H u auster m mandea a hemshorn e pulz m korte
This presentation is the property of its rightful owner.
Sponsored Links
1 / 24

An Automatic Instrument to Measure the Absolute Components of the Earth's Magnetic Field PowerPoint PPT Presentation


  • 63 Views
  • Uploaded on
  • Presentation posted in: General

H.-U. Auster, M. Mandea, A. Hemshorn , E. Pulz, M. Korte. An Automatic Instrument to Measure the Absolute Components of the Earth's Magnetic Field. Outline. Fundamentals of the Method Magnetic field along a rotation axis Elimination of systematic measurement errors

Download Presentation

An Automatic Instrument to Measure the Absolute Components of the Earth's Magnetic Field

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


H u auster m mandea a hemshorn e pulz m korte

H.-U. Auster, M. Mandea, A. Hemshorn, E. Pulz, M. Korte

An Automatic Instrument to Measure the Absolute Components of the Earth's Magnetic Field


Outline

Outline

  • Fundamentals of the Method

    • Magnetic field along a rotation axis

    • Elimination of systematic measurement errors

  • Manually performed test of the method in Niemegk

  • Automation

    • Magnetometers

    • Mechanics & Optics

    • Controlling

    • Set up in Belsk

  • Outlook


Motivation

Motivation

Manually performed absolute measurement in Hermanus by rotation of a fluxgate magnetometer about two well defined axes

Ongoing activities to automate absolute measurement

  • Automating of DI-Flux

  • Manipulation of vector proton magnetometer

  • Automating of rotation of a vector fluxgate magnetometer about two well defined axes

Auster H.U., V.Auster, A new method for performing an absolute measurement of the geomagnetic field,

Meas. Sci. Technol. 14, 1013-1017, 2003


Magnetic field along a rotation axis 1

Magnetic field along a rotation axis (1)

Co-ordinate systems

  • Red: arbitrary oriented fluxgate magnetometer

  • Black: Geophysical reference system

  • Relation between both: Euler angles

    Rotation about Precession angle ivariable

  •  and  constant

  • Bz = Bz(υ,φ)


Magnetic field along a rotation axis 2

Magnetic field along a rotation axis (2)

Computation of field in rotation axis

  • Three independent measurements with arbitrary I necessary

  • Magnitude of B in direction of rotation axis becomes independent from sensor orientation angles  and 

Matrix MB of measurement results

Unit vector of sensor orientation


Measurement procedure

Measurement Procedure

  • Rotation A to adjust mechanical axis to azimuth marks

  • Rotation B to turn the sensor about the mechanical axes

    • Always 360° forward and backward

    • 6 measurement stops each rotation direction (B and azimuth)

  • Rotation C for magnetometer calibration

y

y

x

x

 Measurement time: 30 minutes


Elimination of systematic measurement errors

Elimination of systematic measurement errors

  • Magnetometer errors by scalar calibration

    • Rotation about two axes sufficient for full determination of linear transfer function (offsets, scale factors, non orthogonality)

    • Full Earth field magnetometer necessary, high requirements on linearity (10-5)

  • Orientation of rotation axes

    • Horizontal balance by level tube, misalignment of level tube eliminated by interchanging of its ends

    • Azimuth by telescope, misalignment of optical axis and rotation axis eliminated by rotation of telescope


Measurement results of one year operation in niemegk z

Measurement Results of one year operation in Niemegk - Z

Standard deviation: 1.0nT

2005

2006


Measurement results of one year operation in niemegk d

Measurement Results of one year operation in Niemegk - D

Standard deviation after trend and readjustment correction: 0.6nT

2005

2006


Measurement results of one year operation in niemegk magnetometer

Measurement Results of one year operation in Niemegk - Magnetometer


Steps to automation

Steps to automation

  • Magnetometers

  • Optical control

  • Mechanics: 3 Rotations

    • Rotation about measurement axis

      - arbitrary angles

    • Turn Table

      - arbitrary, but well known angle

    • Sensor rotation

      - arbitrary angle

  • Controlling

    • Hardware

    • Software


Magnetometer s

Magnetometers

basket

magnetometer

  • two digital 3-axes fluxgate magnetometers

    • range: 64000nT

    • resolution: 0.01nT

    • Non linearity < 10-5

    • Serial & Flashcard interface

  • Proton-Magnetometer

    • Range: 20000-64000nT

    • resolution 0.01nT

    • Serial & Flashcard interface

variometer

scalar

magnetometer


Performance of magnetometers

Performance of Magnetometers

Variometer

Basket magnetometer

Observatory Data


Performance of magnetometers1

Performance of Magnetometers

Variometer - Obs

Basket - Obs

Variometer - Basket


Components of the optical system

Components of the optical system

  • Neodym Laser

    • Coupled in by fibre optics

  • PSD 2cm x 2cm

    • Resolution < 0.1 mm

    • Protected from stray light by

      • Band-filter (635nm)

      • Black tube

  • Azimuth Mark

    • Made by ceramics

    • Grounded in concrete

Bild PSD


Performance of optical system

~ 15 m

0.2mm

 = atan(0.2mm/15 m) ~ 3''

Performance of optical system

  • Stability of azimuth mark:

    • Quarzgut 0.5 ppm/°C

    • Displacement < 0.1 mm

      (h=2m, T = 50°C)


Rotation a by pneumatics

Rotation A by Pneumatics

  • Pointing requirements:

    • 1cm/20m

    • 0.1mm/20cm

    • 2arcmin

  • Well defined end positions necessary

  • 7kg has to be rotated

  • Low friction by bearing

  • Importance of surface treatment

  • Pressure supply necessary (2 bar)


Rotation b c by piezo motors

Rotation B & C by Piezo Motors

Attempts to develop non magnetic motors for sensor rotation

(1)Application example

(2)Linear motor

(3)Rotation to linear conversation

(4)Final solution using gravitation


Control unit

Control Unit

  • GPS controlled Timing

  • Motor control

    • rotation about measurement axis by piezo motor

    • Flip mechanism by piezo motor

  • Pneumatic control

    • Turn table rotation by two valves

  • Laser switching and PSD read out

  • Magnetometer control

  • Pre processing of data


Magnetic requirements for accommodation

Magnetic Requirements for Accommodation


Accommodation in belsk

Accommodation in Belsk


Outlook

Outlook

  • System has to run permanently in Niemegk

  • Reliability have to be tested and improved

  • Redesign of laser optics and some mechanical parts

  • Option: Replacement of pneumatics by Piezo motor driven system

  • New design for lower latitudes


Acknowledgement

Acknowledgement

  • GFZ for personal and financial investigation

  • All the the people designed and manufactured the mechanics (in Niemegk Potsdam Braunschweig Lindau and Garching)

  • Magson for magnetometers and software support

  • Belsk observatory for support to install the facility


Measurement results of one year operation in niemegk h

Measurement Results of one year operation in Niemegk - H

Standard deviation: 1.4nT


  • Login