JPS599867B2 - how to do it - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to magnetic field measurement using a Hall element.

As is well known, magnetic field measurement using a Hall element is carried out by passing a control current Ic between control current terminals, which are input terminals, of a Hall element 1 placed at the position where the magnetic field is to be measured, as shown in Figure 1. The Hall effect due to the magnetic flux density B of the magnetic field is
A Hall output voltage VH is detected between the output terminals provided perpendicularly to the control current terminal, and based on the correspondence between the magnetic flux density B and the Hall output voltage VH, the detected Hall output voltage VH generates a magnetic flux. This is a method of measuring density B.

The Hall element has good sensitivity and can detect even weak magnetic fields.

Among these, Hall elements made of indium antimonide vapor deposition are known for their outstanding sensitivity. However, in general, the characteristic values of Hall elements depend on temperature, shape, and raw materials, so their characteristic values vary widely, making it impossible to realize a compatible sensor.
Furthermore, since its temperature characteristics, that is, the dependence of the output on temperature for a constant input, are remarkable, special measures for temperature correction or measures for making the measurement space region constant temperature are required. The purpose of the present invention is to consider the Hall output voltage VH as two conversion factors with the input magnetic flux density B and the temperature T as variables, and to replace the variable temperature T with the corresponding control current terminal voltage Vc. The purpose is to convert the control current terminal voltage Vc into a parameter, and to obtain the magnetic flux density B of the detected magnetic field based on this parameter and the separately obtained Hall output voltage VH. According to the present invention, it is possible to realize a compatible sensor despite large variations in the characteristic values of Hall elements, and the measurement accuracy in the low magnetic field region is improved. There is no need for constant temperature control or constant temperature measurement of the measurement space. The present invention will be described below with reference to the drawings.

Generally, when the control current 1c flowing through the Hall element 1 is kept constant, the Hall output voltage VH depends not only on the magnetic flux density B but also on the temperature T. Therefore, when the control current 1c of the Hall element 1 is kept constant, the Hall output voltage VH
can be regarded as a two-variable rain number with magnetic flux density B and temperature T as variables.

In other words, it can be expressed as.

The function f can be determined based on the characteristics of the Hall element. Now, when detecting a magnetic field using the Hall element 1, when it is known that the temperature T changes within the practical range of 0°C to 40°C, if the control current 1c is kept constant, Based on the characteristics of the Hall element 1, the function f
can be expressed by the following approximate expression.

! n ν ↓λ〜▲′ 1VU〜▲ノXμ
m Here, K(T) is a magnetic field proportionality constant determined by temperature, and Vu(T) is an unexcited output voltage determined by temperature T.

Therefore, if we solve equation (2) for B, we get the following.

Equation (3) expresses the Hall output voltage VH and the magnetic field proportionality constant K(T
) and non-excited output voltage Vu(T), it means that the magnetic flux density B of the detected magnetic field can be found.

The Hall output voltage VH is obtained by placing the Hall element 1 in a detection magnetic field. Next, a method for determining the magnetic field proportionality constant K(T) and non-excited output voltage u(T) will be explained. When we investigated the characteristics of the Hall element 1, we found that when the control current 1c is kept constant in a practical range, the magnetic field proportionality constant K(T) and the temperature T have a corresponding relationship, and the characteristic curve showing this relationship is a gentle curve. It was also found that the unexcited output voltage Vu(T) and the temperature T have a corresponding relationship, and the characteristic curve showing this relationship is a gentle curve.
Furthermore, as a result of investigating the characteristics of the Hall element 1 in a practical range, it was found that the control current terminal voltage Vc of the Hall element 1 remains constant even if the magnetic field changes within a practical range when the control current 1c is kept constant. It was found that it depends only on the temperature T and has a corresponding relationship with it.

Therefore, the control current terminal voltage Vc can be expressed by the following equation. The characteristic curve showing the relationship between the control current terminal voltage Vc and the temperature is a gentle curve.

Therefore, the Hall output voltage VH with the magnetic flux density B and the temperature T as variables can be regarded as a two-variable number with the magnetic flux density B and the control current terminal voltage Vc as variables. this is,
Detect the control current terminal voltage Vc, convert the control current terminal voltage Vc into a parameter, and use this parameter to determine the magnetic field proportionality constant K(T) and the unexcited output voltage Vu(T).
This means that the magnetic flux density B can be determined based on the magnetic field proportionality constant K(T), the unexcited output voltage Vu(T), and the separately obtained Hall output voltage VH. do. Now, as shown in Figure 2, a
When m, which changes monotonically between -b, is expressed using a parameter t, which changes between 0 and 1, it becomes as follows.

, -1'1ν' Similarly, as shown in Fig. 2, n that changes between cmd is
When expressed using a parameter t' varying between 0 and 1, it becomes as follows.

The relationship between the above parametric variables t and t' is J No Kami (11~ノ, Ambiguous) It can be seen as

Therefore, by connecting equations (5) and (6) in the relationship of equation (7), n can be expressed as a MO) function.
The above parameter T. In embodying the relationship l5tl, the relationship can be approximated by the relationship shown in FIG.

That is, if t is taken on the horizontal axis and t' is taken on the vertical axis,
The relationship between t and t' is t' = t line or Yuno displacement, t'
The displacement with respect to t is Δt' at the center and 3 of t
It can be approximated by a polygonal line 5 or 5 having an inflection point at the equal dividing point. The relationship between t and t' in this case can be expressed as follows. Here, by introducing TO)-numbers El and e2 into equations (8), (9), and (substitution), (
Equations 8), Equations (9), and the σ test can be collectively expressed by the following equation.

Furthermore, by introducing the number of rains z into the (auto) equation, Av:. is expressed as follows.

z in this formula represents the trapezoid shown in FIG.

Now, the above m is made to correspond to the control current terminal voltage Vc, and n is the magnetic field proportionality constant K (V) and the non-excited output voltage Vu
(T), the control current terminal voltage Vc
can be converted into a parameter t, and using this parameter t, the magnetic field proportionality constant K(T) and the unexcited output voltage u(T) can be determined.

That is, it can be expressed as

Here, C,,c2,al,a28t'K,ul,u2
, Δt'u are constants that can be determined from the characteristic values of the Hall element, and therefore equations (self) to U6) all indicate that they are linear calculations. Therefore, as is clear from equations (three components and equations (self) to I6), if the control current terminal voltage c and the Hall output voltage H are known, the detected magnetic field B can be calculated using the control current terminal voltage Vc as a parameter. t, and use this parameter t to find the magnetic field proportionality constant K (T) and non-excitation output voltage Vu (T). This magnetic field proportionality constant K (T), non-excitation output voltage Vu (T) and the above. It can be calculated by substituting the Hall output voltage H into the right side of equation (3). Note that the parameter t is not limited to varying between O and 1, but may vary between 0 and 10 or between 0 and 100.
It may also be one that changes a certain area such as between.

FIG. 5 is a block diagram showing an example of an apparatus for carrying out the present invention.

This device consists of analog arithmetic circuits T, z, K(T), Vu
(T), VH-Vu(T), and Ba. When the control current terminal voltage Vc is input to the arithmetic circuit t, Cl
It calculates VC+C2 and outputs a signal t. Arithmetic circuit t
The output signal t from is given to arithmetic circuits Z, K(T), and u(T), respectively. When the signal t is input, the arithmetic circuit z calculates (t+1)-(e1+E2) and outputs the signal z.
Output. The output signal of the arithmetic circuit z is the arithmetic circuit K(T)
, Vu(T). When the signals t and z are input, the arithmetic circuit u(T) calculates U, +U2t±3U2Δt
'Uz is calculated and a signal Vu(T) is output. Output signal Vu of arithmetic circuit Vu(T) ('0 is arithmetic circuit VH-Vu
(T), and this arithmetic circuit VH-Vu(T) is
When the signal u(T) and the Hall output voltage VH are input, VH-Vu(T) is calculated and the signal VH-Vu(T) is output. This output signal VH-VU is applied to arithmetic circuit Ba. When the arithmetic circuit K(T) receives the signals t and z, it calculates a1+A2t±3a2ΔVKZ,
The output signal K(T) is given to the arithmetic circuit Ba. Arithmetic circuit B
When the signals VH-u(T) and K(T) are input, a calculates [VH-Vu(T)]/K(T) and outputs the signal B.
Output. A device for carrying out the invention converts the control current terminal voltage Vc into a parameter t, and converts the control current terminal voltage Vc into a parameter t.
Using the magnetic field proportionality constant K(T) and unexcited output voltage u
(T), and calculate [VH-Vu(T)]/K(T) from these magnetic field proportionality constants K(T), unexcited output voltage Vu(T), and Hall output voltage H obtained from the detected magnetic field. Any analog calculation circuit that can calculate the magnetic flux density B may be used, and is not limited to the illustrated embodiment.

As described above, according to the present invention, since the control current terminal voltage Vc of the Hall element is converted into a predetermined parameter, a magnetic field sensor having a constant characteristic value even if the characteristic value of the Hall element varies. It is possible to realize this method, and since it is a method of determining the magnetic flux density B by separating the unexcited output voltage Vu (T) from the Hall output voltage VH, it is possible to improve measurement accuracy in the low magnetic field region, and it is possible to improve measurement accuracy in the low magnetic field region. It is possible to provide a magnetic field detection method that can follow temperature changes without requiring a temperature sensor.

[Brief explanation of drawings]

Figure 1 is a diagram for explaining the magnetic field measurement method using a Hall element, and Figures 2 to 4 are diagrams for converting the control current terminal voltage Vc into a parametric variable t, as well as the magnetic field proportionality constant K (T) and the non-excitation output voltage. A diagram explaining that Vu(T) can be expressed using a parameter t, and FIG. 5 is a block diagram showing an example of an apparatus for implementing the present invention. 1... Hall element, Ic... Control current, Vc... Control current terminal voltage, B...
Magnetic flux density, VH...Hall output voltage, T, z,
K(T), Vu(T), o-Vu(T), Ba...
...Analog calculation circuit.

Claims (1)

[Claims] 1. A magnetic field measurement method using a Hall element, in which when the control current is kept constant, the Hall output voltage V_H is determined by a two-variable function V_H=f( B
, T) (1), and based on the characteristics of the Hall element, the function f is expressed as V_H=B・K(T)+Vu(T)(2)[K
(T): Magnetic field proportionality constant determined by temperature, Vu (T):
On the other hand, the control current terminal voltage Vc is converted into a parameter t, and using this parameter t, the magnetic field proportionality constant K(T) and the non-excitation output voltage Vu( Calculate the magnetic field proportionality constant K(T), non-excitation output voltage Vu(T), and separately obtained Hall output voltage V_H, and solve the above equation (2) for B to obtain the equation B=V_H. -Vu(T)/K(T
)(3) to find the magnetic flux density B, convert the control current terminal voltage Vc into a parameter t, and use this parameter t.
(T) and the non-excited output voltage V using the magnetic field proportionality constant
Find u(T) and calculate [V_H-Vu(T)]/K(T) from these magnetic field proportionality constant K(T), non-excitation output voltage Vu(T), and Hall output voltage V_H obtained separately. A magnetic field measuring method characterized by setting an analog calculation circuit that performs the following, inputting the control current terminal voltage Vc and the Hall output voltage V_H as electrical signals to the analog calculation circuit, and calculating the magnetic flux density B by the analog calculation circuit. .