Lead structure of manganin shunt, PCB and wiring structure of PCB
Technical Field
The invention relates to the technical field of electronic circuits, in particular to a lead structure of a manganin shunt, a PCB and a routing structure of the PCB.
Background
The manganin shunt is widely applied to the field of instrument current measurement, and can be used for sampling and detecting the backflow, current limiting and current sharing of a communication system, an electronic complete machine, an automatic control power supply and the like. The manganin shunt has the characteristics of good stability and small temperature variation. The device has been used as a current sampling device of an electronic electric energy meter for decades, and is still used as an indispensable sampling device until now.
The existing manganin shunt is usually fixed at the wire inlet end of electronic equipment through a fixed red copper sheet, the current sampling end of the manganin shunt is connected with an electronic circuit PCB board through two current sampling signal wires, and the sampling signal wires adopt a vertical wiring mode or are directly welded on the PCB board. Because the current signal that the manganin shunt gathered is very little, generally microvolt level, so traditional this kind of wiring mode of directly installing on the terminal or series connection on the relay is particularly easily disturbed by alternating magnetic field to lead to current sampling and measurement inaccurate.
According to Faraday's law of electromagnetic induction, the formula for calculating the induced electromotive force generated by the coil is as follows: when an alternating magnetic field interferes, a closed loop is arranged in a gap between the manganin and the manganin or a gap between the manganin and the cable or a gap between the PCB and the manganin, corresponding induced electromotive force can be generated at a sampling end, and the induced electromotive force seriously influences the accuracy of current sampling after subsequent circuit amplification and AD conversion. The existing lawless persons steal electricity by utilizing the defect that the existing electric energy meter based on manganin sampling is easily influenced by an external alternating magnetic field and cannot be accurately metered, and the error caused by stealing electricity by utilizing the means is changed along with the strength of the alternating magnetic field, so that the maximum error can reach 100 percent. In addition, alternating electromagnetic interference inside the manganin shunt in the design is not ignored, for example, the leakage flux of the power frequency transformer affects the running error of the meter; the three-phase meter three-manganese copper symmetrical connection method has the defects that the electromagnetic induction current between phases is overlarge, the influence of small signals is serious, and the like.
Therefore, how to resist the interference of an external alternating magnetic field on the manganin shunt is a problem to be solved.
Disclosure of Invention
The invention aims to provide a lead structure of a manganin shunt, which is resistant to external alternating magnetic field interference, a PCB and a wiring structure of the PCB, and is mainly used for a manganin current sampling device which is resistant to external alternating magnetic field interference in the field of electric energy meters.
The manganin shunt comprises a first current sampling end and a second current sampling end, and is characterized in that the first current sampling end is connected with a first sampling signal wire, and the second current sampling end is connected with a second sampling signal wire;
the first current sampling end and the second current sampling end are positioned on the same side of the manganin shunt; the second current sampling end is interfered by an external alternating magnetic field;
the first sampling signal line forms a ring-shaped wiring on a PCB (printed circuit board) which is arranged in parallel with the manganin shunt, and is connected with the second sampling signal line in a parallel or twisted-pair mode to be connected with the AD sampling of a chip, so that external alternating magnetic field interference is introduced into the first current sampling end, and the first current sampling end is subjected to external alternating magnetic field interference with the same magnitude as the external alternating magnetic field interference on the second current sampling end.
As an implementation mode, the manganin shunt is vertically welded on the first PCB;
a second PCB is arranged on one side of the manganin shunt in parallel;
the first sampling signal line is led to the second PCB from the first current sampling end to form a ring-shaped lead, and then returns to the first PCB, and finally is connected to the AD sampling of the chip together with the second sampling signal line in a parallel or twisted-pair mode.
As an implementation mode, the manganin shunt is welded on the third PCB in parallel;
the first sampling signal line is led to the third PCB from the first current sampling end to form a ring-shaped lead, and then is connected to the AD sampling of the chip together with the second sampling signal line in a parallel or twisted pair mode.
The invention provides a PCB (printed circuit board), which comprises a substrate, wherein a lead structure of the manganin shunt is arranged on the substrate.
The invention provides an electric energy meter which comprises a manganin shunt, wherein the manganin shunt adopts a lead structure of any one of the manganin shunts.
The invention provides a routing structure of a PCB (printed circuit board), which comprises a first PCB, a second PCB and a manganin shunt vertically welded on the first PCB;
the manganin current divider comprises a first current sampling end and a second current sampling end; the second current sampling end is interfered by an external alternating magnetic field;
the first current sampling end is connected with a first sampling signal wire, the second current sampling end is connected with a second sampling signal wire, and the first current sampling end and the second current sampling end are positioned on the same side of the manganin current divider;
the second PCB is positioned on one side of the manganin shunt and is arranged in parallel with the manganin shunt;
the first sampling signal line is led to the second PCB from the first current sampling end to form a ring-shaped lead, and then returns to the first PCB, and finally is connected to the AD sampling of the chip together with the second sampling signal line in a parallel or twisted-pair mode.
The invention provides a routing structure of a PCB (printed circuit board), which is characterized by comprising the PCB and a manganin shunt welded on the PCB in parallel;
the manganin current divider comprises a first current sampling end and a second current sampling end; the second current sampling end is interfered by an external alternating magnetic field;
the first current sampling end is connected with a first sampling signal wire, the second current sampling end is connected with a second sampling signal wire, and the first current sampling end and the second current sampling end are positioned on the same side of the manganin current divider;
the first sampling signal line is led to the PCB from the first current sampling end to form a ring-shaped lead, and then is connected to the AD sampling of the chip together with the second sampling signal line in a parallel or twisted pair mode.
Compared with the prior art, the technical scheme has the following advantages:
according to the lead structure of the manganin shunt, the PCB and the wiring structure of the PCB, the wiring mode of changing the current sampling end of the manganin shunt on the PCB is adopted, the loop area is increased, so that the alternating magnetic field interferes with the second current sampling end, meanwhile, the first current sampling end is introduced, the first current sampling end is interfered by the alternating magnetic field with the same size, and the interference of the alternating magnetic field and the alternating magnetic field is mutually counteracted, so that the sampling interference of the alternating magnetic field on the manganin shunt is prevented. The interference of an external alternating magnetic field can be solved, and the mutual interference of the leakage flux of an internal power frequency transformer and the electromagnetic induction between the phases of the three-phase meter three-manganese-copper symmetrical scheme can be solved.
Drawings
Fig. 1 is a schematic view of a routing structure of a PCB according to an embodiment of the present invention;
fig. 2 is a side view of a routing structure of a PCB board according to a second embodiment of the present invention;
fig. 3 is a top view of a routing structure of a PCB according to a second embodiment of the present invention.
Detailed Description
The above and further features and advantages of the present invention will be apparent from the following, complete description of the invention, taken in conjunction with the accompanying drawings, wherein the described embodiments are merely some, but not all embodiments of the invention.
The lead structure of the manganin shunt provided by the invention prevents sampling interference of an alternating magnetic field to the manganin shunt by changing the traditional lead structure, and is mainly used for a manganin current sampling device which is resistant to external alternating magnetic field interference in the field of electric energy meters.
The manganin shunt is provided with three ends, namely a voltage sampling end, a first current sampling end and a second current sampling end, wherein the first current sampling end is connected with a first sampling signal line, and the second current sampling end is connected with a second sampling signal line. According to the lead structure of the manganin shunt, the first current sampling end and the second current sampling end are positioned on the same side of the manganin shunt; the second current sampling end is interfered by an external alternating magnetic field; the first sampling signal line forms a ring-shaped wiring on a PCB which is arranged in parallel with the manganin shunt, and is connected with the second sampling signal line in a parallel or twisted-pair mode to be connected with the AD sampling of the chip together, so that external alternating magnetic field interference is introduced into the first current sampling end, and the first current sampling end is subjected to external alternating magnetic field interference with the same magnitude as the external alternating magnetic field interference received by the second current sampling end.
It adopts the electric current sample end that changes the manganin shunt to walk the line mode on the PCB board, increases the loop area to with alternating magnetic field to the interference of second electric current sample end, introduce first electric current sample end simultaneously, let first electric current sample end also receive the alternating magnetic field interference of the same size, both disturb and offset each other, thereby prevent that alternating magnetic field from disturbing the sampling of manganin shunt. The interference of an external alternating magnetic field can be solved, and the mutual interference of the leakage flux of an internal power frequency transformer and the electromagnetic induction between the phases of the three-phase meter three-manganese-copper symmetrical scheme can be solved.
According to the invention, by increasing the loop area of the lead, magnetic field interference is introduced into the first current sampling end at the same time, so that the first current sampling end is also interfered by the alternating magnetic field with the same size, and the alternating magnetic field are mutually offset, thereby preventing the sampling interference of the alternating magnetic field on the manganin shunt. The implementation mode can be various, for example, the manganin shunt can be vertically welded on a first PCB, then a second PCB is arranged in parallel on one side of the manganin shunt, a first sampling signal line is led onto the second PCB from a first current sampling end to form a circular line, and then the circular line returns to the first PCB, and finally the circular line and the second sampling signal line are connected to the AD sampling of the chip in a parallel or twisted-pair manner. The manganin shunt can be parallelly welded on a PCB, the first sampling signal wire is led to the CB from the first current sampling end to form a ring-shaped lead, and then the ring-shaped lead and the second sampling signal wire are connected to the AD sampling of the chip in a parallel or twisted-pair mode.
The embodiment of the invention also provides a PCB which comprises a substrate, wherein the lead structure of the manganin shunt is arranged on the substrate.
The following describes the implementation of the present invention in detail by referring to two specific embodiments.
Example one
Referring to fig. 1, the design of the trace structure using the PCB for resisting the interference of the external alternating magnetic field to the manganin shunt provided by this embodiment mainly includes the manganin shunt 03, the first PCB 01 and the second PCB 02. The manganin shunt 03 is vertically welded on the first PCB board 01, the second PCB board 02 is close to the manganin shunt 03 in parallel, the PCB wiring is led from a first current sampling point A of the manganin shunt 03 to the second PCB board 02 to draw an annular wiring 04, then the PCB wiring returns to a point C on the first PCB board 01, and meanwhile, the PCB wiring led out from the second sampling end B of the manganin shunt 03 is connected to the AD sampling of the chip in a parallel or twisted-pair mode.
Originally, when there is not the second PCB 02, the alternating magnetic field only acts on the manganin shunt 03, the induced electromotive force is accumulated on the point B, A, B points enter the AD sampling of the chip, △ UAB is equal to I R + E, after adding the second PCB 02, the induced electromotive force is respectively acted on C, B points, △ UCB is equal to △ UAB- △ UAC is equal to I R + E-E ', the magnitude of the current is close to the actual current, C, B points enter the AD sampling of the chip, wherein I is the current to be sampled, R is the manganin value, E is the induced electromotive force of the power frequency magnetic field acting on the manganin shunt 03, E' is the induced electromotive force of the alternating magnetic field acting on the second PCB 02, and the magnitude and direction of the electromotive force are the same as E.
The lead wire has a simple structure, electromotive force generated by an induced manganin loop at the second current sampling end of the original manganin shunt is also added to the first current sampling end, the electromotive force and the electromotive force are simultaneously added to be the same, and AD sampling is a difference value of two points, so that interference caused by an alternating magnetic field can be mutually offset, an AD sampling value is closer to an actual current value, and the sampling interference of an alternating magnetic field to the manganin shunt can be prevented.
Example two
Referring to fig. 2 and 3, the design of the trace structure using the PCB for resisting the interference of the external alternating magnetic field to the manganin shunt provided by this embodiment mainly includes a sub PCB 10 and a manganin shunt 11. The manganin shunt 11 is parallel to the PCB 10 and welded on the PCB 10, the PCB wiring is led from a first current sampling point A of the manganin shunt 11 to the PCB 10 to draw an annular wiring 12, then the PCB wiring is led back to a point C on the PCB 10, and meanwhile the PCB wiring led out from a second sampling end B of the manganin shunt 11 is connected to the AD sampling of the chip in a parallel or twisted-pair mode.
In a similar way, the lead structure adds the electromotive force generated by the induced manganin loop of the second current sampling end of the original manganin shunt to the first current sampling end, the electromotive force and the AD sampling end are the same in size, and the AD sampling is the difference value of two points, so that the interference caused by the alternating magnetic field can be mutually offset, the AD sampling value is closer to the actual current value, and the sampling interference of the alternating magnetic field to the manganin shunt can be prevented.
Based on the embodiment, the embodiment of the invention also provides an electric energy meter, which comprises the manganin shunt, wherein the manganin shunt adopts the lead structure of the manganin shunt, so that the sampling interference of an alternating magnetic field on the manganin shunt can be effectively prevented, the influence of the electromagnetic induction mutual interference between phases in a three-manganin symmetric scheme of a three-phase meter is solved, and the influence of the leakage flux of a power frequency transformer on the metering of the electric energy meter when the distance between the power frequency transformer and the manganin shunt is short is solved.
Although the present invention has been described with reference to the preferred embodiments, it is not intended to limit the present invention, and those skilled in the art can make variations and modifications of the present invention without departing from the spirit and scope of the present invention by using the methods and technical contents disclosed above.