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1 Standards and Calibration Laboratory, SCL Calibration of Gaussmeters at Axial DC Magnetic Field Direction up to 1 Tesla at SCL Speaker: Chung Yin, Poon.

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Presentation on theme: "1 Standards and Calibration Laboratory, SCL Calibration of Gaussmeters at Axial DC Magnetic Field Direction up to 1 Tesla at SCL Speaker: Chung Yin, Poon."— Presentation transcript:

1 1 Standards and Calibration Laboratory, SCL Calibration of Gaussmeters at Axial DC Magnetic Field Direction up to 1 Tesla at SCL Speaker: Chung Yin, Poon Standards and Calibration Laboratory (SCL) The Government of the Hong Kong Special Administrative Region

2 2 Standards and Calibration Laboratory, SCL Measurement on DC magnetic flux density Measurement instruments – Gaussmeter with Hall Effect transverse / axial test probe – Nuclear Magnetic Resonance (NMR) gaussmeter Sources of magnetic flux density

3 3 Standards and Calibration Laboratory, SCL Sources of Magnetic Flux Density Helmholtz Coils Electromagnet

4 4 Standards and Calibration Laboratory, SCL Calibration on Axial Direction Test probe of the DUT(located at the z-axis of the Helmholtz coil) Test probe of the Reference Meter (located at the x-axis of the Helmholtz coil) B field direction

5 5 Standards and Calibration Laboratory, SCL Calibration on Axial Direction B field direction for axial measurement x

6 6 Standards and Calibration Laboratory, SCL Calibration Needs on Axial Field Toy Safety Standard ASTM F Section 8.24 Magnet Test Method – Measurement parameter : magnetic flux density ( gauss / Tesla ) » Equipment—dc field gauss meter with a resolution of 5 gauss (G) and an axial type probe. » An active area diameter of / mm A distance between the active area and probe tip of / mm. Medical electrical equipment Safety (e.g. IEC )

7 7 Standards and Calibration Laboratory, SCL Automatic calibration system on DC magnetic flux density for working- grade gaussmeter in SCL

8 8 Standards and Calibration Laboratory, SCL An automatic calibration system in SCL The major components of the system contain A modified electromagnet The electromagnet’s power supply A water cooling system for the modified electromagnet A reference gaussmeter A software controlled program

9 9 Standards and Calibration Laboratory, SCL A modified electromagnet system in SCL Small opening at the yoke with size and shape suitable for positioning a common test probe in an axial magnetic field

10 10 Standards and Calibration Laboratory, SCL Photos of the electromagnet Filler rod Opening at the yoke test probe of the tested unit test probe of reference meter

11 11 Standards and Calibration Laboratory, SCL Characterization of the Modified Electromagnet Field Plot with the opening at the RHS yoke pole diameter = 150 mm ; pole gap = 20 mm; z-axis along the pole axis toward the RHS yoke with opening At the center of the yoke

12 12 Standards and Calibration Laboratory, SCL Characterization of the Modified Electromagnet Field Plot with filler rod inserted in the RHS yoke pole diameter = 150 mm ; pole gap = 20 mm; z-axis along the pole axis

13 13 Standards and Calibration Laboratory, SCL Setup of Calibration The measurement will be taken at the location adjacent to the LHS yoke ( i.e. as far away from the opening (i.e. RHS yoke ) )

14 14 Standards and Calibration Laboratory, SCL Field Uniformity On the surface of the LHS yoke Z = 4 mm ; field uniformity ~ 500 x Z = 7 mm ; field uniformity ~ 200 x 10 -6

15 15 Standards and Calibration Laboratory, SCL Automation of the calibration The software tool using Visual Basic for the automatic calibration of working-grade gaussmter which have either IEEE 488, RS232 or USB interface. number of measurements; magnetic field levels for test; polarity of the test field ; settings of the reference meter ; settings of the UUT Test field levels are sorted in ascending order by the program Initial value = (Requested test level )/(electromagnet coefficient)

16 16 Standards and Calibration Laboratory, SCL Measurement Uncertainty Uncertainty contributions due to Field non-uniformity Calibration setup Performance of the test unit Performance of the reference meter Environmental effects The best calibration and measurement capability of the working grade gaussmeter is 0.1 % from 50 mT to 1.0 T for axial direction (k=2, 95% CL)

17 17 Standards and Calibration Laboratory, SCL Thank you


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