JPH08115802A - Four-terminal shunt resistor - Google Patents

Abstract

PURPOSE: To eliminate resistance of soldered connection part by using a strip resistor with a small temperature coefficient of resistance, bending both ends in the current-carrying direction in L-shape, etc., cutting slits into the ends in the same direction so that each end has two split legs, and molding it integrally into four-terminal form. CONSTITUTION: A four-terminal shunt resistor 1, consisting of a strip resistor with a small temperature coefficient of resistance such as manganin one, has a central current measuring part 1c, and both ends in the current-carrying direction or longitudinal direction are bent in L-shape, etc., and the ends have slits cut in the same direction so that each end has two split resistor legs 1a and 1b to be used also as terminals, and then the resistor 1 is molded integrally into four-terminal form. Wiring pattern conductors 2a, 2b on a printed circuit board are connected by soldering with the resistor legs 1a and 1b respectively, in accordance with 1a-2a, 1b-2b. Thus, the occurrence of a stationary error in the current measurement due to the soldered part resistance can be prevented surely.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shunt resistor mounted on a printed circuit board and used for measuring a circuit current of a general-purpose inverter.

[0002]

2. Description of the Related Art As a conventional shunt resistor of this type, the one illustrated in the perspective view of FIG. 3 is known. FIG.
FIG. 4 is a side view of the shunt resistor including an outline of its attached state. First, in FIG. 3, 3 is a shunt resistor composed of a strip-shaped resistor having a small temperature coefficient of resistance such as manganin, 3a is a resistance leg portion bent and formed in an L shape at both ends of this resistor, and 4 is It is a pattern conductor for wiring on a printed circuit board (not shown). Further, in FIG. 4, 6 is the shunt resistor 3 described above.
Is a solder for fixedly connecting to the pattern conductor 4 by its resistance leg portion 3a, and 5 is an insulating substrate of the printed circuit board.

A current measurement using a shunt resistor as shown is that the current I _m passing through this resistor is its known resistance R
_The voltage drop ΔV generated in _SH is measured by a current measuring circuit or instrument with high input impedance, and I _m =
The required current value is obtained from the relationship of ΔV / R _SH . Therefore, the shunt resistor forms a shunt resistor for a current measuring circuit or an ammeter having an input impedance which can be regarded as extremely large as compared with the resistance component R _SH .

[0004]

In order to accurately measure the current by the shunt resistance as described above, the resistance in the energizing path between the current collection points of the voltage drop signal ΔV as the current detection signal is included in order to accurately measure the current. The value must be stable according to the required current measurement accuracy. However, in the conventional shunt resistor which has the shape as shown in FIG. 3 and is fixedly connected to the wiring pattern conductor by its both legs by soldering as shown in FIG. 4, the shunt resistance voltage drop is taken out from the pattern conductor portion. The voltage drop signal, along with the voltage drop of the shunt resistor itself,
The voltage drop of the soldered connection portion at both ends of the shunt resistor is included.

Here, the resistance of the solder portion becomes an error with respect to the resistance component peculiar to the shunt resistance which has been known, and the solder is caused by the finish condition of the soldering work or the temperature change accompanying the energization. It is difficult to accurately stabilize the partial resistance according to the required current measurement accuracy. By the way, when the current is measured by the resistance voltage drop of the shunt resistor having the shape as shown in FIG. 3 and mounted on the printed circuit board as shown in FIG. 4, the specific resistance value of the shunt resistor is R _SH , and its end 2 Let R _L be the sum of the resistance values of the solder joints at the points, and measure current I
_When the voltage drop taken out from the pattern conductor portion when _m is energized to the shunt resistor is ΔV _t ,
The following formula (1) is obtained.

[0006]

## EQU1 ## ΔV _t = I _m (R _SH + R _L ) = I _m R _SH (1 + R _L / R _SH ) ... (1) That is, R _L with respect to the required voltage drop I _m R _SH / R _SH times the main correction amount will be is superimposed, Wakashi, if assumed that the resistance value R _L varies depending on the size or time-of the current I _m, the shunt resistor It is difficult to maintain the accuracy of the current measurement due to.

In view of the above, the present invention provides a shunt resistor capable of eliminating or greatly reducing the solder connection resistance component in the voltage drop measurement value as described above, and improving the current measurement accuracy easily and at low cost. The purpose is.

[0008]

In order to achieve the above object, a four-terminal shunt resistor according to the present invention comprises: 1) a shunt resistor surface-mounted on a printed circuit board for current measurement according to claim 1; And a leg made of a strip-shaped resistor having a small temperature coefficient of resistance, the both ends in the current-carrying direction being bent into an L shape or the like and divided into two by slits cut in the current-carrying direction. It is assumed that it is not formed as a part and is integrally molded into a four-terminal shape.

2) According to a second aspect, in the four-terminal shunt resistor according to the first aspect, with respect to the two-divided leg portions forming both ends thereof, the leg portions on the same side in the direction of current flow are paired. The pair of legs are used as an inlet and an outlet for the current to be measured, and the other pair of legs are used as a portion for extracting a current detection signal applied to a current measuring circuit having a high input impedance.

3) According to claim 3, in the four-terminal shunt resistance according to claim 2, the cut position of the slit forming the two-divided leg part has a required cross-sectional area of the current-carrying leg part to be measured. Mainly, it is appropriately determined in the width direction of the strip resistor.

[0011]

In the conventional current measurement as described above, the value of the electric current from the pattern conductor portion is used as the voltage drop generated in the shunt resistance by the current to be measured.
As shown in the above equation (1), the original voltage drop I _m R _SH
On the other hand, a correction amount of R _L / R _SH times was superimposed.

The present invention is intended to eliminate or drastically reduce the above-mentioned correction required in the measured voltage drop signal, and to provide a connection between the shunt resistor and the pattern conductor portion and to measure the current to be measured. Inside the soldered parts on both ends of the passing shunt resistor, terminals for extracting a voltage drop signal are provided at two positions on the shunt resistor at predetermined intervals.
The shunt resistor is also provided as a leg for attaching the shunt resistor to the pattern conductor portion.

Here, the voltage drop signals taken out from the both terminals are measured by a current measuring circuit having a high input impedance or an ammeter. Therefore, even if there is a line resistance or a resistance of a solder joint between the both terminals and the measuring circuit or the measuring instrument, these resistance values are practically negligible compared with the input impedance of the measuring circuit or the measuring instrument. It is possible to accurately measure only the voltage drop generated by the current to be measured between the two signal extraction positions provided at a predetermined interval on the shunt resistor by designing the circuit as it is. Becomes

That is, the present invention relates to 1) a shunt resistor as a current detecting element which is surface-mounted on a printed circuit board by soldering, using a strip-shaped resistor having a small resistance temperature coefficient,
Both ends in the current-carrying direction are bent into an L shape or the like, and are formed into two legs by slits cut in the current-carrying direction, and are integrally molded into a four-terminal shape.

2) According to a second aspect, in the four-terminal shunt resistor according to the first aspect, with respect to the two-divided leg portions forming both ends thereof, the leg portions on the same side in the direction of current flow are respectively paired. None, the pair of legs are used as the inlet and outlet ends of the current to be measured, and the other pair of legs is used as the extraction portion of the current detection signal applied to the current measuring circuit with high input impedance.

3) According to claim 3, in the four-terminal shunt resistor according to claim 2, the slits forming the two-divided legs are cut at positions where the required current-carrying cross-sectional area of the current-carrying leg is measured. Is mainly determined in the width direction of the strip-shaped resistor.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a perspective view of a four-terminal shunt resistor showing an embodiment including claims 1 to 3 of the present invention, and FIG. 2 shows a current measuring circuit including a four-terminal shunt resistor in an equivalent circuit display. It is a basic circuit diagram.

First, in FIG. 1, reference numeral 1 denotes a four-terminal shunt resistor composed of a strip-shaped resistor having a small temperature coefficient of resistance such as manganin. The current measuring portion 1c is located at the center and both ends in the longitudinal direction, which is the current-carrying direction. According to claim 1, the resistance legs 1a and 1b, which are also used as terminals, are bent into an L-shape and are divided into two by slits cut in the direction of current flow, and are integrally formed into a four-terminal shape. It was done.

Further, 2a and 2b are wiring pattern conductors of a printed circuit board (not shown), which are connected to the resistance leg portions 1a and 1b by soldering in correspondence with 1a-2a and 1b-2b, respectively. It Here, as in claim 2, the combination of 1a-2a forms a conduction path for the current to be measured, and the combination of 1b-2b forms a terminal for extracting a required voltage drop detection signal.

Further, according to a third aspect of the present invention, the width of the resistance leg portion 1a forming the current-carrying path of the current to be measured is determined according to the required cross-sectional area for current-carrying, and the detection signal extracting terminal is provided. The width of 1b is determined in consideration of the width of the corresponding wiring pattern conductor 2b or the restrictions on the integral molding process of the strip-shaped resistor. Both 1a and 1b are defined by the slits provided in the strip-shaped resistor. It is classified.

Next, as shown in FIG. 2, the four-terminal shunt resistor 1 can be regarded as consisting of a combination of five sets of equivalent resistors. That is, the resistance component R _SH of the current measuring unit 1c, which is provided at the center of the resistor 1 and is used for measuring the energizing current I _m , and the resistance of the resistance leg 1a at both the inlet and outlet of the current I _m. Similarly, the resistance components R _L11 and R _L12 , as well as the resistance components R _L21 and R _{L22 of the} resistance leg portion 1b, are _equal to the resistance component R _SH.
It has a structure arranged in four directions centering around. In addition, the leg resistance components R _L11 , R _L12 , R _L21 , and R _L22.
Includes the resistance of the solder connection portion between the leg portion and the wiring pattern conductor.

As shown in the figure, the current I _{m to} be measured is the resistance R
_The voltage drop generated at _SH is taken out via the resistance components R _L21 and R _L22 of the resistance leg portion 1b, input to the high input impedance operational amplifier 7 in the current measurement circuit, and detected as the required measurement current I _md. To be done. Here, although the resistance component R _SH is fixed together with the determination of the shape of the four-terminal shunt resistor 1, it is difficult to accurately calculate the value itself from the beginning, and therefore, the value is known. Pre-calibration of the current measurement value I _md by adjusting the gain of the operational amplifier 7 is required when the current I _m is applied.

According to the current measuring circuit as shown in FIG. 2, during current measurement, only the voltage drop (I _m · R _SH ) of the resistance component R _SH in the current-carrying path of the current I _m to be measured is used as the current measurement signal. The voltage drop [I _m (R _L11 + R _L12 )] of the other part is unnecessary, and therefore the influence of the resistance component of the solder connection portion of the resistance leg portion 1 a included in these resistance components R _L11 and R _L12 is eliminated. It will be.

Further, by making the input impedance of the amplifier 7 extremely large as compared with the resistance components R _L21 and R _L22 of the resistance leg portion 1b, the voltage drop I _m · R
The effects of the resistances R _L21 and R _L22 in the input path of _SH can be ignored, and therefore the effects of the resistance of the solder connection portion of the resistance leg 1b included in these resistances can also be ignored. .

That is, the shunt resistor as the current detecting element mounted on the printed circuit board is an integrally molded four-terminal shunt resistor as shown in FIG. 1, and the shunt resistor is constructed by constructing the current measuring circuit as shown in FIG. It is possible to eliminate or significantly reduce the influence of the resistance component of the solder connection portion of each leg portion.

[0026]

According to the present invention, with respect to the shunt resistor mounted on the printed circuit board and used for measuring the circuit current of the inverter, both ends in the energization direction are bent in the L-shape or the like and are arranged in the same direction. With the slits cut, each leg is divided into two parts with an appropriate width, and the four-terminal shunt resistance is formed by integral molding. Also, regarding the leg parts divided into two, the leg parts on the same side with respect to the current-carrying direction. Each of the above-mentioned legs by forming an input signal take-out part for a high input impedance operational amplifier in the current measuring circuit, and forming a pair as the input and output ends of the current to be measured It becomes possible to eliminate or significantly reduce the influence of the resistance of the solder part in the solder connection part between the wiring part and the wiring pattern conductor of the printed circuit board. The temporal change of generation or measurement error of the constant error in current measurement due to Sunda section resistance can be easily and reliably prevented, it is possible to maintain the required accuracy in current measurement.

[Brief description of drawings]

FIG. 1 is a perspective view of a shunt resistor showing an embodiment of the present invention.

FIG. 2 is a basic circuit diagram of a current measuring circuit including a shunt resistor showing an equivalent circuit.

FIG. 3 is a perspective view of a shunt resistor showing a prior art embodiment.

FIG. 4 is a side view of a shunt resistor corresponding to FIG.

[Explanation of symbols]

 1 Four-terminal shunt resistor 1a, 1b Resistance leg of shunt resistor 1 2 Pattern conductor of printed circuit board 2a, 2b Pattern conductor of printed circuit board 3 Conventional shunt resistor 3a Resistance leg of shunt resistor 3 4 Pattern conductor 5 Insulation of printed circuit board Substrate 6 Solder 7 Operational amplifier

Claims (3)

[Claims] 1. A shunt resistor, which is surface-mounted on a printed circuit board and is used for current measurement, comprising a strip-shaped resistor having a small temperature coefficient of resistance, and its both ends in the current-carrying direction are L-shaped or the like. A four-terminal shunt resistor, which is formed into a four-terminal shape by forming a leg portion divided into two by a slit bent and cut in the direction of current flow. 2. A four-terminal shunt resistor according to claim 1, wherein said two-divided legs forming both ends thereof have pairs of legs on the same side in the direction of current flow. The four-terminal shunt resistor is characterized in that an end portion for an inlet and an outlet of a current to be measured is formed, and another pair of legs serves as a portion for extracting a current detection signal applied to a current measuring circuit having a high input impedance. 3. The four-terminal shunt resistor according to claim 2, wherein the slits forming the two-divided leg portions are formed in the strip shape mainly based on the required cross-sectional area of the current-carrying current-carrying leg portion. A four-terminal shunt resistor, which is appropriately determined in the width direction of the resistor.