A LabVIEW-Based Virtual Instrument System for Laser
Contents
1. Journal of Spectroscopy Journal of l Theoretical Chemistry International Journal of Inorganic Chemistry Pa a Fa J E Journal of Hindawi Publishing Corporation http www hindawi com Volume 2014 International Journal of medrol als aalciay Chromatography Research International Journal of Quantum S Hindawi Publishing Corporation http www hindawi com Journal of T a Analytical Methods g in a Bioinorganic Chemistry and Applications2. ual instruments By clicking on the Access Other Programs button on the excitation spectrum panel in Figure 4 users can select the application program by browsing the computer disks Figure 5 shows the block diagram of the subVI for accessing other programs The Browse Boolean command is wired to the upper case structure which includes a File Dialog Express VI The application can be selected when the file path is displayed on the front panel When the user confirms the file selection the application program is activated via the System Exec vi shown in the lower case structure in Figure 5 3 2 Program for Dispersed Spectra A change in the dispe rsed spectrum program is the addition of synchronizing fluorescence DAQ with a monochromator wavelength scan instead of a dye laser scan The 300i monochromator used in our dispersed LIF experiment was an Omni A3008 spec Journal of Automated Methods and Management in Chemistry E Filename and p System exec vi FIGURE 5 SubVI for Access Other Programs trometer Beijing Zolix Instrument Company Commu nication between the Omni A3008 spectrometer and the computer is achieved via a USB port on the Omni A3008 spectrometer The Omni A3008 spectrometer is operated by a ZolixOmniSpec ActiveX OmniSpec provided by the man ufacturer In the LabVIEW VI system we invoke an ActiveX Container and created a ZolixOmniSpec ActiveX object an Automation Open in the ActiveX functions palette is
3. ot Serial port RS 232 Pump beam Journal of Automated Methods and Management in Chemistry Scan control parallel port External trigger VI system based on LabVIEW AN AEN l GPIB FiGurE 1 Hardware structure of VI System higher energy state is scanned and the total fluorescence is measured Information on lower electronic states can be obtained by dispersed spectra while the excitation spectra reveal parameters energy levels structure information etc of upper level electronic states A conventional experimental setup for obtaining laser induced fluorescence excitation spectra and dispersed spec tra are depicted in Figure 1 The sample vapor is injected into a vacuum chamber whose vacuum is maintained by a molecular pump and a mechanical pump via a supersonic jet The excitation laser beam probe beam is provided by a frequency doubled dye laser pumped by a Nd YAG laser The probe beam intercrosses the sample 10 to 15 mm downstream of the supersonic jet nozzle when free radicals are studied a pump laser beam propagates across the sample close to the nozzle and generates the free radicals Fluores cence of the excited molecules is collected perpendicular to the probe beam by the optics and imaged onto the detection devices For excitation spectra total fluorescence is detected by PhotoMultiplier Tube PMT and converted into elec tronic signals which are received and displayed in real time on an osci
4. called which returns an automation reference number and allows the specific functions programmed in the ZolixOmniSpec object to be accessed Property nodes in the ActiveX palette are used for reading the USB port information The Omni A3008 spectrometer USB serials string is found by calling the SearchZolixUSBDevice and GetZolixUSBSerial invoke methods and then the string is wired to the USBSerials property node The invoke commands Open and Connect are used for setting the connection status of the monochro mator and the status is displayed by the Boolean indicator on the front panel The initial states of the Omni A3008 monochromator components such as the exit port grating and current wavelength are obtained by employing the GetExitPort GetCurrentGrating and CurrentWave methods respectively Next different parameters are set according Journal of Automated Methods and Management in Chemistry FIGURE 7 Program for dispersed spectrum to experimental requirements This step involves the user s input of the experimental parameters by selecting from the pull down menu on the front panel The SetExitPort and SetCurrentGrating in the case structure return to the default state which is set as Do Nothing as soon as the commands are given to avoid sending looped control commands to the OmniSpec The Prompt User for Input function in the Dialog and User Interface is called and it prompts the user to input a specific
5. eight bit parallel bus that provides high speed data transfer and multiple instrument control 18 Detailed programming is shown in the upper left Flat Sequence Structure of Figure 3 We invoked the GPIB Write function from the LabVIEW Instrument I O function to set the GPIB address of the oscilloscope and specify the data parameters to be transferred from the oscilloscope including the portion of the waveform that users want to transfer the waveform source data format and the number of bytes per data point We then invoked the GPIB Read function and wired the corresponding GPIB address of the oscilloscope to the GPIB Read and also specified the number of bytes the function read from the oscilloscope Finally we called the function nodes Math Pattern String Subset Decimate 1D Array and Join Numbers to receive waveform data from the oscilloscope and display it in situ in the front panel waveform graph Data from different oscilloscope channels CH1 CH2 or Dual CHs can be acquired by wiring selected terminals in a combo box to the case structure prior to data acquisition For the end user the above process is easily achieved by choosing the channel from the pull down list on the front panel Figure 4 and clicking on the Acquire button There are two sequential subdiagrams in the upper right case structure of Figure 3 The left one performs the analysis and processing of the fluorescence data obtained from the TDS3032B oscilloscope at
6. from the Major State Basic Research Development Program Grant no 2007CB815206 and the Program for NCET References 1 S Gopalakrishnan L Zu and T A Miller Rotationally reso lved electronic spectra of the B X transition in multiple conformers of 1 butoxy and 1 pentoxy radicals Journal of Physical Chemistry A vol 107 no 26 pp 5189 5201 2003 K H Katharina Quantitative laser induced fluorescence Some recent developments in combustion diagnostics App lied Physics B Photophysics and Laser Chemistry vol 50 no 6 pp 455 461 1990 L Zhang K M Callahan D Derbyshire and T S Dibble Laser induced fluorescence spectra of 4 methylcyclohexoxy radical and perdeuterated cyclohexoxy radical and direct 2 Oo Journal of Automated Methods and Management in Chemistry kinetic studies of their reactions with O2 Journal of Physical Chemistry A vol 109 no 41 pp 9232 9240 2005 J Yang X Zhang D J Clouthier and R Tarroni Heavy atom nitroxyl radicals HI Identification of the Cl P S free radical in the gas phase by laser spectroscopy and ab initio calculations Journal of Chemical Physics vol 131 no 20 pp 204307 204313 2009 H Meng J Li and Y Tang The design and application of virtual ion meter based on LABVIEW 8 0 Review of Scientific Instruments vol 80 no 8 Article ID 084101 5 pages 2009 6 S Nuccio and C Spataro Asses
7. wavelength which is subsequently sent to the wavelength terminal in the MoveToWave method After using the MoveToWave method a Stop function is required to stop the grating from moving The operation panel and program are shown in Figures 6 and 7 A similar comparison case structure is applied here to step the monochromator scan wavelength as the one used in the Excitation LIF spectrum program Identically to the excitation experiment the start position end position step size of the monochromator scan and the gate for fluorescence signal integration will await user input on front panel Executed from the front panel data acquisition will begin and the real time spectrum will be displayed in the XY Graph Using the Save icon on the front panel the experimental data can be stored in the computer via Write to Spreadsheet File vi An Automation Close is programmed in the VI system to disconnect the USB interface to the Omni A3008 and release the system resources when the Dispersed Spectrum subVI is closed 3 3 Program for Data Processing The data processing subVI Figure 8 can conveniently redisplay and analyze previously saved data 21 22 This subVI can automatically accomplish wavelength calibration unit conversion and peak and Data Processing Earslangih to Hirsmmbar s Zero Setting Betarn to Tero Regai D 00 Mo a0 Bo Bo Vaearesber ca Figure 8 Front panel for data processing band width reading of the spe
8. 1 J Ballesteros J I F Palop M A Hern dez R Morales Crespo and S Borrego del Pino LabView virtual instrument for automatic plasma diagnostic Review of Scientific Instruments vol 75 no 1 pp 90 93 2004 22 E Klocke O Dambon U Schneider R Zunke and D Waechter Computer based monitoring of the polishing processes using LabView Journal of Materials Processing Technology vol 209 no 20 pp 6039 6047 2009 23 J A Warren J M Hayes and G J Small Symmetry reduction vibronically induced mode mixing in the S1 state of p methylnaphthalene The Journal of Chemical Physics vol 80 no 5 pp 1786 1790 1983 24 N A Borisevich G G D yachenko V A Petukhov and M A Semenov Fine structure spectroscopy of 2 methylna phthalene cooled in a supersonic jet Optics and Spectroscopy vol 101 no 5 pp 683 690 2006 25 L Wang Q Wu and L Zu Laser induced fluorescence of 1 Methylnaphthalene in a supersonic jet expansion Spec troscopy Spectral Analysis vol 31 no 11 4 pages 2011 International Journal of nedi Chemistry International Journal of Carbohydrate Chemistry The Scientific World Journal Organic Chemistry International lt e International Journal of Analytical ISIE ey A a Advances in Physical Chemistry Hindawi Submit your manuscripts at http www hindawi com
9. Hindawi Publishing Corporation Journal of Automated Methods and Management in Chemistry Volume 2011 Article ID 457156 7 pages doi 10 1155 2011 457156 Research Article A LabVIEW Based Virtual Instrument System for Laser Induced Fluorescence Spectroscopy Qijun Wu Lufei Wang and Lily Zu Department of Chemistry Beijing Normal University Beijing 100875 China Department of Chemistry Bijie University Bijie 551700 China Correspondence should be addressed to Qijun Wu wuqijun1977 yahoo com cn Received 30 July 2011 Accepted 28 September 2011 Academic Editor Lu Yang Copyright 2011 Qijun Wu et al This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited We report the design and operation of a Virtual Instrument VI system based on LabVIEW 2009 for laser induced fluorescence experiments This system achieves synchronous control of equipment and acquisition of real time fluorescence data communicating with a single computer via GPIB USB RS232 and parallel ports The reported VI system can also accomplish data display saving and analysis and printing the results The VI system performs sequences of operations automatically and this system has been successfully applied to obtain the excitation and dispersion spectra of a methylnaphthalene The reported VI system op
10. a particular laser wavelength Four cursors were created and property nodes were set to acquire the cursor s horizontal axis positions on a waveform graph and to define the gate width We then used the Array Subset to return two portions of fluorescence data between the two sets of cursors On the front panel users can directly drag the cursors to where they want or they can simply set positions in the cursor legend to choose the gate on the graph Integrals of data in both gates are computed separately using the 1D Numeric Integration vi in which the integration method is the Trapezoidal Rule The difference between the two gate integrals is calculated for the purpose of background subtraction Finally the fluorescence intensity and the current wavelength are sent to the XY Graph for real time spectroscopy display The front panel of the fluorescence Excitation Spectrum is shown in Figure 4 in which Choose Gates is shown in the upper portion and Spectroscopy Display in the lower part As soon as the data processing is complete a TTL trigger is sent to step the dye laser to the next wavelength TTL subVI shown in the right sequential diagram in the case structure of Figure 3 calls the Outport vi in Port I O which specifies a parallel port address for sending the trigger pulse and also defines the pulse width A BNC cable is made with the inner core wired to the specified TTL pulse pin of the computer parallel port and the outside shie
11. ctrum curve Users can also inspect each dataset using cursor move data refresh figure enlarge and diminish and graph recover tools In the VI programming a File Dialog function will prompt the user to upload a data file The Read From Spreadsheet File vi and Index Array function will convert the wavelength and intensity data to x and y arrays respectively Wavelength unit conversion is realized by the case structures and then the processed data will be sent to the XY Graph for display and saving by Write To Spreadsheet File vi Spectrum graph printing is achieved by using the relevant Report Generation functions 4 Application The VI system reported here has been used to take flu orescence spectra of molecules and free radicals in our laboratory The excitation spectrum of a methylnaphthalene is shown in Figure4 in wavelength nm and Figure 8 in wavenumber cm Dual CHs were used for data acquisition one for studying the fluorescence signal and another for monitoring the laser power fluctuation using a photodiode High resolution and signal to noise ratios were achieved in the spectra The obtained excitation spectrum was consistent with previously reported results 23 24 with spectral origin at 31767 cm 314 80 nm The dispersed fluorescence spectrum of a methylnaphthalene shown in Figure 6 was obtained by exciting the most prominent band at the wavelength of 310 70 nm Dispersed spectra utilizing excitation of other band
12. ens up new possibilities for researchers and increases the efficiency and precision of experiments The design and operation of the VI system are described in detail in this paper and the advantages that this system can provide are highlighted 1 Introduction Laser induced fluorescence LIF is a technique that relies on the measurement of the excited state fluorescence that results from photoexcitation The excitation source for molecular LIF is typically a tunable dye laser so that selective excitation and high resolution can be achieved Combined with the supersonic jet expansion technique LIF has been used to study the excited state structures of molecules and the ultra fast dynamics of molecular systems 1 LIF has also been successfully applied for quantitative measurement of concentrations in combustion plasma spray and flow phenomena in some cases visualizing concentrations down to nanomolar levels 2 Unlike other analytical spectroscopy techniques where ready to use commercial spectrometers have everything for the sample detection in a package laboratories usually design and set up the LIF experimental instruments by themselves in order to satisfy individual research needs In addition to hardware installation LIF also requires synchronized and automated control software for laser function data acquisition and communication between instruments 3 4 Most laboratories develop homemade programs for their experiments using d
13. ere are three icons Excitation Spectrum Dispersed Spectrum and Data Processing on the front page of the virtual instrument system each is dedicated to a specific action or experimental technique When an icon is selected the corresponding subVI program will be activated and it will open the panel where specific tasks can be exe cuted For programming an Event Structure for incident response is used to call the corresponding subVI 17 When the subVI starts the Event Structure waits until the precompiled program code is executed and the task is finished then the Event Structure returns to wait for another event 3 1 Program for Excitation Spectrum To fulfill the require ments of LIF excitation spectra the Excitation Spectrum subVI consists of fluorescence data acquisition data dis play and saving vacuum monitoring communication with other application modules and synchronization of laser wavelength scan subVIs Journal of Automated Methods and Management in Chemistry lt __ _ _ _ lt Stop gt Yes Yes Excitation spectrum Dispersed spectrum Set parameters Set parameters Process Save Print No FIGURE 2 Flow chart of VI system 3 1 1 Data Acquisition and Processing In the experiment the fluorescence signal is collected by the PMT and transferred to a TDS3032B oscilloscope The TDS3032B oscilloscope sup ports the GPIB interface communication with a computer where the interface is an
14. ifferent programming languages such as Visual C LabVIEW Visual Basic or Turbo Pascal but text based languages have the shortcomings of long devel oping cycles and difficulties in maintenance and expansion 5 NI LabVIEW 2009 National Instrument Inc USA is a graphical programming tool which can be employed to develop sophisticated measurements 6 8 and control 9 10 systems using intuitive graphical icons and wires that resemble a flowchart instead of written lines of text 11 16 In this paper a virtual instrument system based on LabVIEW 2009 was developed for LIF experiments This system can simultaneously control the scanning of a dye laser and a monochromator the operation of a molecular pump and data acquisition Furthermore it achieves real time data processing and monitoring of individual instruments An application of this program in the LIF spectroscopy examination of a methylnaphthalene is shown in this paper Simple modifications for adapting this program to different LIF setups are also illustrated 2 Configuration of System Hardware There are two different kinds of spectra in LIF spectroscopy dispersed spectra and excitation spectra The dispersed spectra are obtained with fixed excitation laser wavelength and the fluorescence spectrum is analyzed In excitation spectra the laser wavelength exciting the molecules to a r l Vv a nm Doubled oubled 998 632 nm Nd YAG a methylnaphthalene Ar
15. ld wired to the ground pin Thus a TTL signal can be sent to the dye laser control unit from the computer parallel port when a data collection cycle is completed and the laser is stepped to the next scan wavelength The settings for start position end position and step size of the laser wavelength scan must be identical in our VI program and in the laser control software The TTL subVI is placed in a comparison case structure If the current position is smaller than the end position the comparison function will return a False value to initiate the program TTL vi which will move the laser to the next wave length to start a new data acquisition and processing cycle If the current position is greater than or equal to the end position the True case gives a message dialog box indicating that data acquisition DAQ is finished Subsequently data can be saved by employing the Write to Spreadsheet file and the Build Array and Transpose 2D Array nodes This task is completed by clicking on the save button on the front panel and the fluorescence data will be saved according to the file name entered The data acquisition process can be stopped at anytime by clicking the Acquire button again in case the user wants to interrupt the experiment An abort function is also programmed using the Stop node in the Application Control function so users can terminate the whole VI system by clicking on the Abort Execution button in the upper right corner shown i
16. lloscope synchronized by the triggers from the Nd YAG laser A General Purpose Interface Bus GPIB card installed in the computer transfers data from the oscilloscope to the computer via the GPIB port and data acquisition and processing are executed by the VI system At the same time the VI controls the dye laser scans by sending trigger pulses to the laser controller via the parallel port of the computer The acquisition and control process for dispersed spectra are similar to those for excitation spectra For dispersed spectra the fluorescence signals are transmitted through a monochromator before being collected by the PMT The VI system communicates with and controls the scan of the monochromator via the USB port in the monochromator In addition the VI system also communicates with the vacuum gauge via an RS232 port and the system displays the in situ values of the vacuum The VI system also builds up an interface to communicate with the operating program of the individual instruments e g the dye laser and the molecular pump specific operating programs are usually included with the instruments at the time of purchase 3 Programming Figure 2 shows the flow chart of the VI system that per forms the LIF experiments and data processing tasks It incorporates several subVIs each one of which carries out a specific function including data acquisition and display data processing as well as generating and saving the results Th
17. n Figure 4 For convenience the help function of the program can be shown by clicking on the Help button on the front panel 3 1 2 Vacuum Monitoring and Accessing Other Application Software The program for the real time display of the vacuum gauge is shown in the lower left parallel loop of Figure 3 To communicate with the vacuum gauge the Serial function templates in the LabVIEW Instrument I O can be selected Parameters such as VISA resource name baud rate data bits and parity in the VISA Configure Serial Port are set according to the vacuum gauge communication protocol 19 20 The VISA write function sends command characters 2 Rirpig AbortExecution StartPosition StepSize VaccumMeter EndPosition Current fove 1 to zj 316 000 216010 ChooseChannel Dual CHs 6 000 5 000 4 000 3 000 2 000 1 000 0 000 1 000 1 1 1 1 1 1 1 1 1 1 1 1 1 304 00 305 00 306 00 307 00 308 00 309 00 310 00 311 00 312 00 313 00 314 00 315 00 316 00 317 00 wavelength HAA Figure 4 Front panel for excitation spectrum to the vacuum gauge and receives vacuum values in return The nodes String to Byte Array String to Single Precision Float and Index Array transform the vacuum data into the required format and display the values on the front panel indicator For convenience the VI system was designed to interface with the other applications that already exist for the individ
18. ommunication protocol for the corresponding replacement instrument or change the file path in the Access Other Program subVI by following the instructions provided in the VI The VI system has user friendly front panel windows and is easy to operate Help and Instructions implanted in the program will assist the user in becoming familiar with each application step The VI system was tested extensively and applied in the determination of the excitation spectrum and the dispersed spectrum of a methylnaphthalene with satisfactory exper imental results The VI system promotes and expands the capabilities of individual instruments and it is an intelligent improving for existing hardware sources of laboratory Lots of complicated functional operations are merely finished at the click of button on the VI system The VI system not only avoids the manual error during the separate instrument control data acquisition and data processing but ensures the accuracy and repeatability of experimental data and improves the efficiency of experiment Furthermore the VI system has a wide expandability of functions minor modifications can be applied to a different LIF setups based on automatic measurement and control The VI system will be provided upon request Acknowledgments The authors are pleased to acknowledge financial support of this research by the National Natural Science Foundation of China Grant no 20673013 The authors also acknowledge grants
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20. s 306 50 nm and 314 80 nm were also obtained Spectral analysis was conducted assisted by theoretical calculation and would be reported elsewhere 25 5 Conclusions A VI system for LIF spectroscopy based on LabVIEW 2009 has been developed The VI system integrates a variety of laboratory equipment and controls the experiment data acquisition process using a single computer via GPIB USB RS232 and parallel ports It achieves synchronous control of equipment and real time fluorescence data acquisition Data display saving and analysis can also be accomplished using the reported VI system Furthermore the VI system Journal of Automated Methods and Management in Chemistry can monitor running of individual instruments and chang ing of vacuum and laser power in real time Therefore the users can timely judge analyze and process on site information and high resolution and signal to noise ratios of molecular or free radicals can be easily achieved in the spectra Our approach has been to develop the VI system for general use in LIF experiments The instruments used in this paper such as the Nd YAG laser SurelitelII Continuum dye laser NarrowScan Radiant Dye digital delay generator DG535 Stanford oscilloscope TDS3032B Tektronix and PMT CR110 Hamamatsu are commonly used in many laboratories When different instruments are to be used in an experiment the users simply replace the communication method according to the c
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