NI Helps to Deliver a 21st Century Upgrade to the Oxford Physics Teaching Labs

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"Using LabVIEW and NI DAQ hardware helped us easily update many of the undergraduate labs to make them user friendly, faster, and more informative on a limited budget. "

- Jeff Lidgard, University of Oxford

The Challenge:
Modernising the Oxford University Physics Department teaching laboratories by improving data acquisition and teaching contemporary techniques on a limited budget by updating our current experiments and choosing industry standard tools to teach skills to benefit students in professional research laboratories or future employment.

The Solution:
Using LabVIEW and NI data acquisition hardware, along with guidance from NI’s dedicated academic team, to measure and control a wide variety of experiments to better teach programming and instrumentation to Physics undergraduates.

Author(s):
Jeff Lidgard - University of Oxford

Introduction

Oxford University, which is consistently ranked as one of the top five universities in the world, boasts one of the most competitive physics courses in the United Kingdom. Approximately 600 students pursue an undergraduate physics degree. They complete practical work in their first three years of study to ensure they see the experimental side of a subject that is typically heavy on theory. We feature a broad range of experiments so students receive a good foundation in experimental physics. Practical work helps reinforce theories learned in lectures and teaches the techniques needed to test theoretical ideas and develop new instruments and technology.

The faculty in the experimental labs strive to engage students and keep the laboratory up to date with meaningful, clever experiments, which must clearly demonstrate some physical principle.

We are investing significantly in our teaching labs, but budgetary constraints mean some experiments still need equipment upgrades. One of the challenges we face is aging equipment. These setups can confuse and frustrate even the keenest students. Gathering data from these old experiments can be quite manual and time consuming, which distracts students from the goals of the experiment.

We have strived to update as many of these experiments as possible. Modernising our equipment with capable acquisition has helped simplify and improve student comprehension. It has become increasingly important to teach modern acquisition techniques as modern physics experiments become very demanding of data acquisition. The Large Hadron Collider at CERN reportedly collects more than 25 million gigabytes of data every year. Teaching these techniques also adds value for graduates entering today’s workplace.

Our First Few Steps

Our journey started because an old motor and gearbox that move the mirror on a Michelson interferometer became faulty. We were LabVIEW software beginners but knew LabVIEW made interfacing hardware quite easy. We purchased a USB-6008 DAQ device and began experimenting. We learned how to use the NI-DAQmx driver to control a stepper motor to drive the mirror assembly. We discovered we could also measure the interferometer’s output on a photodiode using the same DAQ device. We could then control the experiment precisely and record its data using the same piece of software.

In that first project, we realised the USB DAQ devices and LabVIEW could benefit many other experiments. They are cost effective and have digital control lines and analogue I/O channels. Plus, we can easily write software that seamlessly interfaces with hardware. Since our initial project was a success, we quickly applied similar solutions to other experiments.

One of our favourite projects was the work we did on the senior year experiment for measuring the hyperfine structure in Cadmium. A Fabry-Perot etalon in a pressurised chamber produces interference fringes. We monitor these while the pressure slowly increases. In the old setup, an ancient manual flow meter controlled the pressure but was quite nonlinear, which required correcting. Students found this tricky to control. A photomultiplier, which was slow to acquire data and used a clunky high voltage supply, read the interference fringe. A pressure scan could easily take a good fraction of an hour, during which a change in background lighting or even a bump to the table could ruin the scan, forcing the student  to start over.

 

Figure 1. Fringes Produced From the Fabry-Perot Etalon

We revamped the experiment with another USB-6008. We purchased a secondhand MKS digital mass flow meter. It had no controller, but we could use the analogue output and digital lines of the device to control it. We replaced the photomultiplier with a speedy photodiode. Now the experiment feels slimmed down, the data can be accumulated in less than five minutes, the pressure is accurate and easy to control, and again, we can do this within the same piece of software. We now have time for additional measurements and can expand the objective of the lab to demonstrate more physics.

  

Figure 2. Apparatus to Study the Hyperfine Structure in Cadmium

Later Efforts

These early successes boosted our confidence and we are more adept with LabVIEW, so we learned to interface to third-party hardware. We discovered much of our existing equipment is well supported by LabVIEW.

In an experiment to measure the magneto-phonon effect, we measure tiny voltage fluctuations in semiconductors. A Keithly multimeter delivers a precise, low-noise measurement. LabVIEW is very well supported with NI certified drivers. We used another USB-6008 to measure the magnetic field with a Hall probe while controlling an electromagnet. Now we can use a single piece of software to sweep and measure the magnetic field simultaneously while measuring the delicate signals of the samples with the multimeters. The impact was immense. The old power supply sweep unit and signal integrators were difficult to use. With these gone, we could control and read data much more easily. Students are happier with the new setup and can focus on physics, not on twisting knobs for hours hoping to find the lucky combination to get the experiment to work.

Figure 3. Student Using the Magneto-Phonon Effect Equipment

In other areas of the laboratory, there were plotters and chart recorders that spewed reams of paper onto the floor. An experiment on electron spin resonance happened to be an academic’s pride and joy. Its rack of electronics is six feet tall with a formidable panel of switches, dials, and numbers, but it produces a beautifully clean signal. However the electromagnet was controlled mechanically and a chart recorder measured the output signal.

Figure 4. Students Interpret Their Results From the Electron Spin Resonance Experiment

We replaced the chart recorder with an analogue input on a USB-6002 device so we could save the results digitally and more easily interpret and analyse further. We used an analogue output to easily and accurately control the electromagnet, the effects of which could now be seen in the software right alongside the signal. When the results came in, the professor was delighted, and the old paper chart recorders are now gone.

Figure 5. A Now Defunct Chart Recorder

Teaching LabVIEW and DAQ

With our success in transforming a number of the labs, it was quite obvious that LabVIEW programming is a transferrable skill that the students could benefit from learning. Many research groups throughout the university have begun to use LabVIEW and NI hardware.

In the atmospheric physics area of the lab, a custom infrared spectrometer was used to sample different black body spectra. The experiment now features an additional learning component to program hardware for data acquisition. The students receive a brief introduction to the basic LabVIEW elements and structures and the use of NI-DAQmx drivers to produce a simple acquisition VI. They can then develop their program to include further functionality and to convert the spectrometer voltage in real time to a radiance. This new creative element is fun, involves students, and inspires new ideas.

Figure 6. Student Using the Infrared Spectrometer in the Atmospheric Physics Practical

When planning the upgrade to the experiment, after choosing LabVIEW as the package to teach, we contacted NI. The company had a local education team that arranged a meeting and came to visit. They  offered us some equipment to use.

The experiment now offers more than it did before, both in terms of what can be physically measured and processed from the instrument, and in terms of learning outcomes since the students can develop transferrable LabVIEW programming skills and benefit from hands-on use of the data acquisition hardware.

Conclusion

Using LabVIEW and NI DAQ hardware helped us easily update many of the undergraduate labs to make them user friendly, faster, and more informative on a limited budget. More efficient acquisition gives us more time to expand the objective of the lab to demonstrate more physics.

Students seem more engaged and at ease with modern, user-friendly equipment, and they produce more from their limited lab time as they gain experience with LabVIEW and develop transferrable skills they can take into the workplace.

Many experiments are updated already, but we still have more to go. Bringing the students in contact with more data acquisition is definitely an aim for the future.

Author Information:
Jeff Lidgard
University of Oxford
Denys Wilkinson Building, Keble Road
Oxford OX1 3RH
Jeffrey.Lidgard@physics.ox.ac.uk

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