| 摘要 |
A method and apparatus for detecting and measuring the areal density of a moving sheet of material having a repetitive pattern by using a scintillation detector operating either in the pulse counting mode or as an analog device includes some means for determining the duration of the repetitive pattern. If the repetition is caused by some characteristic of the production machine, a sensor or pickoff device may be used to synchronize the process; otherwise, the lowest frequency component of a Fourier transform of the variations in areal density is used to determine the repetition interval. Each repetition interval is divided into small measurement increments, and means are employed to average the output of the scintillation detector for each of the corresponding measurement increments in order to provide an accurate and high resolution measurement throughout the repetition interval using an otherwise limited detection device.
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