Interfacing a microcomputer with the Varian EM-360 NMR spectrometer.
Numerous NMR signal enhancement devices (CAT or Computers of Average Transients) are available commercially but at relatively high cost. These also have little or no flexibility of application, i.e., they are essentially signal averagers and nothing else. A far superior alternative, both in economy and range of application, is found in the new generation of computational devices based upon 8-bit LSI microprocessors. This paper reports the practical details of achieving a successful interface between one such microcomputer, the Altair 8800B, and the Varian EM-360 (1)H-NMR spectrometer. The resulting system is programmable in high level language (8k basic) and has sufficient memory to achieve 4096 point (12 bit) field resoltuion. The interface yields an intelligent instrument with multiple capabilities. Several operating modes have been developed using high level language programming, and these include conventional spectrum acquisition with variable field resolution, repetitive scan CAT, difference spectrometry, kinetic NMR spectrometry, progressive saturation analysis (for T1 and T2), and INDOR. The CAT program, for example, required 2 h to develop and debug, while a graphic output subroutine (shared by all modes) was written in 1 h. Correlation spectrometry is under development and requires user defined machine language routines. The system provides a graphic output of digitized data (using the existing recorder), magnetic storage of data files, and immediate data reduction capabilities.
Wright
J R
JR
Department of Physical Sciences, Southeastern Oklahoma State University, Durant, Oklahoma 74701.