Analog Computer for Calculation of Second Moments in NMR

A special purpose analog computer is described for calculating the second moment of the NMR absorption spectrum drawn out by a wide-line spectrometer with an integrating phase-sensitive detector (PSD). An experimental check on NH4Cl yielded a mean second moment within 1% of a previous value, and a standard error over 50 observations of 2%. The integrating PSD enabled these spectra to be recorded over 100-sec sweeps with a signal-to-noise ratio comparable to that obtained using conventional techniques with sweep times at least an order of magnitude longer.