ANAMET Meeting Mechanical Metrology to support NPL Standards

Transcription

1 ANAMET Meeting 2004 Mechanical Metrology to support NPL Standards Nigel Cross March 2004

2 Outline of talk Problem analysis Measurement options Measurement strategy - Co-axial airline Measurement strategy - WGBCO Measurement strategy Search coil

3 Analysing Problem Discuss requirements with Customer Any special requirements fragile, no contact or hazardous? Measurement uncertainty required micrometres/millimetres? Completion date Can the customer afford the work Will the job fit on the equipment required? size and weight Traceability

4 Will it fit?

5 Analysing Problem Break down measurements into geometric components Internal/external diameter Length Form cylindricity, circularity, squareness and concentricity etc Review possible measurement options bearing in mind uncertainty required

6 Measurement options Internal diameter vernier callipers internal micrometers bore gauges Zeiss CMM Leitz CMM (0.050 mm) (0.012 mm) (0.001 mm) (0.002 / * mm) (0.002 / * mm) * Comparator mode

7 Measurement options (cont.) External diameter - vernier callipers (0.050 mm) micrometers (0.001 mm) Vertical comparator ( mm) Horizontal comparator # ( mm) Zeiss CMM (0.002 / * mm) Leitz CMM (0.002 / * mm) # Laser based * Comparator mode

8 Measurement options (cont.) Length vernier callipers, micrometers (as previous) Comparators (as previous ) Zeiss CMM (( L/400) or mm *) Leitz CMM (( L/600) or mm *) NPL step gauge system ( L) mm NPL Length bar m/c ( L)mm NPL primary length bar m/c ( < mm/m) NPL primary gauge block comparator ( to mm) * Comparator mode

9 Measurement options (cont.) Form Talycontour (2-D) (< mm ) Zeiss CMM (( L/400) or mm *) (3-D) Leitz CMM (( L/400) or mm *) (3-D) Form Talysurf (2-D) ( to mm) Talycenta (roundness, concentricity etc) ( mm) Talyrond (roundness) ( mm) * Comparator mode

10 Measurement strategy example 1 Measurement of Co-axial Airlines Parameters 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

11 Measurement of Co-axial Airlines (cont.) What is an Airline? Coaxial Air-line Length of transmission line with characteristic Impedance determined by physical dimensions.

12 Measurement of Co-axial Airlines (cont.) Outer diameter of inner conductor - Strategy Measure using vertical comparator 3 planes, top, middle and bottom - 5 circumferential positions 4 repeat sets of measurements at each plane Each set measure standard, 5 positions, back to standard Calculate anvil compression effects ( mm) Calculate mean diameter and variation, and uncertainties Uncertainties on diameter and on variation

13 Measurement of Co-axial Airlines (cont.) Inner diameter of outer conductor strategy Measure 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 times Measure calibrated ring gauge at 51 positions, 3 planes (x7) Move ring gauge to other side, repeat initial measurement Invert airline, repeat initial measurement

14 Measurement of Co-axial Airlines (cont.) Inner diameter of outer conductor strategy (cont.) Calculate mean internal diameter of ring gauge Calculate mean internal diameter of airline Correct for CMM offset Calculate uncertainties ( mm for each orientation but when combined bore tapered!)

15 Measurement of Co-axial Airlines (cont.)

16 Measurement of Co-axial Airlines (cont.) Roundness of bore strategy Measure using Talycenta 3 positions using peak-to-valley evaluation ( P-V) print out roundness graphs Calculate roundness values ( , , mm)

17 Measurement strategy example 2 Measurement of Waveguide Beyond Cut-off (WGBCO) Parameters required Mean internal diameter of copper cylinder Uncertainty required Best possible

18 Measurement of Waveguide Beyond Cut-off (WGBCO) Ring gauge Initial position Ring gauge Final position

19 Measurement of Waveguide Beyond Cut-off Strategy Measure using CMM Mount waveguide horizontally, supported on Vee blocks Fit long offset probe to CMM Use 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.

20 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 procedure Calculate mean diameter and uncertainty ( mm)

21 Measurement strategy example 3 Measurement of Search coils

22 Measurement of Search coils (cont.) Required Mean diameter of copper coil I leave it to you to guess strategy Based on previous examples no prizes given!

23 The end Thank you