A Cost-Effective Way To Extend an Instrument’s Life

Abstract

Extending the usefulness of the instruments we have has never been more important. The current economic crisis has prompted all of us to re-examine how money is spent and to try to minimize our expenditures because of future uncertainties. Already the economy has affected the replacement of equipment (1), and at least in academia, "there is little flab left to cut" (2). Simultaneously, we are encouraged to be more "green", which, in its encouragement of minimizing electronic waste, should prompt less abandonment of instrumentation that is still usable and relevant. We have been able to breathe new life into an aging 60 MHz NMR spectrometer used by hundreds of undergraduates each year in the second-year organic chemistry sequence. In addition to extending the instrument's life, the updated look of the instrument may positively affect student attitudes about its usefulness (3).A department value at this university is that students should use instruments to collect their own data as early and as often as possible in the chemistry curriculum. For this reason, the 60 MHz spectrometer was obtained nearly 20 years ago through the (obsolete) NSF-ILI program. It is used entirely by second-year students and we estimate that thousands of students have used it; each student using it half a dozen times over the two-semester lab sequence. Having said this, no doubt minor repairs have been necessary over the years, but we hit a seemingly insurmountable obstacle about a year ago when the plotter that came with the Hitachi model 1200 rapid-scan correlation instrument became nonfunctional.The high level of "student traffic" coupled with the minimal chemical maturity of those students precluded simply switching to using the JEOL 300 MHz instrument also available in our department. We were at a crossroads: Do we abandon our commitment to early and frequent student use of instrumentation or do we find a way to keep the old 60 MHz machine going? We chose the latter and would like to share how we modernized our instrument and have successfully extended the already long life of this workhorse NMR. SolutionThe attached plotter received output in the form of Hewlett-Packard graphics language, and we were unable to find an affordable printer to serve as a replacement. Software solutions were also cost-prohibitive. Because our NMR also has an oscilloscope display, we realized that we could tap into that feature and read the voltages controlling the x and y positions of the beam. We estimated that we would require a two-channel data acquisition (DAQ) device with a sample rate of several kHz or more.Our upper-level physics laboratories have used National Instruments USB-600x DAQ modules for some time, so our familiarity with them suggested we employ a USB-6009 (approximately $250). The USB-6009 is shipped with several simple programs suitable for use in a variety of programming languages. One of these is used to gather data from both channels at 5000 Hz for 2 s, requiring user input only to choose a file name and start the acquisition.The dat...

Robust, Efficient, and Economical Magnetic Stirrer: A Device Based on Pulsed Width Modulation, Built Using Mainly Recycled Parts

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