| 摘要 |
PURPOSE:To enable elongation of durability and elimination of measurement error of a photomultiplier tube, by switching a supply voltage of a photomultiplier tube from zerothickness correction value to (set high voltage -zero thickness correction value) in synchronization with arrival of a specimen and stabilizing a high value of output wave and removing a control lag. CONSTITUTION:When a disc arrival signal I is introduced into a AGC circuit 8, a controlling high voltage Va, an output of the circuit 8, is changed from zero thickness an amplifying ratio of a photoelectronic multiplying tube 1 and by this increase, specimen thickness Tm is issued from a counter 3 for actual measurement of the thickness of the 1st. specimen disc. At the end point of this measurement a missing disc signal R is introduced into the circuit 8 and the output is changed from Vs-Vo to a corrected value Vo and the amplifying ratio of the tube 1 is decreased and the disc thickness Tm tends to zero. And, at the time of measurement of the 2nd specimen, the set disc thickness Ts is introduced prior to the 1st, signal and the voltage Vs which has followed the disc thickness Ts is calculated on a setting apparatus 4 and issued into the circuit 8 and similarly, the thickness measurement of the disc is performed on the 2nd specimen. |
