-digital converter (ADC, A/D, or A-to-D) is a system that converts an analog signal, such as a sound picked up by a microphone or light entering a digital camera, into a digital signal. An ADC may also provide ...

digital-to-analog conversion In electronics, a digital-to-analog converter (DAC, D/A, D2A, or D-to-A) is a system that converts a digital signal into an analog signal. An analog-to-digital converter (ADC) performs the reverse function. There are several DAC archit ...

(codec), and signal conditioning. One cascade is for stimulus, one for response. Sandwiched between them is the

device under test A device under test (DUT), also known as equipment under test (EUT) and unit under test (UUT), is a manufactured product undergoing testing, either at first manufacture or later during its life cycle as part of ongoing functional testing and calibra ...

(DUT) that is being measured. A synthetic instrument is the opposite of the

retronym A retronym is a newer name for an existing thing that helps differentiate the original form/version from a more recent one. It is thus a word or phrase created to avoid confusion between older and newer types, whereas previously (before there were ...

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 A gate array is an approach to the design and manufacture of application-specific integrated circuits (ASICs) using a prefabricated chip with components that are later interconnected into logic devices (e.g. NAND gates, flip-flops, etc.) according ...

) could be used to perform the same calculation using appropriate software. One case is specific, the other generic, with the specificity encapsulated in software. At the software level, portability of measurement description is the key attribute that distinguishes a synthetic instrument from the more commonly found instrumentation software—software that is limited to hardware scripting and data flow processing. Not all measurement related software systems inherently provide for the abstract, portable synthesis of measurements. Even if they do have such provisions, they may not typically be applied that way by users, especially if the system encourages non-abstracted access to hardware. Application software packages such as

Measure Foundry Measure may refer to: * Measurement, the assignment of a number to a characteristic of an object or event Law * Ballot measure, proposed legislation in the United States * Church of England Measure, legislation of the Church of England * Measu ...

and

LabVIEW Laboratory Virtual Instrument Engineering Workbench (LabVIEW) is a system-design platform and development environment for a visual programming language from National Instruments. The graphical language is named "G"; not to be confused with G-co ...

are typically used with explicit structural links to the natural measurements made by specific hardware and therefore usually are not synthesizing measurements from an abstract description. On the other hand, should a software system be used to synthesize measurement functions as descriptive behavioral constructs, rather than hardware referenced structural data flow descriptions, this is true measurement synthesis. An analogy here is the distinction between a non portable structural description and an abstract behavioral description of digital logic that we see in HDL systems like

Verilog Verilog, standardized as IEEE 1364, is a hardware description language (HDL) used to model electronic systems. It is most commonly used in the design and verification of digital circuits at the register-transfer level of abstraction. It is also ...

. Synthetic instruments in test and measurement are conceptually related to the

software synthesizer A software synthesizer or softsynth is a computer program that generates digital audio, usually for music. Computer software that can create sounds or music is not new, but advances in processing speed now allow softsynths to accomplish the sam ...

in audio or music. A musical instrument

synthesizer A synthesizer (also spelled synthesiser) is an electronic musical instrument that generates audio signals. Synthesizers typically create sounds by generating waveforms through methods including subtractive synthesis, additive synthesis and ...

synthesizes the sound of specific instruments from generic hardware. Of course, a significant difference in these concepts is that musical instrument synthesizers typically only generate musical sound, whereas a synthetic instrument in test and measurement may be equally likely to generate or to measure some signal or parameter. A similar term commonly used in test and measurement,

Virtual instrumentation Virtual instrumentation is the use of customizable software and modular measurement hardware to create user-defined measurement systems, ''called virtual instruments''. Traditional hardware instrumentation systems are made up of fixed hardware co ...

, is a superset of synthetic instrumentation. All synthetic instruments are virtual instruments; however, the two terms are different when virtual instrument software mirrors and augments non-generic instrument hardware, providing a soft front panel, or managing the data flow to and from a natural instrument. In this case, the PC and accompanying software is supplementing the analysis and presentation capabilities of the natural instrument. The essential point is this: synthetic instruments are synthesized. The whole is greater than the sum of the parts. To use

Buckminster Fuller Richard Buckminster Fuller (; July 12, 1895 – July 1, 1983) was an American architect, systems theorist, writer, designer, inventor, philosopher, and futurist. He styled his name as R. Buckminster Fuller in his writings, publishing more t ...

's word, synthetic instruments are ''synergistic instruments''. Like a triangle is more than three lines, synthetic instruments are more than the triangle of hardware (Control, Codec, Conditioning) they are implemented on. Therefore, one way to tell if you have a true synthetic instrument is to examine the hardware design alone and to try to figure out what sort of instrument it might be. If all you can determine are basic category facts, like the fact that it can be categorized as a stimulus or response instrument, but not anything about what it's particularly designed to create or measure—if the measurement specificity is all hidden in software—then you likely have a true synthetic instrument. The DoD has created a standards body called the Synthetic Instrument Working Group (SIWG) whose role is to define standards for interoperability of synthetic instrument systems. The SIWG defines a synthetic instruments (SI) as: A reconfigurable system that links a series of elemental hardware and software components with standardized interfaces to generate signals or make measurements using numeric processing techniques.SIWG Meeting #2 Statements and Definitions, 11 December 2004

References

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External links

Synthetic Instruments Book-Blog
Measurement

See also

References

External links