Development of 4/16-Channel Data Acquisition System Using Lab
Contents
1. Figure 2 Start Program 2 Acquiring Signal And Processing The second case is acquire signal and process it Event structure is used to create three event case In first event case signal is acquired first and then displayed and give it to statistics block which returns input signal parameters Basic function generator vi and DAQm x read vi are used to acquire signal Function generator generates four types of signals namely sine square sawtooth and triangular DAQmx read vi acquire signal from MAX which already created as a channels Right click at the top of event structure and select edit event option and insert the items with value change application a 0 INPUT SIGNAL signal type 4 16 CHANNELS Value Change Basic Function Generator vi INPUT SIGNAL Maximum Time of Maxiqura maximum el ie j Ces amiji f Minimdm Time of Minimdadex of minimum i pe a j Lise Statistics ff SAF Firsthvaluey Maximum oA fe Index of Max_ f i SELECT re E Tab Control E frequency Hz E P a CHANNELS Figure 3 Acquire signal In the second event case input signal is first filtered using Digital IIR filter vi and output of filter is fed to Power spectrum vi and spectral measurement express vi used to show FFT of signal here also edit events of event structure and add events with value change application Volume 3 Issue 7 July 2014 Licensed Under Creative Commons Attribu2. 2319 7064 All the results are displayed on graphical user interface based program of 4 16 channel data acquisition system which work upon received data and process it effectively for optimum requirement of industry 6 Conclusion and Future Scope The 4 16 channel data acquisition System is basically enwrapped with PC based data acquisition Here data is acquired in the form of electrical pulses of some micro volts range filter them amplify them and finally fed it to PC where a GUI based Program can work upon the received data and process it For developing 4 16 channel data acquisition system it is essential to meet the requirements are Configuration of the analog input Actual reading of the analog input as per the parameters mentioned above Displaying the waveforms data acquired Displaying the various data inferred from the acquired input Post acquisition analysis Saving a data Retrieving the data from a saved file for regeneration and analysis Here conclusion is that software developed acquires data from four and sixteen channel data acquisition system and requisite processing on the data can be done during functioning of software Processing like pre filtering using digital IIR filtering FFT and Power spectrum etc were visualized on front panel As discussed in results FFTs produce the average frequency content of a signal over the entire time that the signal was acquired The power spectrum shows power as the mean square
3. International Journal of Science and Research 1JSR ISSN Online 2319 7064 Impact Factor 2012 3 358 Development of 4 16 Channel Data Acquisition System Using Lab VIEW Kishori Jadhav Nisha Sarwade IPG scholar Electrical department VJTI Matunga 400019 Associate professor Electrical department VJTI Matunga 400019 Abstract The increased performance of personal computers and their reduced cost has made it possible for development of PC based signal processing systems Combining virtual instrument technology to achieve the purpose of physiological measurement has several benefits These systems are efficient and cost effective for acquiring andanalyzingsignals for example Acoustic emission signal bioelectrical signal Utilizing virtual instrumentation to achieve physiological measurement will largely decrease the cost and increase the flexibility of the instruments This work aims at designing a virtual instrument for acquiring and processing of signal Keywords Data acquisition system Lab VIEW 1 Introduction PC based data acquisition and analysis is an efficient and cost effective method for signal acquisition and monitoring Isolation of the subject from the electronic circuitry is very important Also since the signal e g acoustic emission bioelectrical signal level is very low amplification of signals is important Hence a PC based system consists of additional circuits for isolation and amplification
4. http www ni com LabVIEW 2012 14 http www ni com NI DAQmx 9 8 Volume 3 Issue 7 July 2014 www ijsr net Licensed Under Creative Commons Attribution CC BY Paper ID 02014943 40
5. I 2500 3000 3500 4000 Figure 11 Post Processing Third tab on front panel is saving signals Press the save 5 Results and Discussion buttons of signals that to be saved one window is appearing Give destination path to save the image The image is saved The 4 16 channel data acquisition system using LabVIEW in png format The saving signal tab is as shown in figure software is divided as first it acquire signals from user or 12 system and then it filtered it and measure the frequency SAVE SIGNALS content of and convert the results to real world units and displayed it using LabVIEW software Save 1 Acquire Input signal First signal is acquired by selecting channel input or function generator signal input which is also called Save simulated signal pr n INPUT SIGNAL ave t J 100 Aa Save ai z 40 Figure 12 Saving Signal o 20 9 Last tab on front panel is STOP Here the condition of while 3 w loop is satisfied so program stops whole execution The stop 40 tab has stop button as follows is as shown in figure 13 60 I I I I I I I 0 0 002 0 004 0 006 0 008 0 01 0 012 0 014 0 016 STOP EVERYTHING Figure 13 stop everything Volume 3 Issue 7 July 2014 www ijsr net pape Mei Licensed Under Creative Commons Attribution CC BY 38 International Journal of Science and Research 1JSR ISSN Online 2319 7064 Impact Factor 2012 3 358 INPUT SIGNAL Amplitude 1 _ 1 0 0015 0 002 Tim
6. filtering of signal is performed first by using digital IIR Filter The function of a digital IIR filter is to remove unwanted parts of the signal such as random noise or to extract useful parts of the signal such as the components lying within a certain frequency range Due to filtering some amount of amplitude is decreases The system can set filter parameters to get better filtering signal as shown in figure 16 SET FILTER CHARACTERISTICS OR Filter optional IR filter Specifications Tapalag mp Inserer Ehebythp i Digital IR filtered signals ie Fe he specifications 1075 O05 OOS 00 ogiz oas oMr Tene Figure 16 digital IIR filtered signal output 3 FFT and power spectrum of signal LabVIEW comes with built in FFTs that make the process of component separation quick and easy So spectral measurement block is used to show FFT based magnitude spectrum FFTs produce the average frequency content of a signal over the entire time that the signal was acquired Power spectrum which shows energy spreading into frequencies those were not present in original signal The FFT and power spectrum is as shown in figure 17 ES e I I 3500 4000 I 3000 l T 2000 2500 Time 1 FA 1000 1500 Figure 17 FFT and Power spectrum Volume 3 Issue 7 July 2014 www ijsr net pape eas Licensed Under Creative Commons Attribution CC BY International Journal of Science and Research 1JSR ISSN Online
7. of the signals Combining virtual instrumentation technology for physiological measurements is an upcoming technology that is currently rising up at a faster rate The cost can be drastically brought down and the flexibility can be increased by use of virtual instrumentation National Instrument s LabVIEW is a platform and development environment for a visual programming The purpose of such programming is automating the usage of processing and measuring equipment in any laboratory setup A key benefit of LabVIEW over other development environments is the extensive support for accessing instrumentation hardware 2 Data Acquisition System Data acquisition is simply the process of measuring a real world signal such as a voltage and bringing that information into the computer for processing analysis storage Data acquisition and conversion systems are used to acquire analog signals from one or more sources and convert these signals into digital form for analysis or transmission by devices such as digital computers recorders or communications networks The analog signal inputs to data acquisition systems are most often generated from sensors and transducers which convert real world parameters such as pressure temperature stress or strain flow etc into equivalent electrical signals The electrically equivalent signals are then converted by the data acquisition system and are then utilized by the end devices in digital form 3 Constru
8. ESSINGS INPUT SIGNAL j 1 0 01 0 012 0 014 0 016 Time STATISTICAL DATA Figure 10 ACQUIRE SIGNAL The second sub tab of ACQUIRE SIGNAL AND PROCESSING is post processing Here set the filter parameters the digital IIR filtered signal FFT of signal and power spectrum signal are displayed on graph indicator The post processing tab is as shown in figure 11 Volume 3 Issue 7 July 2014 Paper ID 02014943 www ijsr net Licensed Under Creative Commons Attribution CC BY ai International Journal of Science and Research 1JSR ISSN Online 2319 7064 Impact Factor 2012 3 358 VP ALP 4 16 CHANNEL DATA ACQUISITION SYSTEM USING LABVIEW START PROGRAM ACQUIRE SIGNAL AND PROCESSING SAVING SIGNALS STOP ACQUIRE SIGNAL POST PROCESSINGS SET FILTER CHARACTERISTICS Digital OR filtered signals ESPOR 100 OR Filter optional OR filter Specifications specifications 80 Topology Lower PB 60 AM Chebyshev Afio0 00 Ji 40 1 Type Upper PB n Ne zi J Highpass Afo o0 u 20 oa Order Lower SB E a e T J 1 A200 00 amp Lower Fc Upper SB 20 100 00 Al J Fo o0 PA Upper Fc PB Gain 200 00 10 00 60 i PB Ripple SB Gain 80 1 00 Jf s0 00 y i SB Attenuati tn i J 60 00 Time GEETE i SE Ee 80 Amplitude D 5 li 3 w A ak 1 i _ ai 1 A as g Ia SS an 0 500 1000 1500 2000 2500 3000 3500 4000 0 500 1000 1500 2000 frequency Time I I I
9. ation Technology and Cybernetics 2013 08 16 Impact Factor 2012 3 358 2 Patterson Casmir D Mello Sandra D Souza Design and development of a Virtual Instrument for Bio signal Acquisition and Processing using LabVIEW International Journal of Advanced Research in Electrical Electronics and Instrumentation Engineering Vol 1 Issue 1 July 2012 3 HogskoienTelemark LabVIEW programming examples pdf Telemark university Department of Electrical Engineering Information Technology and Cybernetics 4 Jeffery Travis Jim Kring LabVIEW for Everyone Graphical Programming Made Easy and Fun 3rd Edition prantice hall publication 5 National Instruments NI 6115 6120 user manual national instrument corporation November 2002 edition 6 National instruments installation guide BNC 2110 National Instrument Corporation 7 Michael Cerna and Audrey F Harvey The Fundamentals of FFT Based Signal Analysis 8 And Measurement Application Note 041 9 Dr Peter Avitabile Basics of Spectrum Analysis Measurements and the FFT Analyzer Mechanical Engineering 22 403 ME Lab II University of Massachusetts Lowell 10 KishoriJadhav comparative study of four channel data acquisition system using LabVIEW international journal of engineering research and technology volume 3 issue 5 may 2014 11 https decibel ni com content docs DOC 3522 12 http www ni com white paper 333 1 en 13
10. ction The main objective of the current work carried on is to develop a virtual instrument which can acquire signal perform noise elimination and amplification Acquiring signal using NI DAQ designing the suitable low cost amplifier for amplification The acquired signal was displayed using LabVIEW front panel The front panel and block diagram have been designed The basic block diagram of data acquisition system is shown is as shown Data acquisition conditioner Hardware Data analysis and Display on Lab VEW storage Figure 1 Block diagram of data acquisition system 1 Physical medium Physical phenomenon like Temperature voltage pressure force light etc are to be measured using data acquisition system 2 Transducer Providesactual interface between the real world and data acquisition system by converting physical phenomenon into electrical signals that signal conditioning and for data acquisition hardware can accept 3 Signal conditioning Electrical signals generated by transducers often need to be converted to a form acceptable to the data acquisition hardware particularly A D converter which converts signal data to required digital format 4 Data acquisition system Hardware Data Acquisition uses three types of hardware a terminal block a cable and a DAQ device Computer All DAQ devices use the PC as a platform 6 LabVIEW software LabVIEW uses dataflow programming where the flow of data de
11. d amplitude at each frequency line but includes no phase information Because the power spectrum loses phase information use the FFT to view both the frequency and the phase information of a signal The power spectrum and FFT of signal are closely related to each other FFT amplitude spectrum of signal is nothing but square root of power spectrum The data acquisition system developed has certain limitations in terms of accuracy and features like frequency and resolution The system designed using LabVIEW has many advantages over system designed over MATLAB but it is the cost which has restricted LabVIEW to only large scale applications Developed 4 16 channel data acquisition system is LabVIEW independent since it builds executable file in LabVIEW which can run in another computer without using LabVIEW software Also this software can be employed for more no of channels using recent and more advance DAQ devices The four sixteen channel data acquisition system is mainly designed to acquire acoustic emission signals The acoustic emission system are capable of using multiple sensors channels during testing allowing them to record a hit from a single Acoustic emission event This event can be detected on several channels Through the analysis and processing of acquired AE signal any defects inside the material can be detected References 1 Hans Petter Halvorsen Data Acquisition in LabVIEW Department of Electrical Engineering Inform
12. e Figure 14 simulated signal and 4 16 channel input signal 0 0 0005 0 001 0 0025 Statistics block used in designing returns the selected parameter of the input voltage signal in a waveform as shown in figure 15 STATISTICAL DATA Maximum Minimum Time of Maximum 4 90962 4 93893 3 48662E 9 First time Last time Time of Minimum 3 48662E 9 3 48662E 9 3 486624E 9 Index of maximum Index of minimum First value 25 9972 76 0078 0 0659502 Total Samples Time Delta 100 0 268686 2 5E 5 Figure 15 Statistical analyzed data The parameters of input voltage signal which can be measured are as follows Total samples Returns the total no of samples in signal Index of Max Returns the index value of the highest value of the highest pt of the values in signal Index of Min Returns the index value of the lowest pt of the values in signal Last value Returns the last value in signal First value Returns the first value in signal FFT of signal Fa ae gt 2500 ee 1500 2000 frequency 20 Time of Min Returns the time of the lowest pt of values in signal Minimum Returns the lowest pt in a set of values in signal Time of Max Returns the time of the highest pt of values in signal Maximum Returns the highest pt in a set of values in signal First time Returns the first time value in signal Last time Returns the last time value in signal 2 Filtering of signal In this project
13. loop executes At this case condition of while loop is satisfied thus program stops Design of front panel of 4 16 Channel Data Acquisition System The front of 4 16 channel data acquisition is as shown below There are four tabs created on front panel When International Journal of Science and Research 1JSR ISSN Online 2319 7064 Impact Factor 2012 3 358 program start running counting starts It continued until user select new tab otherwise user can stop the program The first tab of START PROGRAM is as shown in figure 9 START PROGRAM START COUNT UNTIL NEW TAB IS SELECTED 0 PROGRAM STOP Figure 9 START program Second tab on front panel is ACQUIRE SIGNAL AND PROCESSING This tab has two sub tabs in first tab signal is acquired Two types of signals namely 4 16 channel input and simulated signal that to be selected first and according to type of signal select their parameters as shown in figure 10 LOCALS 4 16 CHANNEL DATA ACQUISITION SYSTEM USING LABVIEW START PROGRAM ACQUIRE SIGNAL SELECT SIMULATED SIGNALS yi Amplitude CHANNEL INPUT channeli1 k v SIMULATED Maximum Minimum 98 6957 99 7826 0 08875 SIGNAL frequency Hz First time Last time a 0 08 0 095875 0 090125 100 250 500 750 1000 signal type 70 81 8 2609 39 Triangle Wave 128 70 2174 0 000125 ACQUIRE SIGNAL AND PROCESSING Hi ty 4 16 100 4 H CHANNELS 0 002 SAVING SIGNALS STOP POST PROC
14. signal repre ed E Perr rrr reer eee jig mals FFT Peak vpmmnnmerre B 1 1 DIGITAL DR FILTERED SIGNAL Value Change P te Time Digital BR filtered signals ts Write PNG File vi BG Color image Date H Third event case is used to save FFT of signal For that create save button control on block diagram and rename it as FFT of signal Create invoke node with value property and connect it to write to png vi to save the FFT of signal 1 p muar 2 FFT of signal FFT SIGNAL Value Chang p FFT SIGNAL Newall FFT of signal Get image image Depth BG Color Image Data fal Figure 7 save FFT of signal Fourth event case is used to save power spectrum of signal For that create save button control on block diagram and rename it as power spectrum of signal Create invoke node with value property and connect it to write to png vi to save Volume 3 Issue 7 July 2014 www ijsr net Paper ID 02014943 Licensed Under Creative Commons Attribution CC BY 36 the power spectrum of signal The wiring diagram is as shown in figure 8 1 1 ectrum Value Change Power spectrum Image Data f New al SPECTRUM Figure 8 save power spectrum of signal 4 Stop Stop control stops all programming because it is connected to conditional terminal of while loop If condition is satisfy then while
15. termines execution order A Volume 3 Issue 7 July 2014 www ijsr net Licensed Under Creative Commons Attribution CC BY Paper ID 02014943 34 International Journal of Science and Research 1JSR ISSN Online 2319 7064 Impact Factor 2012 3 358 7 Data analysis and Storage data can be analyzed by using post processing methods like FFT processing HR processing etc and saved in computer 4 Design Consideration A Flow Chart of 4 16 Channel Data Acquisition System Design of Block Diagram of 4 16 Channel Data Acquisition System Block diagram is a wiring diagram of system In designing while loop is used along with case structure Tab control is connected to selector label of case structure so that all the cases are execute There are four cases namely start program acquiring signal and processing saving signal and stop created in case structure 1 Start Program The first case is designed to start program Select not equal function from function palette and give two inputs For first input create enum constant and edit items insert the tabs or tab names For second input create property node and select tab control as a reference and value as property Output of not equal function is connected to one input of OR function and another input is stop For counting select numeric control and for timing control select time function and create constant with time 100 in millisecond Not Equal jv
16. tion CC BY Paper ID 02014943 35 INPUT SIGNAL International Journal of Science and Research 1JSR ISSN Online 2319 7064 Impact Factor 2012 3 358 IR Filter Digital DF fittered signals Specdicatrons z z Digital R Filteri options specific Fel Hanning Third event case is timeout Timeout Event Occurs when the Event structure times out Wire a value to the Timeout terminal at the top left of the Event structure to specify the number of milliseconds The Event structure should wait for an event to occur before generating a Timeout event 3 Saving signal Third case is saving signals Event structure is used inside the case structure There are five cases created in event structure which are saving all the results First event case is designed for saving input signal Create control of save button and name it input signal Now create invoke node by right click on input signal indicator and select get image as value property Give output of invoke node to write to png file vi to save the image The wiring diagram is as shown in figure 5 INPUT SIGNAL INPUT SIGNAL a ae Image Data Figure 5 Save input signal Second event case is used to save digital filtered signal For that create save button control on block diagram and rename it as digital filtered signal Create invoke node with value property and connect it to write to png vi to save the digital IIR filtered
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