Instruments are widely used in industries to accumulate and record data in working environment, and/or from a component under test, and finally to display useful information to a user on the basis of such accumulated and recorded data. A number of instruments make use of transducers to detect changes in the set physical parameters, for instance pressure or temperature, and then translate the detected data into e-signals, such as frequency or voltage variations.
Nowadays, instruments are no longer the traditional devices which were operated by individuals manually because of the paradigm shift induced by technological changes. Therefore, instruments may be referred to as physical software devices that analyzes data generated by another remotely-placed instrument and then relays processed information to other recording devices. Technological developments in this field entail employment of modifiable software coupled with ‘modular measurement hardware to create user-defined measurement systems’ in other words referred to as virtual instruments.
Virtual instruments include multimeter, function generator, network analyzer, bode plotter/signal analyzer, spectrum analyzer, digital signal generator, logical analyzer, and XY recorder (National Instruments Corporation 2010). Virtual instruments are currently being widely adopted especially by engineering-based industries to increase their general performance, productivity of their systems, and the accuracy of their machines. They comprise of industry-standard workstations or computers furnished with application software for instance Lab VIEW, commercial hardware e.
g. plug-in boards, as well as driver software. Hence, engineers are capable of building measurement and automation methods that suits user-defined needs instead of limiting themselves to vendor-defined instruments. In every virtual instrument, software is the most essential constituent and up on having the right software development tools, a developer can comfortably make own application. Consequently, such application software necessitates modularity where large projects are involved. This means that each particular task is managed independently and achieves results.
The virtual instrumentation software comprises of three distinct layers: application software, test and data management software, and measurement and control services software. Application software provides the fundamental environment to build-up the system and comprises of software for instance LabVIEW, Measurement Studio, Lab Windows/CVI, VI Logger, and Signal Express (Sumathi & Surekha 2007). The Test and Data Management Software integrates most of the functionality built by application software to offer a system-broad data organization.
Lastly, measurement and control services software comprises of drivers for instance NI-DAQmx for sustaining productivity of software development as well as to communicate with hardware in the system. In virtual instrumentation for design, there are two distinctive stages -designing and testing- as illustrated in the figure below. Initial stages comprises of carrying out research, simulation, verification, and finally manufacturing. Figure 1. Virtual Instrumentation for design In virtual instrumentation, measurement and test has continued to be of importance for majority of companies.
Most of them use Virtual Instruments produced by National Instruments Corporation to carry out the exercise by assuming digitization capabilities of up to 200MS/s. For instance, PXI group offers membership to about 50 individuals to deliver products as well as provision of tests for validation. Therefore, the call for carrying out virtual instrumentation tests has been increasing significantly motivated by rate at which innovations are occurring and the need to need to meet the growing market demand for products.
Subsequently, as there is considerable increase in consumer expectations especially for electronic markets, the need to incorporate dissimilar functions in one place is a must. This has to be cost-effective and reliable. The scarce amount of resources at disposal has however presented limit in achieving the market demand of any industry reliably and consistently. Hence, the need for new verification, validation, and manufacturing tests and attest platform capable of supporting today’s innovations is of major importance.
Bu such platform has to have rapid test tools adjustable enough to be applied in the entire product development. In this regard, precise and orchestrated measurement instruments are necessary for testing compound multifunction merchandise to meet market demands. All the aforementioned challenges can be sufficiently met through virtual instrumentation as it incorporates ‘rapid development software and modular, flexible hardware to create user-defined test systems’.
A virtual instrument brings on board spontaneous software tools to facilitate fast test development, quick and accurate modular based new industrial technologies, and computer-based platform that has incorporated management for high throughput and accuracy (National Instruments Corporation 2010). In all virtual instrumentation tests, software is the most important element to facilitate testing of complex consumer products. This ranges from verifying designs testing the highly programmed systems of manufacturing.
To accomplish this, it is mandatory to have the relevant test development kit which consists of test development, test management, and I/O drivers as represented in the figure below. Figure 2. Architecture of Rapid Development Software The test management software avails a structure for well programmed test systems for instance branching/looping, sequencing, database integration, and report generation. Besides, test management kit has to provide firm combination in the test development settings where application-explicit tests are built.
For instance, National Instruments Corporation has a test management program known as TestStand that incorporates connectivity to the general test development settings. As earlier mentioned, test development setting is the most critical element for accomplishing fast test deployment. Therefore, such environment should make available tools for quickly developing test procedures. A good example is Lab View’s graphical programming that makes use of symbolic functions or icons to pictorially signify action being performed (Sumathi & Surekha 2007).
The fact that test processes are visual makes the general test development and comprehension rapid. In this regard, LabVIEW is the widely used comprehensive graphical development environment. LabVIEW facilitates creation of graphical user interface in which an engineer can run instrumentation program, manage selected hardware, analyze collected data, and display results. A person is capable of customizing front panel using buttons, knobs, graphs, and dials to imitate traditional control panels. The figures below illustrates LabVIEW virtual instrument. Figure 3.
Front Panel Figure 4. Block Diagram Additionally, LabVIEW facilitates may be used to create distinctly user-defined systems by applying modular I/O as illustrated in the diagram below. Figure 4. LabVIEW Customizable Hardware and Virtual Instruments I/O driver software is as well vital element in rapid test development and consists of: instrument drivers –avails human-readable roles to interface with instrument, configuration tools –stores calibration, scaling, and channel information, and rapid I/O assistants –refers to interactive tools to swiftly create a measurement application.
In LabVIEW 7 Express, I/O assistants include DAQ Assistant and Instrument I/O Assistant. For instance, some of the parameters that can be configured in DAQ Assistant panel include: voltage and current –measured using digital multimeter, temperature, resistance, frequency, acceleration, and sound pressure among others (National Instruments Corporation 2010). Nowadays, almost every modern test system is based on a computer-platform. Besides, the computer is not only an element of virtual test system but also a critical integrating platform i.
e. the nerve centre. What makes computer-based test platform ideal is the high GHz processors, open source software, high speed buses, and low cost. Modular I/O is measurement hardware that inherent in circuit board which may be plugged into CompactPCI eXtensions for Instrumentation (PXI) backplane or a PC and makes use of data acquisition and/or modular instruments technology. One of the most applicable test technologies is provided by PXI for Instrumentation which is a model modular I/O built on computer technology.
PXI facilitates timing, synchronization, and channel count into a computer-based architecture. PXI backplane consists of both shared triggers and low-skew click as it appears in the figure below (National Instruments Corporation 2010). Figure 5. The PXI platform In comparing virtual instruments to traditional ones, the former offers wide range of benefits. First, virtual instruments can be configured /customized because they are computer-based and are regularly updated with the advancements in computing. Such advancements are for instance high-speed processors, and more secure operating systems.
Accordingly, most of the applications for instance LabVIEW runs on a wide range of systems such as Windows series, Mac OS, Linux, and Sun Solaris. Secondly, they are portable and this enables recording /analysis of results on real-time basis. Third, virtual instruments offer flexible and scalable as they can be modified on need-basis. Fourth, deployment of virtual solutions lowers costs in terms of capital, and system development and maintenance as well as time needed to market products. In addition, quality of products is greatly improved.
Applications used in manufacturing require reliable, high performance, and interoperable software and this is all offered by virtual instruments. These benefits are necessitated by ability of virtual instruments to integrate a number of features for instance historical data tracking, alarm management, networking, and security. Nevertheless, the most significant challenges posed by adoption of virtual instrumentation solutions is that an industry must automate all its entire systems –financial constrains and train or employ highly skilled staff (National Instruments Corporation 2010).
Virtual instrumentation has greatly liberalized measurement systems to becoming quick and cost-effective. Therefore, industries are capable of considerably reducing development time, increase quality productivity, and ultimately position themselves as real competitors in the market. References National Instruments Corporation 2010, Virtual Instrumentation for Test, Control, and Design, viewed 10 August 2010, < http://zone. ni. com/devzone/cda/tut/p/id/4762>. Sumathi, S & Surekha, P 2007, LabVIEW based Advanced Instrumentation Systems, 1st edn, Springer, New York.