Sartorius Susceptometer - for Precise Measurement of: Susceptibility and Magnetization of Weights

1. Sartorius Susceptometer - for Precise Measurement of:Susceptibility and Magnetizationof Weights Benno Gatzemeier Market Manager Mass Metrology Sartorius AG / Germany June 2007

2. : Contents • : Introduction – Magnetic Properties of weights • : Susceptometer Method • : The Sartorius Susceptometer • : Calibration Procedure and Factory Calibration • : Long term stability of md • : Comparison Measurement

3. : Introduction • Influence Parameters in Mass Comparison : • Air buoyancy • Contamination • Air draft • Object temperature • Magnetic properties • The golden rule in metrology is: • Factors that influence the measurement • are switched off, kept constant or considered. • Magnetic properties

4. N S N N S S : Magnetic properties • The OIML R111 recommends to check the magnetic properties. Magnetization Susceptibility Standard Weights with a Susceptibility F Magnetic Forces Magnetic Forces F Standard Weight with Magnetization Magnet

5. : The new OIML R111

6. H - Hz : Susceptibility  and Magnetization 0M (µT) • Susceptibility  Magnetization 0M (µT) H

7. : Recommended methods regarding the R111

8. : Recommended methods regarding the R111 • Permeability Indicator Gauss meter

9. Susceptibility:  =f (Fa...) F1 + F2 F1 - F2 Fa = Fb = 2 2 F2 = -  m2 * g F1 = - m1 * g F2 F1 µ0MZ =f (Fb...) Magnetization: : The Susceptometer Principe - Regarding the OIML R111

10. F : The Susceptometer Principe - Regarding the OIML R111 • The R111 describes methods for the determination of the magnetic properties. • One of them is the Susceptometer principle. • A) Magnet • B) Weighing Pan • C) Bridge • D) Gauge blocks • Test Weight • Pedestal

11. : Sartorius Suszeptometer • The building guidance was the R111: • A micro mass comparator • Internal magnet • 5 different distances Z0 • Load plate for weights up to 50 kg • Software to compute the formulae • Determination of:- Susceptibility ““- Magnetization “0M” (T)

12. Magnet with md produces a maximum field H Field H should not exceed initially: H 2000 A/m when testing class E1 H 800 A/m when testing class E2 H 200 A/m for classes F1 and F2. Table 1: Initial values for testing class E1, E2, F1 and F2, magnetic (dipole) momentmd0.1 Am2 : Vertical Distances Z0; Magnet <-> Weight This is important to avoid permanent magnetization. Distance may be reduced only if the Susceptometer signal is too weak.

13. : Computation factors for Susceptibility and Magnetization: • Weighing Result of the Magnet H • Distance Z0 : Magnet <-> Weight H • Geometry of the test weight S • magnetic (dipole) moment md [Am2] S • gravitational acceleration [m/s2] S • Local magnet field BEZ–48-60 [µT] S • To measure the Magnetization, we have to rotate the magnet! H

14. : Calculation of the Magnetic properties • Calculation of the susceptibility Calculation of the Magnetization

15. : The vertical rotation mechanics of the magnet • Changes the orientation of the magnet • Parts: • Magnet • Pedestal • Gear • Knob

16. : Application Software • Easy operating • Step by step guide through the measurement procedure • Initial distance is proposed • Results via a serial connection • Calculations, report and export • Recalibrating the necessary constants • Default parameters and user defined configurations • Shape description, OIML knob weights predefined • Export and import function for the sharp of the weights

17. : 1. Select weighing geometry

18. : Own cylinder - Geometry of the test weight

19. : 2. Input parameter

20. : 3. Remove test weight

21. : 4 Adjust vertical position Z2

22. : 5. Adjust test magnet to position “N”

23. : 6. Tare balance : 7. Place test weight

24. : 8. Determine measured value m1 for Z4 : 9. Remove test weight

25. : 10. Adjust test magnet to position “S”

26. : 11. Tare balance : 12. Load test weight

27. : 13. Determine measured value m2 for Z5 : 14. Remove test weight

28. : Push result button

30. : Technical specifications Sartorius Susceptometer • Base area 338 x 286 mm • Height 249 mm • Maximum load 50 kg • Dipole moment of the magnet m ~ 0.1 Am2 • Geometry ratio of the magnet h/d = 0.87 • Height Z0 adjustable in fixed steps Z1=18 / Z2=20 / Z3=27 / Z4=35 / Z5=43mm • Field strength 2700 / 2000 / 800 / 360 / 200 A/m • Readability of the Mass Comparator 10 µg or 1 µg • Reverse gear for magnet external rotary knob with N-S marking

31. Calibration, check of the Susceptometer • Calibration of the Mass comparator (10 g) • Using a Susceptibility Referencewith certificate of the susceptibility • Measure the Susceptibility Reference on the Sartorius Susceptometer • Compare the result of the Susceptometer with the PTB-certificate. • The difference has to be less than 10%

32. Factory calibration • We use a 1 kg stainless steel susceptibility standard (=0.004069) • Additional information is used as check for the factory calibration: • Value of the vertical distance Z0 from the mechanical adjustments in the manufacturing • We use always the same three additional magnets.historical data (md )

33. F1-2 F2-3 F1-4 F1-3 F2-4 F3-4 PTB Calibration procedure / Adjustment • Calibration of the mass comparatoruses a 10 g weight • Calibration of the dipole moment md,uses 3 additional magnets and measure the forces between each pair of magnets6 equations and 4 unknown dipole moments • Calibration of the distance Z0,uses a susceptibility standard at known 

34. Comparison Measurement • Our references Susceptibilities • 4 x NPL Standards 1 x PTB Standard • Question: Calibration with susceptibility standard : =0.00401 • Application range : 0 <   1

35. Our Susceptibility standards

36. Comparison Measurement

37. Long term stability of our reference Susceptibility  • The change of the Susceptibility is in the range of the uncertainty and less than 2 %

38. Long term stability of our reference magnets md

39. Thank you for your attentionBenno GatzemeierMass MetrologySartorius AG / Germany