JP5523983B2 - Correction method for magnetic sensor and evaluation method of magnetic sensor - Google Patents

Description

  The present invention relates to a correction method for a magnetic sensor having a magnetoresistive effect element and correcting a temperature characteristic of a magnetic sensor to which a bias magnetic field is applied, and a magnetic sensor evaluation method for evaluating a magnetic sensor for selection.

  2. Description of the Related Art Conventionally, it is well known to use a magnetic sensor in a detection device such as a rotation detection device or a position detection device to detect rotational movement, linear movement, or the like of a magnetic body or magnet that is a detection target. It is also well known to use a magnetoresistive effect element for such a magnetic sensor. The magnetoresistive effect element has a characteristic that the resistance value changes according to a change in the external magnetic field, and a change in the resistance value is output as a voltage change by forming a bridge circuit with a plurality of magnetoresistive effect elements. It is also known that a bias magnetic field is applied to this type of magnetic sensor in order to improve the characteristics of the magnetic sensor. Examples of this type of magnetic sensor include those shown in Patent Documents 1 to 5 below. In particular, Patent Documents 1 and 2 listed below show magnetic sensors that can determine the NS pole of a magnet that is a detection target and obtain the same output period as the magnetic field period. Patent Document 3 below discloses a magnetic sensor that obtains an output by causing a magnetic field change by an applied bias magnetic field even if it is a magnetic body that does not generate a magnetic field as an object to be detected. Patent Documents 4 and 5 below show magnetic sensors with improved output voltage accuracy.

  However, in this type of magnetic sensor, the output voltage from the bridge circuit in the state where there is no detection target is ideally ½ of the applied voltage in the half-bridge circuit and zero in the full-bridge circuit. In practice, a deviation from an ideal value (hereinafter, this deviation is referred to as a static offset voltage Os) is caused by a difference in resistance values of a plurality of magnetoresistive elements that form an equivalent circuit. In addition, the static offset voltage Os causes a change in offset voltage having no regularity in direction and amount depending on the temperature in both the half bridge circuit and the full bridge circuit (hereinafter, this change is referred to as an offset temperature drift Od). That is, the direction and amount of change of the static offset voltage Os and the offset temperature drift Od are different for each magnetic sensor even if the manufacturing process is the same.

  The static offset voltage Os can be corrected in a room temperature (for example, 25 ° C.) state. However, the offset temperature drift Od that causes a decrease in accuracy is randomly generated for each magnetic sensor, and thus cannot be corrected in the room temperature state. It is. At present, the principle of behavior of the offset temperature drift Od has not been elucidated. Therefore, a method of calculating an offset temperature drift coefficient (change rate of offset temperature drift Od with respect to temperature) from two environments heated to room temperature and individually correcting the magnetic sensor based on this coefficient is disclosed in Patent Document 6 below. Is shown. Patent Document 7 below discloses a method for periodically calculating and correcting the center value of the maximum value and the minimum value of the output amplitude.

Japanese Patent Laid-Open No. 11-21409 JP 2006-208025 A JP 7-294540 A Japanese Unexamined Patent Publication No. 7-38173 JP 2007-64695 A JP 2002-195822 A JP 2000-1331013 A

  However, since the conventional technology of Patent Document 6 requires an environment for heating each individual magnetic sensor and each application using the magnetic sensor, correction of the output voltage of the magnetic sensor or selection of the magnetic sensor is required. There is a problem of incurring an increase in cost for the evaluation. In the prior art of Patent Document 7, since the output center value with respect to the temperature change cannot be obtained in the state where the magnetic body or the magnet is stopped and in the initial driving state, the detection accuracy in the state is not obtained. There is a problem that improvement cannot be expected.

  The present invention is based on the discovery that a magnetic sensor to which a bias magnetic field is applied has a correlation between the static offset voltage of the output value of the magnetic sensor under two conditions at the same temperature and the offset temperature drift. The offset voltage of the two conditions is the offset voltage of the output voltage of the magnetic sensor measured in a state where the external magnetic field does not cause a difference in the resistance value change of the pair of magnetoresistive elements (this offset voltage is the offset voltage of the first condition). Voltage Os1), and an offset voltage (this is the median value of the output amplitude) of the maximum value and the minimum value of the output voltage of the magnetic sensor when the external magnetic field is rotated with respect to a pair of magnetoresistive elements. The offset voltage is the second condition offset voltage Os2. On the other hand, the rate of change of the offset voltage Os1 under the first condition with respect to temperature (offset temperature drift coefficient) and the rate of change of the offset voltage Os2 under the second condition with respect to temperature (offset temperature drift coefficient) are equal to each other. Let Kt. Further, the difference voltage between the offset voltage Os1 under the first condition and the offset voltage Os2 under the second condition at the same temperature is assumed to be Os2-Os1. In this case, although the offset temperature drift coefficient Kt and the differential voltage Os2-Os1 are different for each magnetic sensor, it has been found that the following equation 1 holds for magnetic sensors of the same type (same specifications). The proportionality constant A is a common constant defined in the same type (same specifications) of magnetic sensors. Further, when the predetermined temperature is Trt and the first condition offset voltage Os1 and the second condition offset voltage Os2 at the predetermined temperature Trt are measured, the correction value Oa (T) of the output voltage of the magnetic sensor at the temperature T is as follows. I also found that it is shown by 2.

  The present invention is based on this discovery. The purpose of the present invention is to make it possible to predict an offset temperature drift that is randomly generated by a magnetic sensor at a predetermined temperature (for example, room temperature). The object is to be able to correct the output voltage of the changing magnetic sensor and to evaluate the magnetic sensor for selection. In addition, in the description of each constituent element of the present invention below, in order to facilitate understanding of the present invention, reference numerals of corresponding portions of the embodiment are described in parentheses, but each constituent element of the present invention is The present invention should not be construed as being limited to the configurations of the corresponding portions indicated by the reference numerals of the embodiments.

  In order to achieve the above object, the structural features of the present invention include at least two magnetoresistive effect elements (15, 16, 32-35) extending in 90 degrees and connected in series, Bias means (13) for applying a bias magnetic field in a central direction sandwiched between the two extending directions of the two magnetoresistive elements, and a DC voltage is applied to both ends of the at least two magnetoresistive elements. A magnetic sensor (10) that outputs a voltage that changes sinusoidally around a reference voltage with respect to an external magnetic field that rotates with respect to the at least two magnetoresistive elements from a connection point of the at least two magnetoresistive elements. 30), and a correction method for a magnetic sensor for correcting an output voltage from the magnetic sensor, wherein an external magnetic field is applied to the at least two magnetoresistive elements. A first output voltage acquisition procedure (S21) for acquiring the output voltage of the magnetic sensor in a state that does not cause a difference in resistance value change, and a deviation amount of the output voltage acquired in the first output voltage acquisition procedure from the reference voltage An offset voltage acquisition procedure (S22) for acquiring a first offset voltage representing an external magnetic field at the same temperature as when an output voltage is input from the magnetic sensor in the first output voltage acquisition procedure. The first output amplitude center value is obtained by calculating the median of the maximum value and the minimum value of the output voltage of the magnetic sensor when rotated with respect to the effect element, and acquiring the calculated median value as the output amplitude center value A step (S23) and an offset representing a difference between the second offset voltage representing the deviation of the calculated output amplitude center value from the reference voltage and the first offset voltage. Subtracting the output voltage acquired by the first output voltage acquisition procedure from the output amplitude center value acquired by the first output amplitude center value acquisition procedure, or the first output amplitude center value acquisition procedure Is obtained by subtracting the reference voltage and the first offset voltage from the center value of the output amplitude obtained in step S1, the proportionality constant prepared in advance is A, the obtained first offset voltage is Os1, and the offset voltage difference (Os2-Os1), Trt is the temperature of the magnetic sensor when the output voltage from the magnetic sensor is input in the first output voltage acquisition procedure and the first output amplitude center value acquisition procedure, and the magnetic Under the condition that the temperature of the sensor is T, the output voltage output from the magnetic sensor by applying an external magnetic field is expressed by the equation Oa (T) = A · (Os 2 −Os 1) · (T− rt) + Os1 correction procedure for correcting the correction values Oa (T) defined by (S31 to S34) and in the provision of the.

  Another feature of the present invention is that the proportional constant A is prepared independently of the first output voltage acquisition procedure, the offset voltage acquisition procedure, the first output amplitude center value acquisition procedure, and the correction procedure. In order to achieve the above, an input voltage from the magnetic sensor in a state where an external magnetic field does not cause a difference in resistance value change between the at least two magnetoresistive elements under two different temperature conditions, When the temperature when the output voltage from the magnetic sensor is input is T1 and T2, the input voltage is V1 and V2, respectively, and the temperature drift coefficient is Kt, the equation Kt = (V2−V1) / By executing the calculation of (T2-T1), the temperature drift coefficient calculation procedure (S11, S12) for calculating the temperature drift coefficient Kt, and the external magnetic field is the at least two magnetic fields. A second output voltage acquisition procedure (S13) for acquiring the output voltage from the magnetic sensor in a state where no difference is caused in the resistance value change of the resistance effect element, and the output voltage from the magnetic sensor in the second output voltage acquisition procedure The median of the maximum value and the minimum value of the output voltage of the magnetic sensor when an external magnetic field is rotated with respect to the at least two magnetoresistive elements at the same temperature as the input is calculated. The second output amplitude center value acquisition procedure (S15) for acquiring the median value as the output amplitude center value, and the output amplitude center value and the second output voltage acquisition procedure acquired in the second output amplitude center value acquisition procedure. Using an output voltage, a voltage difference between the output amplitude center value and the output voltage is acquired as an offset voltage difference, and the acquired offset voltage difference is defined as (Os2-Os1). Serial proportional constant A, an expression A = Kt / (Os2-Os1) proportional constant calculation procedure (S17) to calculate the execution of operations and also that the provided. In this case, the procedure may be executed for only a small number of representative magnetic sensors.

  Another feature of the present invention is that the proportional constant A is prepared independently of the first output voltage acquisition procedure, the offset voltage acquisition procedure, the first output amplitude center value acquisition procedure, and the correction procedure. In order to achieve this, an external magnetic field is rotated with respect to the at least two magnetoresistive elements under two different temperature conditions, and an output voltage is input from each of the magnetic sensors. The respective median values of the maximum value and the minimum value of the output voltage respectively input in the above are acquired as the output amplitude center value, and the temperatures when the output voltage from the magnetic sensor is input are defined as T1 and T2, respectively. Assuming that the output amplitude center values are V1 and V2, respectively, and the temperature drift coefficient is Kt, the calculation of the equation Kt = (V2−V1) / (T2−T1) A temperature drift coefficient calculation procedure (S11, S12) for calculating the lift coefficient Kt and an output voltage from the magnetic sensor in a state where the external magnetic field does not cause a difference in resistance value change of the at least two magnetoresistive elements, respectively. The external magnetic field is rotated with respect to the at least two magnetoresistive elements at the same temperature as when the output voltage is input from the magnetic sensor in the second output voltage acquisition procedure (S13) and the second output voltage acquisition procedure. A second output amplitude center value acquisition procedure (S15) for calculating the median of the maximum value and the minimum value of the output voltage of the magnetic sensor at the time, and acquiring the calculated median value as an output amplitude center value; Using the output amplitude center value acquired in the second output amplitude center value acquisition procedure and the output voltage acquired in the second output voltage acquisition procedure, the output amplitude center value A voltage difference from the output voltage is acquired as an offset voltage difference, and the proportional constant A is calculated by executing the expression A = Kt / (Os2-Os1), where the acquired offset voltage difference is (Os2-Os1). There is also the provision of a proportional constant calculation procedure (S17) for calculation. Also in this case, as a magnetic sensor, it is good to perform the said procedure only about a representative small number.

  In the first output voltage acquisition procedure, for example, an output voltage may be input from the magnetic sensor without applying an external magnetic field to the magnetic sensor. In the first output voltage acquisition procedure, an output voltage is input from the magnetic sensor in a state where an external magnetic field is applied in a central direction sandwiched in the extending direction of the at least two magnetoresistive elements or in the opposite direction. May be. Furthermore, the first output voltage acquisition procedure includes inputting an output voltage from the magnetic sensor in a state where an external magnetic field is applied in the extending direction of one of the at least two magnetoresistive elements and in the opposite direction. The median value of the input output voltage may be acquired as the output voltage of the magnetic sensor in a state in which the external magnetic field does not cause a difference in resistance value change between at least two magnetoresistive elements.

  According to the present invention configured as described above, if a proportional constant A common to all magnetic sensors of the same type is prepared by measurement of a representative magnetic sensor, each magnetic sensor has a predetermined temperature (for example, room temperature). As long as the static offset voltages Os1 and Os2 are measured, the output voltage of the magnetic sensor can be corrected by using the temperature at that time each time the output voltage from the magnetic sensor is obtained. As a result, it is possible to correct the output voltage without measuring the offset temperature drift coefficient for each magnetic sensor when using the magnetic sensor, so that the magnetic sensor that changes easily with temperature without labor and cost. The output voltage can be corrected.

  According to another aspect of the present invention, there is provided a magnetic sensor evaluation method configured as described above, wherein an output of the magnetic sensor in a state where an external magnetic field does not cause a difference in resistance value change of the at least two magnetoresistive elements. A first output voltage acquisition procedure (S41) for acquiring a voltage and an external magnetic field applied to the at least two magnetoresistive elements at the same temperature as when the output voltage is input from the magnetic sensor in the first output voltage acquisition procedure A first output amplitude center value acquisition procedure (S43) for calculating the median of the maximum value and the minimum value of the output voltage of the magnetic sensor when rotated with respect to the rotation, and acquiring the calculated median value as the output amplitude center value. ), A first offset voltage representing the amount of deviation of the output voltage acquired in the first output voltage acquisition procedure from the reference voltage, and the first output amplitude center value acquisition procedure. The difference between the output amplitude center value and the second offset voltage representing the amount of deviation from the reference voltage is acquired at least by the output voltage acquired by the first output voltage acquisition procedure and the first output amplitude center value acquisition procedure. An off-voltage difference acquisition procedure (S45) for acquiring an offset voltage difference by calculation using the output amplitude center value, and an evaluation procedure (S46, S47) for evaluating the magnetic sensor using the acquired offset voltage difference; It is in having established.

  According to another aspect of the present invention having the above-described configuration, the offset temperature drift coefficient is proportional to the voltage difference Os2-Os1 as shown in the equation 1, so that the absolute value | Os2-Os1 | of the voltage difference Os2-Os1 is As the value increases, the drift amount (correction amount) of the output voltage with respect to the temperature change of the magnetic sensor tends to increase. This brings about the deterioration of the accuracy of the output voltage for the magnetic sensor, the limit of the correction of the output voltage, etc., so that the magnetic sensor can be evaluated by evaluating the voltage difference Os2-Os1. Therefore, the magnetic sensor can be evaluated only by measuring the first and second offset voltages Os1 and Os2 at a predetermined temperature (for example, room temperature), and the selection of the magnetic sensor 10 is simplified. Further, the value A · (Os2−Os1) obtained by multiplying the voltage difference Os2−Os1 by the proportionality constant A is equal to the offset temperature drift coefficient Kt, as can be understood from the above equation 1, so that the proportionality constant A is considered. For example, the change in the output voltage of each magnetic sensor due to temperature can be accurately evaluated. In selecting a magnetic sensor, the magnetic sensor can be evaluated and selected according to whether the voltage difference Os2-Os1 is positive or negative, that is, depending on the direction of temperature drift of the magnetic sensor, depending on the application.

  Another feature of the present invention is that, in the magnetic sensor evaluation method configured as described above, a first output voltage acquisition procedure similar to the first output voltage acquisition procedure and the first output amplitude center value acquisition procedure ( In addition to S51) and the first output amplitude center value acquisition procedure (S53), the first offset voltage representing the amount of deviation of the output voltage acquired in the first output voltage acquisition procedure from the reference voltage, and the first output amplitude A voltage difference between the output offset center value acquired in the center value acquisition procedure and the second offset voltage representing the amount of deviation from the reference voltage is at least the output voltage acquired in the first output voltage acquisition procedure and the first output amplitude. Obtained as an offset voltage difference by calculation using the output amplitude center value acquired in the center value acquisition procedure, and set A as a proportionality constant prepared in advance and common to the same type of magnetic sensor. The temperature drift coefficient acquisition procedure (S55, S56) for acquiring the temperature drift coefficient Kt of the magnetic sensor by the calculation of the equation Kt = A · (Os2−Os1) with the offset voltage difference as Os2−Os1 and the acquired temperature There is an evaluation procedure (S57, S58) for evaluating the magnetic sensor using the drift coefficient Kt. In this case, a proportional constant A may be prepared separately in the same manner as described above.

  According to another characteristic of the present invention having the above-described configuration, the drift amount (correction amount) of the output voltage with respect to the temperature change of the magnetic sensor 10 increases as the absolute value | Kt | of the temperature drift coefficient Kt increases. Become. This brings about the deterioration of the accuracy of the output voltage with respect to the magnetic sensor, the limit of the correction of the output voltage, etc., so that the magnetic sensor can be evaluated by evaluating the temperature drift coefficient Kt. Therefore, the magnetic sensor can be evaluated simply by measuring the first and second static offset voltages Os1, Os2 at a predetermined temperature (for example, room temperature), and the selection of the magnetic sensor is simplified. Also in this case, when selecting a magnetic sensor, the temperature sensor is evaluated and selected depending on whether the temperature drift coefficient Kt is positive or negative, that is, depending on the direction of temperature drift of the magnetic sensor. You can also.

It is sectional drawing of the magnetic sensor of the half bridge structure which concerns on one Embodiment of this invention. FIG. 2 is an explanatory diagram for explaining a relationship between a silicon substrate on which a magnetoresistive effect element is arranged and a bias magnet in the magnetic sensor of FIG. 1. It is explanatory drawing for demonstrating the arrangement direction of the magnetoresistive effect element on the said silicon substrate. It is the schematic of the detection apparatus for detecting rotation of a rotating shaft using the magnetic sensor of FIG. FIG. 5 is an explanatory diagram for explaining directions of a bias magnetic field and a detection magnetic field with respect to the magnetoresistive effect element in FIG. 4. It is a graph which shows the change characteristic of the resistivity with respect to the intensity | strength of the external magnetic field in a magnetic sensor, and the change state of the magnetic field intensity and resistance with respect to a magnetoresistive effect element. It is a wave form diagram of the output voltage of a magnetic sensor. It is a wave form diagram of the output voltage of a magnetic sensor in the state which rotated the external magnetic field of various intensity | strength 1 time. It is explanatory drawing for demonstrating the relationship between the offset temperature drift of a magnetic sensor, and a static offset voltage. It is a graph which shows the relationship between the offset temperature drift in several magnetic sensors, and a static offset voltage. It is a graph which shows the relationship between the external magnetic field and offset temperature drift in a magnetic sensor. It is the schematic which shows the structural example of the other magnetic sensor of a full bridge structure. It is a graph which shows the relationship between the offset temperature drift regarding several other magnetic sensors, and an offset voltage. It is a graph which shows the other relationship of offset temperature drift and an offset voltage. It is the schematic of the correction apparatus of offset temperature drift. It is a flowchart which shows the proportionality constant detection program run with the computer apparatus of FIG. It is a flowchart which shows the static offset voltage acquisition program performed with the said computer apparatus. It is a flowchart which shows the output voltage correction program performed with the said computer apparatus. It is a flowchart which shows the sensor selection program performed with the said computer apparatus. It is a flowchart which shows the other sensor selection program performed with the said computer apparatus. It is the schematic of the detection apparatus using the biaxial Helmholtz coil which concerns on a modification. It is a figure which shows the output voltage waveform which shows the measurement result by the detection apparatus of FIG. 21, a reference | standard sine wave waveform, and the difference voltage waveform of an output voltage and a reference | standard sine wave waveform. It is an enlarged view of the differential voltage waveform of FIG. It is a figure which shows a cosine wave waveform which has a sine wave waveform and its twice frequency. It is a figure which shows arrangement | positioning with the magnetic sensor which concerns on a modification, and a permanent magnet. It is explanatory drawing for demonstrating the change of the direction of the magnetic field by the permanent magnet of FIG.

a. Hereinafter, embodiments of the present invention will be described. In the magnetic sensor to which a bias magnetic field is applied, the measured value under two conditions of room temperature (for example, 25 ° C.) is an offset temperature drift. This is based on the discovery that there is a correlation. First, the magnetic sensor and this correlation will be described.

a1. Magnetic Sensor As shown in FIG. 1, the magnetic sensor 10 has a bias magnet 13 and a silicon substrate 14 bonded to the lower surface and the upper surface of a lead frame 12 in a mold package 11, respectively. The mold package 11 is made of an epoxy resin, and the lead frame 12 is made of a conductor (for example, copper). As shown in FIGS. 2 and 3, meander-line magnetoresistive elements 15 and 16 whose extending directions are different from each other by 90 degrees are provided on the silicon substrate 14. The magnetoresistive elements 15 and 16 are composed of anisotropic magnetoresistive elements (AMR elements) made of an alloy composed of iron Fe and nickel Ni. These magnetoresistive elements 15 and 16 are connected in series, and both ends thereof are connected to a grounding terminal 17a and a power supply terminal 17b, respectively. An intermediate connection point between the magnetoresistive elements 15 and 16 is connected to the output terminal 17c. The grounding terminal 17a, the power supply terminal 17b, and the output terminal 17c are connected to a plurality of external connection terminals 19 via a plurality of lead wires 18, respectively.

  In using the magnetic sensor 10 configured as described above, a power supply voltage (for example, 5V) is applied between the power supply terminal 17b and the grounding terminal 17a via the lead wire 18 from the external connection terminal 19, The voltage at the output terminal 17 c is taken out as an output voltage to the outside through the lead wire 18 and the external connection terminal 19. Therefore, this magnetic sensor 10 functions as a half bridge. 2 and 3, the bias magnet 13 divides the angle between the extending directions of the magnetoresistive elements 15 and 16 into two, that is, both extending directions. A sandwiched magnetic field in the center direction is applied to the magnetoresistive effect elements 15 and 16.

  Next, the case where the rotation of the rotating shaft 21 of the detection target is detected using the magnetic sensor 10 described above will be described. In this case, as shown in FIG. 4, a disc-shaped permanent magnet 22 having the rotation shaft 21 and the center axis coincided with each other is fixed to the tip of the rotation shaft 21. The permanent magnet 22 is a magnet for generating a magnetic field detected by the magnetic sensor 10, and is polarized in two poles in the circumferential direction, that is, one semicircular part is magnetized in the N pole, and the semicircular part of the other method is used. Is magnetized to the S pole. The board surface of the permanent magnet 22 is opposed to the silicon substrate 14 of the magnetic sensor 10, that is, the surface including the extending direction of the magnetoresistive elements 15 and 16. Thereby, when the rotating shaft 21 is rotated, the external magnetic field by the permanent magnet 22 rotates in a plane parallel to the silicon substrate 14 to which the magnetoresistive effect elements 15 and 16 belong.

  This point will be described with reference to FIG. As shown in FIG. 5, the extending directions of the magnetoresistive effect elements 15 and 16 are shifted by 45 degrees with respect to the X axis and the Y axis, respectively, and shifted by 90 degrees. Then, the direction of the bias magnetic field Hb by the bias magnet 13 of the magnetic sensor 10 can be expressed as the X-axis direction. At this time, the rotation angle θ of the external magnetic field Hr when the direction of the external magnetic field Hr by the permanent magnet 22 is the same as the direction of the bias magnetic field Hb is set to “0”. The external magnetic field Hr rotates in the counterclockwise direction indicated by the arrow in the figure. At this time, a magnetic field represented by a composite vector of the external magnetic field Hr and the bias magnetic field Hb is applied to the magnetoresistive elements (R1, R2) 15 and 16, respectively. FIG. 6 is a graph showing the rate of change in resistance of the magnetoresistive effect elements (R1, R2) 15 and 16 with respect to the strength of the magnetic field. Here, when the external magnetic field Hr is rotated from 0 degree to 360 degrees, a magnetic field indicated by a solid line at the bottom of the graph is applied to the magnetoresistive effect element (R1) 15, and a magnetoresistive effect element (R2) 16 is provided at the bottom of the graph. A magnetic field indicated by a broken line is applied. The resistance change rate of the magnetoresistive effect element (R1) 15 changes as indicated by the solid line on the right side of the graph, and the resistance change rate of the magnetoresistive effect element (R2) 16 changes as indicated by the broken line on the right side of the graph. To do. Therefore, as shown in FIG. 7, the output voltage Vout may change in a sinusoidal shape around the voltage Vcc / 2 that is half of the power supply voltage Vcc, that is, change as α · sin θ + (Vcc / 2). Guessed. The value α indicates the amplitude, and θ is the rotation angle of the external magnetic field Hr.

  Based on this assumption, in the apparatus shown in FIG. 4 described above, the power supply voltage Vcc is 5 V (volts) and the bias magnetic field Hb is 25 mT (millitesla), and the external magnetic field Hr. That is, the output voltage Vout was measured while rotating the external magnetic field Hb (permanent magnet 22) from 0 degrees to 360 degrees by varying the magnetic field strength of the permanent magnet 22 in various ways. The measurement result is as shown in FIG. 8, and in the state where the strength of the external magnetic field Hr is smaller than the strength of the bias magnetic field Hb, the external magnetic field Hr is generated around the voltage Vcc / 2 which is almost half of the power supply voltage Vcc. It becomes a sinusoidal signal of approximately one cycle that can discriminate the pole of the permanent magnet 22. However, when the external magnetic field Hr is 25 mT or more, which is stronger than the bias magnetic field Hb, waveform cracking occurs in the approximate sine wave waveform. As can be seen from the characteristic diagram of FIG. 6, the strength of the combined magnetic field of the external magnetic field Hr and the bias magnetic field Hb also enters the negative region of the magnetic field strength, and the magnetoresistive effect elements (R1, R2) This is probably because the resistance change rates of 15 and 16 have the same value for different values of the combined magnetic field.

  In the magnetic sensor as described above, an offset temperature drift occurs, and the present invention intends to provide a method and apparatus that can easily correct such an offset temperature drift of the magnetic sensor 10. In conclusion, the present invention makes use of the fact that two static offset voltages at a predetermined temperature (for example, room temperature) are correlated with an offset temperature drift in a magnetic sensor to which a bias magnetic field is applied. It is. The inventor found the correlation as follows. Hereinafter, the two conditions and the correlation will be described in detail.

a2. Regarding Discovery of Correlation In this magnetic sensor 10, when the external magnetic field Hr is “0”, that is, when the external magnetic field Hr is not applied, the static offset voltage is changed to the first offset voltage Os1 (the voltage Vcc / 2 from the output voltage Vout). Subtracted voltage). Since the power supply voltage Vcc is 5 V, the output voltage Vout is ideally Vcc / 2, that is, 2500 mV. However, the magnetoresistive effect elements (R1, R2) 15 and 16 have a temperature condition of room temperature (25 ° C.). A first static offset voltage Os1 of 5.1 mV was observed, deviating from the voltage Vcc / 2 (2500 mV) due to the difference in resistance value.

  On the other hand, the magnetic sensor 10 to which such a bias magnetic field is applied is used in a state in which the waveform becomes one cycle with the external magnetic field Hr set to be weaker than the bias magnetic field Hb. Therefore, at room temperature (25 ° C.), the strength of the external magnetic field Hr is set to 20 mT, the external magnetic field Hr is rotated once, and the median value (Vmax + Vmin) / 2 of the maximum value Vmax and the minimum value Vmin of the output voltage Vout. The deviation from the voltage Vcc / 2 (hereinafter referred to as the output amplitude center value) was determined as the second static offset voltage Os2. Furthermore, the magnetic sensor 10 is heated to measure the first and second static offset voltages Os1, Os2 at different temperatures, and the first and second static offset voltages Os1, Os2 at each temperature and the room temperature (25 The offset temperature drifts Od1 and Od2 which are the differences between the first and second static offset voltages Os1 and Os2 at (° C.) were calculated. The first and second static offset voltages Os1, Os2 and the first and second offset temperature drifts Od1, Od2 are shown in Table 1 below.

  From Table 1, it can also be understood that the offset temperature drift Od1 in a state where the external magnetic field Hr is not applied is coincident with the offset temperature drift Od2 in a state where the external magnetic field Hr is applied. It was also found that their offset temperature drift coefficients (change amounts of offset temperature drifts Od1 and Od2 per unit temperature) were +20 μV / ° C.

  Next, the correlation between the two static offset voltages Os1, Os2 and the offset temperature drift Od at a predetermined temperature (for example, room temperature: 25 ° C.) will be described. The inventor has found that there is a correlation as shown in FIG. 9 between the first and second static offset voltages Os1 and Os2 and the offset temperature drift Od (T) with respect to the first static offset voltage Os1 at the temperature T. It was assumed that there was. This relationship is expressed by the following formula 3. In the following formula 3, a predetermined temperature (room temperature: 25 ° C.) when the first and second static offset voltages Os1, Os2 are measured is represented by Trt.

  Here, when the value in Table 1 is applied to Equation 3, since the offset temperature drift coefficient in Table 1 is +20 μV / ° C., 20 μV / ° C. = 1.2 mV / (85 ° C.−25 ° C.) is established. , The temperature Tk in Equation 3 is 85 ° C. A represents a proportional constant 1 / (Tk−Trt), and in this case, A = 1/60. However, in an individual magnetic sensor manufactured according to the same specification, that is, the same type of magnetic sensor (generally, an individual magnetic sensor used as the same magnetic sensor), the change amount and direction of the offset voltage due to temperature. It has been conventionally known that this occurs randomly. Here, in order to check whether or not the relationship of Equation 3 is satisfied, the external magnetic field Hr is not applied at a predetermined temperature (room temperature: 25 ° C.) with respect to the other 40 magnetic sensors manufactured according to the same specification. The static offset voltage Os1 (25) in a state and the static offset voltage Os2 (25) in a state where an external magnetic field Hr of 20 mT is applied at a predetermined temperature (room temperature: 25 ° C.) (output amplitude center value Os2 (25)) Then, the offset voltage Os1 (125) in a state where the external magnetic field Hr was not applied at 125 ° C. was measured. The measurement results are shown in Table 2 below. In Table 2 below, the temperature drift Od1 (125) = Os1 (125) −Os1 (25) of the first static offset voltage Os1 at 125 ° C. with respect to 25 ° C., and the first and second static offset voltages Os1. The voltage difference Os2 (25) −Os1 (25) between (25) and Os2 (25) is also shown. As described above, the temperature drifts Od1 and Od2 of the first and second offset voltages Os1 and Os2 are equal, and the temperature drift Od2 (125) = Os2 (125) of the second offset voltage Os2 at 125 ° C. with respect to 25 ° C. ) -Os2 (25) is also equal to the temperature drift Od1 (125) = Os1 (125) -Os1 (25).

  From Table 2, the change amount and change direction of the temperature drifts Od1 and Od2 of the first and second static offset voltages Os1 and Os2 (changes in the offset voltages Os1 and Os2 due to the temperature rise from 25 ° C. to 125 ° C.) The magnetic sensor changes randomly. However, it can be seen that the changing directions of the offset voltages Os1 and Os2 all coincide with the changing directions of the temperature drifts Od1 and Od2. Next, in order to investigate whether or not Equation 3 holds, the inventor sets the offset voltage to “0” at a predetermined temperature (room temperature: 25 ° C.) for each magnetic sensor as shown in FIG. And a temperature drift Od1 (125) = Os1 (125) −Os1 (25) of the first offset voltage Os1 at 125 ° C. with respect to 25 ° C. (temperature drift Od2 (125) = Os2 (second offset voltage Os2) 125) -Os2 (25)).

  For each magnetic sensor, the difference voltage Os2 (25) -Os1 (25) between the first and second offset voltages Os1 (25) and Os2 (25) was plotted at a position of 85 ° C. As can be seen from FIG. 10, the plot positions of the differential voltage Os2 (25) −Os1 (25) at 85 ° C. are located on each straight line. This proves that each magnetic sensor manufactured with the same specification satisfies the relationship of the above equation (3). In other words, an equation in the following equation 4 is established based on the equation 3, and the offset voltages Os1 (25), Os2 (25), Os1 (125) relating to the 40 magnetic sensors 10 in Table 2 are expressed by the following equation 4 All the temperatures Tk were 85 ° C.

a3. Relationship between External Magnetic Field and Temperature Drift Next, the relationship between external magnetic field strength and temperature drift will be described. In the above description, the static offset voltage Os1 without applying an external magnetic field and an external magnetic field of 20 mT are rotated once in an environment of temperatures of 25 ° C., 50 ° C., 75 ° C., 100 ° C. and 125 ° C. The static offset voltage Os2 was measured. Here, the static offset voltage Os2 was measured by changing the external magnetic field to 10 mT, 15 mT, 25 mT, 30 mT, and 35 mT for the same magnetic sensor 10 as described above under the temperature environment. The measurement results are shown in Table 3 below, with the case where the external magnetic field is not applied and the case where the external magnetic field is 20 mT added. In any case, the offset temperature drift coefficient was 20 μV / ° C., as in the case where the external magnetic field was not applied and the case where the external magnetic field was 20 mT. The relationship between the offset voltages Os1 and Os2 with respect to the temperature T is shown in FIG. 11 every 5 mT over the range from 0 mT (state where no external magnetic field is applied) to 35 mT.

  Thus, even if the strength of the external magnetic field is changed, the offset temperature drift coefficient is always constant, and the above Equation 3 is established even if the external magnetic field is changed. Therefore, even if the external magnetic field is changed, the later-described output voltage Vout can be corrected based on the above formula 3. Since the offset temperature drift coefficient is always constant, the first and second static offset voltages Os1, Os2 are measured at a predetermined temperature Trt (room temperature) at which the first and second static offset voltages Os1, Os2 are measured. If the temperature is the same, it may be changed. The temperature Tk in the above equation 3 also changes by changing the predetermined temperature Trt. However, this fact is only for the same magnetic sensor, and even if the magnetic sensor has the same specification, the offset temperature drift coefficient differs for each magnetic sensor.

b. Temperature drift of other magnetic sensors Next, the results of examining whether the above-described correlation (the relationship of Equation 3) is established regarding the temperature drift by other magnetic sensors will be shown. As shown in FIG. 12, the other magnetic sensor is a magnetic sensor 30 having a full bridge configuration. The magnetic sensor 30 includes meander-line magnetoresistive elements 32, 33, 34, and 35 on a silicon substrate 31. These magnetoresistive effect elements 32, 33, 34, and 35 are composed of anisotropic magnetoresistive effect elements (AMR elements) made of an alloy of iron Fe, nickel Ni, and cobalt Co. The extending directions of the magnetoresistive elements 32 and 33 are different from each other by 90 degrees, and the extending directions of the magnetoresistive elements 34 and 35 are also different from each other by 90 degrees. The extending direction of the magnetoresistive effect elements 32 and 35 is the same, and the extending direction of the magnetoresistive effect elements 33 and 34 is also the same. The magnetic sensor 30 also includes a bias magnet (not shown) similar to the magnetic sensor 10, and the magnetic sensor 10 and the magnetic sensor 10 are viewed from 45 degrees with respect to the extending directions of the magnetoresistive elements 32, 33, 34, and 35. A similar bias magnetic field of 25 mT is applied (see the arrow in the figure).

  The magnetoresistive elements 32 and 33 are connected in series, and both ends thereof are connected to the grounding terminal 36a and the power supply terminal 36b, respectively. An intermediate connection point between the magnetoresistive elements 32 and 33 is connected to the output terminal 36c, and the first output voltage Vout1 is output from the output terminal 36c. The magnetoresistive elements 34 and 35 are also connected in series, and both ends thereof are connected to the grounding terminal 36a and the power supply terminal 36b, respectively. An intermediate connection point between the magnetoresistive elements 34 and 35 is connected to the output terminal 36d, and the second output voltage Vout2 is output from the output terminal 36d. The output terminal 36 c is connected to the positive side input of the differential amplifier 37, and the output terminal 36 d is connected to the negative side input of the differential amplifier 37. The differential amplifier 37 outputs the difference voltage Vout1−Vout2 between the first and second output voltages Vout1 and Vout2 as the output voltage Vout of the magnetic sensor 30. Other configurations are the same as those of the magnetic sensor 10. Also in this case, as shown in FIG. 4, the permanent magnet 22 fixed to the rotation shaft 21 is rotated so as to face the silicon substrate 31 of the magnetic sensor 30.

  In this case, as in the case of the magnetic sensor 10, the external magnetic field Hr is “0” at 25 ° C. (room temperature), that is, the external magnetic field Hr is not applied to the 25 magnetic sensors 30 configured as described above. The static offset voltage in the state was measured as the first offset voltage Os1 (25). Further, the static offset voltage (output amplitude center value) in the state where the external magnetic field Hr was 10 mT, 15 mT, and 35 mT at 25 ° C. (room temperature) was measured as the second offset voltage Os2 (25). Further, the static offset voltage in the state where the external magnetic field Hr is “0”, that is, the external magnetic field Hr is not applied at 125 ° C. was measured as the offset voltage Os1 (125). These offset voltages are shown in Table 4 below. In Table 4 below, the temperature drift Od1 (125) = Os1 (125) −Os1 (25) of the first offset voltage Os1 at 125 ° C. with respect to 25 ° C., and the first for each external magnetic field of 10 mT, 15 mT, and 35 mT. The voltage difference Os2 (25) -Os1 (25) between the second static offset voltages Os1 (25) and Os2 (25) is also shown. The output voltage of the magnetic sensor 30 having the full bridge configuration (the output voltage of the differential amplifier 37) inherently changes in a sine wave shape around 0 V as the reference voltage. Unlike the reference voltage Vcc / 2 in the case of the magnetic sensor 10 having the half bridge configuration, it represents a deviation from the reference voltage 0V.

  Also from Table 4, changes in the temperature drifts Od1 and Od2 of the first and second offset voltages Os1 and Os2 (changes in the first and second offset voltages Os1 and Os2 due to the temperature rise from 25 ° C. to 125 ° C.). The amount and direction of change vary randomly from one magnetic sensor to another. However, it can be seen that the changing directions of the first and second offset voltages Os1, Os2 all coincide with the changing directions of the temperature drifts Od1, Od2. Also in this case, as shown in FIG. 13, for each magnetic sensor, the offset voltage is set to “0” at a predetermined temperature (room temperature: 25 ° C.) and the first offset voltage of 125 ° C. with respect to 25 ° C. The temperature drift of Os1 Od1 (125) = Os1 (125) −Os1 (25) was connected by a straight line.

  The voltage difference Os2 (25) −Os1 (25) between the first and second offset voltages Os1 (25) and Os2 (25) is obtained for each magnetic sensor with respect to each of the external magnetic fields 10mT, 15mT, and 35mT. Plots were made at 65 ° C, 78 ° C and 300 ° C. As can be seen from FIG. 13, the plot positions of the voltage differences Os2 (25) −Os1 (25) at 65 ° C., 78 ° C., and 300 ° C. are located on each straight line. This proves that each magnetic sensor manufactured with the same specification satisfies the relationship of the above formula 3. In other words, when the offset voltages Os1 (25), Os2 (25), and Os1 (25) are substituted into the above equation 4 for the external magnetic fields 10 mT, 15 mT, and 35 mT for the 25 magnetic sensors 10, the temperature Tk Were 65 ° C., 78 ° C., and 300 ° C. for external magnetic fields of 10 mT, 15 mT, and 35 mT, respectively. In the case of these external magnetic fields of 10 mT, 15 mT, and 35 mT, the proportionality constant A in Equation 3 is 1/40, 1/53, and 1/275, respectively.

c. Range of Temperature Drift The measurement results for the range from 25 ° C. (room temperature) to 125 ° C. have been described for both the half-bridge magnetic sensor 10 and the full-bridge magnetic sensor 30. However, as is known in the art, the offset temperature drift is known to change linearly over a wide temperature range, but for the sake of safety, the characteristics over a wide temperature range were measured. In 40 magnetic sensors having the same specifications as the full-bridge magnetic sensor 30, the static magnetic offset at 25 ° C., −30 ° C., and 110 ° C. when the external magnetic field Hr is “0”, that is, the external magnetic field Hr is not applied. Voltages Os1 (25), Os1 (-30), Os1 (110) are measured, and temperature drift Od1 (-30) = Os1 (-30) -Os1 (25), Od1 (110) = Os1 (110)- Os1 (25) was calculated. Then, when temperature drifts Od1 and Od2 are plotted for every 40 magnetic sensors on the basis of 25 ° C. and three points are connected for each magnetic sensor, the three points are connected by a straight line as shown in FIG. . Accordingly, when combined with the description of the characteristic example, it can be understood that the relationship of the above formula 3 is applied in a wide temperature range.

d. Next, a temperature drift correction method and correction apparatus according to an embodiment of the present invention will be described. In the correction of the temperature drift, detection of a common proportionality constant A regarding the magnetic sensor manufactured in the same manufacturing process, that is, a magnetic sensor of the same specification (the same type), and first and second static offset voltages for each magnetic sensor. Acquisition of Os1 and Os2 and correction of the output voltage Vout for each magnetic sensor are performed.

d1. Proportional Constant Detection First, the detection of the proportionality constant A will be described. An operator measures voltage and temperature using a measuring instrument such as a voltmeter and a thermometer, and inputs the measurement result to a computer device or the like. However, since it is more efficient to use the program processing by the computer device together, a method using the computer device will be described.

  The case where the present invention is applied to the half-bridge magnetic sensor 10 facing the permanent magnet 22 fixed to the rotating shaft 21 described with reference to FIG. 4 will be described. As shown in FIG. Output voltage Vout is input via the A / D converter 41. The A / D converter 41 converts the output voltage Vout of the analog signal into a digital value and outputs it. The computer device 40 includes a CPU, a ROM, a RAM, a hard disk, a display, an input device, and the like, and stores a proportional constant detection program for detecting the proportional constant A. In addition, a temperature sensor 42 is assembled to the magnetic sensor 10. The temperature sensor 42 detects the temperature T of the magnetoresistive effect elements 15 and 16 in the magnetic sensor 10 and generates an analog signal representing the detected temperature. The temperature T represented by the analog signal is also converted into a digital value by the A / D converter 43 and input to the computer device 40. If a temperature sensor is incorporated in the magnetic sensor 10, the incorporated temperature sensor is used. If the temperature of the magnetoresistive effect elements 15 and 16 can be detected, various temperature measuring devices such as a temperature measuring device for measuring the environmental temperature where the magnetic sensor 10 is placed can be used. Furthermore, a cooling device 44 for heating and cooling the magnetic sensor 10 is also provided.

  In response to an instruction from the operator to start the proportional constant detection program, the computer device 40 starts executing the proportional constant detection program in step S10 of FIG. After the execution of this program is started, the computer device 40 inputs offset voltages V1, V2 at two or more different temperatures T1, T2 together with the temperatures T1, T2 in step S11. An operator raises or lowers the temperature of the magnetic sensor 10 (the magnetoresistive effect elements 15 and 16) by operating the overheating and cooling device 44. In this case, as the input offset voltages V1 and V2, the external magnetic field by the permanent magnet 22 is applied even when the external magnetic field by the permanent magnet 22 is not applied (corresponding to the first offset voltage Os1). Any offset voltage of the offset voltage (output amplitude center value) (corresponding to the second offset voltage Os2) may be used.

  In the former case, the digital value of the output voltage Vout when the temperature of the magnetic sensor 10 is T1 and T2 is input, and the voltage Vcc / 2 that is half the power supply voltage Vcc is subtracted from the input output voltage Vout. Set as voltages V1 and V2. On the other hand, in the latter case, the digital value of the output voltage Vcc obtained by rotating the permanent magnet 22 once in the state where the temperature of the magnetic sensor 10 is T1 and T2 is taken at a predetermined sampling period, and the maximum value is obtained. A median value with respect to the minimum value is calculated, and a voltage Vcc / 2 that is half of the power supply voltage Vcc is subtracted from the calculated median value to set offset voltages (output amplitude center values) V1 and V2. As will be described later, the offset voltages V1 and V2 use the subtraction value V2-V1 obtained by the calculation of the following equation 5, so that the subtraction processing of the voltage Vcc / 2 which is half the power supply voltage Vcc is not performed. The input output voltage Vout and the median value may be left as they are.

  In this case, the temperatures T1 and T2 are predetermined or specified by the operator, and the temperature T detected by the temperature sensor 42 reaches the predetermined temperatures T1 and T2 specified by the operator. When the computer device 40 detects this, the computer device 40 may input the output voltage Vout. However, the temperature T detected by the temperature sensor 42 is displayed on the display device of the computer device 40, and the operator instructs the input of the output voltage Vout using the input device while watching the display temperature. Also good. Further, regarding the number of different temperatures and offset voltages, at least two are necessary, but in order to improve the accuracy of an offset temperature drift coefficient Kt described later, it is preferable to input three or more temperatures and offset voltages. However, it is not necessary to input a large number of temperatures and offset voltages.

  Next, in step S12, the computer device 40 uses the set offset voltages V1 and V2 and the temperatures T1 and T2 to offset the offset voltage change per unit temperature (the slope of the offset voltage with respect to the temperature). The temperature drift coefficient Kt is calculated according to the following formula 5. When three or more offset voltages and temperatures are measured, the offset temperature drift coefficients calculated based on two sets of offset voltages and temperatures may be averaged to obtain the final offset temperature drift coefficient Kt.

  Next, in step S13, the computer apparatus 40 sets the output voltage Vout in a state where an external magnetic field is not applied at a predetermined temperature (for example, a room temperature of 25 ° C.) Trt previously determined or designated by the operator. Input from the magnetic sensor 10. Also in this case, the operator operates the overheating and cooling device 44 to increase or decrease the temperature of the magnetic sensor 10 (magnetoresistance effect elements 15 and 16). When the computer device 40 detects that the temperature T detected by the temperature sensor 42 has reached the predetermined temperature Trt, the computer device 40 inputs the output voltage Vout from the magnetic sensor 10. Also in this case, the temperature T detected by the temperature sensor 42 is displayed on the display device of the computer device 40, and the operator instructs the input of the output voltage Vout using the input device while watching the display temperature. You may make it do. Next, in step S14, the computer apparatus 40 obtains the first static offset voltage Os1 by subtracting the voltage Vcc / 2 which is half of the power supply voltage Vcc from the input Vout.

  Next, in step S15, the computer apparatus 40 acquires the output amplitude center value in a state where an external magnetic field is applied at the same predetermined temperature (for example, a room temperature of 25 ° C.) Trt as in step S13. Also in this case, the operator operates the overheating and cooling device 44 to increase or decrease the temperature of the magnetic sensor 10 (magnetoresistance effect elements 15 and 16). When the computer device 40 detects that the temperature T detected by the temperature sensor 42 has reached the predetermined temperature Trt, the output voltage Vout from the magnetic sensor 10 obtained by rotating the permanent magnet 22 once is predetermined. And the median value between the maximum value and the minimum value is calculated, and the calculated median value is set as the output amplitude center value. Also in this case, the temperature T detected by the temperature sensor 42 is displayed on the display device of the computer device 40, and the operator instructs the input of the output voltage Vout using the input device while watching the display temperature. You may make it do. The predetermined temperature Trt does not always have to be the same as long as the temperatures at the time of obtaining the first and second static offset voltages Os1 and Os2 are the same. Next, in step S16, the computer apparatus 40 obtains a second static offset voltage Os2 by subtracting a voltage Vcc / 2 that is half the power supply voltage Vcc from the calculated output amplitude center value.

  Next, in step S17, the computer 40 uses the calculated offset temperature drift coefficient Kt and the input first and second static offset voltages Os1 and Os2 to calculate the proportionality constant A of the equation 3 below. Calculate according to Equation 6. In step S18, the computer apparatus 40 ends the execution of the proportional constant detection program.

  By executing the proportional constant detection program, the proportional constant A is detected. This proportional constant A is common to all the magnetic sensors 10 having the same specification. Therefore, although the user of the magnetic sensor 10 may detect the proportional constant, the manufacturer of the magnetic sensor 10 may provide the proportional constant A to the user. In the above embodiment, the proportionality constant A is determined by measuring only one magnetic sensor 10. However, in order to improve accuracy, the proportionality constant A is obtained for each of the representative magnetic sensors 10. You may make it employ | adopt those average values. However, it is not necessary to measure the proportionality constant A for many magnetic sensors 10.

  In the proportional constant detection program, the first and second static offset voltages Os1 and Os2 are acquired in steps S14 and S16 and used in the calculation of the above equation (6). However, the voltage difference Os2-Os1 between the first and second static offset voltages Os1, Os2 is a voltage difference between the output voltage Vout input from the magnetic sensor 10 in step S13 and the amplitude center value calculated in step S15. equal. Therefore, when the first and second static offset voltages Os1 and Os2 are not necessary, the processes of steps S14 and S16 are omitted, and the amplitude center value calculated in step S14 is input from the magnetic sensor 10 in step S13. The difference voltage Os2-Os1 may be calculated by subtracting the output voltage Vout.

d2. Acquisition of static offset voltage Next, acquisition of the first and second static offset voltages Os1 and Os2 will be described. In this case as well, measurement is performed by measuring voltage and temperature using a measuring instrument such as a voltmeter and a thermometer. Although the result may be input to a computer device or the like, a device including the computer device 40 as shown in FIG. 15 may be used. In this case, the computer apparatus 40 stores a static offset voltage acquisition program for acquiring the first and second static offset voltages Os1 and Os2. In response to an instruction from the operator to start the static offset voltage acquisition program, the computer device 40 starts executing the static offset voltage acquisition program in step S20 of FIG. However, the acquisition of the first and second offset voltages Os1 and Os2 in this case is for the individual magnetic sensors 10.

  After the start of execution of this program, the computer apparatus 40 performs the first static offset voltage Os1 in a state in which no external magnetic field is applied by the processes of steps S21 and S22 similar to the processes of steps S13 and S14 of FIG. To get. Next, the computer device 40 performs the same processes of steps S23 and S24 as the processes of steps S15 and S16 of FIG. 16 at the same predetermined temperature (for example, room temperature of 25 ° C.) Trt as that of step S21. A second static offset voltage (offset voltage of the output amplitude center value) Os2 in a state where an external magnetic field is applied is acquired.

  And the computer apparatus 40 complete | finishes execution of this static offset voltage acquisition program in step S26. In this case, the acquired first and second static offset voltages Os1 and Os2 are stored in correspondence with the identification numbers that identify the magnetic sensors 10. After the acquisition of the first and second static offset voltages Os1 and Os2 of such a specific magnetic sensor 10, if the temperature correction of the other magnetic sensor 10 is necessary, the above-mentioned other magnetic sensor 10 is described above. Execute the process. Then, by repeating such processing, the first and second static offset voltages Os1 and Os2 for each magnetic sensor 10 are acquired for the plurality of magnetic sensors 10.

  In the static offset voltage acquisition program, the predetermined temperature Trt is a constant temperature. However, the predetermined temperature Trt does not necessarily have to be constant, and the first and second static offset voltages Os1 and Os2 are acquired. It is sufficient if the temperature T is the same. Accordingly, in this case, in the static offset voltage acquisition program of FIG. 17, the temperature T detected by the temperature sensor 42 and converted into a digital value by the A / D converter 43 as in step S25 indicated by a broken line. Is registered as a predetermined temperature Trt.

  By executing such a static offset voltage acquisition program, the first and second static offset voltages Os1 and Os2 are detected. These first and second static offset voltages Os1 and Os2 are detected for each magnetic sensor 10. Different. Therefore, the detection of the first and second static offset voltages Os1 and Os2 may be performed by the user of the magnetic sensor 10. Although it is conceivable that the manufacturer of the magnetic sensor 10 performs, in this case, it is necessary to provide the user with the first and second static offset voltages Os1, Os2 for each magnetic sensor 10. Further, as described above, in some cases, a non-constant temperature may be registered as the predetermined temperature Trt. In this case, the registered predetermined temperature Trt is used for the next output voltage correction process.

d3. Next, the correction of the output voltage Vout will be described. In this case, a computer device 40 as shown in FIG. 15 is incorporated in a detection device using the magnetic sensor 10. The computer device 40 stores an output voltage correction program for correcting the output voltage Vout. In this case, the computer device 40 is integrated with the computer device for detecting the physical quantity to be detected in the detection device, and executes the output voltage correction program in conjunction with the operation of the detection device using the magnetic sensor 10. To do. In this case, the heating and cooling device 44 in FIG. 15 is not necessary.

  The output voltage correction program is started in step S30 in FIG. 18. After the execution is started, the computer device 40 is detected by the temperature sensor 42 and converted into a digital value by the A / D converter 43 in step S31. Enter the measured temperature T. Next, in step S32, the computer apparatus 40 calculates a voltage correction value Oa (T) by the calculation of the following equation (7). In this case, the proportionality constant A is a constant common to the magnetic sensors 10 of the same specification detected by executing the proportionality constant detection program. The first and second static offset voltages Os1 and Os2 are detection values for each magnetic sensor 10 detected by executing the static offset voltage acquisition program. The predetermined temperature Trt is a predetermined temperature or a temperature registered in step S25 of the static offset voltage acquisition program. By executing the calculation of Equation 7, the correction value Oa (T) of the voltage for each magnetic sensor 10 taking into account the temperature drift described in the characteristic example of the magnetic sensor is calculated.

  After the process of step S32, the computer apparatus 40 inputs the output voltage Vout output from the magnetic sensor 10 and converted into a digital value by the A / D converter 43 in step S33. Next, in step S34, the computer 40 corrects the output voltage Vout by subtracting the calculated voltage correction value Oa (T) from the input output voltage Vout. And the computer apparatus 40 complete | finishes execution of an output voltage correction program in step S35. Thereby, the output voltage Vout which is not influenced by temperature drift can be obtained for each magnetic sensor 10. Since the corrected output voltage Vout is used for measurement of the physical quantity detected by the detection device in which the magnetic sensor 10 is incorporated, an accurate physical quantity that is not affected by temperature drift by the magnetic sensor 10 is detected. Become. The first and second static offset voltages Os1 and Os2 are values measured at a predetermined temperature (for example, room temperature), and the proportionality constant A is commonly given to the magnetic sensor. Correction of Vout is easily performed.

  In step S32 of the output voltage correction program, the calculation of Equation 7 is performed using the first and second static offset voltages Os1 and Os2 acquired by the processing of steps S21 to S24 of the static offset voltage acquisition program. And the voltage correction value Oa (T) is calculated. However, the difference voltage Os2−Os1 between the static offset voltages Os1 and Os2 in the equation 7 is the difference voltage between the output voltage Vout input from the magnetic sensor 10 in step S21 and the output amplitude center value calculated in step S23. equal. Therefore, when the offset voltage Os2 is not necessary, the output voltage Vout input in step S21 is subtracted from the output amplitude center value calculated in step S23 without performing the calculation process of the static offset voltage Os2 in step S24. Alternatively, the differential voltage Os2-Os1 may be acquired. Since the static offset voltage Os1 is necessary for the calculation of Equation 7, the static offset voltage Os1 is calculated in Step S22.

e. Selection of Magnetic Sensor Next, the selection of the magnetic sensor 10 will be described. In this case as well, the voltage and temperature are measured using a measuring instrument such as a voltmeter and a thermometer, and the measurement result is input to a computer device or the like. However, an apparatus including the computer apparatus 40 as shown in FIG. 15 may be used. In this case, the computer device 40 stores a sensor selection program for selecting (selecting) the magnetic sensor 10. The computer device 40 starts executing the sensor selection program in step S40 of FIG. 19 in response to an instruction from the operator to start the sensor selection program. However, the magnetic sensor 10 in this case is also an individual magnetic sensor 10.

  After the start of execution of this program, the computer apparatus 40 performs the first static offset voltage Os1 in a state in which no external magnetic field is applied by the processes of steps S41 and S42 similar to the processes of steps S13 and S14 of FIG. To get. Next, at the same predetermined temperature (for example, a room temperature of 25 ° C.) Trt as in step S41, the computer device 40 performs steps S43 and S44 similar to the steps S15 and S16 in FIG. A second static offset voltage (offset voltage of the output amplitude center value) Os2 in a state where an external magnetic field is applied is acquired. In this case as well, the predetermined temperature Trt may not always be the same as long as the temperatures at the time of obtaining the first and second static offsets Os1 and Os2 are the same.

  After the processing in steps S41 to S44, the computer device 40 subtracts the first static offset voltage Os1 from the second static offset voltage Os2 and displays the subtraction result (difference voltage) Os2-Os1 in step S45. Display on the instrument. Next, in step S46, the computer 40 determines whether the absolute value | Os2-Os1 | of the subtraction result is larger than a predetermined selection value Oso. The selection value Oso may be a constant stored in advance in the program, or may be input to the computer device 40 by an operator. If the absolute value | Os2−Os1 | is larger than the predetermined selection value Oso, the computer device 40 determines “Yes” in step S46, and the offset temperature of the magnetic sensor is large in step S47. Is displayed, or the fact that this magnetic sensor is not adopted is displayed, and the execution of the sensor selection program is terminated in step S48. If the absolute value | Os2−Os1 | is equal to or smaller than the predetermined selection value Oso, the computer device 40 makes a “No” determination at step S46 and ends the execution of the sensor selection program at step S48. To do.

  According to such a sensor selection program, the magnetic sensor 10 is selected (selected) by the difference voltage Os2-Os1 between the first and second static offset voltages Os1, Os2. This is because as the absolute value | Os2-Os1 | of the differential voltage Os2-Os1 increases, the drift amount (correction amount) of the output voltage with respect to the temperature change of the magnetic sensor 10 tends to increase. This brings about deterioration of the accuracy of the output voltage, the limit of correction of the output voltage, and the like. Therefore, as described above, the magnetic sensor 10 can be selected simply by measuring the first and second static offset voltages Os1, Os2 at a predetermined temperature (for example, room temperature), and the selection of the magnetic sensor 10 is simplified. The value A · (Os2−Os1) obtained by multiplying the differential voltage Os2−Os1 by the proportionality constant A is equal to the offset temperature drift coefficient Kt, as can be understood from the above equation 6. Is determined to be inversely proportional to the proportionality constant A, it is possible to evaluate the amount of change in the output voltage of each magnetic sensor 10 due to temperature. In selecting the magnetic sensor 10, the magnetic sensor 10 is evaluated and selected according to whether the differential voltage Os2-Os1 is positive or negative, that is, depending on the direction of temperature drift of the magnetic sensor 10, depending on the application. It may be.

  Such a magnetic sensor must be selected for each magnetic sensor, for example, before the manufacturer delivers the magnetic sensor to the user, or before the user uses the magnetic sensor. Or better. Moreover, in the said embodiment, the process of step S46, S47 may be abbreviate | omitted, and a manufacturer or a user may select (select) a magnetic sensor by the display of the offset difference voltage Os2-Os1 by a display. Conversely, the process of step S45 may be omitted, and the selection (selection) of the magnetic sensor may be performed only by displaying on the display that the offset temperature drift is large (not adopted).

  In the sensor selection program, the first and second static offset voltages Os1, Os2 are acquired by the processes of steps S41 to S44, and the difference between the first and second static offset voltages Os1, Os2 is acquired in step S45. The voltage Os2-Os1 is calculated. However, also in this case, the difference voltage Os2-Os1 is equal to the voltage difference between the output amplitude center value calculated in step S43 and the output voltage Vout input from the magnetic sensor 10 in step S41. Therefore, when the first and second offset voltages Os1 and Os2 are not necessary, the processing of steps S42 and S44 is omitted, and the first and second static offset voltages Os1 and Os2 are not calculated. The difference voltage Os2-Os1 may be obtained by subtracting the output voltage Vout input from the magnetic sensor 10 in step S41 from the output amplitude center value calculated in step S43.

f. Next, a modified example of the selection of the magnetic sensor in accordance with the sensor selection program shown in FIG. 19 will be described. In this case, the computer device 40 executes the sensor selection program shown in FIG. The processing of steps S51 to S55 of this sensor selection program is the same as the processing of steps S41 to S45 of the sensor selection program of FIG. After the processing of steps S51 to S55, the computer apparatus 40 calculates the offset temperature drift coefficient Kt by executing the following equation 8 in step S56. The difference voltage (Os2-Os1) in the following equation 8 is the calculation result of step S55, and the proportionality constant A is a value common to the magnetic sensors of the same specification, and the proportionality constant detection program of FIG. It is obtained by processing.

  Next, in step S57, the computer apparatus 40 determines whether the calculated absolute value | Kt | of the offset temperature drift coefficient Kt is larger than a predetermined selection value Kto. This selection value Kto may also be a constant stored in advance in the program, or may be input to the computer device 40 by the operator. If the absolute value | Kt | is larger than the predetermined selection value Kto, the computer 40 determines “Yes” in step S57, and displays that the offset temperature drift coefficient Kt is large in step S55. Or displaying that the magnetic sensor is not adopted, and the execution of the sensor selection program is terminated in step S59. If the absolute value | Kt | is equal to or less than the predetermined selection value Kto, the computer device 40 determines “No” in step S57, and ends the execution of the sensor selection program in step S59.

  According to such a sensor selection program, the magnetic sensor 10 is selected (selected) by the offset temperature drift coefficient Kt. This is because as the absolute value | Kt | of the offset temperature drift coefficient Kt increases, the drift amount (correction amount) of the output voltage with respect to the temperature change of the magnetic sensor 10 increases. This brings about deterioration of the accuracy of the output voltage, the limit of correction of the output voltage, and the like. Therefore, as described above, the magnetic sensor 10 can be selected simply by measuring the first and second static offset voltages Os1, Os2 at a predetermined temperature (for example, room temperature), and the magnetic sensor 10 can be easily selected.

  In this case as well, the offset temperature drift coefficient Kt calculated by the process of step S56 may be displayed on the display device so that the operator can select the magnetic sensor 10. Also in this case, in selecting the magnetic sensor 10, the magnetic sensor 10 is evaluated depending on whether the offset temperature drift coefficient Kt is positive or negative, that is, the temperature drift direction of the magnetic sensor 10, depending on the application. You may make it do.

  Further, the offset temperature drift coefficient Kt calculated in step S56 is multiplied by an appropriate temperature (50 degrees, 100 degrees, etc.) to display a specific offset temperature drift voltage value due to a temperature change, The magnetic sensor may be evaluated according to the magnitude of the voltage value.

  Also in the sensor selection program of FIG. 20, the first and second static offset voltages Os1 and Os2 are obtained by the processing of steps S51 to S54, and the first and second static offset voltages Os1 are obtained in step S55. , Os2 differential voltage Os2-Os1 is calculated. In this case, however, the difference voltage Os2-Os1 is equal to the voltage difference between the output amplitude center value calculated in step S53 and the output voltage Vout input from the magnetic sensor 10 in step S51. Therefore, when the offset voltages Os1 and Os2 are not necessary, the processing in steps S52 and S54 is omitted, and the first and second static offset voltages Os1 and Os2 are calculated in step S53. The difference voltage Os2-Os1 may be obtained by subtracting the output voltage Vout input from the magnetic sensor 10 in step S51 from the output amplitude center value.

g. Application to Full-Bridge Configuration Magnetic Sensor In the above d and e, the offset temperature drift correction and the selection of the magnetic sensor 10 of the half-bridge configuration magnetic sensor 10 have been described. However, as described above, the magnetic sensor 30 having the full bridge configuration has the same characteristics as those of the magnetic sensor 10 and Equation 3 is established. Therefore, also for the magnetic sensor 30 having the full bridge configuration, the correction of the output voltage and the selection thereof are performed by the same apparatus and method as the above-mentioned “d. Correction of temperature drift” and “e. Selection of magnetic sensor”. However, as described above, the magnetic sensor 30 having a full bridge configuration inherently outputs a voltage that changes sinusoidally around the reference voltage 0 V. Therefore, in the calculation of the offset voltage, the output voltage Vout That is, the output voltage of the differential amplifier 37 is used as it is.

h. First Modified Example of Offset Voltage Acquisition In the embodiment and the modified example described above, the first static offset voltage Os1 is acquired in a state where no external magnetic field is applied, but the following method can also be employed. As shown in FIG. 5, the external magnetic field Hr and the mechanical positional relationship between the magnetoresistive effect element 15 (R1) and the magnetoresistive effect element 16 (R2) of the magnetic sensor 10 are clear. As can be seen from the waveform diagrams of FIGS. 7 and 8, when the rotation angle of the external magnetic field Hr is 0 degrees and 180 degrees (π), it matches the static offset voltage Os1 in the state where the external magnetic field Hr is not applied. To do. That is, when the rotation angle of the external magnetic field Hr is 0 degree and 180 degrees (π), the resistance values of the magnetoresistive effect elements 15 and 16 (magnetoresistive effect elements 32, 33 and 34, 35) constituting the bridge are set. In this state, there is no difference in the strength of the magnetic field that influences, that is, the strength of the magnetic field in the direction perpendicular to the extending direction of the magnetoresistive elements 15 and 16 (the magnetoresistive elements 32, 33 and 34, 35). Thereby, when the rotation direction of the external magnetic field Hb is 0 degree and 180 degrees (π), that is, when the rotation direction of the external magnetic field Hb is the same as or opposite to the bias magnetic field Hb, The output voltage Vout of the magnetic sensors 10 and 30 may be acquired, and the first static offset voltage Os1 may be acquired by subtracting the voltage Vcc / 2 that is half the power supply voltage Vcc from the output voltage Vout.

i. Second Modified Example of Offset Voltage Acquisition In “g. First Modified Example of Offset Voltage Acquisition”, the resistance values of the magnetoresistive effect elements 15 and 16 (the magnetoresistive effect elements 32, 33 and 34, 35) constituting the bridge are described. In other words, the offset voltage Os1 from the output voltage Vout is obtained when there is no difference in the strength of the magnetic field that affects the angle, that is, when the rotation angle of the external magnetic field Hr is 0 degrees and 180 degrees. However, on the contrary, the median value of the output voltages Vout1 and Vout2 at both angles 45 and 225 degrees, which maximizes and minimizes the resistance value of one magnetoresistive element 16 (magnetoresistive elements 33 and 35), that is, It is also conceivable to obtain the first offset voltage Os1 by subtracting the voltage Vcc / 2 which is half of the applied voltage Vcc from the average value (Vout1 + Vout2) / 2. Similarly, the average value (Vout1 + Vout2) / Vout2 of the output voltages Vout1 and Vout2 at both angles 135 and 315 degrees, which maximizes and minimizes the resistance value of the other magnetoresistive element 15 (magnetoresistive elements 32 and 34), respectively. It is also conceivable to obtain the first offset voltage Os1 by subtracting the voltage Vcc / 2 which is half of the applied voltage Vcc from 2. According to this, the external magnetic field Hr is involved only in one of the magnetoresistive effect elements 15 and 16 (the magnetoresistive effect elements 32, 33 and 34, 35) constituting the bridge, and the same participation. The influence on the resistance value of the magnetoresistive effect element is canceled. Therefore, the first static offset voltage Vs1 may be acquired as described above.

  This point can also be understood from the following explanation. In this case, a biaxial Helmholtz coil 50 was used to improve accuracy. As shown in FIG. 21, the biaxial Helmholtz coil includes a pair of X-axis coils 51 and 52 that generate a magnetic field in the X-axis direction, and a pair of Y-axis coils 53 and 54 that generate a magnetic field in the Y-axis direction. It has. Then, a sine wave current is passed through the X-axis coils 51 and 52 and a cosine wave current is passed through the Y-axis coils 53 and 54 to generate sine wave and cosine wave balanced magnetic fields in the X axis direction and the Y axis direction, respectively. . As a result, a rotating magnetic field in the direction of the arrow shown in the figure is generated in a space surrounded by the X-axis coils 51 and 52 and the Y-axis coils 53 and 54, and the magnetic sensor 10 shown in FIGS. .

  In this case, the strength of the rotating magnetic field was 10 mT, and the angle of the rotating magnetic field was 0 degree when it was in the same direction as the bias magnetic field Hb by the magnetic sensor 10. The output voltage Vout of the magnetic sensor 10 was output through a buffer amplifier, and measurement results were obtained for each angle obtained by dividing 360 degrees into 2000 pieces. In Table 5 below, the measurement results are extracted and shown. Further, in Table 5, a sine wave having the same amplitude as the output voltage Vout is assumed as a reference sine wave, and the instantaneous value is shown for each extracted angle, and the instantaneous value of the reference sine wave is subtracted from the output voltage Vout. The values obtained are also shown for each extracted angle. FIG. 22 shows the change of the output voltage Vout, the reference sine wave and the subtraction value from 0 degree to 360 degrees, and FIG. 23 shows the change of the subtraction value from 0 degree to 360 degrees.

  It can be confirmed from FIG. 23 that the difference between the second static offset voltage Os2 and the first static offset voltage Os1 described above is −αcos2θ. In this case, the positive / negative relationship of the difference Os2-Os1 and the positive / negative relationship of αcos2θ are reversed. As can be understood from FIG. 24 showing the relationship between sin θ and cos 2θ, the first static offset voltage Os1 in a state where no external magnetic field is applied is an instantaneous value of 45 degrees and 225 degrees where cos 2θ is “0”. The average value and the average value of 135 ° and 315 ° instantaneous values where cos 2θ is “0” are respectively obtained. Therefore, this may be adopted as the first static offset voltage Os1.

  Note that the first static offset voltage Os1 is also applied to the magnetic sensor 30 having a full bridge configuration. That is, the magnetic sensor 10 of the half bridge configuration and the magnetic sensor 30 of the full bridge configuration are different in the number of magnetoresistive effect elements, but the extension direction of the magnetoresistive effect elements is the same. The same applies to the sensor 30.

  Further, the first offset voltage Os1 may be acquired by using the biaxial Helmholtz coil 50 by the method of “g. First modification of offset voltage acquisition”. That is, the voltage Vcc / 2 which is half of the applied voltage Vcc is subtracted from the output voltage Vout of the magnetic sensors 10 and 30 in a state where the rotation angle of the external magnetic field by the 2-axis Helmholtz coil 50 is 0 degree or 180 degrees. Thus, the first static offset voltage Os1 may be acquired. Further, when this method is applied to the magnetic sensor 30 having the full bridge configuration, the subtraction of the voltage Vcc / 2 is unnecessary as described above.

j. Other Modifications Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the object of the present invention. .

  In the embodiment and the modification, the permanent magnet 22 is rotated with respect to the magnetic sensors 10 and 30, but the permanent magnet may be linearly moved with respect to the magnetic sensors 10 and 30. In this case, as shown in FIG. 25, a permanent magnet 61 composed of an N pole and an S pole is positioned on the side of the magnetic sensors 10, 30, and the magnetoresistive effect elements 15, 16, 32-of the magnetic sensors 10, 30. In the plane to which 35 belongs, the permanent magnet 61 is moved in a direction perpendicular to the direction of the bias magnetic field. Due to the movement of the permanent magnet 61, a rotating magnetic field is generated by the permanent magnet 61 as indicated by an arrow in FIG. 26 in the plane to which the magnetoresistive elements 15, 16, 32 to 35 of the magnetic sensors 10, 30 belong. become. Therefore, all the contents described in the above-described embodiments and modifications are also applied to a magnetic sensor applied to a detection device that linearly moves the permanent magnets 10 and 30. In this case, in FIG. 25 and FIG. 26, the permanent magnet 61 is moved in a direction perpendicular to the direction of the bias magnetic field. However, when such a permanent magnet 61 is moved linearly, the movement direction of the permanent magnet 61 is changed. The direction of the bias magnetic field may be parallel.

  Moreover, in the said embodiment and modification, the bias magnet 13 which consists of a permanent magnet was used as a means to apply the bias magnetic field Hb. However, instead of this, the magnetic bias field Hb may be generated using a magnetic thin film, a thin film coil, or the like.

  Furthermore, in the said embodiment and modification, although the anisotropic magnetoresistive effect element (AMR element) was employ | adopted as the magnetoresistive effect element 15,16,32-35, these magnetoresistive effect elements 15,16,32- A giant magnetoresistive element (GMR element) may be adopted as 35.

15, 16, 32 to 35 ... magnetoresistive effect element, 10, 30 ... magnetic sensor, 13 ... bias magnet, 14, 31 ... silicon substrate, 22, 61 ... permanent magnet, 37 ... differential amplifier, 40 ... computer device, 42 ... temperature sensor, 44 ... heating and cooling device, 50 ... helmholtz coil

Claims (10)

At least two magnetoresistive elements extending in 90 degrees different directions and connected in series;
Bias means for applying a bias magnetic field in a central direction sandwiched between the extending directions of the at least two magnetoresistive elements,
With respect to an external magnetic field rotating with respect to the at least two magnetoresistive effect elements from a connection point of the at least two magnetoresistive effect elements in a state where a DC voltage is applied to both ends of the at least two magnetoresistive effect elements. In a correction method for a magnetic sensor that is applied to a magnetic sensor that outputs a voltage that changes sinusoidally around a reference voltage, and that corrects an output voltage from the magnetic sensor,
A first output voltage acquisition procedure for acquiring an output voltage of the magnetic sensor in a state in which an external magnetic field does not cause a difference in resistance value changes of the at least two magnetoresistive elements;
An offset voltage acquisition procedure for acquiring a first offset voltage representing an amount of deviation from the reference voltage of the output voltage acquired in the first output voltage acquisition procedure;
The maximum output voltage of the magnetic sensor when an external magnetic field is rotated with respect to the at least two magnetoresistive elements at the same temperature as when the output voltage is input from the magnetic sensor in the first output voltage acquisition procedure. A first output amplitude center value acquisition procedure for calculating a median of a value and a minimum value, and acquiring the calculated median as an output amplitude center value;
The output obtained by the first output amplitude center value obtaining procedure for the offset voltage difference representing the difference between the second offset voltage representing the deviation amount of the calculated output amplitude center value from the reference voltage and the first offset voltage. The reference voltage and the first offset voltage are obtained by subtracting the output voltage acquired by the first output voltage acquisition procedure from the amplitude center value or from the output amplitude center value acquired by the first output amplitude center value acquisition procedure. Obtained by subtracting, the proportionality constant prepared in advance as A, the first offset voltage as Os1, the obtained offset voltage difference as (Os2−Os1), the first output voltage obtaining procedure and the first Trt is the temperature of the magnetic sensor when the output voltage from the magnetic sensor is input in one output amplitude center value acquisition procedure, and the magnetic sensor Under the condition that the degree is T, the output voltage output from the magnetic sensor by applying an external magnetic field is corrected by the formula Oa (T) = A · (Os 2 −Os 1) · (T−Trt) + Os 1 A correction method for a magnetic sensor, comprising: a correction procedure for correcting with a value Oa (T). The correction method for a magnetic sensor according to claim 1, wherein the first output voltage acquisition procedure, the offset voltage acquisition procedure, the first output amplitude center value acquisition procedure, and the correction procedure are independent of each other. In order to prepare the proportionality constant A,
An output voltage from the magnetic sensor is input in a state where an external magnetic field does not cause a difference in resistance value change between the at least two magnetoresistive elements under two different temperature conditions, and the output voltage from the magnetic sensor is input. When T1 and T2 are respectively input temperatures, V1 and V2 are respectively input output voltages, and Kt is a temperature drift coefficient, Kt = (V2−V1) / (T2−T1) A temperature drift coefficient calculation procedure for calculating the temperature drift coefficient Kt by executing the calculation;
A second output voltage acquisition procedure for acquiring each output voltage from the magnetic sensor in a state in which an external magnetic field does not cause a difference in resistance value changes of the at least two magnetoresistive elements;
The maximum output voltage of the magnetic sensor when an external magnetic field is rotated relative to the at least two magnetoresistive elements at the same temperature as when the output voltage is input from the magnetic sensor in the second output voltage acquisition procedure. A second output amplitude center value acquisition procedure for calculating a median of a value and a minimum value, and acquiring the calculated median as an output amplitude center value;
Using the output amplitude center value acquired in the second output amplitude center value acquisition procedure and the output voltage acquired in the second output voltage acquisition procedure, the voltage difference between the output amplitude center value and the output voltage is determined as an offset voltage. A proportional constant calculation procedure is provided in which the proportional constant A is obtained by executing the calculation of the equation A = Kt / (Os2-Os1), with the obtained offset voltage difference being (Os2-Os1). A correction method for a magnetic sensor. The correction method for a magnetic sensor according to claim 1, wherein the first output voltage acquisition procedure, the offset voltage acquisition procedure, the first output amplitude center value acquisition procedure, and the correction procedure are independent of each other. In order to prepare the proportionality constant A,
Under two different temperature conditions, an external magnetic field is rotated with respect to the at least two magnetoresistive elements, respectively, and output voltages are input from the magnetic sensors, respectively, and output voltages respectively input under the two different temperature conditions Median values of the maximum value and the minimum value are respectively obtained as output amplitude center values, the temperatures when the output voltage from the magnetic sensor is input are T1 and T2, respectively, and the obtained output amplitude center values are respectively obtained. A temperature drift coefficient calculation procedure for calculating the temperature drift coefficient Kt by executing the calculation of the equation Kt = (V2−V1) / (T2−T1), where V1 and V2 and the temperature drift coefficient is Kt,
A second output voltage acquisition procedure for acquiring each output voltage from the magnetic sensor in a state in which an external magnetic field does not cause a difference in resistance value changes of the at least two magnetoresistive elements;
The maximum output voltage of the magnetic sensor when an external magnetic field is rotated relative to the at least two magnetoresistive elements at the same temperature as when the output voltage is input from the magnetic sensor in the second output voltage acquisition procedure. A second output amplitude center value acquisition procedure for calculating a median of a value and a minimum value, and acquiring the calculated median as an output amplitude center value;
Using the output amplitude center value acquired in the second output amplitude center value acquisition procedure and the output voltage acquired in the second output voltage acquisition procedure, the voltage difference between the output amplitude center value and the output voltage is determined as an offset voltage. A proportional constant calculation procedure is provided in which the proportional constant A is obtained by executing the calculation of the equation A = Kt / (Os2-Os1), with the obtained offset voltage difference being (Os2-Os1). A correction method for a magnetic sensor. The correction method for a magnetic sensor according to any one of claims 1 to 3,
The first output voltage acquisition procedure is a correction method for a magnetic sensor in which an output voltage is input from the magnetic sensor without applying an external magnetic field to the magnetic sensor. The correction method for a magnetic sensor according to any one of claims 1 to 3,
In the first output voltage acquisition procedure, an output voltage is input from the magnetic sensor in a state where an external magnetic field is applied in a central direction sandwiched in the extending direction of the at least two magnetoresistive elements or in the opposite direction. Correction method for a magnetic sensor. The correction method for a magnetic sensor according to any one of claims 1 to 3,
The first output voltage acquisition procedure includes inputting an output voltage from the magnetic sensor in a state where an external magnetic field is applied in the extending direction of one of the at least two magnetoresistive elements and in the opposite direction, A correction method for a magnetic sensor, wherein a median value of input output voltages is acquired as an output voltage of the magnetic sensor in a state where the external magnetic field does not cause a difference in resistance value change of at least two magnetoresistive elements. At least two magnetoresistive elements extending in 90 degrees different directions and connected in series;
Bias means for applying a bias magnetic field in a central direction sandwiched between the extending directions of the at least two magnetoresistive elements,
With respect to an external magnetic field rotating with respect to the at least two magnetoresistive effect elements from a connection point of the at least two magnetoresistive effect elements in a state where a DC voltage is applied to both ends of the at least two magnetoresistive effect elements. In a magnetic sensor evaluation method that is applied to a magnetic sensor that outputs a voltage that changes sinusoidally around a reference voltage, and evaluates the magnetic sensor for selection,
A first output voltage acquisition procedure for acquiring an output voltage of the magnetic sensor in a state in which an external magnetic field does not cause a difference in resistance value changes of the at least two magnetoresistive elements;
The maximum output voltage of the magnetic sensor when an external magnetic field is rotated with respect to the at least two magnetoresistive elements at the same temperature as when the output voltage is input from the magnetic sensor in the first output voltage acquisition procedure. A first output amplitude center value acquisition procedure for calculating a median of a value and a minimum value, and acquiring the calculated median as an output amplitude center value;
A first offset voltage representing an amount of deviation of the output voltage acquired in the first output voltage acquisition procedure from the reference voltage, and an output amplitude center value acquired in the first output amplitude center value acquisition procedure from the reference voltage. The voltage difference from the second offset voltage representing the amount of deviation is calculated by using at least the output voltage acquired in the first output voltage acquisition procedure and the output amplitude center value acquired in the first output amplitude center value acquisition procedure. Offset voltage difference acquisition procedure to acquire as offset voltage difference,
An evaluation method for evaluating the magnetic sensor using the acquired offset voltage difference is provided. At least two magnetoresistive elements extending in 90 degrees different directions and connected in series;
Bias means for applying a bias magnetic field in a central direction sandwiched between the extending directions of the at least two magnetoresistive elements,
With respect to an external magnetic field rotating with respect to the at least two magnetoresistive effect elements from a connection point of the at least two magnetoresistive effect elements in a state where a DC voltage is applied to both ends of the at least two magnetoresistive effect elements. In a magnetic sensor evaluation method that is applied to a magnetic sensor that outputs a voltage that changes sinusoidally around a reference voltage, and evaluates the magnetic sensor for selection,
A first output voltage acquisition procedure for acquiring an output voltage of the magnetic sensor in a state in which an external magnetic field does not cause a difference in resistance value changes of the at least two magnetoresistive elements;
The maximum output voltage of the magnetic sensor when an external magnetic field is rotated with respect to the at least two magnetoresistive elements at the same temperature as when the output voltage is input from the magnetic sensor in the first output voltage acquisition procedure. A first output amplitude center value acquisition procedure for calculating a median of a value and a minimum value, and acquiring the calculated median as an output amplitude center value;
A first offset voltage representing an amount of deviation of the output voltage acquired in the first output voltage acquisition procedure from the reference voltage, and an output amplitude center value acquired in the first output amplitude center value acquisition procedure from the reference voltage. The voltage difference from the second offset voltage representing the amount of deviation is calculated by using at least the output voltage acquired in the first output voltage acquisition procedure and the output amplitude center value acquired in the first output amplitude center value acquisition procedure. An offset voltage difference is acquired, and a proportional constant that is prepared in advance and is common to the same type of magnetic sensor is A, and the acquired offset voltage difference is Os2−Os1, and the temperature drift coefficient Kt of the magnetic sensor is expressed by the equation Kt = A. The temperature drift coefficient acquisition procedure acquired by the calculation of (Os2-Os1),
An evaluation method for a magnetic sensor, comprising: an evaluation procedure for evaluating the magnetic sensor using the acquired temperature drift coefficient Kt. The magnetic sensor evaluation method according to claim 8, wherein the first output voltage acquisition procedure, the first output amplitude center value acquisition procedure, the temperature drift coefficient calculation procedure, and the evaluation procedure are independent of each other, and In order to prepare the proportionality constant A,
An output voltage from the magnetic sensor is input in a state where an external magnetic field does not cause a difference in resistance value change between the at least two magnetoresistive elements under two different temperature conditions, and the output voltage from the magnetic sensor is input. When T1 and T2 are respectively input temperatures, V1 and V2 are respectively input output voltages, and Kt is a temperature drift coefficient, Kt = (V2−V1) / (T2−T1) A temperature drift coefficient calculation procedure for calculating the temperature drift coefficient Kt by executing the calculation;
A second output voltage acquisition procedure for acquiring each output voltage from the magnetic sensor in a state in which an external magnetic field does not cause a difference in resistance value changes of the at least two magnetoresistive elements;
The maximum output voltage of the magnetic sensor when an external magnetic field is rotated relative to the at least two magnetoresistive elements at the same temperature as when the output voltage is input from the magnetic sensor in the second output voltage acquisition procedure. A second output amplitude center value acquisition procedure for calculating a median of a value and a minimum value, and acquiring the calculated median as an output amplitude center value;
Using the output amplitude center value acquired in the second output amplitude center value acquisition procedure and the output voltage acquired in the second output voltage acquisition procedure, the voltage difference between the output amplitude center value and the output voltage is determined as an offset voltage. A proportional constant calculation procedure is provided in which the proportional constant A is obtained by executing the calculation of the equation A = Kt / (Os2-Os1), with the obtained offset voltage difference being (Os2-Os1). A method for evaluating a magnetic sensor. The magnetic sensor evaluation method according to claim 8, wherein the first output voltage acquisition procedure, the first output amplitude center value acquisition procedure, the temperature drift coefficient calculation procedure, and the evaluation procedure are independent of each other, and In order to prepare the proportionality constant A,
Under two different temperature conditions, an external magnetic field is rotated with respect to the at least two magnetoresistive elements, respectively, and output voltages are input from the magnetic sensors, respectively, and output voltages respectively input under the two different temperature conditions Median values of the maximum value and the minimum value are respectively obtained as output amplitude center values, the temperatures when the output voltage from the magnetic sensor is input are T1 and T2, respectively, and the obtained output amplitude center values are respectively obtained. A temperature drift coefficient calculation procedure for calculating the temperature drift coefficient Kt by executing the calculation of the equation Kt = (V2−V1) / (T2−T1), where V1 and V2 and the temperature drift coefficient is Kt,
A second output voltage acquisition procedure for acquiring each output voltage from the magnetic sensor in a state in which an external magnetic field does not cause a difference in resistance value changes of the at least two magnetoresistive elements;
The maximum output voltage of the magnetic sensor when an external magnetic field is rotated relative to the at least two magnetoresistive elements at the same temperature as when the output voltage is input from the magnetic sensor in the second output voltage acquisition procedure. A second output amplitude center value acquisition procedure for calculating a median of a value and a minimum value, and acquiring the calculated median as an output amplitude center value;
Using the output amplitude center value acquired in the second output amplitude center value acquisition procedure and the output voltage acquired in the second output voltage acquisition procedure, the voltage difference between the output amplitude center value and the output voltage is determined as an offset voltage. A proportional constant calculation procedure is provided in which the proportional constant A is obtained by executing the calculation of the equation A = Kt / (Os2-Os1), with the obtained offset voltage difference being (Os2-Os1). A correction method for a magnetic sensor.

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