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[en] Complete text of publication follows. Since the beginning of this decade fast DIDD magnetometers have been also applied to record the geomagnetic variation as an 'INTERMAGNET standard' instrument. The principle of this instrument makes it clear, that the values recorded by DIDD are void from offset and scalar factor errors. For the description of the reference frame only four parameters are needed: The angle between the two magnetic axes of the coil system (εID) and the three orientation angles (I0, D0 and ε0). Two methods were developed in the past to find and monitor the coordinate system of the DIDD by using independent geomagnetic measurements. The first method uses absolute measurements to calibrate the DIDD (Schott and Pankratz 2001) while the other is the inter-calibration process developed in Tihany Geophysical Observatory (Heilig 2007). The second method is based on simultaneous recordings of a DIDD and a tri-axial fluxgate magnetometer. A simple new procedure is applied in order to measure εID value directly from DIDD recordings themselves. The sensitivity of this calculation is at the order of arc seconds at the geomagnetic latitude of Tihany Geophysical Observatory. The advantage of this method is double. First, we will be able to adjust the orthogonality accurately, and on the other hand we can monitor the value of this angle periodically. The cognition of this angle is an important station in the development of DIDD instrument, because it gives the possibility for self-calibration of the orthogonality. After the orthoganality error is eliminated only the three orientation angles including the levelling of the D axis (ε0) left to be determined. This can be done using absolute measurements. The poster will describe the new methods and present the first test results to demonstrate the accuracy and the limitation of the new observatory practices.
[en] Recently, we have shown the emergence of oscillations in overdamped undriven nonlinear dynamic systems subject to carefully crafted coupling schemes and operating conditions. Here, we summarize experimental results obtained on a system of N=3 coupled ferromagnetic cores, the underpinning of a 'coupled-core fluxgate magnetometer' (CCFM); the oscillatory behaviour is triggered when the coupling constant exceeds a threshold value (bifurcation point), and the oscillation frequency exhibits a characteristic scaling behaviour with the 'separation' of the coupling constant from its threshold value, as well as with an external target DC magnetic flux signal. The oscillations, which can be induced at frequencies ranging from a few Hz to high-kHz, afford a new detection scheme for weak target magnetic signals. We also present the first (numerical) results on the effects of a (Gaussian, exponentially correlated) noise floor on the spectral properties of the system response
[en] Fluxmetric and magnetometric demagnetizing factors, Nf and Nm, for cylinders along the axial direction are numerically calculated as functions of material susceptibility χ and the ratio γ of length to diameter. The results have an accuracy better than 0.1% with respect to min(Nf,m,1-Nf,m) and are tabulated in the range of 0.01=<γ=<500 and -1=<χ<∼. Nm along the radial direction is evaluated with a lower accuracy from Nm along the axis and tabulated in the range of 0.01=<γ=<1 and -1=<χ<∼. Some previous results are discussed and several applications are explained based on the new results
[en] Complete text of publication follows. Five sets of variometers are continuously operated at the NCK observatory for different purposes. Three sets of fluxgate, one set of torsion magnetometer and one semi-absolute vector magnetometer had been tested for scale value, sensor orientation, temperature effects and long term stability by using natural variations. Differences between measured and calculated total field, as well as baseline variations were considered and different transfer functions among components were analyzed to achieve higher accuracy.
[en] Complete text of publication follows. The U. S. Geological Survey Geomagnetism Program is now collecting one-second triaxial fluxgate magnetometer data at its observatories. Extensive testing is being done to validate the data and document its resolution and timing accuracy. Magnetometer resolution is evaluated by examining the second-to-second differences of each individual component to estimate the noise level. The noise level is determined for the data acquisition system itself and then at each observatory site. Timing accuracy is tested by using the one pulse per second (PPS) output from a GPS clock to trigger a pulse generator with delay. Through this test we are able to quantify the delay introduced by each component of our data acquisition system, including the fluxgate magnetometer and A/D converter. As a second test of timing accuracy, a sine wave is used to examine the delay in the analog output from the fluxgate. The results of these tests are compared with the standards of 0.01 nT resolution and 10 millisecond time accuracy as proposed by Intermagnet in 2008.
[en] We report the design, fabrication, and characterization of a new system that combines the performances of two different types of magnetic characterization systems, Alternating Gradient Force Magnetometers (AGFM) and susceptometers. The flexibility of our system is demonstrated by its capability to be used as any of them, AGFM or susceptometer, without any modification in the experimental set-up because of the electronics we have developed. Our system has a limit of sensitivity lower than 5 × 10−7 emu. Moreover, its main advantage is demonstrated by the possibility of measuring small quantities of materials under DC or AC magnetic fields that cannot properly be measured with a commercial vibrating sample magnetometers or AGFM
[en] Although fluxgates may have a resolution of 50 pT and an absolute precision of 1 nT, their accuracy is often degraded by crossfield response, non-linearities, hysteresis and perming effects. The trends are miniaturization, lower power consumption and production cost, non-linear tuning and digital processing. New core shapes and signal-processing methods have been suggested
[en] A computer-driven, three-dimensional magnetic fluxmeter to be used also for magnetic field dosimetry has been developed. A magnetic monitor applicable to this object should be measurable to an absolute value of local magnetic field strength and also be able to record its time integration as a measure of exposed dose to the magnetic field. The present fluxmeter consists of signal amplifiers, rectifiers, an A/D converter, and a pocket computer (PC). The signal outputs from the sensors are processed with the PC to compose an absolute strength of magnetic flux density and its time-integrated value. The whole system is driven by a battery and is quite compact in size to be used as a handy portable system. Further details of the design, idea, construction, specification, and testing result of the fluxmeter are described. The measurable range are from 0.4G to 20,000G in normal mode and 8mG to 400G in high-sensitivity AC mode, and the sensitivity is well independent of the magnetic field direction. These measured data are displayed in real time on the LCD panel of the PC and memorized in RAM files. Possible application of the fluxmeter are discussed with special attention to the search of the leakage and/or disturbing error fields around LHD (large Helical Device) and other magnetic systems, the individual dose control to the workers in strong magnetic fields, and the evaluation of the effects of long irradiation of magnetic fields. (author)
[en] The paper describes the functioning and design of a direct-reading proton magnetometer. It was shown that the desired accuracy of less than 1/2 gamma can hardly be reached by simple frequency methods. The method of period measurement described and applied here seems to be rather time-consuming, but the required accuracy can be reached. However, advances in semiconductor technology make many switching details appear outdated; but the development conception is still valid. (orig.)
[de]Diese Arbeit beschreibt Wirkungsweise und Aufbau eines direktanzeigenden Protonenmagnetometers. Es wurde gezeigt, dass die gewuenschte Ganauigkeit von weniger als 1/2 Gamma mit einfachen Frequenzmessverfahren nicht ohne weiteres erreichbar ist. Der hier beschriebene und beschrittene Weg der Periodendauermessung erscheint aufwendig, genuegt aber den Anforderungen an die Genauigkeit. Fortschritte der Halbleitertechnologie lassen viele Schaltungseinzelheiten schon wieder veraltet erscheinen; das Entwicklungskonzept hat jedoch nach wie vor Gueltigkeit. (orig.)