anamet meeting 2004 mechanical metrology to support npl...

ANAMET Meeting 2004

Mechanical Metrology to support NPL Standards

Nigel CrossMarch 2004

Problem analysisMeasurement optionsMeasurement strategy -Co-axial airlineMeasurement strategy -WGBCOMeasurement strategy –Search coil

Outline of talk

Analysing Problem

Discuss requirements with Customer

Any special requirements – fragile, no contact or hazardous?Measurement uncertainty required – micrometres/millimetres?Completion dateCan the customer afford the workWill the job fit on the equipment required? – size and weightTraceability

Will it fit?

Analysing Problem

Break down measurements into geometric components

Internal/external diameterLengthForm – cylindricity, circularity, squareness and concentricity etcReview possible measurement options bearing in mind uncertainty required

Measurement options

Internal diameter – vernier callipers (0.050 mm)internal micrometers (0.012 mm)bore gauges (0.001 mm)Zeiss CMM (0.002 / 0.000 3* mm)Leitz CMM (0.002 / 0.000 3* mm)

* Comparator mode

Measurement options (cont.)

External diameter - vernier callipers (0.050 mm)micrometers (0.001 mm)Vertical comparator (0.000 3 mm)Horizontal comparator# (0.000 1 mm)Zeiss CMM (0.002 / 0.000 3* mm)Leitz CMM (0.002 / 0.000 3* mm)

# Laser based* Comparator mode


Length – vernier callipers, micrometers (as previous)Comparators (as previous )

Zeiss CMM ((0.000 8 + L/400) or 0. 000 2 mm *)Leitz CMM ((0.000 5 + L/600) or 0. 000 2 mm *)NPL step gauge system (0.000 1 + 0.000 3L) mmNPL Length bar m/c (0.000 12 + 0.000 26L)mmNPL primary length bar m/c ( < 0.000 1 mm/m)NPL primary gauge block comparator ( 0.000 03 to

0.000 05 mm)* Comparator mode


Form – Talycontour (2-D) (< 0.002 mm )Zeiss CMM ((0.001 3 + L/400) or 0. 000 5 mm *) (3-D)Leitz CMM ((0.000 8 + L/400) or 0. 000 5 mm *) (3-D)Form Talysurf (2-D) ( 0.000 1 to 0.000 5 mm)Talycenta (roundness, concentricity etc) ( 0.000 06 mm)Talyrond (roundness) (0.000 005 mm)

* Comparator mode

Measurement strategy – example 1

Measurement of Co-axial AirlinesParameters required – Outer diameter of inner conductor

Inner diameter of outer conductor Roundness of bore (three planes)

Uncertainty required – Best possible for first two, roundness less critical

Measurement of Co-axial Airlines (cont.)

CoaxialAir-line

Length of transmission line with characteristic Impedance determined

by physical dimensions.

What is an Airline ?


Outer diameter of inner conductor - StrategyMeasure using vertical comparator

3 planes, top, middle and bottom - 5 circumferential positions 4 repeat sets of measurements at each planeEach set – measure standard, 5 positions, back to standard

Calculate anvil compression effects ( 0.000 075 mm)Calculate mean diameter and variation, and uncertainties

Uncertainties – 0.000 09 on diameter and 0.000 08 on variation


Inner diameter of outer conductor – strategyMeasure using co-ordinate measuring machine (CMM) –comparator mode

Measure calibrated ring gauge at 51 positions, 3 planes (x7)Measure airline 54 positions, 3 planes – repeat 7 timesMeasure calibrated ring gauge at 51 positions, 3 planes (x7)Move ring gauge to other side, repeat initial measurementInvert airline, repeat initial measurement


Inner diameter of outer conductor – strategy (cont.)

Calculate mean internal diameter of ring gaugeCalculate mean internal diameter of airlineCorrect for CMM offsetCalculate uncertainties ( 0.000 2 mm for each orientation but 0.001 4 when combined – bore tapered!)


Roundness of bore – strategyMeasure using Talycenta

3 positions using peak-to-valley evaluation ( P-V)print out roundness graphs

Calculate roundness values (0.000 83, 0.000 87, 0.001 2 mm)

Measurement strategy – example 2

Measurement of Waveguide Beyond Cut-off (WGBCO)

Parameters required – Mean internal diameter of copper cylinder

Uncertainty required – Best possible

Measurement of Waveguide Beyond Cut-off (WGBCO)

R ing gauge In itia l position

R ing gauge F ina l position

Measurement of Waveguide Beyond Cut-off

Strategy – Measure using CMM

Mount waveguide horizontally, supported on Vee blocksFit long offset probe to CMMUse special probe calibration (30 points)Measure calibrated ring gauge across 2 diameters spaced at 90

degrees apart (N-S, E-W), at each diameter repeat measurement 5 times. Position ring gauge at position of far end of WGBCO

Measure diameter of WGBCO (N-S, E-W) at every 10 mm along length (38 positions), repeat 5 times.

Measurement of Waveguide Beyond Cut-off (cont.)

Strategy (cont.)Measure calibrated ring gauge across 2 diameters spaced at 90

degrees apart (N-S, E-W), at each diameter repeat measurement 5 times. Position ring gauge at position of near end of WGBCO

Rotate WGBCO 45 degrees and repeat whole procedureCalculate mean diameter and uncertainty (0.001 6 mm)

Measurement strategy – example 3Measurement of Search coils

Measurement of Search coils (cont.)

Required – Mean diameter of copper coil

I leave it to you to guess strategyBased on previous examples – no prizes given!

The end

Thank you

anamet meeting 2004 mechanical metrology to support npl...

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