Sensitivity calibrating method for detector of comparator

• US 6,062,062 A
• Filed: 06/22/1998
• Issued: 05/16/2000
• Est. Priority Date: 06/25/1997
• Status: Expired due to Fees

• Current Assignee: Mitutoyo Corporation
• Original Assignee: Mitutoyo Corporation
• Inventors: Horikawa, Toshiro, Toida, Yoichi
• Primary Examiner(s): NOLAND, THOMAS
• Application Number:
  US09/102,119
• Time in Patent Office: 694 Days
• Field of Search: 73/1.79, 73/1.81, 33/502, 702/97, 702/94, 702/95
• US Class Current: 73/1.81
• CPC Class Codes: G01B 21/02 for measuring length, width, or thickness G01B21/10 takes precedence

Abstract

The object of present invention is to provide a sensitivity calibrating method for a detector of a comparator, which enables easy and highly accurate sensitivity calibration for a first and a second detector for measuring opposing position of an object. Heights of two pairs of reference gauge blocks, a first reference gauge block W1 and a second reference gauge block W2, and the second reference gauge block W2 and a third reference gauge block W3 is first measured, and thereafter, sensitivity coefficients for calibrating the sensitivity of an upper detector 10 and a lower detector 20 are calculated by applying the measured value to a predetermined formula. The calculation is repeated three times, and each value is renewed for the upper and the lower detector 10 and 20 respectively.

Claims

1. A method for calibrating a sensitivity of a detector for a comparator comprising a table for an object to be put on and a first and a second detector for detecting a first and second opposing surface of the object, said first and second detector outputs measured value by multiplying a respectively detected position output by a sensitivity coefficient so that the comparator measures a distance between the first surface and the second surface of the object, the method comprising the steps of:

providing a first reference gauge block and a second reference gauge block on the table, said first and second reference gauge block having different distance between the first and second surface and accurately known calibration value for the distance respectively;

substantially aligning the second surface position of each reference gauge block;

primarily measuring the first surface of each of said reference gauge blocks with said first detector;

providing a third reference gauge block and any one of said first and second reference gauge blocks, said third reference gauge block having different distance between the first and second surface with any one of said first and second reference gauge blocks and accurately known calibration value for the distance respectively;

substantially aligning the first surface position of said third reference gauge block and any one of said first and second blocks;

secondarily measuring the first surface of said third reference gauge block and any one of said first and second reference gauge block with said second detector;

calculating a first sensitivity coefficient for calibrating the sensitivity of said first detector from a predetermined formula according to a difference in the calibration value of said first and second reference gauge blocks and a difference in the measured value of said first and second reference gauge blocks measured in the primarily measuring step, and a second sensitivity coefficient for calibrating the sensitivity of said second detector from a predetermined formula according to a difference in the calibration value of said third reference gauge block and any one of said first and second reference gauge blocks and a difference in the measured value of said third reference gauge block and any one of said first and second reference gauge locks measured in the secondarily measuring step; and

renewing said first sensitivity coefficient and said second sensitivity coefficient calculated in the calculating step as a sensitivity coefficient of said first and second detectors.

2. The method for calibrating a sensitivity of a detector for a comparator according to claim 1, wherein the first sensitivity coefficient G1 for calibrating said first detector is calculated from the formula of;

space="preserve" listing-type="equation">G1=|(A0+Ad)-(B0+Bd)|/(|Au-Bu|/Gu0)

and wherein the second sensitivity coefficient G2 for calibrating said second detector is calculated from the formula of;

space="preserve" listing-type="equation">G2=|{B0+(Bu×

G1/Gu0)}-{C0+(Cu×

G1/Gu0)}|(.vertline.Bd-Cd|/Gd0)

each parameter being as follows;

A0;

calibration value of said first reference gauge block

B0;

calibration value of said second reference gauge block

C0;

calibration value of said third reference gauge block

Gu0;

presently registered sensitivity coefficient for said first detector

Gd0;

presently registered sensitivity coefficient for said second detector

Au;

measured value of said first reference gauge block by said first detector

Ad;

measured value of said first reference gauge block by said second detector

Bu;

measured value of said second reference gauge block by said first detector

Bd;

measured value of said second reference gauge block by said second detector

Cu;

measured value of said third reference gauge block by said first detector

Cd;

measured value of said third reference gauge block by said second detector.

3. The method for calibrating a sensitivity of a detector for a comparator according to claim 2, wherein a new sensitivity coefficient G1n of said first detector and a new sensitivity coefficient G2n of said second detector is calculated using the sensitivity coefficient G2 of said second detector to improve accuracy of sensitivity by the formula of:

space="preserve" listing-type="equation">G1n=|{A0+(Ad*G2/Gd0)}-{B0+(Bd*G2/Gd0)}|/(|Au-Bu.vertline./Gu0)

space="preserve" listing-type="equation">G2n=|{B0+(Bu*G1n/Gu0)}-{C0+(Cu*G1n/Gu0)}|/(|Bd-Cd|/Gd0)

and wherein a more accurate sensitivity coefficient G1m of said first detector and a more accurate sensitivity coefficient G2m of said second detector are determined from the sensitivity coefficient G2n in the same manner.

4. The method for calibrating a sensitivity of a detector for a comparator according to claim 1, wherein the detector is a displacement detector with a spindle to be abutted to an object to be measured.

5. The method for calibrating a sensitivity of a detector for a comparator according to claim 1, wherein the comparator further comprises a holder movable along the surface of the table for moving a plurality of objects to be successively applied to said detector.

6. The method for calibrating a sensitivity of a detector for a comparator according to claim 1, wherein the first surface and the second surface of the object is an upper surface and lower surface respectively, and wherein said first detector measures the upper surface of said reference gauge block disposed on the table and said second detector measures the lower surface of said reference gauge block disposed on the table.

7. The method for calibrating a sensitivity of a detector for a comparator according to claim 6, wherein said second detector is disposed below the table, and wherein said second detector is applied to the lower surface of the object through a hole formed on the table.