JP2001272423A - Noncontact-type sensor and offset adjusting method for sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an offset adjusting method in which a change in an offset current due to a temperature change can be reduced, in which a Hall element can be used without sorting and whose operability can be enhanced. SOLUTION: A power-supply circuit 30 supplies a voltage across the power- supply terminal T1 and the power-supply terminal T3 of the Hall element H1. The element H1 is installed at the gap of a core on which a coil is wound. A voltage according to a magnetic flux generated inside the core is generated across an output terminal T2 and an output terminal T4. A differential amplifier IC1 amplifies a voltage difference between both ends of the terminals T2, T4. A current buffer 60 makes a current proportional to a voltage from the amplifier IC1 flow to the coil from the output terminal when one out of a first transistor TR2 and a second transistor TR3 is ON-operated according to a voltage from the amplifier IC1. The amplifier IC1 is offset-adjusted by resistances R11 to R13. The change in the offset current due to the temperature change is reduced by a second adjusting resistance R14 which is connected across the terminal T2 and the terminal T1 and by a third adjusting resistance R15 which is connected across the terminal T2 and the terminal T3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact sensor for measuring voltage or current in a non-contact manner, and more particularly to a non-contact sensor capable of reducing a change in offset current due to a temperature change, and an offset adjustment of the sensor. About the method.

[0002]

2. Description of the Related Art Conventionally, a non-contact type sensor comprising a current-voltage sensor using a zero magnetic flux method capable of measuring a current or a voltage in a non-contact manner has been known. This non-contact sensor
As shown in the schematic diagram of FIG. 6, a one-turn current line to be measured 1b is passed through a C-shaped core 1a and a coil 1c of a plurality of turns is wound, and a Hall element H is inserted into a gap of the core 1a.
1 is arranged.

A differential amplifier IC1 for amplifying the output voltage of the Hall element H1 is provided.
Two power sources of -V are applied, and + V power source and -V are applied to the transistors TR2 and TR3 of the push-pull configuration, respectively.
V power is applied. Transistors TR2 and TR3
Constitutes a current amplifier circuit.

According to the non-contact type sensor configured as described above, when the primary current I1 flows through the measured current line 1b passing through the core 1a, a magnetic flux is generated in the core 1a in proportion to the primary current I1. Then, the same magnetic flux also passes through the Hall element H1 inserted into the gap in the core 1a, and an output voltage proportional to the magnitude of the magnetic flux is generated from the Hall element H1.

Next, the generated output voltage is supplied to the differential amplifier I
The secondary current I2 is amplified by C1 and flows through the coil 1c wound around the core 1a via the current amplification circuit. The current amplifying circuit operates so as to generate a magnetic flux of opposite polarity by the secondary current I2 in a direction to cancel the magnetic flux generated by the primary current I1, and to make the magnetic flux in the core 1a zero.

At this time, the relationship between the primary current I1 and the secondary current I2 flowing through the coil 1c is expressed by the following equation.

N1 · I1 = N2 · I2 N1 is the number of turns of the measured current line 1b, and N2 is
This is the number of turns of the coil 1c. If N1 is one turn, the secondary current I2 is I2 = I1 / N2. That is, since the ampere-turn equation is established, the voltage at the resistor R0 through which the secondary current I2 flows is an output voltage proportional to the primary current, that is, the current to be measured.

FIG. 7 shows a detailed circuit diagram of a conventional non-contact type sensor using the zero magnetic flux method. Power supply circuit 30
Stabilizes the unstable operating voltage and supplies it to the Hall element drive circuit 40. The Hall element drive circuit 40 converts the voltage stabilized by the power supply circuit 30 into a network resistance R.
The voltage required for driving is divided by a Hall element H
1 between the power terminals T1 and T3.

The output voltage generated from the output terminals T2 and T4 of the Hall element H1 is amplified by the differential amplifier circuit 50.
Further, the current is amplified by the current buffer 60, and the secondary current I2 is output through the coils A and D.

Further, adjusting resistors R11 and R12 are connected in series between the non-inverting input terminal (+) of the differential amplifier IC1 and the power supply terminal T3 of the Hall element H1.
An adjustment resistor R13 is connected between the connection point of the first and the R12 and the power supply terminal T1 of the Hall element H1.

The offset adjustment of the differential amplifier IC1 is performed by adjusting the resistance values of the adjustment resistors R11 to R13. In this offset adjustment, after the circuit is assembled, that is, while the circuit is under negative feedback, the input voltage is set to 0 V, and the output voltage is monitored by an oscilloscope or a digital voltmeter.
Adjust the resistance value so that

[0012]

However, in the non-contact type sensor shown in FIG. 7, even if the temperature characteristics of the sensor circuit are good, the internal resistance of the Hall element H1 changes due to a change in temperature, and The offset current of the differential amplifier IC1 has changed due to the change in the internal resistance of the element H1. That is, the temperature characteristic of the offset current is determined by the Hall element H1.
Was greatly influenced by the temperature characteristics of the unbalanced voltage.

For this reason, in order to manufacture a high-precision sensor having good temperature characteristics, it is necessary to select a Hall element having a small change in offset current due to a change in temperature. Many Hall elements had to be prepared. In particular, when a non-contact type sensor is mass-produced, if the Hall elements are selected, the productivity is extremely deteriorated.

According to the present invention, there is provided a non-contact type sensor capable of minimizing a change in offset current due to a temperature change and using a Hall element without selection, thereby improving workability. It is an object to provide a method for adjusting the offset of the sensor.

[0015]

To solve the above problems, the present invention employs the following means. The non-contact type sensor according to the first aspect of the present invention is provided in a gap of a core around which a coil is wound, and detects a magnetic flux generated in the core when a measured current flows through a measured current line penetrating the core. A Hall element for generating a corresponding voltage at the first and second output terminals, a power supply circuit for supplying a power supply voltage between the first and second power supply terminals of the Hall element, and both ends of the first and second output terminals A differential amplifier circuit that amplifies the voltage difference between the first and second transistors, and an output terminal connected to one of the coils, and one of the first and second transistors is turned on in response to a voltage from the differential amplifier circuit. A current buffer that causes a current proportional to a voltage from the differential amplifier circuit to flow from the output terminal to the coil, and is connected to one of the first and second power supply terminals and an input terminal of the differential amplifier circuit; And the offset of the differential amplifier circuit A first adjustment resistor for performing a reset adjustment, a second adjustment resistor connected to one of the first and second output terminals and the first power supply terminal, the one output terminal and the second power supply A third adjustment resistor connected to the terminal.

According to the first aspect of the present invention, the offset adjustment of the differential amplifier circuit is performed by the first adjustment resistor, and the first and second output terminals are connected to one of the output terminals and the first power supply terminal. Since the second adjustment resistor and the third adjustment resistor connected to the one output terminal and the second power supply terminal are provided, the combined resistance of the Hall element internal resistance and the second adjustment resistance, the Hall element internal resistance and the third Each of the combined resistance with the adjustment resistance has a small resistance change with respect to a temperature change. Therefore, the change of the offset current due to the temperature change can be reduced, and the Hall element can be used without any selection, thereby improving the workability.

According to a second aspect of the present invention, in the non-contact sensor according to the first aspect, each of the second adjustment resistor and the third adjustment resistor has an internal resistance value of the Hall element at a low temperature and an internal resistance value at a high temperature. The resistance value is adjusted so as to be substantially the same as the smaller internal resistance value of the resistance values.

According to the second aspect of the present invention, each of the second adjustment resistor and the third adjustment resistor is a smaller one of the low-temperature internal resistance and the high-temperature internal resistance of the Hall element. Since the resistance is adjusted to be substantially the same as the value, for example, the combined resistance at a low temperature becomes substantially the same as the smaller internal resistance, and the combined resistance at a high temperature is approximately half of the smaller internal resistance. Thus, the difference between the combined resistance value at low temperature and the combined resistance value at high temperature becomes considerably small. Therefore, for example, the offset current at a low temperature becomes substantially the same as the current value at a high temperature, and a highly accurate sensor with good temperature characteristics can be obtained.

According to a third aspect of the invention, there is provided a method for adjusting an offset of a non-contact sensor, wherein a current to be measured flows in a current line to be measured which is provided in a gap of a core around which a coil is wound and passes through the core. A power supply voltage is supplied between a first power supply terminal and a second power supply terminal of a Hall element that generates a voltage corresponding to a magnetic flux generated in the first and second output terminals.
The voltage difference between both ends of the output terminal is amplified by the differential amplifier circuit,
One of the first and second transistors is turned on in response to the voltage from the differential amplifier circuit, and a current proportional to the voltage from the differential amplifier circuit is caused to flow from the output terminal to the coil. Offset adjustment of the differential amplifier circuit is performed by a first adjustment resistor connected to one of the first and second power supply terminals and the input terminal of the differential amplifier circuit. A temperature characteristic is investigated, and when the temperature characteristic is poor, a second adjusting resistor is connected to one of the first and second output terminals and the first power supply terminal, and the one output terminal is connected to the first output terminal. And a third adjustment resistor connected to the second power supply terminal.

According to the third aspect of the present invention, the offset adjustment of the differential amplifier circuit is performed by the first adjustment resistor, and the temperature characteristic of the offset current of the differential amplifier circuit is investigated. Since the second adjustment resistor is connected to one of the first and second output terminals and the first power supply terminal, and the third adjustment resistor is connected to the one output terminal and the second power supply terminal, the Hall element Each of the combined resistance of the internal resistance and the second adjustment resistance and the combined resistance of the Hall element internal resistance and the third adjustment resistance has a small resistance change with respect to a temperature change.
Therefore, the change of the offset current due to the temperature change can be reduced, and the Hall element can be used without any selection, thereby improving the workability.

According to a fourth aspect of the present invention, in the offset adjusting method for the non-contact type sensor according to the third aspect, each of the second adjustment resistor and the third adjustment resistor is an internal resistance value of the Hall element at a low temperature. It is characterized in that the internal resistance is adjusted to be substantially the same as the smaller one of the internal resistances at high temperatures. According to the invention of claim 4, the same effect as that of claim 2 can be obtained.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the non-contact type sensor and the method for adjusting the offset of the sensor according to the present invention will be described. FIG. 1 shows a detailed circuit configuration diagram of the non-contact type sensor according to the embodiment. The non-contact sensor shown in FIG. 1 is a current sensor for measuring a current in a non-contact manner, and is different from the conventional non-contact sensor shown in FIG. 7 in that an adjustment resistor for reducing a change in offset current due to a temperature change. Is added to the Hall element H1.

The schematic configuration of the non-contact type sensor according to the embodiment is the same as the general configuration of the conventional non-contact type sensor using the zero magnetic flux method shown in FIG.
One turn of the measured current line 1b is penetrated and a plurality of turns of the coil 1c are wound, and the Hall element H1 is arranged in the gap of the core 1a.

As shown in FIG. 1, the non-contact type sensor of the embodiment has a coil 1c, a Hall element H1, a power supply circuit 3
0, a Hall element drive circuit 40, a differential amplifier circuit 50, a current buffer 60, and an output circuit 70.

In the power supply circuit 30, the sensor voltage Vdd1
A capacitor C1 is connected therebetween, and the sensor voltage is applied to the collector of the transistor TR1 via F1. A resistor R1 is connected between the collector and the base of the transistor TR1, and a zener diode ZD1 is connected between the base of the transistor TR1 and the ground.

Next, in the Hall element drive circuit 40,
The emitter of the transistor TR1 is connected to the power supply terminal T1, the adjustment resistor R11, and one end of the chip network resistors R7 to R10 of the Hall element H1, and the other ends of the chip network resistors R7 to R10 are grounded. Resistance R
The connection point between the resistor 7 and the resistor R8 is connected to a non-inverting input terminal (hereinafter, referred to as + terminal) of the IC 2, and a capacitor C8 is provided between the + terminal and the inverting input terminal (hereinafter, referred to as-terminal). Is connected, and a capacitor C9 is connected between the + terminal and the ground.

A capacitor C10 is connected between the output terminal of IC2 and the ground, and the output terminal of IC2 is connected to a resistor R6.
Is connected to the base of the transistor TR4. The collector of the transistor TR4 is grounded, the emitter is connected to the + terminal of the IC2, a capacitor C10 is connected between the connection point and the ground, and the connection point is connected to the power supply terminal T3 and the adjustment resistor R13 of the Hall element H1. It is connected. An adjusting resistor R14 is connected in parallel to the power terminal T1 and the output terminal T2 of the Hall element H1, and an adjusting resistor R15 is connected in parallel to the power terminal T3 and the output terminal T2 of the Hall element H1.

Next, in the differential amplifier circuit 50, one end of a resistor R2 is connected to the output terminal T4 of the Hall element H1, and one end of a resistor R3 is connected to the output terminal T2 of the Hall element H1. The other end of the resistor R2 is connected to the negative terminal of the IC1 composed of a differential amplifier, and the other end of the resistor R3 is connected to I-terminal.
The + terminal of C1 is connected. A sensor voltage + Vdd1 is supplied to IC1, and a capacitor C3 is connected between the sensor voltage + Vdd1 and the ground.

A capacitor C4 is connected between the + terminal and the-terminal of IC1, a capacitor C5 is connected between the-terminal of IC1 and the ground, and a capacitor is connected between the + terminal and the ground of the IC1. C6 is connected. A capacitor C7 is connected between the output terminal of IC1 and the ground. The + terminal of IC1 is an adjustment resistor R connected in series.
Power supply terminal T3 of Hall element H1 through R12 and R13
The adjustment resistor R11 is connected between the connection point of the adjustment resistors R12 and R13 and the power supply terminal T1 of the Hall element H1.

Next, in the current buffer 60, the n-channel first transistor TR2 and the p-channel second transistor TR3 are connected in series to form a push-pull circuit. The base of the first transistor Tr2 and the base of the second transistor TR35 have a resistance R
4 is connected.

The sensor voltage + Vdd1 is supplied to the collector of the first transistor TR2, and the second transistor T2
The collector of R3 is grounded. The emitter of the first transistor TR2 and the emitter of the second transistor TR3 are connected, and the connection point is connected to one end A of the coil 1c (for example, 2000T) via F2 as an output terminal. The connection point is connected to the negative terminal of C1 via a capacitor C2 and a resistor R5 connected in series. The sensor voltage is supplied to a diode D1, which is connected to one end D of the coil 1c.

The measured current line 1b is 1T, and the measured current I1 flows through the measured current line 1b. One of the first transistor TR2 and the second transistor TR3 is turned on in accordance with the differentially amplified output of the IC1 output from the resistor R4 to amplify the current, and the current amplified from the middle point is supplied to the coil 1c. Is output. A secondary current I2 is output from the other end D of the coil 1c, a resistor R0 is connected to the other end D, and an output voltage VOUT can be obtained from the secondary current I2 flowing through the resistor R0 and the resistor R0. I have.

Next, the operation of the non-contact type sensor configured as described above will be described. First, the sensor voltage + Vdd1 from the power supply circuit 30 is applied to the Hall element drive circuit 40, the differential amplifier circuit 50, and the current buffer 60. Power supply circuit 30
When the sensor voltage + Vdd1 is supplied to the collector of the transistor TR1 and a predetermined voltage is applied to the base via the resistor R1, the Zener diode ZD breaks down.

Then, a constant voltage is supplied to the Hall element drive circuit 40 from the emitter of the transistor TR1.
The Hall element drive circuit 40 divides the voltage stabilized by the power supply circuit 30 by using network resistors R7 to R10,
The voltages necessary for driving are supplied to the power terminals T1, T of the Hall element H1.
Supply between three. Therefore, an emitter current flows from the power supply terminal T1 to the power supply terminal T3, and the Hall element H1 operates.

On the other hand, the measured current I1 is connected to the measured current line 1b.
, A magnetic flux Φ1 is generated in the core 1a. At this time, the magnetic flux Φ is applied to the terminals T2 and T4 of the Hall element H1.
1 and an output voltage corresponding to the resistor R
2, a differential amplifier IC in a differential amplifier circuit 50 via R3
1 is input. The input voltage is amplified by the IC 1 and input to the current buffer 60 via the resistor R4. Further, the current is amplified by the current buffer 60,
A secondary current I2 is output between the coils A and D.

Here, a case where the current I to be measured in the positive direction is measured will be described. That is, the potential of the output terminal T2 of the Hall element H1 is set to be higher (positive) than the potential of the output terminal T4 according to the measured current I in the positive direction. At this time, IC1
Causes the first transistor TR2 in the current buffer 60 to operate.

Then, a secondary current I2 for generating a magnetic flux Φ2 for canceling the magnetic flux Φ1 on the coil 1c side flows to the first transistor TR2, the coil 1c, and the ground. That is, since the magnetic flux in the opposite direction to the magnetic flux Φ1 by the current I1 flowing through the current line to be measured is generated, the inside of the coil is always in a magnetic equilibrium state. As a result, as the voltage at the resistor R0 through which the secondary current I2 flows, an output voltage proportional to the primary current, that is, the measured current is obtained.

Next, a method of adjusting the offset of the non-contact type sensor according to the embodiment will be described. First, the adjustment resistors R11 to R
13, the differential amplifier IC1
Offset adjustment is performed. In this offset adjustment, the input voltage is set to 0 V after the circuit is assembled, that is, while the circuit is under negative feedback, and the output voltage is adjusted to 0 V while monitoring the output voltage with an oscilloscope or a digital voltmeter. Adjust the resistance value.

Next, at the time of assembly, the temperature characteristics of the sensor are investigated. That is, a normal shipping inspection is performed. At this time, if the temperature characteristics of the sensor are good, the sensor is shipped as an accurate sensor without adding the adjustment resistors R14 and R15 to the Hall element H1.

On the other hand, when the temperature characteristics of the sensor are poor, that is, as shown in FIG. 3, the internal resistance value of the Hall element changes from the resistance value RL to the resistance value RH from the low temperature TL to the high temperature TH, as shown in FIG. Now, it is assumed that the offset current changes greatly from the current value IL to the current value IH over the low temperature TL to the high temperature TH.

In this case, an adjusting resistor R14 is connected between the power supply terminal T1 and the output terminal T2 of the Hall element H1,
The adjustment resistor R15 is connected between the power supply terminal T3 and the output terminal T2 of the Hall element H1 to perform temperature correction.

Although the offset current changes due to the adjustment resistors R14 and R15, the internal resistance (InSb) of the Hall element is changed.
3 has a temperature characteristic as shown in FIG. 3. Due to the influence of this characteristic, the change in the offset current due to the values of the adjustment resistors R14 and R15 is larger at lower temperatures and smaller at higher temperatures. For this reason, the adjustment resistors R14, 1 are set so that the offset current at low temperature becomes substantially the same as the current value at high temperature.
Adjust 5 That is, the offset current is adjusted based on the current value on the high temperature side (determined by the operating temperature range of the sensor).

This offset adjustment method will be described with reference to the equivalent circuit of FIG. First, the Hall element H1 includes an internal resistance RH1-2 between the power supply terminal T1 and the output terminal T2, an internal resistance RH2-3 between the output terminal T2 and the power supply terminal T3,
The internal resistance RH3- between the power supply terminal T3 and the output terminal T4
4. Internal resistance RH between output terminal T4 and power supply terminal T1
1-4 and an adjusting resistor R in parallel with the internal resistor RH1-2.
14 and the adjusting resistor R in parallel with the internal resistor RH2-3.
15 are connected.

Here, the combined resistance when the adjustment resistance R14 is connected in parallel with the internal resistances RH1-2 is expressed by equation (1). Note that RH represents the internal resistance RH1-2.

RH · R14 / (RH + R14) (1) This combined resistance is smaller than the internal resistance RH1-2,
By appropriately selecting the adjustment resistor R14, the combined resistance value can be made substantially the same from a low temperature to a high temperature. To explain by taking an example, the internal resistance value at low temperature is, for example, 10
0 Ω, the internal resistance at high temperature is, for example, 20 Ω,
The adjustment resistor R14 is set to a value substantially equal to the internal resistance value at high temperature (for example, 20Ω). Then, the combined resistance at low temperature is about 20
And the combined resistance at high temperature is approximately 10Ω, and the change is about 10Ω. Therefore, the offset current has substantially the same value from low temperature to high temperature, and a sensor having good temperature characteristics can be obtained.

If the temperature characteristic of the internal resistance of the Hall element is as shown in FIG. 3, the resistance value of the adjustment resistor R14 having a negative temperature coefficient decreases as the temperature decreases.
15 may be added. As described above, the combined resistance when an adjustment resistor without a negative temperature coefficient is added to the internal resistance changes from a high temperature to a low temperature, for example, from approximately 10Ω to approximately 20Ω, and an adjustment resistor having a negative temperature coefficient The lower the temperature, the lower the resistance gradually.

Therefore, when the adjustment resistance having a negative temperature coefficient is added to the internal resistance, the combined resistance has substantially the same resistance value from low temperature to high temperature. Accordingly, the offset current from low to high temperatures has substantially the same value, and the temperature characteristics of the offset current can be further improved.

Further, even if the temperature characteristic of the internal resistance of the Hall element has a relationship opposite to the characteristic shown in FIG. 3, that is, the resistance value decreases from high temperature to low temperature, the adjustment resistance is not changed at low temperature. The temperature characteristic of the offset current can be improved by making the value substantially equal to the internal resistance value.

As described above, according to the non-contact type sensor and the method of adjusting the offset of the sensor according to the embodiment, the change in the offset current due to the temperature change is reduced by adding the adjustment resistors R14 and R15 to the Hall element H1. As a result, a high-precision sensor having good temperature characteristics can be obtained, and the Hall element H1 can be used without selection, thereby improving workability.

The present invention is not limited to the non-contact type sensor and the method of adjusting the offset of the sensor according to the above-described embodiment. In the non-contact sensor and the method of adjusting the offset of the sensor according to the embodiment, the adjustment resistor R14 is connected between the power terminal T1 and the output terminal T2 of the Hall element H1, and the power terminal T3 and the output terminal T2 of the Hall element H1 are connected. However, instead of this, for example, an adjustment resistor R14 is connected between the power supply terminal T1 and the output terminal T4 of the Hall element H1, and the adjustment resistance R15 is connected to the power supply terminal T3 of the Hall element H1. Even if the adjustment resistor R15 is connected between the terminal T4 and the terminal T4, the same effect as that of the embodiment can be obtained.

[0051]

According to the first aspect of the present invention, the offset adjustment of the differential amplifier circuit is performed by the first adjustment resistor, and one of the first and second output terminals is connected to the first power supply terminal. And the third adjustment resistor connected to the one output terminal and the second power supply terminal, the combined resistance of the Hall element internal resistance and the second adjustment resistance, and the Hall element internal resistance Each of the combined resistors with the third adjustment resistor has a small resistance change with respect to a temperature change. Therefore, the change of the offset current due to the temperature change can be reduced,
In addition, the Hall elements can be used without any selection, thereby improving workability.

According to the second aspect of the present invention, each of the second adjusting resistor and the third adjusting resistor is a smaller one of the low-temperature internal resistance and the high-temperature internal resistance of the Hall element. Since the resistance is adjusted to be substantially the same as the value, for example, the combined resistance at a low temperature becomes substantially the same as the smaller internal resistance, and the combined resistance at a high temperature is approximately half of the smaller internal resistance. Thus, the difference between the combined resistance value at low temperature and the combined resistance value at high temperature becomes considerably small. Therefore, for example, the offset current at a low temperature becomes substantially the same as the current value at a high temperature, and a highly accurate sensor with good temperature characteristics can be obtained.

According to the third aspect of the invention, the same effect as that of the first aspect is obtained, and according to the fourth aspect, the same effect as that of the second aspect is obtained.

[Brief description of the drawings]

FIG. 1 is a detailed circuit configuration diagram of a non-contact type sensor according to an embodiment.

FIG. 2 is a diagram showing a temperature change of an offset current.

FIG. 3 is a diagram showing a temperature change of the internal resistance of the Hall element.

FIG. 4 is a diagram showing an equivalent circuit when an adjustment resistor is added to a Hall element.

FIG. 5 is a diagram illustrating an example of adjustment of an offset current by an adjustment resistor.

FIG. 6 is a schematic diagram of a conventional non-contact sensor using a zero magnetic flux method.

FIG. 7 is a detailed circuit configuration diagram of a conventional non-contact sensor using a zero magnetic flux method.

[Explanation of symbols]

 1a Core 1b Current line to be measured 1c Coil H1 Hall element 30 Power supply circuit 40 Hall element drive circuit 50 Differential amplifier circuit 60 Current buffer 70 Output circuit IC1 Differential amplifier T1, T3 Power supply terminal T2, T4 Output terminal

Claims (4)

[Claims] 1. A voltage corresponding to a magnetic flux generated in the core when a current to be measured flows through a current line to be measured which is provided in a gap of a core around which a coil is wound and which passes through the core. A Hall element generated at a second output terminal; a power supply circuit for supplying a power supply voltage between the first and second power supply terminals of the Hall element; and a difference for amplifying a voltage difference between both ends of the first and second output terminals. A dynamic amplifier circuit, an output terminal connected to one of the coils, one of the first and second transistors being turned on in response to a voltage from the differential amplifier circuit, and A current buffer for flowing a current proportional to a voltage from the amplifier circuit to the coil; one of the first and second power terminals and a differential amplifier circuit connected to an input terminal of the differential amplifier circuit; Of the first offset adjustment Integer resistor and one of the output terminals first of said first and second output terminals
A non-contact sensor comprising: a second adjustment resistor connected to a power terminal; and a third adjustment resistor connected to the one output terminal and the second power terminal. 2. The second adjustment resistor and the third adjustment resistor each have substantially the same value as the smaller one of the low-temperature internal resistance and the high-temperature internal resistance of the Hall element. 2. The non-contact type sensor according to claim 1, wherein the sensor is adjusted so as to be as follows. 3. A voltage corresponding to a magnetic flux generated in the core when a current to be measured flows through a current line to be measured that is provided in a gap between the cores around which the coil is wound and penetrates the core. Supplying a power supply voltage between the first and second power supply terminals of the Hall element generated at the second output terminal; amplifying a voltage difference between both ends of the first and second output terminals by a differential amplifier circuit; One of the first and second transistors is turned on in response to the voltage from the circuit, and a current proportional to the voltage from the differential amplifier circuit flows from the output terminal to the coil, and the first and second transistors are turned on. Offset adjustment of the differential amplifier circuit is performed by a first adjustment resistor connected to one of the power supply terminals and an input terminal of the differential amplifier circuit, and a temperature characteristic of an offset current of the differential amplifier circuit is investigated. And the temperature characteristics are poor The, while connecting the second adjusting resistor to one output terminal of said first and second output terminal and said first power supply terminal, the said one output terminal and the second
A method for adjusting an offset of a non-contact type sensor, comprising connecting a third adjustment resistor to a power supply terminal. 4. The second adjustment resistor and the third adjustment resistor each have substantially the same value as the smaller one of the low-temperature internal resistance and the high-temperature internal resistance of the Hall element. The method for adjusting the offset of a non-contact sensor according to claim 3, wherein the offset is adjusted so as to be adjusted as follows.