Advanced science.  Applied technology.


NMR Moisture Measurements: 4,701,705


In the preferred and illustrated embodiments hereof, a method and apparatus for conducting NMR moisture measurements is set forth. In various forms, hydrogen transient NMR signal peak amplitude values indicative of total hydrogen concentration of the tested material space. The hydrogen concentration is converted by a constant into water concentration. In one embodiment, a comparison is made between the NMR peak voltage of the unknown material and the NMR peak voltage from a standard sample having a specified water content to obtain a calibration for determining moisture content as a weight percentage in the tested specimen. If the densities of the two samples vary, the weights of each are necessary for accurate measurements. An alternative procedure involves determining moisture and material from the hydrogen in the water and in the material itself. In this procedure, the spin-spin relaxation T.sub.2 for the moisture is preferably more than three times longer than the T.sub.2 for the hydrogen in the solid or substrate hygroscopic material. Subsequently, two separate measurements can be obtained at separate times and their proportion is related to the percent water. An alternate procedure is used when the T.sub.2 of the water varies as a function of the percentage of water. In that instance, the values proportional to the total hydrogen in the sample and to the hydrogen in the water must be obtained at the same time so that the ratio is proportional to the percent water independent of the variations in T.sub.2. In the last two procedures, weight measurement is not required.

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William L. Rollwitz;