Patent ID: 7219533

Claim:
A small hole diameter measuring apparatus for a plate which successively and continuously measures diameters of a plurality of small holes formed in a plate, said small hole diameter measuring apparatus for a plate comprising: a flow rate measurement section (B) substantially comprising an automatic pressure control device ( 4 ) which supplies a fluid to an inlet side of small holes ( 8 ) in a plate ( 7 ) while maintaining an outlet-side pressure P 2 of said small holes ( 8 ) and an inlet-side pressure P 1 of said small holes ( 8 ) in a critical state of the fluid and while controlling the inlet-side pressure P 1 to a desired predetermined inlet-side pressure P 1 ; a plate holding section (D) which is comprised of: a plate supporting device ( 12 ) which holds said plate ( 7 ) so that said plate ( 7 ) is free to rotate, a test probe supporting device ( 13 ) which is provided above said plate supporting device ( 12 ) and supports a test probe ( 6 ) that is in air-tight contact with said inlet side of said small holes ( 8 ) and that supplies a fluid from said flow rate measurement section (B), so that said test probe ( 6 ) can be freely raised and lowered and freely moved in a horizontal direction, and control devices ( 14 ) and ( 15 ) for both of said supporting devices ( 12 ) and ( 13 ); and a control section (C) which is comprised of: a calculation and judgment part (C 2 ) which calculates a hole diameter or a cross-sectional area of said small holes ( 8 ) during a supply of the fluid on the basis of a measured value of a flow rate from said flow rate measurement section (B), and an external output part (C 3 ) which outputs a calculated value to outside of said control section.