Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R33/00—Arrangements or instruments for measuring magnetic variables
  • G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
  • G01R33/04—Measuring direction or magnitude of magnetic fields or magnetic flux using the flux-gate principle
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R33/00—Arrangements or instruments for measuring magnetic variables
  • G01R33/0023—Electronic aspects, e.g. circuits for stimulation, evaluation, control; Treating the measured signals; calibration

Definitions

• the principle of magnetic field measurement with fluxgate sensors is widely used in practice.
• the measurement principle is based on the alternating remagnetization of a soft magnetic core with the aid of an excitation coil and the detection of the time-dependent magnetic flux generated with a detector coil.
• the flux change is determined by the magnetization curve of the soft magnetic core as a function of the external magnetic field to be measured.
• a known measuring method measures the time of the magnetic reversal based on the voltage excursion of the detector coil. This time depends on the external magnetic field and thus is a measure of the strength of the magnetic field to be measured.
• the measuring range of the fluxgate sensor depends on the exciter voltage of the exciter coil. The higher the excitation voltage, the more space there is for a shift in the remagnetization, ie, the larger the external magnetic fields can be measured.
• the relationship between excitation voltage and the measurable size of the external magnetic field is almost linear.
• interference fields may be superimposed on the magnetic field of interest. If these interference fields are constant and their size is known, they can be compensated for the measurement. The problem, however, is that the interference fields can be much larger than the magnetic field to be measured. In this case, the measuring range must be extended so that the sum of the interference field and the magnetic field to be measured can be measured. This means that the excitation voltage must be increased accordingly, which entails a higher power consumption of the measuring device.
• the invention is therefore a reduction of the power consumption of a Fluxgatesensormessvortechnische for magnetic field measurement under the influence of strong interference to the task.
• a first aspect of the invention therefore introduces a measuring device for measuring a magnetic field with an exciter coil arranged around a soft magnetic core and connected to an exciter signal generator and a detector coil arranged around the soft magnetic core and connected to an evaluation unit, in which the exciter signal generator is formed Generate excitation signal for the generation of a magnetic field and to the
• the exciter signal generator comprises a DC generator for generating a constant exciter signal and an AC generator for generating an alternating exciter signal, wherein the DC generator and the alternating signal generator are interconnected in such a way that superimpose the constant excitation signal and the alternating exciter signal.
• the constant excitation signal causes the compensation of the known constant interference field during the measurement, while the amplitude of the alternating
• Exciter signal can be reduced as much as it allows the size of the magnetic field to be measured. As a result, the power consumption of the measuring device caused by the generation of the excitation signal thereby decreases significantly compared with the previously known case of increasing the amplitude of the exciter signal.
• the DC signal generator is designed to generate the constant excitation signal with a selectable value.
• the alternating signal generator can be designed to generate the alternating excitation signal with a selectable amplitude.
• the alternating signal generator is designed to generate the alternating exciter signal with a selectable amplitude greater than the constant exciter signal generated by the DC generator. This ensures that the excitation signal resulting from the superimposition of the constant exciter signal and the alternating excitation signal always realizes a magnetic reversal on which the measuring principle is based.
• This can be realized, for example, in that the alternating signal generator and the DC generator are connected to one another and that the alternating signal generator adds in terms of magnitude to the selected amplitude the selected size of the constant exciter signal and optionally an offset value.
• an excitation signal without sign change can also be used.
• the alternating signal generator and the DC generator can be realized, for example, as series-connected voltage sources or as parallel-connected current sources.
• a second aspect of the invention provides a measuring method for measuring a
• Magnetic field comprising the following steps: Generating an excitation signal and outputting the excitation signal to an exciting coil arranged around a soft magnetic core;
• a constant exciter signal and an alternating exciter signal are superimposed to the exciter signal in the step of generating the exciter signal.
• a value of the constant exciter signal and / or an amplitude of the alternating exciter signal can be predeterminable.
• the amplitude of the alternating exciter signal is greater than a value of the constant exciter signal.
• an excitation signal without sign change can also be used.
• FIG. 1 shows the structure of a fluxgate sensor
• FIG. 2 shows typical signal waveforms of the exciter signal and the measuring signal in three sub-figures
• FIG. and FIG. 3 shows an example of a compensation of a known constant interference field according to the invention with simultaneously optimized power consumption of the measuring device in two sub-images.
• FIG. 1 shows the structure of a fluxgate sensor.
• An exciting signal generator 1 1 is connected to both ends of an exciting coil 21 (solid line) which is arranged around a soft magnetic core 30.
• an detector coil 22 (dashed line) whose two ends are connected to an evaluation unit 12.
• Exciter coil 21 and detector coil 22 are electrically isolated from each other and from the soft magnetic core 30.
• FIG. 2 shows typical signal profiles of the exciter signal and the measuring signal in three sub-figures.
• Sub-figure a) shows waveforms of exciter signal (lower
• Time beam Time beam
• measurement signal upper time beam
• the measurement signal output by the detector coil 22 shows at the times at which a sign change or zero crossing of the exciter signal takes place, a brief voltage excursion, the sign of which depends on the direction of the sign change of the exciter signal.
• Sub-figure b) shows corresponding signal curves for a case in which the soft-magnetic core 30 is penetrated by an external field which remains constant during the course of the measurement. Due to the superposition of the external field and the field generated by the excitation signal in the soft magnetic core
• the times of the short voltage shifts of the measurement signal are shifted from those of the zero crossings, wherein the shift direction depends on the sign of the short voltage excursion or the direction of the sign change of the exciter signal, for which reason a pair of voltage pulses approximates each other.
• Voltage excursion is a measure of the strength of the external field.
• the third subfigure c) shows a further case for the presence of an external field, which, however, has an inverted sign compared to the case of subfigure b). Again, the times of the move short voltage excursions of the measuring signal with respect to the zero crossings of the exciter signal, wherein due to the reverse sign of the external field, the direction of displacement reverses.
• Sub-figure a) shows waveforms corresponding to those of sub-picture c) of FIG. 2.
• the amplitude of the exciter signal In order to carry out the measurement of the strong external field, the amplitude of the exciter signal must be correspondingly large. In the case of a measurement of a small field which is superimposed by a strong known interference field, in the prior art the amplitude of the excitation signal is therefore chosen so large that the small field plus the strong known interference field can be measured.
• Subfigure b) shows how the strong known interference field is compensated according to the invention without simultaneously increasing the amplitude of the exciter signal beyond what is necessary for the measurement of the small field.
• the excitation signal shown in the lower time beam of the sub-image b) has a DC component V 0 , which is dimensioned such that the strong known interference field in the soft-magnetic core 30 is compensated.
• the DC component V 0 is shown in subfigure b) as a horizontal dashed line.
• the small field to be measured is equal to 0, which is why the times of the short voltage excursions in the measurement signal coincide with those of the passes of the alternating component of the exciter signal by the DC component V 0 (see vertical dashed lines).
• the amplitude of the excitation signal remains the same when using the measurement principle according to the invention, only the generation of the DC component V 0 means a certain increase in power consumption of the measuring device. Overall, the required power is greatly reduced.
• the number of measurements per unit of time or the frequency (of the alternating component) of the exciter signal can be increased while the steepness of the exciter signal (AV / At) remains constant, which is utilized inter alia for an improvement of the measurement result by averaging several measurements or for the measurement of rapidly changing fields can be.

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• Physics & Mathematics (AREA)
• Condensed Matter Physics & Semiconductors (AREA)
• General Physics & Mathematics (AREA)
• Measuring Magnetic Variables (AREA)

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• 2009
  • 2009-09-24 DE DE102009044988A patent/DE102009044988A1/de not_active Withdrawn
• 2010
  • 2010-08-03 CN CN201080042524.7A patent/CN102576058A/zh active Pending
  • 2010-08-03 KR KR1020127007581A patent/KR20120088680A/ko not_active Application Discontinuation
  • 2010-08-03 EP EP10742466A patent/EP2480904A1/de not_active Withdrawn
  • 2010-08-03 WO PCT/EP2010/061313 patent/WO2011035973A1/de active Application Filing
  • 2010-08-03 JP JP2012530193A patent/JP2013505453A/ja active Pending
  • 2010-08-03 US US13/497,336 patent/US20120313633A1/en not_active Abandoned
  • 2010-09-23 TW TW099132125A patent/TW201126187A/zh unknown

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