A measurement circuit and method for solving inherent errors of three-wire system

Abstract

The present invention discloses a measurement circuit for resolving inherent errors in a three-wire system, characterized in that it includes: a switch module, wherein the switch module includes a first electronic switch K1, a second electronic switch K2, a third electronic switch K3, and a fourth electronic switch K4, wherein a terminal b of the first electronic switch K1 is connected to a terminal g of the fourth electronic switch K4, a terminal c of the second electronic switch K2 is connected to a terminal a of the first electronic switch K1, and a terminal d of the second electronic switch K2 is connected to a terminal f of the third electronic switch K3; a constant current source, wherein the constant current source includes a first constant current source Iexc1 and a second constant current source Iexc2; and the switch module is electrically connected to the constant current source. The present invention discloses a measurement circuit and method for resolving inherent errors in a three-wire system, thereby improving measurement accuracy and resolving the problem that inherent errors cannot be eliminated, thereby affecting measurement results; reducing the amount of wiring, effectively reducing wiring and measurement costs, making it more suitable for large-scale project applications and having significant economic benefits.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit measurement, and in particular to a measurement circuit and method for solving the inherent error of a three-wire system. Background Art

[0002] The traditional three-wire measurement method can be found in the appendix of the manual. Figure 2 In the circuit, Iexc is a constant current source; r1, r2, and r0 are core resistances; R2 and R1 are resistances to be measured; and Rref is a reference standard resistance. When measuring the voltage and resistance ratio across R2 and R1, the excitation current Iexc flows through r2, R2, R1, r1, and Rref to ground. The voltage across R2 is U2_1 = U2-U1 = Iexc*(r2+R2); the voltage across R1 is U1_0 = U1-U0 = Iexc*(r1+R1); the voltage across Rref is Uref = Iexc*Rref; at the same time, R2 = Rref*U2_1 / Uref–r2; R 1=Rref*U1_0 / Uref–r1. Since r1 and r2 cannot be measured, we will approximate that: R2=Rref*U2_1 / Uref; R1=Rref*U1_0 / Uref; R2 / R1=U2_1 / U1_0. In other words, the measured value of R1 is the sum of R1 and r1, and the measured value of R2 is the sum of R2 and r2. This produces an inherent error r1 and r2 that cannot be eliminated, making it impossible to obtain high-precision data, resulting in large errors in subsequent individual data calculations. At the same time, the five-core measurement method is very costly and economically intensive when the wiring distance is long and the number of wiring points is large. Therefore, it is urgent to invent a high-precision and cost-effective measurement circuit and method. Summary of the Invention

[0003] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of this application to avoid obscuring the purpose of this section, the abstract and the title of the invention, and such simplifications or omissions should not be used to limit the scope of the present invention.

[0004] In view of the above-mentioned problems, the present invention is proposed.

[0005] Therefore, the technical problem solved by the present invention is that the existing three-wire measurement circuit and method cannot measure r1 and r2, which will produce an inherent error r1 and r2, and cannot meet the low-cost requirements of long-distance and multi-point circuits.

[0006] To solve the above technical problems, the present invention provides the following technical solution: a measurement circuit for solving the inherent error of a three-wire system, comprising:

[0007] a switch module, the switch module comprising a first electronic switch K1, a second electronic switch K2, a third electronic switch K3, and a fourth electronic switch K4, wherein a terminal b of the first electronic switch K1 is connected to a terminal g of the fourth electronic switch K4, a terminal c of the second electronic switch K2 is connected to a terminal a of the first electronic switch K1, and a terminal d of the second electronic switch K2 is connected to a terminal f of the third electronic switch K3;

[0008] A constant current source, comprising a first constant current source Iexc1 and a second constant current source Iexc2;

[0009] The switch module is electrically connected to the constant current source.

[0010] As a preferred solution of the measurement circuit for solving the inherent error of the three-wire system described in the present invention, the second constant current source Iexc2 is respectively connected to the other end h of the fourth switch K4 and one end e of the third electronic switch K3.

[0011] As a preferred solution of the measurement circuit for solving the inherent error of the three-wire system described in the present invention, it also includes a measuring resistance module, which includes a first measuring resistor R1 and a second measuring resistor R2, and one end j of the first measuring resistor R1 is connected to one end m of the second measuring resistor R2.

[0012] As a preferred solution of the measurement circuit for solving the inherent error of the three-wire system described in the present invention, one end i of the first measuring resistor R1 is connected to one end g of the fourth switch K4, and the other end j is also connected to the first constant current source Iexc1.

[0013] As a preferred solution of the measurement circuit for solving the inherent error of the three-wire system described in the present invention, one end m of the second measuring resistor R2 is connected to the first constant current source Iexc1, and the other end n is connected to one end f of the third electronic switch K3.

[0014] As a preferred solution of the measurement circuit for solving the inherent error of the three-wire system described in the present invention, it further includes a reference resistor Rref, which is connected to one end a of the first electronic switch K1 and one end c of the second electronic switch K2.

[0015] A method for solving the inherent error of three-wire measurement, comprising:

[0016] Control the opening and closing of the switch module to change the flow direction of the first constant current source Iexc1 and the second constant current source Iexc2;

[0017] measuring the voltages of the first measuring resistor R1 and the second measuring resistor R2 respectively;

[0018] Disconnect the switch module and calculate the resistance ratio.

[0019] As a preferred solution to the measurement method for solving the inherent error of the three-wire system according to the present invention, the control of opening and closing of the switch module includes:

[0020] The first electronic switch K1 and the third electronic switch K3 are closed simultaneously, or the second electronic switch K2 and the fourth electronic switch K4 are closed simultaneously.

[0021] As a preferred solution of the measurement method for solving the inherent error of the three-wire system according to the present invention, the voltage of the second measuring resistor R2 is:

[0022] U2_0=U2-U0=Iexc2*R2+Iexc2*r2–Iexc1*r0=Iexc2*R2

[0023] Set Iexc2 = Iexc1, the core wire lengths are equal, that is, r0 = r2;

[0024] The voltage of the first measuring resistor R1 is:

[0025] U1_0=U1-U0=Iexc2*R1+Iexc2*r2–Iexc1*r0=Iexc2*R1

[0026] Set Iexc2 = Iexc1, and the core wire lengths are equal, that is, r0 = r1.

[0027] As a preferred solution to the measurement method for solving the inherent error of the three-wire system described in the present invention, the resistance ratio is:

[0028] Uref=(Iexc1+Iexc2)*Rref=2*Iexc2*Rref

[0029] R2=2*Rref*U2_0 / Uref;

[0030] R1=2*Rref*U1_0 / Uref

[0031] R2 / R1=U2_0 / U1_0

[0032] The beneficial effects of the present invention are as follows: providing a high-precision switching circuit to improve measurement accuracy, solving the problem that inherent errors cannot be eliminated and thus affect measurement results; reducing the amount of wiring, effectively reducing wiring and measurement costs, making it more suitable for large-scale engineering applications, and having obvious economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them:

[0034] Figure 1 A schematic diagram of the overall structure of a circuit for solving the inherent error measurement of a three-wire system provided by one embodiment of the present invention;

[0035] Figure 2 A schematic diagram of the overall structure of an original three-wire measurement circuit provided by one embodiment of the present invention;

[0036] Figure 3 A measurement method and current flow diagram of a method for solving the inherent error of a three-wire system provided by an embodiment of the present invention;

[0037] Figure 4 Another measurement method and current flow diagram for solving the inherent error of a three-wire measurement method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0038] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, the following detailed description of the specific embodiments of the present invention is given in conjunction with the accompanying drawings. It is obvious that the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in this field without creative work should fall within the scope of protection of the present invention.

[0039] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0040] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0041] The present invention is described in detail with reference to schematic diagrams. For ease of illustration, cross-sectional views of device structures may be partially enlarged and not to scale when describing embodiments of the present invention. Furthermore, the schematic diagrams are merely illustrative and should not limit the scope of the present invention. Furthermore, in actual production, the three-dimensional dimensions of length, width, and depth should be included.

[0042] In the description of the present invention, it should be noted that the terms "upper, lower, inner, and outer" and other references to orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first, second, or third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0043] In this disclosure, unless otherwise specified or limited, the terms "mounted," "connected," and "connected" should be interpreted broadly. For example, they may refer to fixed, removable, or integral connections. They may also refer to mechanical, electrical, or direct connections, indirect connections through an intermediary, or internal communication between two components. Those skilled in the art will understand the specific meanings of these terms in this disclosure.

[0044] Example 1

[0045] Reference Figures 1-2 , as one embodiment of the present invention, provides a measurement circuit for solving the inherent error of a three-wire system, comprising:

[0046] A switch module includes a first electronic switch K1, a second electronic switch K2, a third electronic switch K3, and a fourth electronic switch K4. Terminal b of the first electronic switch K1 is connected to terminal g of the fourth electronic switch K4. Terminal c of the second electronic switch K2 is connected to terminal a of the first electronic switch K1. Terminal d of the second electronic switch K2 is connected to terminal f of the third electronic switch K3.

[0047] A constant current source, the constant current source including a first constant current source Iexc1 and a second constant current source Iexc2;

[0048] The switch module is electrically connected to the constant current source.

[0049] It should be noted that four electronic switches are provided, which can be opened and closed according to measurement needs, thereby achieving the effect of quickly switching the circuit for measurement and realizing the conversion of the flow direction of the two constant current sources. The constant current source can provide a stable current to ensure the stable operation of other circuits.

[0050] Furthermore, the second constant current source Iexc2 is connected to the other end h of the fourth switch K4 and the one end e of the third electronic switch K3 respectively.

[0051] Furthermore, a measuring resistor module is included, the measuring resistor module includes a first measuring resistor R1 and a second measuring resistor R2, and one end j of the first measuring resistor R1 is connected to one end m of the second measuring resistor R2.

[0052] Furthermore, one end i of the first measuring resistor R1 is connected to one end g of the fourth switch K4 , and the other end j is also connected to the first constant current source Iexc1 .

[0053] Furthermore, one end m of the second measuring resistor R2 is connected to the first constant current source Iexc1, and the other end n is connected to one end f of the third electronic switch K3.

[0054] Furthermore, a reference resistor Rref is included, and the reference resistor Rref is connected to a terminal a of the first electronic switch K1 and a terminal c of the second electronic switch K2.

[0055] It should be noted that this high-precision measurement circuit is used to measure R2 and R1 of a three-wire differential resistance sensor and the resistance ratio R2 / R1. The error usually depends on the difference in the resistance values ​​of the core wires. However, the core wires of the present invention are of equal length, so the difference in the resistance values ​​of the core wires is very small and can be ignored. Under the combined effect of current flow direction and core wire selection, r0 = r2 and r0 = r1 are achieved, and the effect achieved can fully meet engineering applications. Figure 2 The existing circuit wires required 5, but now only three are enough. Under normal circumstances, the wire length used is about 500 meters. Compared with the traditional five-core measurement method, it can save the core wire cost. When the wiring distance is long and there are more wiring points, the economic benefits are particularly obvious. One set can reduce the cost by at least 400 yuan, and the company sells at least 2,000 sets a year, and the annual cost expenditure can save at least 800,000 yuan.

[0056] Example 2

[0057] Reference Figures 3-4 , as an embodiment of the present invention, provides a measurement method for solving the inherent error of the three-wire system, comprising:

[0058] Control the opening and closing of the switch module to change the flow direction of the first constant current source Iexc1 and the second constant current source Iexc2;

[0059] Furthermore, the opening and closing of the switch module is controlled, including:

[0060] The first electronic switch K1 and the third electronic switch K3 are closed simultaneously, or the second electronic switch K2 and the fourth electronic switch K4 are closed simultaneously.

[0061] It should be noted that the reference Figure 3 When K1 and K3 are closed, the excitation current Iexc2 = 1mA, as shown by the solid arrow in the figure, flows through K3, r2, R2, R1, r1, K1, Rref, to the ground. The excitation current Iexc1 = 1mA, as shown by the dotted arrow in the figure, flows through r0, R1, r1, K1, Rref to the ground, forming a series loop.

[0062] It should be noted that the reference Figure 4 When K2 and K4 are closed, the excitation current Iexc2 = 1mA, as shown by the solid arrow in the figure, flows through K4, r1, R1, R2, r2, K2, Rref, to the ground. The excitation current Iexc1 = 1mA, as shown by the dotted arrow in the figure, flows through r0, R2, r2, K2, Rref, to the ground, forming a series loop.

[0063] measuring the voltages of the first measuring resistor R1 and the second measuring resistor R2 respectively;

[0064] Specifically, the voltage of the second measuring resistor R2 is:

[0065] U2=Iexc2*(r2+R2)+U01

[0066] U0=Iexc1*r0+U01

[0067] U2_0=U2-U0=Iexc2*R2+Iexc2*r2–Iexc1*r0=Iexc2*R2

[0068] Since Iexc2=Iexc1, the core wire lengths are equal, that is, r0=r2, so the measured U2_0 is the voltage across R2.

[0069] Specifically, the voltage of the first measuring resistor R1 is:

[0070] U1=Iexc2*(r1+R1)+U01

[0071] U0=Iexc1*r0+U01

[0072] U1_0=U1-U0=Iexc2*R1+Iexc2*r2–Iexc1*r0=Iexc2*R1

[0073] Since Iexc2 = Iexc1 and the core wire lengths are equal, that is, r0 = r1, the measured voltage U1_0 is the voltage at the R1 terminal. This avoids the occurrence of inherent errors.

[0074] Furthermore, the switch module is disconnected, the measurement is completed, and the resistance ratio is calculated.

[0075] Specifically, the resistance ratio calculation process is:

[0076] Uref=(Iexc1+Iexc2)*Rref=2*Iexc2*Rref

[0077] R2=2*Rref*U2_0 / Uref;

[0078] R1=2*Rref*U1_0 / Uref

[0079] R2 / R1=U2_0 / U1_0

[0080] Through the above circuit and method, the control of the switch module is switched and measured, and the core wires of equal length are used to solve the inherent error of the resistance value difference between R1 and R2, while reducing the layout of the core wires and thus greatly improving the economic benefits.

[0081] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A measurement circuit for solving the inherent error of a three-wire system, characterized in that: include: a switch module, the switch module comprising a first electronic switch K1, a second electronic switch K2, a third electronic switch K3, and a fourth electronic switch K4, wherein the second end (b) of the first electronic switch K1 is connected to the first end (g) of the fourth electronic switch K4, the first end (c) of the second electronic switch K2 is connected to the first end (a) of the first electronic switch K1, and the second end (d) of the second electronic switch K2 is connected to the second end (f) of the third electronic switch K3; A constant current source, comprising a first constant current source Iexc1 and a second constant current source Iexc2; The switch module is electrically connected to the constant current source; The second constant current source Iexc2 is connected to the second end (h) of the fourth switch K4 and the first end (e) of the third electronic switch K3 respectively; A first end (i) of the first measuring resistor R1 is connected to a first end (g) of the fourth switch K4 , and a second end (j) of the first measuring resistor R1 is connected to the first constant current source Iexc1 .

2. The measurement circuit for solving the inherent error of a three-wire system according to claim 1, characterized in that: The invention also includes a measuring resistance module, wherein the measuring resistance module includes a first measuring resistor R1 and a second measuring resistor R2, wherein the second end (j) of the first measuring resistor R1 is connected to the first end (m) of the second measuring resistor R2.

3. The measurement circuit for solving the inherent error of a three-wire system as claimed in claim 2, characterized in that: A first end (m) of the second measuring resistor R2 is connected to the first constant current source Iexc1 , and a second end (n) of the second measuring resistor R2 is connected to a second end (f) of the third electronic switch K3 .

4. The measurement circuit for solving the inherent error of a three-wire system as claimed in claim 3, characterized in that: The device further includes a reference resistor Rref, which is connected to the first end (a) of the first electronic switch K1 and the first end (c) of the second electronic switch K2.

5. A measurement method for solving the inherent error of a three-wire system, the measurement method applying the measurement circuit for solving the inherent error of a three-wire system according to claim 1, characterized in that: Control the opening and closing of the switch module to change the flow direction of the first constant current source Iexc1 and the second constant current source Iexc2; measuring the voltages of the first measuring resistor R1 and the second measuring resistor R2 respectively; Disconnect the switch module and calculate the resistance ratio.

6. The measurement method for solving the inherent error of the three-wire system according to claim 5, characterized in that: The control of the opening and closing of the switch module includes: The first electronic switch K1 and the third electronic switch K3 are closed simultaneously, or the second electronic switch K2 and the fourth electronic switch K4 are closed simultaneously.

7. The measurement method for solving the inherent error of the three-wire system according to claim 6, characterized in that: The voltage of the second measuring resistor R2 is: U2_0=U2-U0=Iexc2*R2+Iexc2*r2–Iexc1*r0=Iexc2*R2 Set Iexc2 = Iexc1, the core wire lengths are equal, that is, r0 = r2; The voltage of the first measuring resistor R1 is: U1_0=U1-U0=Iexc2*R1+Iexc2*r2–Iexc1*r0=Iexc2*R1 Set Iexc2 = Iexc1, and the core wire lengths are equal, that is, r0 = r1.

8. The measurement method for solving the inherent error of the three-wire system according to claim 7, characterized in that: The resistance ratio is: Uref=(Iexc1+Iexc2)*Rref=2*Iexc2*Rref R2=2*Rref*U2_0 / Uref; R1=2*Rref*U1_0 / Uref R2 / R1=U2_0 / U1_0.

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