Instruments4Chem

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National Instruments LabVIEWTM


LabVIEWTM is a powerful graphical programming language developed by National Instruments Corporation. It has emerged as a widely used proprietary standard for instrument data acquisition and control.

LabVIEWTM is based on the concept of VI's or "virtual instruments". A VI has a "front panel" that contains a collection of "controls" and "indicators" through which the user interacts. Controls allow user inputs, while indicators display data. LabVIEWTM front panels can be designed to look exactly like the professional front panels found on commercial instruments.

At right is a very simple vi, whose front panel takes 3 user inputs and computes 16 bit DAC values for an up-down linear ramp that is to be used as an excitation waveform in an electrochemistry experiment. The waveform is displayed in a graph window.
Fundamental to, but normally hidden from the end user is the VI's "diagram" - an example of which is seen above. This is a graphical representation of how the VI functions - or put in another way - how the inputs get transformed into outputs.

One of the real strengths of LabVIEWTM is that the user can construct VI's without needing to know a programming language - LabVIEWTM takes the user's diagram and converts it into a program automatically. A user diagram is created by placing icons onto the working area and wiring these up with a "wiring" tool, in a manner closely resembling how electronic components are soldered together when building a circuit. The diagram above generates the scan waveform shown previously. In this diagram are various sub-vi's, some simple math operators, a true/false decision making block, a looping structure, some array functions, and a graph structure for displaying the scan waveform.

For building custom instruments LabVIEWTM offers many attractive features - extensive mathematical function libraries, access to the PC’s serial ports for data-logging, the ability to effortlessly produce great graphical displays with numerous plotting options, powerful data analysis libraries including access to Fourier transform techniques, data smoothing routines and file I/O utilities for generating data files suitable for loading into spreadsheets. By making use of each of these features it is possible to develop sophisticated instruments whose capabilities can grow without requiring much in the way of changes to the basic hardware.

A full version of LabVIEWTM is required to develop and modify VI's. But a run-time executable, or RTE, on the other hand, can be distributed without licensing fees; this allows other users to run an already developed vi but with the qualification that it may not be built or modified.

In order to use a LabVIEWTM RTE the user must first download a package called the LabVIEW Run-Time engine onto their PC. The LabVIEWTM 2013 run-time engine can be obtained from the National Instruments web site at http://www.ni.com/download/labview-run-time-engine-2013/4059/en/. Newer versions are likely to be available when you read this.

A second package that you will need to run LabVIEWTM RTE’s is the VISA runtime engine, which can be found in the downloads area here. You should download the same version as for the run-time engine discussed above. NI-VISA provides support for the serial communications that are used between the PC and most of the instruments described on this website.

LabVIEWTM run-time executables are PC applications that will run under both the Windows 7/8 and Vista operating systems. Although yet to be confirmed they should also run successfully in a Windows partition on a Mac computer running VMWare Fusion or a similar emulation program. Support for runtime engine installation problems is available on the National Instruments web site at this link.

Distributable RTE’s are an extremely attractive feature, since an instrument's GUI then becomes available to end-users at no cost. For use in schools and undergraduate teaching labs with large class sizes, for example, this is a major advantage in putting low cost instrumentation in front of students. RTE's are available for each of the instruments described on this website - if you are interested just email a request to instruments4chem@gmail.com.

Some exciting news is that a LabVIEWTM Home edition has recently become available at very low cost; for full details see the LabVIEWMakerHub website. Armed with this version of LabVIEWTM a user can develop their own vi’s.

Further information and technical support for LabVIEWTM is available at http://www.ni.com/labview/.