Measuring instrument
First Claim
1. In a surface measurement apparatus of the type wherein a sensor is traversed along a path in sensing relation with the surface of a component under test and operates to produce sensor output signals representing the surface under test,the improvement wherein:
- said sensor comprises first, second and third transducers,each said transducer being individually and equally sensitive to surface variations and operating to produce an output signal P1, P2, P3 respectively,common support means mounting said first, second and third transducers spaced from one another by respective predetermined distances, and in relative positions such that each transducer traverses substantially the same path over the surface of the component upon relative movement of said common support and the component under test, the spacing of said common support from the surface of the component under test providing a reference datum for the transducers in generating the output signals thereof, amplifier means for amplifying the said output signals P1, P2, P3 from said first, second and third transducers respectively such that said output signals are related by relative factors of a, l and b respectively, andmeans for combining the output signals from the transducers to produce a composite signal S of the form S = aP2 + bP3 - 2P1 which includes no component due to significant imperfections in the reference datum.
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Accused Products
Abstract
A surface measurement apparatus of the type in which a sensor is traversed along a path in contact with or adjacent the surface of a component under test. The sensor has three or more transducers which, in the described embodiment, physically contact the surface under test and produce individual signals as they are traversed along the same path over the surface of the component under test. The signals produced by the transducers are amplified and combined in such a way that the composite signal so produced is not dependent on any variation in the position of the body of the transducers as the device is traversed along the surface of the component under test thereby allowing the use of sensors which are not mounted on accurately preformed datum-determining mounts such as a flat bed or an accurate spindle.
33 Citations
31 Claims
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1. In a surface measurement apparatus of the type wherein a sensor is traversed along a path in sensing relation with the surface of a component under test and operates to produce sensor output signals representing the surface under test,
the improvement wherein: -
said sensor comprises first, second and third transducers, each said transducer being individually and equally sensitive to surface variations and operating to produce an output signal P1, P2, P3 respectively, common support means mounting said first, second and third transducers spaced from one another by respective predetermined distances, and in relative positions such that each transducer traverses substantially the same path over the surface of the component upon relative movement of said common support and the component under test, the spacing of said common support from the surface of the component under test providing a reference datum for the transducers in generating the output signals thereof, amplifier means for amplifying the said output signals P1, P2, P3 from said first, second and third transducers respectively such that said output signals are related by relative factors of a, l and b respectively, and means for combining the output signals from the transducers to produce a composite signal S of the form S = aP2 + bP3 - 2P1 which includes no component due to significant imperfections in the reference datum. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. In a surface measurement apparatus of the type wherein a sensor is traversed along a path in sensing relation with the surface of a component under test and operates to produce sensor output signals representing the surface under test,
the improvement wherein: -
said sensor comprises first, second, third and fourth transducers, each said transducer being individually sensitive to surface variations and operating to produce an output signal P1, P2, P3, P4 respectively, common support means mounting said first, second, third and fourth transducers spaced from one another by respective predetermined distances, and in relative positions such that each transducer traverses substantially the same path over the surface of the component upon relative movement of said common support and the component under test, the spacing of said common support from a fixed surface providing a reference datum for the transducers in generating the output signals thereof, amplifier means for amplifying said output signals P1, P2, P3 and P4 from said first, second, third and fourth transducers in such a way that, after amplification, said output signals are related by factors l, a, b, and c respectively where l+a+b+c=0, and means for combining the output signals from the transducers to produce a composite signal S of the form S = P1 +aP2 +bP3 +cP4 which includes no component due to significant imperfections in the reference datum. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
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20. The surface measurement apparatus of claim 18, wherein said first, second, third and fourth transducers have substantially equal sensitivities and said amplifier means introduces said factors l, a, b and c by amplifying said output signals P1, P2, P3 and P4 by respective gains related to said factors l, a, b and c.
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21. The surface measurement apparatus of claim 18, wherein said first, second, third and fourth transducers have relative sensitivities of l, a, b, and c respectively, and said amplifier means operate to amplify said output signals P1, P2, P3 and P4 substantially equally.
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22. The surface measurement apparatus of claim 18, wherein said common support for said plurality of transducers of said sensor is provided with at least one wheel which, in use of the apparatus, rolls over the surface of said component under test whereby to space said common support from the surface of the component under test to form said reference datum.
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23. The surface measurement apparatus of claim 22, wherein said common support is also provided with a lateral guide engageable on said component under test for ensuring that the transducers all follow substantially the same path over the surface of the component under test.
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24. The surface measurement apparatus of claim 22, wherein said at least one wheel of said common support is provided with means sensitive to the rotation thereof to provide an output signal containing information concerning the position of said common support with respect to said surface of said component.
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25. The surface measurement apparatus of claim 22, wherein there is further provided a towing wire system for providing an output signal representing the position of said transducers along the surface under test.
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26. The surface measurement apparatus of claim 18, wherein said common support for said plurality of transducers of said sensor is provided with at least one wheel,
a reference surface adjacent the surface of said component under test, said at least one wheel of said sensor, in use of the apparatus, rolling over said reference surface adjacent said component under test whereby to space said common support from the surface of the component under test to form said reference datum. -
27. The surface measurement apparatus of claim 26, wherein said common support is also provided with a lateral guide engageable on said component under test for ensuring that the transducers all follow substantially the same path over the surface of the component under test.
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28. The surface measurement apparatus of claim 18, wherein there is further provided an analysing computer for analysing instantaneous changes in slope of said composite signal and for converting these into an analysed signal representing the profile of the surface under test.
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29. The surface measurement apparatus of claim 28, wherein there is further provided a low pass filter in advance on said computer.
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30. The surface measurement apparatus of claim 28, wherein said computer includes low pass filtering means.
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31. The surface measurement apparatus of claim 28, wherein said computer includes means for deriving from said analysed signal, a signal representing a best fit line with respect to said analysed signal.
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Specification