LabVIEW Device and Instrument Control

LabVIEW Device and Instrument Control D.Ursutiu 1, P.Cotfas 1 and C.Samoila 2 1 University Transylvania of Brasov / Physics Department, Brasov, Romania 2 University Transylvania of Brasov / UTSM Department, Brasov, Romania Abstract This work intends to present the actual developments done by the team from Center for Valorization and Transfer of Competences CVTC (University Transylvania of Brasov) in the field of devices and instruments control using Graphical Programming (such as LabVIEW, VEE-Pro). At CVTC we develop and implement new technologies in the field of Remote Controlled Laboratories. The permanent evolution of devices and the new DAQ systems impose us to develop new drivers (based on.net technologies) and to implement controls through the Interchangeable Virtual Instrument (IVI) technologies. Index Terms - Graphical Programming, IVI, Remote Labs, Virtual Instruments. I. INTRODUCTION In our developments at Transylvania University of Brasov Romania, in connection with Remote laboratory and Remote control we selected and intensively used LabVIEW and VEE-Pro software. We are trying to develop drivers and interfaces for different measurement and data acquisition systems. If we have a look at different actual strategies connected with remote control, device interchangeability, software compatibility, virtual instruments (VI) and communication facilities we can and must adapt our development strategies to the actual evolution. Because we work in a polytechnic university we must use different measurement systems (with or without the necessary drivers) and at the same time we also have to use many Data Acquisition Cards (DAQs). The permanent evolution of devices and the selection of software for control impose us to develop drivers (based on.net technologies) and to implement controls through the Interchangeable Virtual Instrument (IVI) technologies. II. IVI DRIVERS AND DEVICE CONTROL Systems designed with IVI drivers enjoy the benefits of standardized code that can be interchanged into other systems. This code also supports the interchanging of measurement devices helping to prevent hardware obsolescence. Interchangeability is supported on three levels. The IVI architecture specifications allow architectural interchangeability that is a standard driver architecture that can be reused. The class specifications provide syntactic interchangeability which supports instrument exchange with minimal code changes. The highest level of interchangeability is achieved by using the IVI signal specifications. Many new engineering field applications deal with the corrosions and electrochemical measurements. At Faculty of Technological Engineering we need to provide laboratory facilities controlled by computer and by remote systems for corrosion and electrochemical applications. In this research and virtual instrumentation direction we have been collaborating with EcoChemie from Netherlands and we developed LabVIEW drivers for all their AUTOLAB - PGSTAT electrochemical measurement devices. These drivers development in LabVIEW, based on control of Dynamic Link Libraries (.NET DLLs) will be presented in our paper. For the same measurement and laboratory works we need DAQ cards to measure, control and simulate different processes. Because of the permanent evolution of software and hardware systems we selected the new line of USB DAQ cards from Agilent Technologies (the series of U23XXA) and the corresponding IVI drivers. These cards can be used together with the 6-slot USB Modular Instrument Chassis U2781A which offers a high density of measurement channels at an excellent resolution and uses only one USB connection [5]. The Center for Valorization and Transfer of Competence (CVTC) from Transylvania University of Brasov Romania was selected and involved by Agilent Technologies in the beta test program for this USB DAQ card. In this way, we were able to receive these cards and to test and develop applications before their first release on the market. III. VIRTUAL INSTRUMENTS FOR ELECTROCHEMICAL DEVICES CONTROL During the last years the CVTC from Transylvania University of Brasov Romania together with the young Romanian company, EPI SITEM SRL were involved in a collaboration with ECO CHEMIE Company from Netherlands in sales and promotion in Romania of AUTOLAB electrochemical instruments. In a bilateral agreement with ECO CHEMIE, CVTC developed a class of Virtual Instruments (VIs) as the necessary bricks useful for the researcher to build any electrochemical measurement strategies and to control the PGSTAT (electrochemical device from AUTOLAB line of devices). In Figure 1 we present these simple elementary VIs (the bricks for the new developments) and in Figure 2 some simple examples how to use these VIs to build REV 2007 - www.rev-conference.org 1

one application that uses the Analog Digital Converter (ADC) to monitor one signal with the PGSTAT system. For developing a.net application in LabVIEW, there is a previously created palette containing all the necessary functions (Figure 3) to communicate with.net Assembly [6]. Also, different methods or actions of the object can be invoked using the Invoke Node function. When finishing working with the object instance, the instance must be closed using the Close Reference function. An example of using this technology can be seen in Figure 4. This application creates an Autolab Instruments instance that is necessary for communicating with Autolab System [1]. Figure 1 Elementary VI s for Autolab Figure 4 Creating Autolab Instruments interface Figure 2 Autolab ADC example: Panel and Diagram The first step in starting to build an application is the creation of an instance of an object. This can be done using a.net constructor and associate this constructor with the desired object. If the object instance creation succeeds then, using the new reference offered by this constructor, the proprieties of the object can be get or set using the Property Node function. Figure 3 The.NET Functions Palette The researcher can now develop any application or he can increase the number of parameters in an already built application after his own desire. Also our students who use these interfaces with a low level of programming knowledge can build new measuring scenarios and test them on the Autolab systems. In Figure 2 is presented a simple example of using the set of icons presented in Figure 1. The example is dedicated to control the Analog Digital Converter. At first it is necessary to establish the communication with the Autolab system interface. This is realized with the load interface icons. Then, the Autolab Instruments instance that is presented in Figure 4 has to be created. If these steps succeed then the ADC object can be called. For this is necessary to follow the next steps: Initialize the ADC interface ADC Init icon Read the value from ADC ADC read icon Close the ADC interface ADC release icon At the end of the application, the Autolab system interface must be released by using the release interface icon. In Figure 5 is presented the Autolab Manual Control example that controls all the facilities of Autolab that were implemented in LabVIEW [1]. REV 2007 - www.rev-conference.org 2

After that, for an easier integration with the Autolab systems (or any other laboratory or research applications) we developed a line of LabVIEW drivers which interact with the IVI drivers and in the same way they can be used with any similar DAQ cards. These drivers (Figure 6) were developed in a similar structure as the virtual instruments presented in Figure 1 and will be the new bricks for development of any data acquisition system based on these USB DAQ cards. In Figure 7 we present one IVI application able to generate (using the digital analog channel of the DAQ card) different waveforms and at the same time to measure using one or more analog digital channels. Figure 5 The Autolab Manual Control example: Panel and Diagram IV. LABVIEW DAQ CONTROL USING IVI We used a USB DAQ card from Agilent (for example the U2353A) which comes with one IVI driver. At first we tested and we controlled the DAQ card in VEE-Pro graphical programming offered by Agilent Technologies with this family of cards [5]. Figure 7 Agilent U23XXA DAQ example: Panel and Diagram Programming in IVI technology is almost the same as programming in.net technology. In Figure 8 is presented the Initialize application for Agilent U235x DAQ. The difference is that instead of using a constructor, here an Automation Open function must be used [7]. Another example of using the icons from Figure 6 is presented in Figure 9. This application is dedicated to the monitoring and controlling of pollution with CO 2 in a room. Also, the application allows the monitoring of temperature in the room. In order to determine the CO 2 level, a STEINEL sensor was used and for determining the temperature, a K type thermocouple was used. The signals given by the two sensors were measured by using the first two channels of Agilent U235x DAQ. When exceeding the accepted levels of CO 2 and temperature, a ventilating fan is starting. The ventilating fan is controlled by using the DIO ports of the DAQ card. Figure 6 Elementary VIs for Agilent U23XXA DAQ boards REV 2007 - www.rev-conference.org 3

A similar control as in the application presented in Figure 9 can be done using CORES ZigBee wireles sensors (see Figure 10). The Wireless Node (WN-K100) family of 14 wireless measurement modules deliver information in real-time from environments and processes where data collection is impossible or impractical through wired sensors. The WN-family utilizes the 802.15.4 (ZigBee) protocol and provides small size, compact and low-cost modules for both measurement and connectivity to the PC. Figure 8 The Initialize icon for Agilent U235X DAQ: Panel and Diagram Figure 10 CORES ZigBee Wireless modules The user interface of the application that uses the ZigBee wireless technology described above is presented in Figure 11 [2]. Figure 11 The interface of CO 2 &Temp application with Wireless Nodes V. CONCLUSIONS Using LabVIEW we can easily implement drivers (with the.net DLLs or IVI technologies) and offer an easy way for researchers and students to develop more sophisticated applications. Based on these virtual instruments we can integrate new measuring devices and DAQ cards in local and remote controlled laboratories. These technologies increase the development speed and offer a relative immunity of our labs to the permanent exchanges registered at the equipment and DAQ cards level. Students and researchers with beginner knowledge of LabVIEW programming can play with these VIs and develop new applications. Figure 9 Temperature and CO 2 monitoring application: Panel, Diagram and a system Picture REV 2007 - www.rev-conference.org 4

REFERENCES [1] P. Cotfas, D. Ursutiu, C. Samoila D. Cotfas Controlling in LabVIEW of the Eco Chemie - AUTOLAB measurement systems, CNIV2006, 29 Mai, Bucharest, ISBN (10) 973-648- 579-X, ISBN (13) 978-973-648-579-4; [2] Petru Cotfas, Doru Ursuţiu, Daniel Cotfas, Cornel Samoilă Sistem Wireless pentru monitorizarea nivelului de CO 2 din aer, CNIV2007, 28 Mai, Bucuresti, ISBN 978-973-648-657-9; [3] Doru Ursuţiu, Petru Cotfas, Cornel Samoilă, Daniel Cotfas Tehnologii utilizate în laboratoarele controlate la distanţă, CNIV2007, 28 Mai, Bucuresti, ISBN ISBN 978-973-648-657-9; [4] What are Instrument Drivers and I/O Software?, http://volt.ni.com/niwc/products/inst_drivers_io_sw_what_is.jsp [5] U2300A Series USB Modular Multifunction Data Acquisition, http://www.home.agilent.com/agilent/product.jspx?cc=us&lc=en g&ckey=823921&nid=-35823.0.00&id=823921; [6].NET Support in LabVIEW 7 Express, http://zone.ni.com/devzone/cda/tut/p/id/4888; [7] Agilent U235x Documentation, Agilent Technologies, 2006. AUTHORS D. Ursutiu, Prof. Dr., Transylvania University of Brasov, Department of Physics, udoru@unitbv.ro P. Cotfas, Lecturer Dr., Transylvania University of Brasov, Department of Physics, pcotfas@unitbv.ro C. Samoila, Prof. Eng. Dr., Transylvania University of Brasov, Department of Science of Materials, csam@unitbv.ro REV 2007 - www.rev-conference.org 5