Resistance voltage division sampling circuit and standard electric energy meter

Abstract

The utility model discloses a resistor voltage division sampling circuit, which comprises a resistor R1 and a resistor R2 which are mutually connected in series, one end of the resistor R1 is connected with one end of a measuring voltage U, the other end of the resistor R1 is connected with one end of the resistor R2, the other end of the resistor R2 is connected with the other end of the measuring voltage U, and the resistor R1 and the resistor R2 adopt metal foil resistors after accelerated aging. By using the metal foil resistor subjected to accelerated aging, the resistance voltage division sampling precision and stability index of the resistance sampling circuit are improved, the measurement requirement of the 0.01 standard electric energy meter is further met, and the purpose of full localization of the device is achieved.

Description

Technical Field

[0001] The utility model relates to the field of electric energy measurement, in particular to a resistor voltage-dividing sampling circuit and a standard electric energy meter. Background Art

[0002] The main application scenarios of 0.01-level standard energy meter products are high-precision detection devices and value traceability in the field of energy measurement, such as energy measurement calibration and laboratory measurement benchmarks. At present, the commonly used 0.01-level standard energy meter products in China rely on imports, mainly the American Thunderbolt and German ZERA standard energy meters. In recent years, there have also been 0.01-level standard energy meter products developed in China, but compared with the imported 0.01-level standard meters, although their accuracy can meet the 0.01-level measurement requirements, the domestic 0.01-level standard energy meter products have low long-term stability (annual stability index) and are greatly affected by temperature (temperature coefficient index), and the key components inside, such as precision resistors, operational amplifiers, and analog-to-digital conversion chips, are all foreign devices. In addition, in addition to high accuracy, the 0.01-level standard energy meter has a wide voltage measurement range, generally 20V-500V, to support three-phase electrical measurement. In order to resolve foreign technical barriers and trade embargoes, promote breakthroughs in key core technologies of major "bottleneck" power equipment as soon as possible, and support the realization of nationally produced 0.01-level standard electric energy meter products, the key voltage signal acquisition circuit must also be able to be realized on the basis of nationally produced devices. The voltage sampling circuit can be used in 0.01-level standard electric energy meter products, and the sampling circuit must have good annual stability indicators (resistance change <5ppm / year) and temperature coefficient indicators (temperature coefficient <1ppm / ℃) while ensuring a measurement accuracy of 0.01 or above.

[0003] At present, the voltage sampling circuit of the 0.01-level standard electric energy meter is mainly realized by the active voltage transformer sampling method. In order to ensure the sampling accuracy of wide-range voltage sampling and small-signal voltage, the voltage transformer needs to add some compensation circuits, such as zero flux circuits. The circuit form is relatively complex, and the types of devices are relatively large. It is difficult to localize the circuit devices. The main difficulty lies in the need for high-precision operational amplifiers for signal feedback in the voltage sampling compensation circuit. The high-precision operational amplifiers currently used are all selected from foreign manufacturers. In addition, due to the electromagnetic characteristics, the voltage sampling circuit based on the voltage transformer is greatly affected by the frequency. When the voltage signal frequency of some 0.01-level standard electric energy meter products is greater than 200Hz, the line measurement accuracy is reduced to less than 0.01%. And as a semiconductor device, it is difficult for the operational amplifier to improve its own indicators through pre-processing methods such as accelerated aging. Considering the differences between domestic and foreign operational amplifiers and the current situation that it is difficult to improve the indicators of operational amplifiers, it is difficult to achieve national localization of the voltage sampling circuit based on the voltage transformer.

[0004] In addition to the above-mentioned voltage transformer sampling, the voltage sampling method of the 0.01-level standard electric energy meter can also be realized by using the resistor voltage division method. The resistor voltage division sampling circuit is relatively simple, and the types of devices are relatively small, which makes it easy to realize the localization of voltage sampling circuit devices. However, most manufacturers currently use foreign high-precision metal foil resistors because their temperature coefficient can reach ±0.2×10 -6 / ℃, annual stability is less than ±2×10 -6 / year, can be directly applied to 0.01-level standard meter products, but this type of resistor is usually customized, expensive and has a long procurement cycle. In recent years, it has been subject to trade controls and is difficult to import. The best performance gold-sealed metal foil resistor in China currently has a temperature coefficient of ±5×10 -6 / ℃, the annual stability index is 20×10 -6 / year. Comparing domestic and foreign indicators with the requirements of the 0.01-level standard electric energy meter, there is no metal-encapsulated alloy foil resistor that can be directly applied to the 0.01-level AC standard electric energy meter products in China. Utility Model Content

[0005] The purpose of the utility model is: to address the above-mentioned problems, the utility model provides a resistor voltage divider sampling circuit, in which metal foil resistors after accelerated aging are used to improve the resistor voltage divider sampling accuracy and stability index of the resistor sampling circuit, thereby meeting the measurement requirements of the 0.01 standard electric energy meter and achieving the goal of national production of devices.

[0006] The technical solution adopted by the utility model is as follows:

[0007] A resistor voltage-dividing sampling circuit comprises a resistor R1 and a resistor R2 connected in series, wherein one end of the resistor R1 is connected to one end of a measured voltage U, the other end of the resistor R1 is connected to one end of the resistor R2, and the other end of the resistor R2 is connected to the other end of the measured voltage, wherein the resistor R1 and the resistor R2 are metal foil resistors after accelerated aging.

[0008] Preferably, the resistor R1 is formed by connecting a plurality of metal foil resistors with the same resistance in series.

[0009] A resistor voltage-dividing sampling circuit comprises a resistor RA1, a resistor RA2, a resistor R3 and a resistor RA4 connected in series in sequence, a resistor RB1, a resistor RB2, a resistor RB3 and a resistor RB4 connected in series in sequence, a resistor RC1, a resistor RC2, a resistor RC3 and a resistor RC4 connected in series in sequence, one end of the resistor RA1 is connected to a measurement voltage UA, one end of the resistor RB1 is connected to a measurement voltage UB through a control unit K1, one end of the resistor RC1 is connected to a measurement voltage UC, one end of the resistor RA4 is connected to one end of the resistor RA through a control unit KA, one end of the resistor RA4 is also connected to one end of the resistor RA6, the other ends of the resistor RA5 and the resistor RA6 are grounded respectively, one end of the resistor RB4 is connected to one end of the resistor RB5 through a control unit KB, one end of the resistor RB4 is also connected to one end of the resistor RB6, the other ends of the resistor RB5 and the resistor RB6 are grounded respectively, one end of the resistor RC4 is connected to one end of the resistor RC5 through a control unit KC, one end of the resistor RC4 is also connected to one end of the resistor RC6, and the other ends of the resistor RC5 and the resistor RC6 are grounded respectively.

[0010] Preferably, the control unit K1 is a single-pole double-throw switch, and one end of the resistor RB1 is also connected to the rated voltage UN through the control unit K1, and the rated voltage UN is connected to the reference ground GND.

[0011] A standard electric energy meter comprises the above-mentioned resistor voltage-dividing sampling circuit.

[0012] Preferably, the standard electric energy meter is a 0.01-level standard electric energy meter.

[0013] Preferably, the voltage measurement range of the standard electric energy meter is 20V-500V.

[0014] Due to the adoption of the above technical solution, the beneficial effects of the utility model include:

[0015] (1) Before the metal foil resistor is installed in the resistor voltage divider sampling circuit, the metal foil resistor is aged according to the designed accelerated aging method, thereby improving the stability index of the resistor voltage divider sampling circuit;

[0016] (2) Adding control units KA / KB / KC to the resistor voltage-dividing sampling circuit to adjust the voltage-dividing ratio of the circuit can meet the high-precision sampling requirements of 20V-500V of the 0.01-level standard electric energy meter. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of a resistor voltage-dividing sampling circuit of the utility model;

[0018] Figure 2 It is a structural schematic diagram of the high-voltage pulse accelerated aging device of the utility model;

[0019] Figure 3 It is the resistance value-temperature variation curve of the 200Ω metal foil resistor after aging of the utility model;

[0020] Figure 4 It is the resistance value-temperature variation curve of the 20Ω metal foil resistor after aging of the utility model;

[0021] Figure 5 It is a structural schematic diagram of a resistor voltage-dividing sampling circuit according to another embodiment of the present utility model;

[0022] Figure 6 The utility model is a resistor voltage-dividing sampling device with domestically produced components. DETAILED DESCRIPTION

[0023] The utility model is described in detail below in conjunction with the accompanying drawings.

[0024] In order to make the purpose, technical solution and advantages of the utility model more clear, the utility model is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the utility model, rather than to limit the utility model.

[0025] Figure 1 The utility model is a structural schematic diagram of a resistor voltage-dividing sampling circuit.

[0026] As shown in the figure, a resistor voltage-dividing sampling circuit includes a resistor R1 and a resistor R2 connected in series, one end of the resistor R1 is connected to one end of a measured voltage U, the other end of the resistor R1 is connected to one end of the resistor R2, and the other end of the resistor R2 is connected to the other end of the measured voltage, wherein the resistor R1 and the resistor R2 are metal foil resistors after accelerated aging.

[0027] The measured voltage U is sampled by dividing the voltage by resistors R1 and R2. In the implementation of the circuit, both resistors R1 and R2 are made of domestic metal foil resistors. Optionally, resistor R1 is formed by connecting a plurality of metal foil resistors with the same resistance in series.

[0028] The main material of metal foil resistors is nickel-chromium alloy. The temperature coefficient of resistance of metal foil resistors made of nickel-chromium alloy changes with temperature in a trend close to a quadratic parabola, and the resistance changes linearly with temperature. It is possible to consider improving the temperature coefficient of metal foil resistors by compensating the resistance through a fitting curve. In addition, the long-term stability of resistance is an indicator of the change of resistance over time, which cannot be matched or compensated. However, according to the change of resistance over time, the metal foil resistor is aged faster, so that the metal foil resistor quickly passes through the early unstable period and enters the slow change period, reducing the drift of the metal foil resistor over time.

[0029] Figure 2It is a structural schematic diagram of the high-voltage pulse accelerated aging device of the utility model. As shown in the figure, the device includes a high and low temperature box, DC voltage sources U1 and U2, switches S1 and S2, and a control unit. During the accelerated aging process, the DC voltage source energizes the resistors R1 and R2 respectively, and the switches S1 and S2 control the states of the voltage sources U1 and U2 to energize the metal foil resistors R1 and R2, and the states of the switches S1 and S2 are uniformly controlled by the control unit.

[0030] The above device is used to accelerate the aging of the metal foil resistor before it is installed on the circuit board. The specific steps of the accelerated aging method include: placing the metal foil resistors R1 and R2 in a high and low temperature box, and setting the temperature in the high and low temperature box to 125°C, and the control unit controls the state of switches S1 and S2 to achieve a cycle state in which switches S1 and S2 are closed for 1s (i.e., powered on for 1s), disconnected for 5s, powered on for 1s... Under such electrical stress and temperature stress conditions, the metal foil resistor is continuously accelerated to age.

[0031] Figure 3 The utility model is a resistance value-temperature variation curve of the 200Ω metal foil resistor after aging. Figure 4 This is the resistance-temperature change curve of the 20Ω metal foil resistor after aging of the utility model. As shown in the figure, after the metal foil resistor is accelerated by the accelerated aging device and the accelerated aging method, the metal foil resistor test analysis results show that after about 9 days of accelerated aging, the resistance change of the metal foil resistor is <1ppm / day, and the temperature coefficient of the metal foil resistor after aging is <±3ppm / ℃ in the temperature range of 10℃-40℃, and the resistance changes nearly linearly with temperature.

[0032] After accelerated aging of domestic metal foil resistors, the drift of their resistance over time is small enough to meet the use of 0.01-level standard electric energy meters. Figure 3 It can be concluded that the relationship between the resistance of the metal foil resistor and time is approximately:

[0033] (1)

[0034] Where: R is the resistance of the metal foil resistor; T is the ambient temperature; a and b are calculated based on the resistance and temperature of the metal foil resistor after aging. Different resistance values ​​will correspond to different a and b values.

[0035] After obtaining such corresponding changes, the voltage sampling signal is compensated in the processing unit of the 0.01-level standard electric energy meter product in combination with the actual working environment temperature value collected, so that each temperature point is consistent with the metal foil resistance value at room temperature (25°C, which can be set according to the working environment of the standard meter).

[0036] Figure 5 It is a structural schematic diagram of a resistor voltage-dividing sampling circuit according to another embodiment of the present invention.

[0037] As shown in the figure, a resistor voltage-dividing sampling circuit comprises a resistor RA1, a resistor RA2, a resistor R3 and a resistor RA4 connected in series in sequence, a resistor RB1, a resistor RB2, a resistor RB3 and a resistor RB4 connected in series in sequence, a resistor RC1, a resistor RC2, a resistor RC3 and a resistor RC4 connected in series in sequence, one end of the resistor RA1 is connected to a measured voltage UA, one end of the resistor RB1 is connected to a measured voltage UB through a control unit K1, one end of the resistor RC1 is connected to a measured voltage UC, one end of the resistor RA4 is connected to one end of the resistor RA through a control unit KA, one end of the resistor RA4 is also connected to one end of the resistor RA6, the other ends of the resistor RA5 and the resistor RA6 are grounded respectively, one end of the resistor RB4 is connected to one end of the resistor RB5 through a control unit KB, one end of the resistor RB4 is also connected to one end of the resistor RB6, the other ends of the resistor RB5 and the resistor RB6 are grounded respectively, one end of the resistor RC4 is connected to one end of the resistor RC5 through a control unit KC, one end of the resistor RC4 is also connected to one end of the resistor RC6, and the other ends of the resistor RC5 and the resistor RC6 are grounded respectively.

[0038] In the figure, resistors RA1-RA6, RB1-RB6, and RC1-RC6 are metal foil resistors that have been treated by the accelerated aging device and accelerated aging method. UA / UB / UC / UN are the three-phase voltage lines to be measured. The designed circuit is compatible with three-phase three-wire and three-phase four-wire wiring methods. When the input is three-phase three-wire, the control switch K1 connects phase B to the rated voltage UN (reference ground GND); when the input is three-phase four-wire, phase B is connected to the corresponding sampling circuit of RB1, and UN is connected to the reference ground GND. In addition, since the measurement range of UA / UB / UC is wide, in order to ensure the accuracy of the voltage sampling signal and reduce the influence of line interference on the voltage sampling signal, that is, when the input is the maximum voltage (500V) or the minimum voltage (20V), the sampled signal VA / VB / VC is large enough, so the circuit is designed with switches KA / KB / KC to control whether RA5 / RB5 / RC5 is connected to the circuit to adjust the voltage division ratio of the voltage sampling circuit. The closed and open states of KA / KB / KC are consistent. The status of switches K1 and KA / KB / KC is controlled by the signal on the control module of the 0.01-level standard meter product, that is, Figure 6 Pins 14 and 15 of the connector.

[0039] For the VA / VB / VC signal values ​​obtained after voltage division, curve fitting can be performed according to the resistance value versus temperature curve measured during the aging process, and the VA / VB / VC values ​​can be compensated based on the fitting results to reduce the drift caused by temperature changes.

[0040] like Figure 6 As shown, during implementation, the resistor voltage-dividing sampling circuit can be made into a pluggable module, and the external shell is fully sealed with a technical material to shield the interference of the external environment on the circuit, thereby further improving the accuracy and stability of the voltage sampling circuit.

[0041] Optionally, the control unit K1 is a single-pole double-throw switch, and one end of the resistor RB1 is also connected to the rated voltage UN through the control unit K1, and the rated voltage UN is connected to the reference ground GND.

[0042] The utility model also provides a standard electric energy meter, comprising the above-mentioned resistor voltage-dividing sampling circuit.

[0043] Optionally, the standard electric energy meter is a 0.01-level standard electric energy meter.

[0044] Optionally, the voltage measurement range of the standard electric energy meter is 20V-500V.

[0045] The principles and implementation methods of the present invention are described in this article using specific embodiments. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. It should be pointed out that for ordinary technicians in this technical field, the present invention can also be improved and modified without departing from the principle of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A resistor voltage-dividing sampling circuit, characterized in that: It includes a resistor R1 and a resistor R2 connected in series, one end of the resistor R1 is connected to one end of a measuring voltage U, the other end of the resistor R1 is connected to one end of the resistor R2, and the other end of the resistor R2 is connected to the other end of the measuring voltage U, wherein the resistor R1 and the resistor R2 are metal foil resistors after accelerated aging.

2. The resistor voltage-dividing sampling circuit according to claim 1, characterized in that: The resistor R1 is formed by connecting a plurality of metal foil resistors with the same resistance in series.

3. A resistor voltage-dividing sampling circuit, characterized in that: It includes a resistor RA1, a resistor RA2, a resistor R3 and a resistor RA4 connected in series in sequence, a resistor RB1, a resistor RB2, a resistor RB3 and a resistor RB4 connected in series in sequence, and a resistor RC1, a resistor RC2, a resistor RC3 and a resistor RC4 connected in series in sequence, one end of the resistor RA1 is connected to a measurement voltage UA, one end of the resistor RB1 is connected to a measurement voltage UB through a control unit K1, one end of the resistor RC1 is connected to a measurement voltage UC, one end of the resistor RA4 is connected to one end of a resistor RA5 through a control unit KA, one end of the resistor RA4 is also connected to one end of a resistor RA6, and the other ends of the resistor RA5 and the resistor RA6 are grounded respectively, one end of the resistor RB4 is connected to one end of the resistor RB5 through a control unit KB, one end of the resistor RB4 is also connected to one end of the resistor RB6, and the other ends of the resistor RB5 and the resistor RB6 are grounded respectively, one end of the resistor RC4 is connected to one end of the resistor RC5 through a control unit KC, one end of the resistor RC4 is also connected to one end of the resistor RC6, and the other ends of the resistor RC5 and the resistor RC6 are grounded respectively.

4. The resistor voltage-dividing sampling circuit according to claim 3, characterized in that: The control unit K1 is a single-pole double-throw switch. One end of the resistor RB1 is also connected to a rated voltage UN through the control unit K1. The rated voltage UN is connected to a reference ground GND.

5. A standard electric energy meter, characterized in that: The invention comprises the resistor voltage-dividing sampling circuit as described in any one of claims 1 to 3.

6. The standard electric energy meter according to claim 5, characterized in that: The standard electric energy meter is a 0.01-level standard electric energy meter.

7. The standard electric energy meter according to claim 5, characterized in that: The voltage measurement range of the standard electric energy meter is 20V-500V.

Images