High precision field measurement method for geomagnetic vectors and a device thereof
View Patent ↗A tripod, a vertical coil and a total-field magnetometer are utilized to measure a geomagnetic field T 0 without an additional magnetic field imposed, as well as two composite magnetic field values T −1 and T −2 when the geomagnetic field is added with a vertical upward magnetic field T f and a double vertical upward magnetic field 2T f , respectively. Calculate a vertical component Z, a horizontal component H and a geomagnetic inclination I of the geomagnetic field. Set up a horizontal coil such that a geometric center of the horizontal coil coincides with a geometric center of the vertical coil. Use the total-field magnetometer to measure two composite magnetic field values T +∥ and T −∥ after the geomagnetic field has been added with a horizontal forward magnetic field and a horizontal reverse magnetic field, respectively. Calculate a geomagnetic declination D.
1. A high precision field measurement method for geomagnetic vectors, the method comprising:
using a tripod, a vertical coil and a total-field magnetometer to measure a geomagnetic field T 0 without an additional magnetic field imposed;
measuring two composite magnetic field values T −1 and T −2 when the geomagnetic field is added with a vertical upward magnetic field T f and is added with a double vertical upward magnetic field 2T f , respectively;
calculating a vertical component Z, a horizontal component H and a geomagnetic inclination I of the geomagnetic field as follows:
Z
=
T
-
2
2
-
4
T
-
1
2
+
3
T
0
2
8
(
T
-
2
2
-
2
T
-
1
2
+
T
0
2
)
H
=
T
0
2
-
Z
2
cos
(
I
)
=
H
T
0
;
setting up a horizontal coil such that a geometric center of the vertical coil coincides with a geometric center of the horizontal coil;
using the total-field magnetometer to measure two composite magnetic field values T +∥ and T −∥ after the geomagnetic field has been added with a horizontal forward magnetic field and a horizontal reverse magnetic field, respectively; and
calculating a geomagnetic declination as follows:
cos
(
D
1
)
=
T
+
//
2
-
T
-
//
2
T
0
cos
(
I
)
8
(
T
+
//
2
+
T
-
//
2
-
2
T
0
2
)
Geomagnetic
declination
D
=
D
0
-
D
1
:
wherein D0 is an included angle between an axial line of the horizontal coil and a geographical north direction, a known preset value.
2. The high precision field measurement method for geomagnetic vectors of claims 1 , the method further comprising:
mounting the horizontal coil on the vertical coil such that the geometric center of the vertical coil coincides with the geometric center of the horizontal coil;
placing the probe of the total-field magnetometer at a location where the geometric centers of the two coils coincide, wherein the horizontal coil is a Helmholtz coil;
using the total-field magnetometer to measure the composite magnetic fields wherein the geomagnetic field has been added with a horizontal forward magnetic field T +∥ and a horizontal reverse magnetic field T −∥ ; and
calculating the geomagnetic declination as follows:
cos
(
D
1
)
=
T
+
//
2
-
T
-
//
2
T
0
cos
(
I
)
8
(
T
+
//
2
+
T
-
//
2
-
2
T
0
2
)
Geomagnetic
declination
D
=
D
0
-
D
1
:
wherein D0 is the included angle between the axial line of the horizontal coil and the geographic north direction, a known preset value.
3. A high precision field measurement method for geomagnetic vectors, the method comprising:
using a tripod, a vertical coil and a total-field magnetometer to measure a geomagnetic field T 0 without an additional magnetic field imposed;
measuring two composite magnetic field values T −1 and T −2 when the geomagnetic field is added with a vertical upward magnetic field T f and is added with a double vertical upward magnetic field 2T f , respectively; and
calculating a vertical component Z, a horizontal component H and a geomagnetic inclination I of the geomagnetic field,
wherein the method comprises the following steps:
placing a probe of the total-field magnetometer inside the vertical coil and mounting the vertical coil on the tripod, wherein the vertical coil is a Helmholtz coil;
connecting the vertical coil to an excitation power supply through a conducting wire, the excitation power supply provided with a wave-band switch thereon;
adjusting the switch on the excitation power supply such that the excitation power supply does not power on the vertical coil, and using the total-field magnetometer to measure the geomagnetic field T o without an additional magnetic field imposed;
adjusting the switch on the excitation power supply such that the excitation power supply reversely powers on the vertical coil with a current intensity I, generating inside the vertical coil the vertical upward magnetic field T f , and using the total-field magnetometer to measure the composite magnetic field T −1 of the magnetic field T f and the geomagnetic field; and
adjusting the switch on the excitation power supply such that the excitation power supply reversely powers on the vertical coil with a current intensity 2I, generating inside the vertical coil the vertical upward magnetic field 2T f , using the total-field magnetometer to measure the composite magnetic field T −2 of the magnetic field 2T f and the geomagnetic field; and using T o , T −1 and T −2 to calculate the vertical component Z, the horizontal component H and the geomagnetic inclination I of the geomagnetic field as follows:
Z
=
T
-
2
2
-
4
T
-
1
2
+
3
T
0
2
8
(
T
-
2
2
-
2
T
-
1
2
+
T
0
2
)
H
=
T
0
2
-
Z
2
cos
(
I
)
=
H
T
0
.
4. The high precision field measurement method for geomagnetic vectors of claim 3 , further comprising the following steps:
mounting a horizontal coil on the vertical coil such that a geometric center of the vertical coil coincides with a geometric center of the horizontal coil, and connecting the horizontal coil to the excitation power supply, wherein the horizontal coil is a Helmholtz coil;
adjusting the switch on the excitation power supply such that the excitation power supply forwardly powers on the horizontal coil and generates a forward magnetic field, and using the total-field magnetometer to measure a composite magnetic field T +∥ of the forward magnetic field of the horizontal coil and the geomagnetic field;
adjusting the switch on the excitation power supply such that the excitation power supply reversely powers on the horizontal coil and generates a reverse magnetic field, using the total-field magnetometer to measure a composite magnetic field T −∥ of the reverse magnetic field of the horizontal coil and the geomagnetic field, and using the measured values of T o , T −1 , T −2 , T +∥ and T −∥ to calculate a geomagnetic declination D of the geomagnetic field, as follows:
Z
=
T
-
2
2
-
4
T
-
1
2
+
3
T
0
2
8
(
T
-
2
2
-
2
T
-
1
2
+
T
0
2
)
H
=
T
0
2
-
Z
2
cos
(
I
)
=
H
T
0
cos
(
D
1
)
=
T
+
//
2
-
T
-
//
2
T
0
cos
(
I
)
8
(
T
+
//
2
+
T
-
//
2
-
2
T
0
2
)
Geomagnetic
declination
D
=
D
0
-
D
1
:
wherein D0 is an included angle between an axial line of the horizontal coil and a geographic north direction, a known preset value.
5. A device for high precision field measurement of geomagnetic vectors, comprising:
a tripod;
a horizontal dial mounted on the tripod;
a tumbler mounted on the horizontal dial;
a fixed column mounted in the tumbler;
a coil holder mounted on the fixed column;
two half-shaft brackets mounted on the coil holder;
two half-shafts each mounted at a top end of a respective one of the two half-shaft brackets;
a vertical coil frame connected to each of the two half-shafts via a corresponding connecting plate;
a horizontal coil frame connected with the vertical coil frame;
a horizontal coil wound along the horizontal coil frame;
a vertical coil wound along the vertical coil frame, with geometric centers of the vertical coil and the horizontal coil coinciding with each other;
a coil excitation power supply connected to both the vertical coil and the horizontal coil through conducting wires; and
a probe connected via a conducting wire to a total-field magnetometer, the probe mounted at a location where the geometric centers of the vertical coil and the horizontal coil coincide.
6. The device for high precision field measurement of geomagnetic vectors of claim 5 , further comprising:
a supporting plate mounted on the horizontal coil frame;
two mutually orthogonal long glass level bubbles mounted on the supporting plate; and
a plane on which the two long glass level bubbles are located is parallel with a plane of the vertical coil.
7. The device for high precision field measurement of geomagnetic vectors of claim 5 , further comprising:
a rotating base mounted at an upper end of the horizontal dial and around an outer periphery of the tumbler, with an upper-end surface of the rotating base connected with the coil holder, and with a locking bolt mounted on a side surface of the rotating base.
8. The device for high precision field measurement of geomagnetic vectors of claim 5 , wherein the vertical coil frame and the horizontal coil frame mounted on the two half-shafts of the coil holder are mutually orthogonal, wherein the coil frames can vertically rotate by 180° around the horizontal half-shafts, and wherein the coil holder can horizontally rotate by 180° around the fixed column.