KMEM 3116: INSTRUMENTATION ANDMEASUREMENT TECHNIQUESACTIVE LEARNING 2 REPORTNAME : Ahmad Aliff Bin AzmiMATRIC NO. : KEB090001SUBMIT DATE : 3 November 2011LECTURER : En. Ahmad Saifizul Bin Abdullah
QUESTION: Build a VI that can perform data acquisition using simulated DAQ-mxdevice (no hardware is required). A simulated device behaves similar to a realdevice. It is necessary to use Measurement and Automation Explorer (MAX) tocreate a simulated device and DAQ Assistant VI to quickly aquire data andgenerate signal. The VI front panel should be able to change the aquisition setupsuch as physical channel, buffer size(samples per channel), sampling rate and inputrange. 1. How to create the simulated NI-DAQmx device in MAX 2. How to configure the virtual channel using DAQ Assistant VI 3. How to configure signal input and output setting using DAQ Assistant VI 4. Observe the waveform graph when the acquisition setup changed to different setting. Explain the changes.INTRODUCTIONNI-DAQmx is a programming interface you can use to communicate with dataacquisition devices. Measurement & Automation Explorer (MAX) is a toolautomatically installed with NI-DAQmx and used to configure National Instrumentshardware and software. With NI-DAQmx we can create simulated devices in MAX,so no data acquisition hardware is required. An NI-DAQmx simulated device is asoftware replica of data acquisition hardware.OBJECTIVE 1) To create virtual application by using Labview 2) To understand front panels, block diagrams, icons, and connecter panels. 3) To use built-in Labview function.SOLUTIONStep A: Create the simulated NI-DAQ-mx device 1) Measurement and Automation is used to create simulated NI-DAQ-mx device. 2) Click My System and right-click Devices and Interfaces 3) Select Create New... in the drop-down menu. 4) Select NI-DAQmx Device » NI-DAQmx Simulated Device and click Finish. The Choose Device window will prompt to select a device. 5) Select M Series DAQ » NI USB-6221 and click OK. The NI-DAQmx simulated device will appear in the Configuration pane within MAX. 6) Switch to Front Panel.
Step B: Front Panel 1) Waveform Graph is selected from Controls>>Graph Indicators>>Chart and placed on the front panel. 2) Switch to Block Diagram.Step C: Block Diagram 1) DAQmx Create Virtual Channel.vi is selected from Measurement I/O>>DAQmx-Data Acquisition and place it on the block diagram. Then, create control on maximum value, minimum value and physical channel by right click on them. Analog Input Voltage is selected for this function. 2) DAQmx Timing.vi is selected from Measurement I/O>>DAQmx-Data Acquisitionand place it on the block diagram. Then, create control on samples per channel and rate by right click on them. Sample mode is made to be constant (continuous sample). 3) The AI voltage’s task out terminal is wired to the task in terminal of the sample clock. 4) DAQmx Start Task.vi is created from Measurement I/O>>DAQmx-Data Acquisition and place it on the block diagram. 5) The task out terminal of the sample clock is wired to the task in terminal of the start task. 6) DAQmx Read.vi is created from Measurement I/O>>DAQmx-Data Acquisition and place it on the block diagram. 7) Multiple Waveform is selected by right click on the Analog Wfm 1 Chan NSamp>>Analog>>signal channel. 8) The task out terminal of the DAQmx Start Task is connected to the task in terminal of the DAQmx Read. Then, create control on number of samples per channel. The data terminal is connected to the waveform graph. 9) While Loop is created from Functions>>All Function>>Structuresand surrounding the Analog Wfm 1 Chan NSamp and the Waveform Graph.Step D: Running the VI (Front Panel) 1) The maximum value and minimum value are set as 10 and -10. 2) Physical channel must be selected one. 3) 100 are set for the samples per channel and its rate. 4) From the front panel, click the Run Continuously button to run the VI. 5) Click the Abort Execution to stop the program.
DISCUSSIONM Series multifunction data acquisition (DAQ) modules for USB are optimized forsuperior accuracy at fast sampling rates. They provide an onboard NI-PGIA 2amplifier designed for fast settling times at high scanning rates, ensuring 16-bitaccuracy even when measuring all available channels at maximum speed. Allexternally powered M Series devices have a minimum of 16 analog inputs, 24 digitalI/O lines, digital triggering, and two counter/timers. USB M Series devices are ideal fortest, control, and design applications including portable data logging, fieldmonitoring, embedded OEM, in-vehicle data acquisition, and academic. NI USB-622x M Series devices have a one-year calibration interval.. M Series devices areideal for test, control, and design applications including:• Portable data logging• Field-monitoring applications• Embedded OEM applications• In-vehicle data acquisition• Academic lab use – academic discounts availableA Waveform Graph accepts arrays of data in various forms, e.g. array, waveform, ordynamic data. It then plots all the received points at once. It does not accept singlepoint values. When an array of points is wired to a waveform graph, it assumes thepoints are equally spaced out. This can be changed in the properties of the graph orusing property nodes. These are the reasons to choose waveform graph in thisassignment.The Waveform Graph receives the initial time and time differencescontained within the waveform and displays the data accordingly. Unlikethe Waveform Chart, a waveform chart only remembers and displays a certainnumber of points by storing them in a buffer. When the buffer gets full, the chartstarts overwriting the oldest points with new ones. As the data points becomeavailable, the chart displays received data in addition to already existing points.When the sampling rate is increased, the frequency of the graph will increases. Thecurve of the curve will gets ‘thicker’When the maximum and minimum value of the voltage value changes, theamplitude of the graph will change.If the sampling rate and samples per channel are very low, the shape of the graphwill be slightly change and the curve shape will near to flatten.
CONCLUSIONPC-based data acquisition uses a combination of modular hardware and flexiblesoftware to transform your standard laptop or desktop computer into a user- definedmeasurement or control system.National Instruments DAQ devices provide high-performance I/O, industry-leading technologies, and software-driven productivitygains for your application.In this assignment, I manage to create a VI that can perform data acquisition byshowing waveform graph with different buffer size and sampling rate by usingsimulated DAQ-mx device which is NI USB-6221.Appendix 1) http://sine.ni.com/ds/app/doc/p/id/ds- 10/lang/enhttp://sine.ni.com/ds/app/doc/p/id/ds-9/lang/en 2) http://zone.ni.com/devzone/cda/tut/p/id/3698