JPH05322576A - Electronic azimuth meter - Google Patents

Abstract

PURPOSE:To accurately calculate the azimuth of acting magnetism by detecting the max. value in a magnetic detection direction even when there is a detection error in the magnetic detection direction of a magnetic detection means and correcting detection data on the basis of the max. value to calculate an azimuth. CONSTITUTION:A magnetic sensor 10 has a plurality of reluctance elements MR1, MR2, MR3, MR4 having different magnetic detection directions and two bias coils CL1, CL2 are wound around the reluctance elements MR1, MR2, MR3, MR4 so as to cross each other at a right angle. When a correction mode is set, a CPU detects the detection signals of the max. values MX, MY among detection data X1, X2 as first detection signals outputted to all azimuths of the magnetic field on which the reluctance elements MR1, MR2, MR3, MR4 being magnetic detection means act and detection data Y1, Y2 as second detection signals and corrects the detection data X1, X2, Y1, Y2 on the basis of the max. values MX, MY to calculate an azimuth from the corrected detection data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic azimuth meter, and more particularly to an electronic azimuth meter that corrects a detection error of a magnetic detecting means and accurately calculates a magnetic azimuth.

[0002]

2. Description of the Related Art Conventionally, there is a method in which an electronic azimuth meter is provided with a magnetic sensor having two magnetic detection directions orthogonal to each other, and the intensity of the two magnetic detection direction components of the earth magnetism is detected by the magnetic sensor. .. Then, the azimuth of geomagnetism is calculated based on the detection signals of the two magnetic detection direction components output from the magnetic sensor. Further, in order to accurately detect the direction and magnitude of the earth's magnetism in the electronic azimuth meter as described above, the bias coils are wound in two directions orthogonal to the magnetic sensor, and the bias coils are used to orthogonalize each other. A method of detecting the earth's magnetism in a state in which a bias magnetic field in two directions is applied is known.

[0003]

However, in such a conventional electronic azimuth meter, the geomagnetism is simply divided into two magnetic detection direction components which are orthogonal to each other, and the magnetic field is detected by the magnetic sensor. Since the azimuth of the geomagnetism is only calculated based on the detection signal for each magnetic detection direction component of the sensor, an error occurs in the detection result of the geomagnetism due to an error in the detection accuracy of the two magnetic detection directions of the magnetic sensor, There was a problem that the direction of geomagnetism could not be calculated accurately. The error in the detection accuracy in the magnetic detection direction of the magnetic sensor is caused by the detection error of the magnetic sensor itself, or in an electronic azimuth meter that applies a bias magnetic field, due to the bias coil, two directions orthogonal to each other are generated. It is caused by the difference in the magnitude of the bias magnetic field. Therefore, an object of the present invention is to provide an electronic azimuth meter which can correct an error in a detection signal in each magnetic detection direction of the magnetic detection means and calculate an accurate azimuth.

[0004]

To achieve the above object, the present invention has two magnetic detection directions that are orthogonal to each other.
Magnetic detection means for outputting a first detection signal and a second detection signal for each magnetic detection direction in accordance with the strength of each magnetic detection direction component of the applied magnetic field, and the total magnetic field applied by the magnetic detection means. Maximum value detection means for detecting the maximum value of the first detection signals output as the azimuth as the maximum first detection signal and the maximum value of the second detection signals as the maximum second detection signal; and the maximum value detection. Storage means for storing the maximum first detection signal and the maximum second detection signal detected by the means, and the maximum first detection signal and the maximum first storage signal stored in the storage means for the magnetic field of the acting arbitrary direction. Two correction signals are respectively corrected, and an azimuth calculation means for calculating the azimuth of the acting magnetic field from the correction values of the first detection signal and the second detection signal corrected by the correction means. As That.

[0005]

According to the electronic azimuth meter of the present invention, the azimuth can be calculated by correcting the detection error in each magnetic detection direction of the magnetic detection means as follows, and the azimuth of the magnetic field acting can be calculated. Can be accurately calculated. If there is no error in each detection direction in the magnetic detection means, the maximum first detection signal and the maximum second detection signal should have the same value. Therefore, when there is an error in each detection direction, the maximum first detection signal and the maximum second detection signal serve as an index indicating the degree of the error. For example, it is possible to correct the error by using both maximum detection signals stored in the storage means by normalizing the measured value with both maximum detection signals.

[0006]

EXAMPLES The present invention will be specifically described below based on examples. 1 to 8 are views showing an embodiment of an electronic azimuth meter according to the present invention. FIG. 1 is a plan view of the electronic azimuth meter 1. The electronic azimuth meter 1 is provided with a display unit 3, a main switch 4, a correction mode switch 5, and a azimuth arrow 6 on a body case 2.

The display unit 3 is, for example, a liquid crystal display device, and displays and outputs information necessary for the electronic azimuth meter 1, in particular, a clockwise angle with north as 0 degree.

The main switch 4 is a switch for turning on / off the power supply of the electronic azimuth meter 1, and the correction mode switch 5 is a switch to be turned on when performing a correction mode process described later.

The azimuth arrow 6 is an arrow indicating the direction in which the electronic azimuth meter 1 is desired to measure the azimuth, and the azimuth is measured with the arrow aligned with this direction.

The electronic compass 1 has a magnetic sensor 10 shown in FIG.

The magnetic sensor (magnetic detecting means) 10 includes four magnetoresistive elements MR1, MR2, MR3, MR4 and four pads P1, P2, P3, on a substrate 11 formed of, for example, glass or alumina. P4 is formed.

The magnetoresistive elements MR1, MR2, MR
3, MR4 are formed, for example, by vacuum-depositing a ferromagnetic material such as permalloy on the substrate 11, and the pads P1, P2, P3, P4 are formed on the substrate 11, for example, by using a normal wiring material. It is formed by vacuum evaporation.

The magnetoresistive elements MR1, MR2, MR
3 and MR4 are arranged at angles that are orthogonal to the magnetic detection directions of the other magnetoresistive elements MR1, MR2, MR3, and MR4 whose magnetic detection directions are adjacent to each other.
For the direction arrow 6 attached on the main body case 2,
Each detection direction is formed to have an inclination of 45 degrees. That is, the magnetic sensor 10 includes a plurality of (four in the embodiment) magnetoresistive elements MR1 and M having different magnetic detection directions.
It has R2, MR3, and MR4.

Each of these magnetoresistive elements MR1, MR2, M
R3 and MR4 are connected in a bridge shape, and a predetermined voltage is applied between the pads P1 and P3 facing each other. Each magnetoresistive element MR1, MR2, MR3, MR4
As is generally known, the resistance value changes due to the action of a magnetic field. Now, when a predetermined voltage is applied between the pads P1 and P3, the magnetic field acts and the resistance value changes. Then, a predetermined potential is generated on the pads P2 and P4. That is, the potential of the pad P2 is V
1. If the potential of the pad P4 is V2, a potential difference VS of V1-V2 is generated between the pad P2 and the pad P4.

Further, in the magnetic sensor 10, two bias coils CL1 and CL2 are wound around magnetoresistive elements MR1, MR2, MR3 and MR4 so as to be orthogonal to each other.

The bias coil CL1 generates a bias magnetic field BX which is phase-reversed in a direction indicated by an arrow X in FIG. 2 depending on a direction of a current flowing therethrough, and the magnetoresistive elements MR1, MR2, MR3, M.
Apply to R4.

The bias coil CL2 applies a bias magnetic field BY, which is phase-reversed in the direction shown by arrow Y in FIG. 2 depending on the direction of the current flowing, to the magnetoresistive elements MR1, MR2, MR3, M.
Apply to R4.

That is, the bias coils CL1 and CL2
Directions of bias magnetic fields BX, BY applied by
And the magnetic detection directions of the magnetoresistive elements MR1, MR2, MR3, and MR4 are deviated from each other by 45 degrees.

Therefore, the magnetic sensor 10 has two magnetic detection directions orthogonal to each other, and the potential V1 is used as the first detection signal and the second detection signal for each magnetic detection direction according to the strength of the magnetic field acting. , V2, that is, the potential difference VS is output.

FIG. 3 is a block configuration diagram of an electronic azimuth meter 1 using the magnetic sensor 10 of FIG. 2 described above. The electronic azimuth meter 1 includes an element drive circuit 21, a magnetoresistive element section 22, and a differential amplifier. Circuit 23, A / D conversion circuit 24, register (R
1) 25, bias coils CL1 and CL2, coil drive circuit 26, waveform synthesis circuit 27, register (R2) 28,
CPU (Central Processing Unit) 29, display unit 3, R
OM (Read Only Memory) 30, RAM (Random Access)
A memory) 31 and a switch unit 32 are provided.

The magnetoresistive element section 22 includes magnetoresistive elements MR1, MR2, MR3 and MR connected in the bridge shape.
The element driving circuit 21 supplies a predetermined voltage V to be applied to the pad P1 of the magnetic sensor 10 in which the magnetoresistive elements MR1, MR2, MR3 and MR4 are formed. The magnetoresistive element unit 22 outputs the detection voltages V1 and V2 from the pads P2 and P4 to the differential amplifier circuit 23.
Output to.

The differential amplifier circuit 23 is a normal differential amplifier circuit, and has a detection voltage V input from the magnetoresistive element section 22.
A / D by amplifying the potential difference VS (V1-V2) between 1 and V2
Output to the conversion circuit 24.

The A / D conversion circuit 24 is a differential amplifier circuit 23.
The potential difference VS input from is converted to digital and output to the register (R1) 25.

On the other hand, the bias currents from the coil drive circuit 26 are applied to the bias coils CL1 and CL2, respectively.
1, I2 are supplied. These bias currents I1 and I2
The bias currents I1 and I2
By reversing the direction of, the bias coils CL1, C
As shown in FIG. 2, L2 applies a bias magnetic field BX and a bias magnetic field BY which are orthogonal to each other and reversed to the magnetoresistive elements MR1, MR2, MR3 and MR4.

The coil driving circuit 26 includes the waveform synthesizing circuit 2
7, the signals S1 and S for instructing the direction of the bias current and the conduction timing, that is, the directions of the bias magnetic fields BX and BY.
2, S3, S4 are input, and the coil drive circuit 26 supplies the bias currents I1, I2 to the bias coils CL1, CL2 based on the signals S1, S2, S3, S4.
The operation is stopped, and the directions of the bias currents I1 and I2 are switched.

The waveform synthesizing circuit 27 outputs the signals S1, S2, S3 and S4 to the coil driving circuit 26 and stores the detection data X1, X2, Y1 and Y2 of the RAM 31 corresponding to the bias magnetic fields BX and BY. Output to the register (R2) 28, and the conversion timing signal Sa for instructing the A / D conversion timing to the A / D conversion circuit 24 based on the signals S1, S2, S3, S4. Output.

On the other hand, the A / D conversion circuit 24 is
The in-conversion signal Sb indicating that the / D conversion is being performed is output to the waveform synthesizing circuit 27.

Further, the waveform synthesizing circuit 27 has a CPU 29.
Signal I for instructing to start the data rewriting process
After outputting NT, the CPU 29 starts the rewriting process of the data in the RAM 31 based on the interrupt signal INT.

The register (R1) 25 has detection data X1, X2, Y of the potential difference VS from the A / D conversion circuit 24.
1 and Y2 are temporarily stored, and CP is sent in response to a request from the CPU 29.
The detection data X1, X2, Y1, Y of the potential difference VS is stored in U29.
2 is output.

The register (R2) 28 temporarily stores the area signals A1 and A0 from the waveform synthesizing circuit 27, and stores them in the CPU.
In response to the request of 29, it outputs the data of the area signals A1 and A0 to the CPU 29.

The ROM 30 stores a program as the electronic azimuth meter 1, for example, an azimuth calculation processing program or detection data X1, X2 of the potential difference VS detected by the magnetic sensor 10.
The rewrite processing program and the correction processing program for Y1 and Y2 are stored.

The RAM 31 has areas D, X, Y, and
It is divided into a region X1, a region X2, a region Y1, a region Y2, a region MX, and a region MY. The regions X1 and X2 are the detection data X1 and X2 of the potential difference VS when the bias magnetic field BX is applied by the bias coil CL1. Areas to store, areas Y1 and Y2 are areas to store detection data Y1 and Y2 of the potential difference VS when the bias magnetic field BY is applied by the bias coil CL2, and areas X are when the bias magnetic field XB is applied by the bias coil CL1. The region Y for storing the difference data X (X1-X2) between the detection data X1 and X2 is the difference data Y (Y1-Y2) between the detection data Y1 and Y2 when the bias magnetic field YB is applied by the bias coil CL2. Is an area for storing
A region where the azimuth data D calculated by the PU 29 is stored, a region MX is a region where the maximum value MX of the difference data X between the detection data X1 and X2 when a bias magnetic field XB detected in a correction mode process described below is applied, The area MY is an area for storing the maximum value MY of the difference data Y between the detection data Y1 and Y2 when the bias magnetic field YB detected in the correction mode described later is applied.

The CPU 29 controls each part of the electronic azimuth meter 1 according to the program in the ROM 30 to detect the potential difference VS, and detects the difference data X from the detected data X1, X2, Y1, Y2 of the detected potential difference VS. And the difference data Y are calculated, and the difference data X and the difference data Y are calculated.
The azimuth D is calculated based on The CPU 29 detects the detection data X1, X2, Y1, Y2 of the detected potential difference VS.
The difference data X, Y and the calculated azimuth data D are stored in the RAM 31.
And the calculated azimuth is displayed and output on the display unit 3.

When the correction mode is set, the CPU 29 causes the magnetoresistive elements MR1 and MR2 in all directions to move.
Detection data X1 for each magnetic detection direction of MR3, MR4,
Maximum value MX of difference data X of X2 and detection data Y1, Y
The maximum value MY of the difference data Y of 2 is detected, and the detected maximum values MX and MY are written in the areas MX and MY of the RAM 31.

Therefore, the CPU 29 causes the magnetoresistive elements MR1, MR2, MR3, MR4 as magnetic detecting means.
Detection data X1 and X2 (specifically, difference data X) as first detection signals and detection data Y1 and Y2 as second detection signals output in all directions of the magnetic field acting by
(Specifically, it functions as a maximum value detecting means for detecting detection signals of maximum values MX and MY of the difference data Y). Then, the CPU 24 corrects the detection data X1, X2, Y1, Y2 (specifically, the difference data X, Y) based on the maximum values MX, MY, and calculates the azimuth from the corrected detection data. Therefore, the CPU 24 functions as a correction unit and a direction calculation unit.

The switch section 32 is a general term for the main switch 4 and the correction mode switch 5, and is shown in FIG.
In particular, only the correction mode switch 5 is displayed.

Next, the operation will be described. Electronic compass 1
As described above, the magnetic sensor 10 uses the magnetoresistive elements MR1, MR2, MR3, and MR4, and the magnetoresistive elements MR1, MR2, MR3, and MR4 are coupled in a bridge shape. The element drive circuit 21 is provided between the opposing pads P1 and P3 of the magnetoresistive elements MR1, MR2, MR3 and MR4 coupled in the bridge shape.
The driving voltage V is applied from the magnetic sensor 10 to the magnetic sensor 10, and the magnetic sensor 10 detects the potentials of the other pads P2 and P4 of the magnetoresistive elements MR1, MR2, MR3 and MR4 facing each other as the detection potentials V1 and V2.
To the differential amplifier circuit 23.

In the magnetic sensor 10, bias coils CL1 and CL2 are wound in directions orthogonal to each other.
The coil drive circuit 2 is provided for the bias coils CL1 and CL2.
Bias currents I1 and I2 are supplied from 6 respectively.
The bias currents I1 and I2 are reversed in direction, and the bias currents I1 and I2 are reversed in direction, so that the bias coils CL1 and CL2 respectively reverse the bias magnetic field BX as shown in FIG. And the bias magnetic field BY is applied to the magnetoresistive elements MR1, MR2, MR3, MR.
4 is applied. Therefore, the magnetic sensor 10 detects the geomagnetism by time division for each magnetic detection direction and outputs the potentials V1 and V2 as magnetic intensity signals.

By the way, there is an error in the detection sensitivity of the magnetoresistive elements MR1, MR2, MR3, and MR4 used in the magnetic sensor 10 in the detection direction, and the bias coil CL.
1, there is a difference in the magnitude of the bias magnetic fields BX and BY generated by CL2, the detection signal output from the magnetic sensor 10 has a maximum value α in the X direction as shown in FIG. 4, for example. In the Y direction, the maximum value is β, and an error occurs in the detection signal. As a result, the azimuth cannot be calculated accurately.

Therefore, in this embodiment, as will be described later,
By correcting the detection signal of the magnetic sensor 10, the azimuth can be accurately calculated.

The electronic compass 1 is composed of the magnetic sensor 1
The potential V1 of the pad P1 and the potential V2 of the pad P2 detected at 0 are output to the differential amplifier circuit 23 as described above, and the differential amplifier circuit 23 outputs the potential difference VS between these potentials V1 and V1.
Is amplified and output to the A / D conversion circuit 24. The A / D conversion circuit 24 receives the potential difference V input from the differential amplifier circuit 23.
Digitally convert S to detect data X1, X2, Y
1 and Y2 are output to the register (R1) 25, but the potential difference VS is digitally converted based on the conversion timing signal Sa input from the waveform synthesizing circuit 27.

That is, the waveform synthesis circuit 27 converts the conversion timing signal Sa into the A / D conversion circuit 2 as shown in FIG.
When the conversion timing signal Sa is input, the A / D conversion circuit 24 starts the digital conversion of the potential difference VS and outputs the in-conversion signal Sb indicating that the conversion is in progress to the waveform synthesis circuit 27. Output.

The A / D conversion circuit 24 registers the digitally converted detection data X1, X2, Y1 and Y2 in a register (R).
1) 25, and the register (R1) 25 temporarily stores the input detection data X1, X2, Y1, Y2.

The waveform synthesis circuit 27 includes an A / D conversion circuit 24.
When the input of the conversion-in-progress signal Sb disappears, the CPU 29 outputs the interrupt signal INT for instructing the CPU 29 to start the data rewriting process, and the CPU 29 outputs the interrupt signal I
When NT is input, the detection data X1, X2, Y1, and Y2 are read from the register (R1) 25, and data rewriting processing and azimuth calculation processing are started.

As shown in FIG. 5, the waveform synthesizing circuit 27 outputs signals S1, S2, S3 and S4 for causing the coil driving circuit 26 to generate the bias magnetic fields BX and BY, and the coil driving circuit 26 , Signals S1, S2, S3, S
4, the supply / stop of the bias currents I1 and I2 to the bias coils CL1 and CL2 and the bias current I1,
The direction of I2 is switched.

Then, the waveform synthesizing circuit 27 converts the conversion timing signal Sa into the signals S1, S2, S3 and S4.
Output when the output is stable around the middle of the output period.

Therefore, as described above, the bias magnetic field BX is applied to the magnetoresistive elements MR1, MR2, MR3 and MR4.
BY is applied.

Further, the waveform synthesizing circuit 27 detects data X1, X2 to the RAM 31 according to the output timing of the signals S1, S2, S3, S4 to the coil driving circuit 26, that is, the application timing of the bias magnetic fields BX, BY. , Y
The area signals A1 and A0 indicating the storage areas of 1 and Y2 are output to the register (R2) 28, and the register (R2) 28 temporarily stores the area signals A1 and A0. Register (R
2) The area signals A1 and A0 stored in 28 are the CPU1
9 read. As shown in FIG. 5, the area signals A1 and A0 specify four areas X1, X2, Y1 and Y2 by the combination of the area signal A1 and the area signal A0.

As described above, when the interrupt signal INT is input from the waveform synthesizing circuit 27 and an interrupt occurs, the CPU 29 performs the data rewriting process shown in FIG.

That is, the CPU 29 determines that the interrupt signal IN
When an interrupt occurs due to T, the area signals A1 and A0 are read from the register (R2) 28, and the area signal A0 is "0".
It is checked whether or not (step S1).

When the area signal A0 is "0", it is checked whether the area signal A1 is "0" (step S2).
When the area signal A1 is not "0", the register (R
1) The detection data read from 25 is written in the area X1 (step S3).

When the area signal A1 is "0" in step S2, the detection data of the register (R1) 25 is written in the area X2 (step S4), and the difference between the detection data of the area X1 and the detection data of the area X2 is written. Data X (X =
X1-X2) is calculated and written in the area X (step S
5).

When the area signal A0 is not "0" in step S1, it is checked whether the area signal A1 is "0" (step S6). When the area signal A1 is not "0", the detection data of the register 25 is detected. Is written in the area Y1 (step S7).

In step S6, when the area signal A1 is "0", the detection data of the register 25 is written in the area Y2 (step S8), and the difference data Y between the detection data Y1 of the area Y1 and the detection data Y2 of the area Y2. (Y = Y1-Y
2) is calculated and written in the area Y (step S9).

The CPU 29 reads one detection data from the register 25 each time the interrupt signal INT is input, and rewrites the detection data in the RAM 31.

Steps S5 and S9 of FIG. 6 described above.
At the CPU 29, the CPU 29 detects the difference data X (X1-X2) between the detection data X1 and X2 of the potential difference VS when the bias magnetic field BX is applied by the bias coil CL1 and the potential difference VS when the bias magnetic field BY is applied by the bias coil CL2. Difference data Y (Y
1-Y2), which is different from the detection data X1, X2, Y1, Y2 itself of the respective potential differences VS when the bias magnetic fields BX, BY are applied in the reverse direction, rather than the difference data X, This is because Y can increase the output with respect to changes in the geomagnetism and can improve the detection sensitivity.

When the above rewriting process is completed, the CPU exits the interrupt process and performs the azimuth calculation process, the display output process to the display unit 3, etc. (FIG. 7).

However, as described above, the magnetoresistive element M
If there is an error in the detection results of R1, MR2, MR3, and MR4, the CPU 29 cannot accurately calculate the azimuth. Therefore, as shown in FIG.
After performing the correction mode process, the azimuth calculation process and the display process are performed.

That is, when the electronic azimuth meter 1 is powered on, the CPU 29 starts the flow of FIG. 7 and first performs a correction mode process (step P).
1).

In this correction mode processing, as shown in FIG. 8, the maximum value M is obtained from the detection data of all directions of the electronic azimuth meter 1.
This is a process of detecting X and MY and storing them in the RAM 31.

Therefore, in the correction mode processing, the user rotates the electronic azimuth meter 1 in the direction indicated by the arrow in FIG. 1 so that the azimuth arrow 6 slowly rotates 360 degrees on the plane, and all directions are corrected. The magnitude of the geomagnetism is detected, and the maximum values MX and MY are detected from the detected data.

As described above, while the electronic azimuth meter 1 is rotating 360 degrees, the electronic azimuth meter 1 performs the correction mode process as shown in FIG.

That is, the CPU 29 receives the area signal A from the register (R2) 28 as in the data writing process.
1, A0 is read and it is checked whether the area signal A0 is "0" (step Q1).

When the area signal A0 is "0", it is checked whether the area signal A1 is "0" (step Q2).
When the area signal A1 is not "0", the register (R
1) The detection data read from 25 is written in the area X1 (step Q3).

When the area signal A1 is "0" in step Q2, the detection data of the register (R1) 25 is written in the area X2 (step Q4), and the difference between the detection data of the area X1 and the detection data of the area X2 is written. Data X (X =
X1-X2) is calculated and written in the area X (step Q
5). When the writing of the difference data X is completed, the RAM 31
The maximum value MX is read from the maximum value area MX and the difference data X written this time is checked whether it is larger than the maximum value MX (step Q6). When the difference data X is not larger than the maximum value MX, the processing is terminated without rewriting the maximum value MX, and when the difference data X is larger than the maximum value MX, the difference data X is stored in the maximum value area MX of the RAM 31 to the maximum. The value MX is written (step Q7).

When the area signal A0 is not "0" in step Q1, it is checked whether the area signal A1 is "0" (step Q8). When the area signal A1 is not "0", the register (R1) 25 The detection data of is written in the area Y1 (step Q9).

When the area signal A1 is not "0" in step Q8, the detection data of the register (R1) 25 is written in the area Y2 (step Q10), and the detection data Y1 of the area Y1 and the detection data Y2 of the area Y2 are combined. Difference data Y
(Y = Y1-Y2) is calculated and written in the area Y (step Q11). When the writing of the difference data Y is completed, R
Read the maximum value MY from the maximum value area MY of AM31,
It is checked whether the difference data Y written this time is larger than the maximum value MY (step Q12). When the difference data Y is not larger than the maximum value MY, the process is terminated without rewriting the maximum value MY. When the difference data Y is larger than the maximum value MY, the difference data Y is stored in the RAM 31.
The maximum value MY is written as the maximum value MY (step Q13).

The above process is performed at every predetermined sampling timing, and the correction process is performed for a plurality of directions in all directions. In this case, for example, if the processing time of 0.25 seconds is required for each of the bias magnetic fields BX and BY in the X-direction and the Y-direction that are the bias magnetic field directions, one correction processing is performed once. It will be necessary for a second. Therefore, in the correction mode, a processing time of about 40 seconds is provided and the correction mode processing is performed for 10 azimuths.

By performing the correction mode process in this way, the maximum value MX and the maximum value MY are stored in the maximum value areas MX and MY of the RAM 31.

As described above, the correction mode process is performed not only when the power of the electronic azimuth meter 1 is turned on, but also when the mode switch 5 shown in FIG. 1 is turned on.
It receives and executes an interrupt signal indicating that the mode switch 5 is turned on.

When the correction mode process is completed, the CPU 29 performs the azimuth calculation process and the display process shown in FIG.

That is, the CPU 29, as described above,
When the interrupt signal INT is received from the waveform synthesis circuit 27,
The detection data X1, X2, Y1, and Y2 of the potential difference VS are RA
The detection data X1, X2 and the detection data Y1, Y2 are stored in the respective areas X1, X2, Y1, Y2 of M31.
Difference data X and Y are calculated and stored in areas X and Y, and the interrupt processing is exited.

Next, the CPU 29 reads out the difference data X and Y and the maximum values MX and MY from the RAM 31, and calculates the azimuth D by the following equation (step P2). D = tan ⁻¹ (MX · Y / MY · X) ………… (1)

However, tan ^-1 (MX · Y / MY ·
As for the value of (X), the value alone does not determine which value is from 0 degree to 360 degrees. Therefore, in this embodiment, X,
The azimuth is determined based on the magnitude of the Y value.

That is, first, it is checked whether or not the difference data X is negative (step P3). When the difference data X is negative, a value obtained by adding 180 degrees to the azimuth D calculated in step P2 is adopted as the azimuth D. , In the D area of the RAM 31 (step P4).

The direction D stored in the RAM 31 is driven by the display section 3 to be displayed on the display section 3 (step P).
5).

When the difference data X is not negative in step P3, it is checked whether the difference data Y is negative (step P6). When the difference data Y is negative, step P2
A value obtained by adding 360 degrees to the D direction calculated in step 3 is calculated as the direction D and stored in the D area of the RAM 31 (step P7). The calculated azimuth is displayed on the display unit 3 (step P5).

Further, when the value of the difference data Y is not negative in step P6, the azimuth D calculated in step P2 is directly adopted as the azimuth D, and the azimuth D is displayed and output on the display unit 3 (step P5).

As described above, even if there is a detection error in the magnetic detection directions X and Y of the magnetoresistive elements MR1, MR2, MR3, and MR4 of the magnetic sensor 10, the maximum of the magnetic detection directions X and Y is obtained by the correction mode processing. The values MX and MY are detected, the difference data X and Y are corrected by the maximum values MX and MY, and the azimuth can be calculated, so that the azimuth can be accurately calculated.

In the above embodiment, the magnetic sensor 10 has four magnetoresistive elements MR1, MR2, MR3 and M.
Although it is composed of R4, it is not limited to this, and may use two magnetoresistive elements, or connect four or more magnetoresistive elements in series or in parallel to form a bridge. Then, it may be configured. Further, it is not limited to the one formed in a bridge shape.

In one correction mode process, 1
The maximum value is detected from the azimuth of 0, but this is 1
The correction is not limited to 0, and the more it is, the more accurate correction can be performed.

Further, the magnetic detecting means is not limited to the one using the magnetoresistive element as in the above embodiment.

It is also possible to correct with the minimum value instead of the maximum value. Further, the rotation at the time of detecting the maximum value may not be caused by human power but may be caused by a motor or the like.

The electronic azimuth meter of the present invention is not limited to the azimuth meter dedicated device, but can be incorporated in an electronic wrist watch, an altimeter, or the like, or can be applied to a navigation device for an automobile or an aircraft.

[0085]

According to the present invention, with a very simple structure,
Even if the magnetic detection means has a detection error in each magnetic detection direction, it can detect the maximum value in each magnetic detection direction, correct the detection data by this maximum value, and calculate the azimuth. It is possible to accurately calculate the direction of the magnetism that acts.

[Brief description of drawings]

FIG. 1 is a plan view of an electronic azimuth meter according to an embodiment of the present invention.

2 is a plan view of a magnetic sensor incorporated in the electronic compass of FIG. 1. FIG.

FIG. 3 is a circuit block diagram of the electronic compass shown in FIG.

FIG. 4 is a waveform diagram of a detection signal of the magnetic sensor when the magnetic sensor has a detection error.

FIG. 5 is a timing chart of output signals of the respective units in FIG.

FIG. 6 is a flowchart showing a detection data writing process.

FIG. 7 is a flowchart showing an azimuth calculation process.

FIG. 8 is a flowchart showing correction mode processing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electronic azimuth meter 2 Main body case 3 Display section 4 Main switch 5 Mode switch 6 Direction arrow 10 Magnetic sensor 11 Board 21 Element drive circuit 22 Magnetoresistive element section 23 Differential amplifier circuit 24 A / D conversion circuit 25, 28 Register 26 Coil drive circuit 27 Waveform synthesis circuit 29 CPU 30 ROM 31 RAM 32 Switch section MR1, MR2, MR3, MR4 Magnetoresistive element P1, P2, P3, P4 Pad BX, BY Bias magnetic field CL1, CL2 Bias coil

Claims (1)

[Claims] 1. Having two magnetic detection directions orthogonal to each other,
Magnetic detection means for outputting a first detection signal and a second detection signal for each magnetic detection direction according to the strength of each magnetic detection direction component of the applied magnetic field; Maximum value detection means for detecting the maximum value of the first detection signals output for the azimuth as the maximum first detection signal and the maximum value of the second detection signals as the maximum second detection signal; and the maximum value detection. Storage means for storing the maximum first detection signal and the maximum second detection signal detected by the means; the maximum first detection signal and the maximum first storage signal stored in the storage means for the magnetic field of the acting arbitrary direction. Correction means for respectively correcting with two detection signals, and azimuth calculating means for calculating the azimuth of the magnetic field acting from the correction values of the first detection signal and the second detection signal corrected by the correction means. When That electronic compass.