Interfacing Physics Sensors

Using National Instruments Educational Laboratory Virtual Instrumentation Suite & LabVIEW by Eric Ethridge

Left to right: motion detector, force sensor, gas pressure sensor, temperature probe

National Instruments Educational Laboratory Virtual Instrumentation Suite (NI ELVIS)

Introduction

The purpose of my project is to gain a basic understanding of how to use LabVIEW in conjunction with physics sensors connected to ELVIS, and to create virtual instruments to work with real-life physics labs. I am taking lab manuals and creating virtual instruments (VI’s) for each of the labs while slowly taking away certain objects so that students can learn how to program using LabVIEW. The object is to allow students to have enough experience with LabVIEW so that if they were to encounter it elsewhere they would already have a basic knowledge of how to use LabVIEW.

Materials & Methods

The materials I worked with, as seen in the above pictures, consisted of the National Instruments Educational Laboratory Virtual Instrumentation Suite or NI ELVIS and several sensors from Vernier Software & Technology. To explain how to use LabVIEW, first I had to learn how to use it myself. I used John Essick’s book Advanced LabVIEW Labs to help get myself acquainted with the LabVIEW graphical programming language and using the Data Acquisition (DAQ) Board. I was then able to begin creating VI’s of my own. I took VI’s that were created for the sensors and taking my knowledge of LabVIEW, re-programmed them for a purpose that suited a particular lab. For example, I took the VI created for the motion detector and programmed the VI to calculate and display the velocity of an object on a graph.

Results

I was successfully able to create VI’s for every lab in the Mechanics and Thermodynamics books of the RealTime Physics lab manual series. These included VI’s that incorporated the use of two sensors working together. For example, one lab required that you calculate the spring constant of a spring, then use the spring constant to calculate the mechanical energy. This process can be seen in Figure 1. Figure 1-1 shows the VI that calculates the initial distance from the spring to the motion detector which is in turn used to calculate the spring constant. Figures 1-2 and 1-3 show the process of placing weights onto the spring to collect force and distance data which is then used along with the initial distance to calculate the spring constant. The spring constant is calculated using the equation k=F/x, F being the force exerted on the spring and x being the distance between the spring and motion detector. Figure 1-4 shows the results of calculating the spring constant graphically. The slope is the spring constant. Figure 1-5 shows the final VI where the mechanical energy is calculated and graphed. Figure 1-6 is the code that makes up the final VI.

I also experimented with electrical circuits. Figure 2-1 shows a parallel circuit that is using two current probes to read the current that is flowing through each bulb when the switch is either open or closed. Figure 2-2 shows a circuit using a 10 ohm resistor is having the current running through the resistor monitored. Figure 2-3 shows a parallel circuit with two different sections.

Figure 1-2 Figure 1-3Figure 1-1 Figure 1-4 Figure 1-5 Figure 1-6

Figure 2-1

Figure 2-2

Figure 2-3

Conclusions

Learning how to program using LabVIEW was very intuitive. Explaining how to program a VI can make it sound very complicated but it is fairly simple. My manual gives students very concise instructions to quickly create VI’s to help with their labs.

References

Essick, John. Advanced LabVIEW Labs.

Laws, Priscilla W. David R. Sokoloff. Ronald K. Thornton. RealTime Physics.

Acknowledgments

I would like to thank Dr. Julie Talbot for letting me work on this project and Dr. Bob Powell for providing the equipment.

I would also like to thank the National Science Foundation STEP grant #DUE-0336571 for funding the work on my poster.

Further Information

http://www.ni.com for information on ELIVS and LabVIEW