計測と制御

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The radiation thickness gage offers many advantages, but other problems remain to be studied. In this paper the following four subjects are studied. (1) Measurement of small thicknesses and small differences of thickness. (2) Statistical errors in the output of the gage. (3) Faster response. (4) Spatial characteristics of ionization chamber.
The 1st and 2nd subjects are related together, since statistical errors are a common problem. The errors are caused by many factors, such as the counting rate of the radiation, the pulse spectrum induced in the radiation detector, the transfer function of the measuring system and the absorption characteristics of the measured object. The relationship between these factors have been given by a formula. Using this formula, the optimum radiation intensity for detection of the thickness is induced.
As to the fast response of a thickness gage with an ionization chamber, 1ms of time constant can be obtained by adding a newly developed compensation circuit. For continuous gaging of a moving plate by a radiation thickness gage, its response is varied by the spatial frequency of the irregurality of the thickness (rad/cm) and by the moving speed of the plate v (cm/sec). This characteristic can be described by an optical transfer function (O. T. F.). The O. T. F.'s of ionization chambers with circular, with square and with rhombic windows are obtained experimentally.
The analysis and synthesis of a control system that consists of such elements can be easier to make in the spatial domain than in the time domain. One example is given here of a synthesis of this kind carried out both theoretically and experimentally.

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