Incorporating National Instruments LabVIEW into an Intermediate Laboratory Experience

1. Incorporating National Instruments LabVIEW into an Intermediate Laboratory Experience Steven C. Sahyun Physics Department, University of Wisconsin - Whitewater, Whitewater, Wisconsin 53190 Abstract A novel approach to the Intermediate Physics Laboratory is to use the resources of the Synchrotron Radiation Center (SRC) national laboratory located in Stoughton, WI and run by the University of Wisconsin - Madison. [1] Students collect data at the laboratory in person and remotely through the use of a Web interface. This experience relies heavily on the use of LabVIEW for data acquisition and remote instrument control. To provide students with a better understanding of how the process occurs, the first three weeks of the course are devoted to learning LabVIEW in order to collect data and to control basic circuits. This poster will detail how LabVIEW is incorporated into the course structure. Equipment Students worked in pairs for three weeks at a computer workstation equipped with a computer and a National Instruments NI-6009 USB interface unit. Each computer had LabVIEW 8.2 installed. A department site license was acquired through a National Instruments grant. UWW College of L&S Dean provided funds to purchase NI-6009 USB interface units for the laboratory workstations. Small supplementary items (LEDs, photocells, motors) were purchased from Radio Shack with instructional funds. LabVIEW Virtual Instrument Result for “Exercise 2” NI USB-6009 interface unit. 14-Bit, 48 kS/s Multifunction Data Acquisition for USB. 8 analog input channels, 14-bit resolution, 12 digital I/O lines, 2 analog outputs. The “Block Diagram” contains the program of components wired together. The “Front Panel” contains Controls and Indicators Why LabVIEW? SRC experiment and the need to learn LabVIEW The Synchrotron Radiation Center (SRC) is a highlight feature of the Intermediate Physics Laboratory course at the University of Wisconsin - Whitewater. Students have the opportunity to visit and perform remote experiments at the SRC. The facility consists of an electron accelerator and the Aladdin storage ring, and produces intense, broad-spectrum electromagnetic radiation from infrared to x-ray frequencies. Result for Task 5: Run a small motor with LabVIEW. Photocell uncovered, Motor is off. Photocell covered, Motor is on. Darlington circuit to increase the current to the motor LabVIEW front panel. A research station at the SRC, called Students Performing Experiments Collaboratively Thorough Remote Access (SPECTRA), is dedicated to outreach programs. This research station enables students to conduct local or remote experiments and collect real-time data using LabVIEW and a Web interface. Because LabVIEW plays such an important role in data acquisition and equipment control in the SRC experiment, as well as at other laboratories and in industry, it was decided to provide students an opportunity to learn LabVIEW at the beginning of this course to better prepare them as future physicists. Instructional Practice A hands-on guided set of six exercises provided the structure for basic understanding of the LabVIEW environment. This method was similar to that used at National Instruments workshops where concepts would be introduced and then students would have time to complete specific tasks. The guided exercises were tailored to the specific needs of I/O functions that would be seen on equipment later in the semester. Many of the students began with little or no programming and/or electronics knowledge. At the end of the three week period, students were bread-boarding circuits and programming LabVIEW to control a small motor and to acquire and record data. LabVIEW block diagram controlling the circuit. Course Overview Because the USB 6009 interface unit does not provide enough current to directly run the motor, students discover that they need to create a Darlington circuit to increase the current. [A pre-lab assignment asked them to research the use of a Darlington circuit and draw its circuit diagram.] In this activity, students learn rudimentary breadboard and circuit design skills, which they may not encounter unless they take an optional electronics course. The LabVIEW Virtual Instrument monitors the light level from a photocell and sends a signal to the motor such that when the photocell’s signal is below a critical value (when covered) the motor will operate. The Intermediate Physics Laboratory is a two-credit semester-long course. It meets twice a week for two hours each session for 15 weeks. The course is divided into a series of Lab Stations that the students experience, usually in groups of 2 or 3. Topic Exercise Creating a Virtual Instrument Exercise 0 - Perform a mathematical function on two numbers. Working with Loops Exercise 2 - Add a loop structure to convert the temperature from degrees Celsius to Fahrenheit so that it will run until stopped. Controls and data Types Exercise 3 - Switches, lights, Boolean and conversion. Make this work. Using loops and Charts Exercise 4 – Build a vi to display a simulated “noisy” sine signal (Functions Þ Express Þ Input) to a Waveform graph (Controls Þ Modern Þ Graph). Include “Reset Signal” and variable time delay controls. DAQ – Data Acquisition with the 6009 Exercise 5: Acquire and graph an input signal from a function generator. Start with InputStarter.vi Create and view 1 and 2D arrays Analyzing and Logging Data Exercise 6 – Create a vi that will record a graph’s data using the “Write to Measurement File” subVI. Include a “Save” control connected to the “enable” input. Lab Station 1: Computer Interfacing. (3 Weeks) Students learn basics of LabVIEW programming to acquire data and control devices. Student groups then rotate through the following lab stations Lab Station 2: Electron properties. (2 Weeks) Helmholtz coil field mapping. e/m ratio Millikan Oil Drop Lab Station 3: Magnetism (2 Weeks) Magnetic dipole moment and torque experiments and a brief introduction to vacuum systems. • Lab Station 4:Material Properties. • (2 Weeks) • Using a spectrophotometer to investigate materials. • Scanning Tunneling Microscope. CONCLUSION The inclusion of a LabVIEW module appealed to the students. The methodical buildup of skills provided the students with a straightforward approach to learning the environment and they enjoyed the engineering aspect of designing systems to accomplish a goal. A better appreciation of the program occurred later in the semester when they again used it for data collection in subsequent lab station experiments and more importantly with their SRC project. By having this short introduction at the beginning of the semester, they were able to understand this type of computer aided data collection, rather than seeing it as a black box. This understanding was also important when they needed to trouble-shoot data errors with their remote data collection experiment at the SRC. Student Assignment for the 3-Week Lab Session • Physics 221: Intermediate Laboratory • Station 1 Assignment: Computer Interfacing • Objectives: • You will learn basic functions and methods for transferring data from devices to computers and use computers to generate signals to remote devices. You will become acquainted with a digital storage oscilloscope as well as the LabView program. • 1. Complete the Introduction to LabVIEW exercises. • 2. Complete a LabVIEW program to graph and save data • 3. Complete a LabVIEW program to create a Decimal to Binary converter; use two LED lights connected to the NI-6009 interface to display the result. • 4. Use the NI-6009 interface to turn on a LED diode when triggered by a signal from a photocell. • Use the NI-6009 interface to run a small motor when triggered by a signal from a photocell. This will require the use of a “Darlington” circuit. • Create a LabVIEW program to acquire and save to a file the waveform produced by a function generator. • Extra credit: Pass the LabVIEW fundamentals exam at http://www.ni.com/training/labview_exam.htm • Supplemental LabVIEW material available on request. • Progress and programs will be kept track of in your Laboratory Notebook. At the end of the Lab Station, you will turn in your notebook as well as a lab report detailing your activities. Grading will follow guidelines of the rubrics handed out in the course syllabus. SRC Experience: (3 Weeks) Students use the SRC for photoemission studies of materials of their own choosing. EFNMR Lab (2 Weeks) References [1] Sahyun, S.C., Polak, J. M., Moore, C. J. Undergraduate student laboratory experience at the Synchrotron Radiation Center. Am. J. Phys. 74, 987 (2006) [2] Essick, J. Advanced LabVIEW Labs. Prentice Hall. (1999) [3] Moriarty, P.J., et al. Graphical computing in the undergraduate Laboratory: Teaching and interfacing with LabVIEW. Am. J. Phys. 71, 1062 (2003) [4] Green, A. Introducing Students to LabVIEW without tying up the semester. 2006 AAPT Summer Meeting, Syracuse, NY Previous literature show several examples of incorporating LabVIEW into course structures. Essick [2] provides a complete full semester course text and Moriarty [3] provides further details on how to tailor a semester-long course for students who have had electronics courses. However, the focus of this course is centered on the SRC project, and LabVIEW is not the end, but a means. Also students taking this course are mostly sophomore level, with no electronics experience so the full semester courses previously described are not satisfactory. Instead, a three week series of 6 two-hour classes was implemented loosely based on the philosophy of Green [4] but with a lower level cohort. The classes used a modified version of National Instrument’s “Learn LabVIEW in 6 hours” as a presentation base but focused the activities on the I/O nature of LabVIEW. This was followed by independent student activities. The experiments conducted at the Synchrotron Radiation Center, University of Wisconsin-Madison, is supported by the NSF Award No. DMR-0084402. Funding for the UW-Whitewater Physics Departmental Site License provided by the National Instruments Equipment Grant Program. National Instruments, NI, and LabVIEW are trademarks of National Instruments Corporation.