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INSIDE iR-337
Figure 7. Schematic diagram of external planer attachment and screw terminal box for Perkin-Elmer Model 337.
Figure 6. NMR spectra of dilute ethanol: A) 1 scan recorded under " m r m l " conditions; El) 30 scans collected, signal-averaged,and plotted by the computer.
pulated" so that the tallest peak (we assume TMS will always be the tallest peak) is placed in array position 3400 (the choice of this array position is somewhat arhitrary). By makine TMS the lareest - neak . in the snectrum and hv alwavs plating it in the same array position; we have eliminated the need for a signal lock feature on the EM-360 NMR. The computer the.,, collects the next scan of the sample. It then shifts thearray positionsso that TMS isat onsition 3400and adds the scan-to the previous scan. This process continues until the desired number of scans have been collected and added together. The data is then scaled, with TMS being scaled separately and plotted on the X-T recorder or an X-Y plotter. TMS is scaled separately because it is usually so much larger than any other peak in the spectrum. Thus in the final spectrum all peaks are approximately the same height. If desired, the program can be expanded t o include integration of the spectrum and storage of the spectrum on a disk. Typical results are shown in Figure 6. The NMR spectrum shown in Figure 6A is a sample of dilute ethanol in carbon tetrachloride. The ethanol peaks are almost unobservable, whereas the TMS peak is easily discernible. The spectrum shown in Figure 6B is the same sample after collecting and averaging 30 scans. The ethanol peaks are easily observed; however, the amplitude of the TMS signal has not changed due to the scaling of this peak by the program.
Perkin-Elmer Model 337 Infrared Spectrophotometer Interfaced to an IBM PC Myrna S. Pearson Wheaton College Norton. MA 02766 Salvatore J. TUZZO Tuzzo Englneering Associates Norton, MA 02766
In an attempt to respond to the trend toward computerbased laboratory automation, management, and networking, our chemistry department opted to initiate a program of interfacing its current instruments to an IBM PC, beginning with the Perkin-Elmer Model 337 Infrared Spectrophotometer. Initially the following equipment was purchased: an IBM PC system unit with dual disk drives and 192K RAM, IBM DOS 1.1,a colorlgraphics card, a colorlgraphics monitor and adapter, a graphics printer (Epson RX-100) and 1074
Journal of Chemical Education
CIRCUIT 15 MOUNTED IYSlOE SCREW IERIIINAL BBI Figure 8. Schematic diagram of circuit mounted insids screw terminal box to generate interrupt pulse.
adapter, and a MetraByte Data Acquisition and Control System ($607 with accessories). The major component in the MetraByte system is the DASCON-1 data acquisition and control interface board (model no. DASOI), multifunction analog and digital inputloutput board designed to plug into one of the expansion slots inside the IBM PC. This board enables the IBM PC to control low speed (30 samplesls, integrating) A/D data acSign. Additional quisition with a resolution of 12 Bit DASCON-1 accessories required for the project include a screw terminal hoard (model no STAOI), which allows all the functions of the DASCON-1 t o be accessible to the user externally with a minimum of wiring and affords easy status checks of the digital I10 lines through the use of lightemitting diodes, and a ribbon cable (model no. C1800) to connect DASCON-1 to the screw terminal hoard. The Perkin-Elmer Model 337 Infrared Spectrophotometer is a double-beam grating instrument that covers the range 4000 to 400 cm-' using two gratings (one operating from 4000 to 1200 cm-' and the other from 1333 to 400 cm-'). Thus, two scans and two data files are required to store the entire spectrum for any given compound. With our system spectra are recorded using a linear frequency (cm-') ahscissa presentation and a linear ordinate scale in percent transmittance while employing the slow (24-min) scan for maximum resolution.
a
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Acknowledgment Financial support from a Wheaton College Venture Grant and the Campbell Soup Fund is gratefully acknowledged. In addition, the authors express their appreciation t o Herbert Ellison for his helpful suggestions and to Suzanne Mahrouk for her assistance in collecting spectra.
UV Spectral Data Acquisition. Spectral Search, and Library Software Package for the IBM 9420 Spectrophotometer FILE REI--991
SAMPLE: WLYSIYRENE RCFRNC: NONE
David A. Jencen and James K. Hardy University of Akron Akron, OH 44325
JOB # 10 (Sl
COMIENI: FERXIN-ELMER REFERENCE slLN
N E R b?lION (. Saw, hint, Ewand, List Pegion, bin Menu, Quit)? I Figure 9. Screen display from IBM PC showing IR spectrum of obtained from Perkin
