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Werner + Martin Eckel GbR
Am Teich 5
D-19348 Berge GT Grenzheim
Phone: +49 (38785) 60 91-0
Fax: +49 (38785) 60 91-1
E-Mail: info@eckelgbr.com

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Korea: Hankwang Corporation
Hankwang Corp.

Continuous calibration system

Unfortunately we are not allowed to reproduce the Bosch test instruction exactly for copyright reasons. Thus we offer a changed version in own words.

Magnet measurement with the Robograph 2:

The design data for the flux measuring insert are calculated from the drawing of the magnet segment. From this geometry of the flux measuring insert and under consideration of the magnet dimensions and material values the flux and the limits are determined using a finite element program.

The Robograph 2 software includes the calculation of the measuring inserts and an approximation of the flux calculation. If possible a finite element program should be preferably used as it provides more accurate results.

The flux calculation is made as follows.

  • Data entry of magnet geometry.
  • Design of measuring insert.
  • Calculation of the magnetic flux related to Br min.
  • Takeover of calculation into magnet drawing.
  • Φ*Rmin = calculated flux - 1%
  • Φ*Rmax = Φ*Rmin + 10%
  • Φ*RGmin = Φ*Rmin * 0.94

The mentioned numerical values can be varied by the user.

Since the accuracy of the test air gap has great influence in the result, it is produced by wire erosion.

Continuous calibration system:

To test the quality of the magnets processed within the production, magnets that have been measured with the Robograph are integrated in a pole housing. As a result it is possible to establish a relation of the magnet drawing related single segment measurement to the flux measurement of the pole housing.

Flux data obtained from Robograph measurements cannot be directly converted to pole housing measurements since the measurement is performed with different geometry. Thus magnet segments are measured by means of the Robograph unit and are classified in groups with equal flux data for one pole housing. This pole housing is marked with a value in percent related to the Φ*Rmin specification given in the drawing.

Example: Φ measured = 0.300 mVs, Φ*Rmin = 0.294 mVs.
Φ% = 100 / 0.294 * 0.300 = 102%

This pole housing with flux equalling magnet segments and a corresponding labelling can be used for calibration of flux meters.

Calibration of flux meters:

The calibration pole housing is entered to the normal production process.

  • Move calibration pole housing into magnetizing station
  • Magnetization to saturation
  • Flux measurement
  • Evaluation of the flux measurement: The display of the flux meter corresponds to the %-reading at the calibration pole housing, e.g. measured value 0.300 mVs = 102%
  • Setting of limits at the flux meter:
    Lower limit = 100%, upper limit = 110%

    Example: Pole housing labelling = 102%
    Measured value = 0.300 mVs
    Lower limit = 0.300 / 102 * 100 = 0.294 mVs
    Upper limit = 0.294 * 1.1 = 0.323 mVs

At the ECKEL DFM flux meter this process is automatically performed. After the measurement of the calibration pole housing and after data entry of the indicated percentage value the upper an lower limits are set automatically.