Measurement amplification circuit and current sensor

Abstract

The invention discloses a measurement amplification circuit and a current sensor, and belongs to the technical field of current measurement, the measurement amplification circuit comprises an operational amplification unit used for amplifying a voltage signal, an isolation output unit used for receiving and isolating a signal of the operational amplification unit, and a power supply unit used for supplying power to the operational amplification unit; the operational amplification unit comprises a resistor R2 used for adjusting an amplification coefficient; according to the measurement amplification circuit and the current sensor, the voltage is directly taken from the copper busbar, the rated current value is 2mV, the power consumption is small, the heat is small, and compared with a diverter with the same size, the power consumption is reduced by 97%, and the temperature is reduced by 85%; the device has the advantages of high safety, small volume, signal isolation, high measurement precision, measurement range of 12 times of rated value, strong output signal, difficulty in electromagnetic field interference, convenience in installation, contact installation, no cutting of a copper busbar and no increase of use risk.

Description

Technical Field

[0001] The present invention belongs to the technical field of current measurement, and particularly relates to a measurement and amplification circuit and a current sensor. Background Art

[0002] Currently, in the process of large-current power transmission, the components used for large-current measurement are basically current transformers, current shunts, and integrated combined current sensors;

[0003] There are mainly two types of current transformers: the through-type current transformer and the split-core current transformer. The through-type current transformer is one of the most commonly used products, and its disadvantages are: large volume, large space occupied by the equipment during installation, a large amount of enameled wire and silicon steel materials used, low measurement accuracy, small measurement range only 1.2 times the rated value, and there is a risk of open circuit at the secondary during the subsequent installation process. It is inconvenient to be inserted into the current wire during installation.

[0004] Split-core current transformer: Due to its convenient installation during use, the product has begun to be widely used. Its disadvantages are: this method is generally only applicable to small-current circuits. Since the silicon steel magnetic material is not cut as a whole, a large amount of magnetic flux density is lost and the measurement accuracy is reduced. The measurement range is small, only 1.2 times the rated value. When the current wire is inserted at different positions inside the transformer, the measurement results vary greatly.

[0005] Current transformers are mainly made of copper wire and alloy magnetic materials, which waste a lot of materials, have a high cost, are difficult to wind the secondary winding, have a large volume, low accuracy, a small measurement range only 1.2 times, and there is a risk of high voltage generation due to open circuit at the secondary during use.

[0006] Due to the advantage of small volume, current shunts are often used in current measurement. The sampling voltage is 75 mV at the rated current value. Its disadvantages are: high power consumption, large heat, the signal needs to be isolated at the subsequent stage, the measurement range is small, only 1.2 times the rated value, the output signal is weak and is easily interfered by the electromagnetic field, and it needs to be embedded in the busbar copper row, increasing the risk. As Figure 9 shown, due to the need for sampling and measuring the voltage, a manganin resistor chip is embedded in the current copper row for the current shunt. Since the resistance value of the manganin chip is stable when the temperature changes, when the rated current passes through, the sampling voltage at both ends of the manganin resistor chip is 75 mV, which increases the resistance of the current loop. After the resistance of the current loop increases, the power consumption increases and the heat rises rapidly. In the case of the rated current passing through for 5 minutes, the temperature of the shunt will rise by more than 120 °C, and the output voltage signal is not isolated and needs to be isolated and amplified for subsequent use.

[0007] Integrated combined current sensor, currently an embedded sensor, has the advantages of directly taking voltage on the busbar copper row, with a value of 2 mV at the rated current, low power consumption, low heat generation, and a 97% reduction in power consumption and an 85% reduction in temperature compared to shunts of the same volume. It has high safety, small size, signal isolation, high measurement accuracy, a large measurement range of 12 times the rated value, and a strong output signal that is not easily affected by electromagnetic fields. The disadvantage is that it needs to be embedded in the busbar copper row, increasing the risk.

[0008] Therefore, it is necessary to develop a new measurement and amplification circuit and current sensor to solve the existing problems. Summary of the Invention

[0009] The purpose of the present invention is to provide a measurement and amplification circuit and a current sensor to solve the problem of low accuracy in large current measurement.

[0010] To achieve the above purpose, the present invention provides the following technical solution: A measurement and amplification circuit, including:

[0011] An operational amplifier unit for amplifying the voltage signal, an isolation output unit for receiving the signal of the operational amplifier unit and isolating it, and a power supply unit for supplying power to the operational amplifier.

[0012] Among them, the operational amplifier unit includes: a resistor R2 for adjusting the amplification coefficient.

[0013] Preferably, the type of the resistor R2 is a positive temperature coefficient thermistor.

[0014] Preferably, the operational amplifier unit further includes: an operational amplifier, a resistor R1 connected to the negative input terminal of the operational amplifier, and a resistor R3 connected between the output terminal and the negative input terminal of the operational amplifier;

[0015] Among them, the resistor R2 is in parallel with the resistor R1.

[0016] Preferably, the type of the resistor R2 is a negative temperature coefficient thermistor.

[0017] Preferably, the operational amplifier unit further includes: an operational amplifier, a resistor R1 connected to the negative input terminal of the operational amplifier, and a resistor R3 connected between the output terminal and the negative input terminal of the operational amplifier;

[0018] Among them, the resistor R2 is in parallel with the resistor R3.

[0019] The present invention further provides a current sensor, including: the above measurement and amplification circuit;

[0020] And a heat conduction connecting piece connected to the measurement and amplification circuit.

[0021] Preferably, the heat-conducting connecting member is in contact connection with the resistor R2.

[0022] Preferably, the heat-conducting connecting member is contact-mounted on the metal conductive member.

[0023] Preferably, one end of the resistor R1 is connected to the first voltage input sampling terminal for collecting the voltage of the first collection point of the metal conductive member;

[0024] One end of the operational amplifier is connected to the second voltage input sampling terminal for collecting the voltage of the second collection point of the metal conductive member;

[0025] Wherein, the other end of the resistor R1 is connected to the operational amplifier.

[0026] Preferably, the heat-conducting connecting member is made of a high heat-conducting material.

[0027] The technical effects and advantages of the present invention: The measurement amplification circuit and the current sensor directly obtain the voltage on the busbar. When the rated current value is 2 mV, the power consumption is small, the heat is small, and compared with a shunt of the same volume, the power consumption is reduced by 97% and the temperature is reduced by 85%. It has high safety, small volume, signal isolation, high measurement accuracy, a large measurement range of 12 times the rated value, a strong output signal that is not easily affected by electromagnetic fields, convenient installation, and contact installation. It does not cut off the busbar and does not increase the use risk. The current sensor component is placed on the original current-carrying copper bar of the power transmission. Regardless of the magnitude of the transmitted current, the volume of the current sensor remains unchanged, which not only saves the use cost but also saves a large installation space. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a connection schematic diagram of the current sensor of the present invention;

[0029] Figure 2 It is a schematic diagram of the acquisition position of the current sensor of the present invention;

[0030] Figure 3 It is a front view of the current sensor of the present invention;

[0031] Figure 4 It is a side view of the current sensor of the present invention;

[0032] Figure 5 It is a side view when the current sensor of the present invention is installed with the current copper bar;

[0033] Figure 6 It is a front view when the current sensor of the present invention is installed with the current copper bar;

[0034] Figure 7 It is a circuit diagram of the measurement amplification circuit of Embodiment 1 of the present invention;

[0035] Figure 8This is the circuit diagram of the measurement and amplification circuit in Embodiment 2 of the present invention;

[0036] Figure 9 This is the schematic diagram of the current shunt measurement in the prior art of the present invention.

[0037] In the figure: 1. Metal conductive part; 1-1. First voltage input sampling point; 1-2. Second voltage input sampling point; 2-1. First voltage input sampling terminal; 2-2. Second voltage input sampling terminal; 1-3. Contact end of the heat conduction body connecting part; 2-4. Operational amplifier unit; 2-5. Isolation output unit; 2-6. Power supply unit; 3. Heat conduction body connecting part; 2. Current sensor; 4. Mounting and fixing part; 2-3. Wiring terminal. Detailed implementation manners

[0038] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0039] Embodiment 1

[0040] The present invention provides a measurement and amplification circuit as shown in Figure 1 , Figure 7 which includes: an operational amplifier unit 2-4 for amplifying the collected voltage signal, an isolation output unit 2-5 for receiving the signal sent by the operational amplifier unit 2-4 and isolating it, and a power supply unit 2-6 for supplying power to the operational amplifier 2-4;

[0041] The operational amplifier unit 2-4 is provided with a resistor R2 for adjusting the amplification coefficient as the resistivity increases with the increase in temperature. The type of the resistor R2 is a positive temperature coefficient thermistor. A positive temperature coefficient thermistor is a type of thermistor, and its resistivity increases with the increase in temperature. It should be noted that the amplification coefficient (gain) refers to the absolute value of the amplification coefficient (gain);

[0042] The operational amplifier unit 2-4 includes an operational amplifier, a resistor R1, and a resistor R2. The resistor R1 is connected to the negative input terminal of the operational amplifier A2, the resistor R3 is connected between the output terminal and the negative input terminal of the operational amplifier A2, and the positive temperature coefficient thermistor is connected in the resistor R1 circuit.

[0043] Embodiment 2

[0044] Different from the embodiment: as shown in Figure 8As shown, the type of resistor R2 is a negative temperature coefficient thermistor. The negative temperature coefficient thermistor is connected in parallel in the circuit of resistor R3, and the operational amplifier A2 obtains the correct output voltage value, so that a stable voltage linearly related to the input current is obtained at the output end.

[0045] Embodiment 3

[0046] The present invention further provides a current sensor 2, such as Figure 3 , Figure 4 , Figure 5 which includes a measurement and amplification circuit, a metal conductive member 1, and a heat conduction connection member 3 in Embodiment 1 or 2. One end of the heat conduction connection member 3 is thermally connected to the metal conductive member 1, and the other end of the heat conduction connection member 3 is thermally connected to the resistor R2, coupling the temperature of the metal conductive member 1 to the resistor R2 of the operational amplifier unit 2-4; the heat conduction connection member is made of a highly heat-conductive material such as gold, silver, copper, iron, or aluminum; in this embodiment, the metal conductive member 1 is a current copper bar.

[0047] The current sensor 2 is further provided with a terminal block 2-3, and the terminal block 2-3 includes: a power input terminal of the power supply unit 2-6 and a sampling output terminal connected to the isolation output unit 2-5.

[0048] The input voltage is directly extracted on the current copper bar body. After the collected voltage is amplified by the operational amplifier A2, it is then electrically isolated and output. The copper bar structure is not changed, the copper bar resistance is not increased, and a micro-voltage of 2 mV is extracted at the rated current. During use, it is in contact installation with the current copper bar and fixed by a buckle; there is no increase in any power consumption and no increase in any temperature due to measurement and sampling. The measurement range is increased by 10 times and can reach more than 12 times the rated current.

[0049] The metal conductive member 1 is installed in the power transmission line to carry a large current. When the current flows through, a voltage will be generated on the metal conductive member 1. This voltage is sent to the inverting input terminal of the operational amplifier A2 through the resistor R1 and the resistor R2 connected in parallel with it for amplification processing.

[0050] By collecting and amplifying the voltage signal of the metal conductive member 1, and transferring the temperature of the metal conductive member 1 to the temperature-sensitive resistor R2 through the heat conduction connection member 3, the temperature-sensitive resistor R2 is corrected, and the operational amplifier A2 obtains the correct output voltage value, so that a stable voltage linearly related to the input current is obtained at the output end.

[0051] Current input: When the current passes through the current copper bar, a voltage is generated due to the resistance of the current copper bar. The operational amplifier A2 amplifies the voltage collected on the current copper bar and then sends it to the isolation output unit 2-5 for output.

[0052] Temperature Input: The temperature coefficient of resistivity of copper is not a fixed value and it changes with temperature. The temperature coefficient of resistivity of copper is approximately 0.0039 / °C near room temperature, which means that when the temperature increases by 1°C, the resistivity of copper increases by 0.0039 times its resistivity at 20°C. When the input current flows into the current copper bar, the current copper bar generates heat and its temperature rises with the magnitude of the current, the resistance increases, the voltage value of the current copper bar increases, the sampling voltage of operational amplifier A2 increases, and the output voltage of operational amplifier A2 becomes larger. At the same time, the heat on the copper bar is conducted to resistor R2 through the heat conduction connection member 3, and the resistance value of resistor R2 also increases accordingly. The input resistance value of the parallel connection of resistor R1 and resistor R2 increases, the output voltage of operational amplifier A2 decreases, and the output of operational amplifier A returns to within the standard value range, thus achieving the standard value corresponding to the input current value.

[0053] As Figure 5 , Figure 6 shown, Contact Installation: Install the first voltage input sampling terminal 2-1, the second voltage input sampling terminal 2-2, and the contact end 1-3 of the heat conduction body connection member above the current copper bar, and then fasten the installation and fixing member 4. The installation and fixing member 4 can be a fixed clip; As Figure 2 shown, the first voltage input sampling terminal 2-1 and the second voltage input sampling terminal 2-2 are in contact with the first voltage input sampling point 1-1 and the first voltage input sampling point 1-2 on the current copper bar.

[0054] The current sensor 2 in this embodiment is small in size. Placing the current sensor 2 on the original current copper bar for power transmission, regardless of the magnitude of the transmitted current, the volume of the current sensor 2 remains unchanged, which not only saves the usage cost but also saves a large amount of installation space; In Table 1, for the existing shunt and the current sensor 200A current specification product in this embodiment, under the same current copper bar, the electrical parameters are compared;

[0055] Table 1

[0056]

[0057]

[0058] Compared with the shunt of the same specification, under the rated input condition, the power consumption of this product is reduced by 97%, the temperature drops by 120 degrees, the power consumption and temperature decrease significantly, and no power consumption is generated during actual operation. During use, it is in contact installation with the current copper bar, and there is no need to cut the current copper bar and embed it therein, improving safety and reliability; The working current is large. Compared with the shunt of the same specification, the working current is increased by 10 times, reaching 12 times the rated current.

[0059] Finally, it should be noted that the above are only preferred embodiments 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 foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A measurement amplifier circuit, characterized in that: include: An operational amplifier unit for amplifying a voltage signal, an isolation output unit for receiving and isolating the operational amplifier unit signal, and a power supply unit for supplying power to the operational amplifier; Wherein, the operational amplifier unit includes: a resistor R2 for adjusting the amplification factor.

2. A measurement amplifier circuit according to claim 1, characterized in that: The resistor R2 is a positive temperature coefficient thermistor.

3. A measurement amplifier circuit according to claim 2, characterized in that: The operational amplifier unit further includes: an operational amplifier, a resistor R1 connected to the negative phase input terminal of the operational amplifier, and a resistor R3 connected between the output terminal and the negative phase input terminal of the operational amplifier; The resistor R2 is connected in parallel with the resistor R1.

4. A measurement amplifier circuit according to claim 1, characterized in that: The resistor R2 is a negative temperature coefficient thermistor.

5. A measurement amplifier circuit according to claim 4, characterized in that: The operational amplifier unit further includes: an operational amplifier, a resistor R1 connected to the negative phase input terminal of the operational amplifier, and a resistor R3 connected between the output terminal and the negative phase input terminal of the operational amplifier; The resistor R2 is connected in parallel with the resistor R3.

6. A current sensor, characterized in that: include: The measurement amplifier circuit according to any one of claims 1 to 5; and a heat-conducting connecting piece which is in contact with the measuring amplifying circuit.

7. A current sensor according to claim 6, characterized in that: The thermally conductive connecting member is in contact with and connected to the resistor R2.

8. A current sensor according to claim 7, characterized in that: The heat-conducting connecting piece is mounted on the metal conductive piece in a contacting manner.

9. A current sensor according to claim 6, characterized in that: One end of the resistor R1 is connected to a first voltage input sampling end for collecting the voltage of a first collection point of the metal conductive member; One end of the operational amplifier is connected to a second voltage input sampling end for collecting the voltage of a second collection point of the metal conductive member; The other end of the resistor R1 is connected to the operational amplifier.

10. A current sensor according to claim 8, characterized in that: The thermally conductive connecting piece is made of a high thermally conductive material.

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