JPH01250775A - Measuring device of mutual interference between pickup coils - Google Patents

Abstract

PURPOSE:To obtain a measuring device of mutual interference between pickup coils which contributes to the accurate lead-out of a magnetic field of a substance to be measured, by disposing a plurality of calibration coils just below or around each pickup coil. CONSTITUTION:Seven pickup coils 4-1, 4-2...4-7 are juxtaposed in the tail of a Dewar of a SQUID magnetometer. When a calibration coil 7-3 alone is turned ON, for instance, outputs of the same value are obtained in the coils 4-1 and 4-2 by a leakage magnetic field of said calibration coil 7-3. Now, when a secondary magnetic field due to the leakage magnetic field is regarded as 0, the output of the coil 4-2 on the occasion when the calibration coil 7-1 is turned ON is equivalent to the sum of the leakage magnetic field of an adjacent calibration coil and the secondary magnetic field of the coil 4-2. Accordingly, the secondary magnetic field, i.e. an interference part, of the coil 4-1 can be measured by a method wherein the output of the coil 4-2 at the time when the calibration coil 7-3 is turned ON is subtracted from the output of the coil 4-2 at the time when the calibration coil 7-1 is turned ON. An interference part between other pickup coils can be calculated also quite in the same way.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a pickup coil mutual interference measuring device for measuring mutual interference of pickup coils in a multi-channel skid magnetometer.

(B) Prior Art In recent years, multi-channel skid magnetometers have been developed in which a large number of pickup coils are arranged in parallel in one dual tail. In this type of skid magnetometer, a large number of pickup coils are arranged in parallel, so when the magnetic flux φ from the magnetic field generation source 51 interlinks with the pickup coil 52, as shown in FIG. Magnetic flux of secondary magnetic field φ5
occurs, causing mutual interference. For this reason, the pickup coils are placed apart from each other to the extent that mutual interference can be ignored.

Further, in order to perform sensitivity calibration using mutual interference as described above, a calibration coil is wound around the dual tail, and a mutual inductance method is adopted.

(c) Problems to be Solved by the Invention In the conventional multi-channel skid magnetometer described above, in order to avoid mutual interference, the pickup coils are placed far apart to the extent that mutual interference can be ignored. The volume of the coil portion becomes large, leading to an increase in the size of the dual unit.

On the other hand, depending on the size of the object to be measured, the number of pickup coils is restricted, which poses a problem that becomes an obstacle to high-density measurements.

Further, even if the effect is negligible, it is not the magnetic field itself generated from the object to be measured, and this becomes a negative factor against the advantage of the multi-channel system in accurately identifying the position of the source of the magnetic field. Furthermore, the method of winding a coil around a dual tail to obtain mutual inductance also requires sensitivity calibration that includes actual mutual interference, so there is a problem in that mutual interference bones cannot be measured.

This invention was made in view of the above-mentioned problem, and involves measuring the mutual interference between the pickup coils of a multi-channel skid magnetometer, removing the interference through calculation, and deriving the accurate magnetic field of the object to be measured. The object of the present invention is to provide a pickup coil mutual interference measurement device that contributes to the

(d) Means and Effects for Solving the Problems The pick-up coil mutual interference measuring device of the present invention includes a plurality of pick-up coils having the same size as the pick-up coils and arranged directly under and around each of the pick-up coils. a calibration coil, an oscillating current source for causing current to flow through the calibration coil, a switch group circuit that individually turns ON/OFF the current flowing from the oscillating current source to each of the calibration coils, and a current flowing to each calibration coil. It consists of a group of ammeters that individually measure .

In this pick-up coil mutual interference measuring device, by turning on the individual switches, a polar magnetic field can be easily generated using the individual calibration coils, so that mutual interference measurement can be performed.

(E) Examples The present invention will be explained in more detail with reference to Examples below.

FIG. 1 is a schematic diagram showing how a pick-up coil mutual interference device according to an embodiment of the present invention is used, and FIG. 2 is a circuit configuration diagram of the same mutual interference measuring device. Here, the case where it is applied to a 7-channel skid magnetometer is shown.

Seven pickup coils 4-1, 4-2, . . . , 4-9 are arranged in parallel at the tail 3 of the dual 2 of the skid magnetometer 1. Structurally, this multichannel skid magnetometer 1 itself is not particularly different from the conventional one. A mutual interference measuring device 5 is installed directly below the dual tail 3. This mutual interference measuring device 5 includes 19 calibration coils 7-2, 71, 7-3, . . . , 7-4 . is located. These calibration coils L,,'1. ．． 7
-3, . . . , 7-19 are all pickup coils 4-1. Of the 19 calibration coils, calibration coils 7-1, 7-2, . . .
, 7-1 is the pickup coil 4-1.44, . . .
, 4-7, and the other calibration coil 7-s
l, 7-9, ..., 7-1° are calibration coils 7-8
．． 7-2,...,7-? are arranged around.

Each calibration coil 7-1.7-2.7-3,..., 7-1
．． From the oscillator/current source 8, each switch 9-1.9-t, 94, . . . , 9-19 of the switch group circuit 9, and adjustment resistors R1, Rz, R3, . ,1,
The current is configured to be turned ON/OFF individually to flow through the ammeters 101, 108, 103, . . . , 10-, . - In this mutual interference measurement device, for example, as shown in FIG. 3, when focusing on pickup coils 4-1 and 4-2 and inputting a signal, that is, a magnetic field, through calibration coil 7-I,
A large output (signal output) can be obtained from the pickup coil 4-+, which is interlinked with the magnetic flux caused by the magnetic field. On the other hand, (1) the leakage magnetic field of the calibration coil 7-3 and (2) the secondary magnetic field due to the magnetic field input to the pickup coil 4-1 enter the pickup coils 4-2. However, in this case, the ratio of the magnetic field (■) to the magnetic field (2) is not certain.

Next, as shown in FIG. 4, the pickup coil 4-2
Calibration coil 7-1.7- arranged on a concentric circle around
Focusing on 3.7-1.7-8.7-19-, 7-7,
By operating these calibration coils, input-output relationships can be obtained, and by calculating these, the magnitude of mutual interference can be determined. For example, calibration coil 7-3
When only the calibration coil 7-3 is turned on, the leakage magnetic field of the calibration coil 7-3 causes the pickup coils 4-1 and 4. gives equivalent output. Now, assuming that the secondary magnetic field due to the leakage magnetic field is 0, the output of the pickup coil 4-2 when the calibration coil 7-1 is ONL will be the same as the leakage and magnetic field of the adjacent calibration coil, as described above. Since it corresponds to the sum of the secondary magnetic fields of the pickup coil 4-8, the calibration coil 1-I
By subtracting the output of the pickup coil 4-2 when the calibration coil 74 is ON from the output of the pickup coil 4-2 when the calibration coil 74 is ON, the secondary magnetic field of the pickup coil 4-5, that is, the interference component can be measured. Interference between other pickup coils can also be measured in exactly the same way.

If the mutual interference component can be measured as described above, the true value of the magnetic field generated by the object to be measured can be derived by removing the mutual interference component from the measured value when actually measuring the object to be measured.

(f) Effects of the Invention According to the present invention, it is possible to measure the mutual interference of the pickups of a multi-channel skid magnetometer, thereby realizing high density multi-channel measurement. Also, by removing mutual interference,
Since the true value of the magnetic field from the magnetic field source can be derived, the position of the signal can be accurately specified, especially when applied to biomagnetic measurements.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of the use of a pick-up coil mutual interference measuring device according to an embodiment of the present invention, FIG. 2 is a circuit diagram of the same mutual interference measuring device, and FIGS. An explanatory diagram for explaining the operation of the interference measurement device, FIG.
FIG. 3 is an explanatory diagram for explaining mutual interference between pickup coils. 4-t・4-! ...4-9: Pick-up coil, 7-2, 7-2...7-14: Calibration coil, 8: Oscillator/current source, 9: Switch group circuit, 10-1, 10- 2...10-19: Ammeter. Patent Applicant Shimadzu Corporation Agent Patent Attorney Shigeru Nakamura Figure 3 Figure 5 O Stone Drum! -Takashi Iwazu

Claims (1)

[Claims] (1) A device for measuring mutual interference between each pickup coil of a multi-channel skid magnetometer equipped with a plurality of pickup coils, the device having a size similar to that of the pickup coil, and a device for measuring mutual interference between each pickup coil. A plurality of calibration coils arranged directly below and around the calibration coils, an oscillating current source for causing current to flow through the calibration coils, and a group of switches that individually turn ON/OFF the current flowing from the oscillating current source to each of the calibration coils. A pick-up coil mutual interference measuring device comprising: a circuit; and a group of ammeters that individually measure the current flowing through each calibration coil.