Intelligent instrument

Abstract

The utility model discloses an intelligent instrument which comprises an MCU and a voltage and current sampling circuit which is electrically connected with the MCU and is used for collecting voltage signals and current signals. The voltage and current sampling circuit comprises five CON interfaces, a plurality of resistors, a plurality of capacitors and a current and voltage sampling chip U7. The intelligent instrument can measure voltage, current and battery temperature. According to the voltage and current sampling circuit, the sampling value is filtered and quantized for multiple times, the difference between the obtained sampling voltage value and the actual voltage value is small, and the difference between the sampling current value and the actual current value is small, so that the measurement precision is improved, and the voltage and current detection precision is improved. According to the temperature sensing module, sampling values are filtered and quantified for multiple times, and final temperature conversion is carried out by adopting a table look-up method, so that the battery temperature detection precision is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of instrument measurement, and specifically relates to an intelligent electric energy meter. Background Art

[0002] With the rapid development of the power system and the improvement of the intelligent level, the requirements for the monitoring and control of the power system are also getting higher and higher. Traditional power meters usually only provide basic measurement functions, such as the measurement of voltage, current and power, and cannot meet the needs of modern power systems for intelligence, networking and automation. Therefore, developing an intelligent meter with high performance, flexibility and security has become the current technological trend.

[0003] Most of the existing intelligent meters use a microprocessor or a microcontroller as the main control, and realize the comprehensive monitoring and control of the power system by integrating a variety of sensors and communication modules. However, these meters still have some deficiencies in signal processing, communication protocols and user interfaces, such as low signal conditioning accuracy, incompatible communication protocols, and unfriendly user interfaces. Therefore, it is necessary to further improve and optimize an intelligent meter. Summary of the Utility Model

[0004] Aiming at the deficiencies in the prior art, the technical problem to be solved by the utility model is to provide an intelligent meter. The purpose of designing this intelligent meter is to improve the measurement accuracy of the meter.

[0005] To solve the above technical problem, the utility model is realized through the following solutions: An intelligent meter of the utility model includes an MCU, and a voltage and current sampling circuit electrically connected to the MCU and used for collecting voltage signals and current signals;

[0006] The voltage and current sampling circuit includes five CON interfaces, multiple resistors, multiple capacitors and a current and voltage sampling chip U7;

[0007] The CON interfaces include interface J1, interface J2, interface J3, interface J4, and interface J5;

[0008] The multiple capacitors include capacitor C59, capacitor C60, capacitor C64, capacitor C61, capacitor C62, capacitor C63 and capacitor C64;

[0009] The multiple resistors include resistor R140, resistor R141, resistor R142, resistor R143, resistor R144, resistor R145, resistor R146, resistor R147, resistor R148, and resistor R149. Among them, the resistors R140, R141, R142, and R143 are connected in series to form a first voltage reduction circuit. The first end of this first voltage reduction circuit is connected to the interface J1, and the second end of this first voltage reduction circuit is respectively connected to the first end of resistor R144 and the 5th pin VP of the current-voltage sampling chip U7. The second end of resistor R144 is connected to the interface J2 and grounded. The capacitor C59 is connected in parallel with resistor R144;

[0010] A capacitor C60 is connected between the interface J3 and the interface J4. The interface J3 is connected to the 7th pin GND of the current-voltage sampling chip U7;

[0011] The resistors R146, R147, and R148 are connected in series to form a second voltage reduction circuit. The capacitor C64 is connected in parallel with resistor R148. The first end of the second voltage reduction circuit is connected to the interface J4, and the second end of this second voltage reduction circuit is connected to the 4th pin IN1 of the current-voltage sampling chip U7;

[0012] The 4th pin IN1 of the current-voltage sampling chip U7 is connected to the 6th pin VN of the current-voltage sampling chip U7 and is connected to the 7th pin GND of the current-voltage sampling chip U7;

[0013] The interface J5 is connected to the first end of resistor R149. The second end of resistor R149 is connected to the first end of capacitor C64. The second end of capacitor C64 is connected to the 4th pin IN1 of the current-voltage sampling chip U7;

[0014] The 3rd pin IP1 of the current-voltage sampling chip U7 is connected to the circuit node between resistor R149 and capacitor C64;

[0015] The first end of the parallel connection of capacitor C61 and capacitor C62 is connected to GND. The second end of the parallel connection of capacitor C61 and capacitor C62 is connected to the 1st pin VDD of the current-voltage sampling chip U7. The 1st pin VDD of the current-voltage sampling chip U7 is connected to the power supply VCC;

[0016] The 13th pin DO-2 of the current-voltage sampling chip U7 is connected to the first end of resistor R145. The second end of resistor R145 is connected to the 10th pin SEL of the current-voltage sampling chip U7 and the first end of capacitor C63. The second end of capacitor C63 is connected to GND. The 10th pin SEL of the current-voltage sampling chip U7 is also connected to the power supply VCC.

[0017] Further, the intelligent meter further includes:

[0018] A temperature sensing module electrically connected to the MCU and used for adopting temperature signals;

[0019] A communication module electrically connected to the MCU and used for realizing data transmission between the instrument and external devices;

[0020] A digital tube display module electrically connected to the MCU and used for displaying the operation status and measurement results of the instrument;

[0021] A user input module electrically connected to the MCU and used for users to set and modify the instrument;

[0022] A memory electrically connected to the MCU and used for storing the operation parameters and historical data of the instrument.

[0023] Further, the MCU is an 8-bit single-chip microcomputer based on the 8051 core, which has flash memory and RAM and supports ISP programming and IAP programming.

[0024] Compared with the prior art, the beneficial effects of the present utility model are:

[0025] 1. The voltage and current sampling circuit of the present utility model obtains a sampled voltage value with a small difference from the actual voltage value through multiple filtering and quantization of the sampled values, with high measurement accuracy, improving the detection accuracy of the battery voltage.

[0026] 2. The voltage and current sampling circuit of the present utility model obtains a sampled voltage value with a small difference from the actual voltage value through multiple filtering and quantization of the sampled values, with high measurement accuracy, improving the detection accuracy of the battery voltage. Description of the Drawings

[0027] Figure 1 It is a schematic block diagram of an intelligent instrument of the present utility model.

[0028] Figure 2 It is a circuit diagram of the voltage and current sampling circuit of the present utility model.

[0029] Figure 3 It is a circuit diagram of the temperature detection module of the present utility model.

[0030] Figure 4 It is a circuit diagram of the display module of the present utility model.

[0031] Figure 5 It is a circuit diagram of the MCU of the present utility model.

[0032] Figure 6 It is a circuit diagram of the 485 communication module of the present utility model.

[0033] Figure 7 It is a circuit diagram of the key module of the present utility model. Specific Embodiments

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present utility model with reference to the accompanying drawings in the embodiments of the present utility model, so that the advantages and features of the present utility model can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present utility model. Obviously, the described embodiments of the present utility model are only a part of the embodiments of the present utility model, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts belong to the protection scope of the present utility model.

[0035] In addition, the technical features involved in different embodiments of the present utility model described below can be combined with each other as long as they do not conflict with each other.

[0036] Embodiment 1: The specific structure of the present utility model is as follows:

[0037] Please refer to the attached Figure 1-7 An intelligent meter of the present utility model includes an MCU, and the model of the MCU adopted in the present utility model is STC8A8K32S4. The MCU is an 8-bit single-chip microcomputer based on the 8051 core, which has flash memory and RAM, and supports ISP programming and IAP programming. The STC8A8K32S4 chip is an 8-bit single-chip microcomputer based on the 8051 core. This single-chip microcomputer has 8KB of flash memory and 256 bytes of RAM, supports ISP programming and IAP programming methods, and is suitable for various mid- to low-end embedded control systems. It has built-in various peripheral interfaces, such as UART serial ports, timers / counters, PWM outputs, etc., as well as rich I / O ports.

[0038] The intelligent meter of the present utility model further includes a voltage and current sampling circuit electrically connected to the MCU and used for collecting voltage signals and current signals. The voltage and current sampling circuit includes five CON interfaces, multiple resistors, multiple capacitors, and a current-voltage sampling chip U7.

[0039] The CON interfaces include interface J1, interface J2, interface J3, interface J4, and interface J5.

[0040] The multiple capacitors include capacitor C59, capacitor C60, capacitor C64, capacitor C61, capacitor C62, capacitor C63, and capacitor C64.

[0041] The multiple resistors include resistor R140, resistor R141, resistor R142, resistor R143, resistor R144, resistor R145, resistor R146, resistor R147, resistor R148, and resistor R149. Among them, the resistors R140, R141, R142, and R143 are connected in series to form a first step-down circuit. The first end of the first step-down circuit is connected to the interface J1, and the second end of the first step-down circuit is respectively connected to the first end of the resistor R144 and the 5th pin VP of the current-voltage sampling chip U7. The second end of the resistor R144 is connected to the interface J2 and grounded. The capacitor C59 is connected in parallel with the resistor R144. The 5th pin VP of the current-voltage sampling chip U7 is connected to a voltage sampling circuit. When the voltage sampling circuit samples the voltage, the battery voltage or the battery charging voltage V out is obtained through a voltage division circuit as V out1 , V out1 =A 1 V out (A 1 is the amplification gain, and here A 1 is generally less than 1). Taking V out1 as the input signal of the MCU, V out1 is sampled, filtered, quantized, and converted multiple times to obtain the sampled value ADC DATA , and then the reference voltage V REF is obtained. V REF= ADC REF *ADC resolution / ADC DATA , ADC REF is the internal test voltage of the ADC, which is 1.344V, and ADC resolution is the resolution of the 12-bit ADC, which is 4095. Finally, the actual voltage value V voltage is obtained: V voltage =V REF *ADC DATA / ADC resolution . Through multiple filtering and quantization of the sampled value, the difference between the sampled voltage value and the actual voltage value is very small, and the measurement accuracy is not less than 99.7%, improving the battery voltage detection accuracy.

[0042] A capacitor C60 is connected between the interface J3 and the interface J4, and the interface J3 is connected to the 7th pin GND of the current-voltage sampling chip U7.

[0043] The resistors R146, R147, and R148 are connected in series to form a second step-down circuit. The capacitor C64 is connected in parallel with the resistor R148. The first end of the second step-down circuit is connected to the interface J4, and the second end of the second step-down circuit is connected to the 4th pin IN1 of the current-voltage sampling chip U7.

[0044] The 4th pin IN1 of the current and voltage sampling chip U7 is connected to the 6th pin VN of the current and voltage sampling chip U7 and is connected to the 7th pin GND of the current and voltage sampling chip U7.

[0045] The interface J5 is connected to the first end of the resistor R149. The second end of the resistor R149 is connected to the first end of the capacitor C64. The second end of the capacitor C64 is connected to the 4th pin IN1 of the current and voltage sampling chip U7.

[0046] The 3rd pin IP1 of the current and voltage sampling chip U7 is connected to the circuit node between the resistor R149 and the capacitor C64. The circuit connected between the 3rd pin IP1 and the 4th pin IN1 of the current and voltage sampling chip U7 is the current sampling signal circuit. When the current sampling signal circuit detects the battery current, the current sensor generates a voltage signal V proportional to the current magnitude. ITEMP Then the amplifier amplifies the weak voltage signal output by the current sensor to a range suitable for the input of the ADC (P1.4) for digital processing, and obtains the voltage value V input to the ADC. IN11 ,V IN11=VITEMP* A (A is the amplifier magnification). The ADC samples, filters, quantizes, and converts V IN11 multiple times to obtain the sampled value ADC I，通过采样值ADCI to obtain the ADC reference voltage V REF and then obtains the actual voltage value V voltage : V voltage =V REF *ADC I / ADC resolution . Finally, the detected current I current is obtained, I current =V voltage / B, where B is the voltage-current ratio in the current sensor. Through multiple filtering and quantization of the sampled values, the difference between the sampled current value and the actual current value is very small, and the measurement accuracy is not less than 99.7%, improving the battery current detection accuracy. The current sampling signal circuit of the present invention can support the input of multiple signals, such as: current Hall sensors, shunts, sampling resistors, etc., and can collect the charging and discharging currents of the battery, that is, the current is positive during charging and negative during discharging.

[0047] The first end after the capacitors C61 and C62 are connected in parallel is connected to GND, and the second end after the capacitors C61 and C62 are connected in parallel is connected to the 1st pin VDD of the current and voltage sampling chip U7. The 1st pin VDD of the current and voltage sampling chip U7 is connected to the power supply VCC;

[0048] The 13th pin DO-2 of the current and voltage sampling chip U7 is connected to the first end of the resistor R145. The second end of the resistor R145 is connected to the 10th pin SEL of the current and voltage sampling chip U7 and the first end of the capacitor C63. The second end of the capacitor C63 is connected to GND, and the 10th pin SEL of the current and voltage sampling chip U7 is also connected to the power supply VCC.

[0049] The intelligent meter of the present utility model further includes:

[0050] A temperature sensing module electrically connected to the MCU and used for sampling temperature signals. The temperature sensing module is provided with a temperature sensing circuit 3;

[0051] A communication module electrically connected to the MCU and used for realizing data transmission between the meter and external devices. The communication module adopts a 485 communication module;

[0052] A digital tube display module electrically connected to the MCU and used for displaying the operation status and measurement results of the meter ( Figure 4 as shown);

[0053] A user input module electrically connected to the MCU and used for users to set and modify the meter ( Figure 7 as shown);

[0054] A memory electrically connected to the MCU and used for storing the operation parameters and historical data of the meter.

[0055] As Figure 3 shown, both ends of the resistors R17, R18, R19, and R21 in series in the temperature sensing circuit 3 are respectively connected to the P1.5 pin of the MCU ( Figure 5 the 6th pin of the MCU), the P1.6 pin of the MCU ( Figure 5 the 7th pin of the MCU). Among them, the circuit node between the resistors R18 and R19 is connected to the second end of the resistor R16. The circuit node between the resistors R17 and R18 is respectively connected to the first end of the capacitor C6 and the temperature acquisition sensor. The second end of the capacitor C6 is respectively connected to the first end of the resistor R20. The second end of the resistor R20 is connected to the circuit node between the resistors R19 and R21, and the capacitor C7 is in parallel with the resistor R20.

[0056] The temperature sensing circuit 3 is connected to the P1.5 pin of the MCU, which is a 12-bit high-precision ADC inside the single-chip microcomputer. Temperature detection of the battery is usually realized by using an NTC thermistor. The resistance value of the thermistor decreases with the increase of temperature. The voltage output terminal V OUT1 of the thermistor is connected to the ADC channel of the P1.5 pin of the MCU, and the other end is connected to the battery to form a voltage division circuit. The ADC measures V OUT1Perform multiple samplings, filterings, quantizations, and conversions to obtain the sampled value ADC TEMP , and compare the sampled value ADC TEMP with the NTC resistance table. When NTC A

[0057] As Figure 3 shown, VREF provides a stable reference source to the two-channel temperature acquisition through resistors R18 and R19. Resistor R20 is for precisely collecting the internal operating temperature of the NTC, TEMP_BT is for collecting the operating temperature of the external battery, and resistors R17, capacitor C6, resistor R21, and capacitor C7 are current-limiting resistors and filter capacitors to the ADC of the MCU.

[0058] As Figure 6 shown, Figure 6 is the circuit diagram of the 485 communication module of the present invention. TXD2 (P1.1) of the MCU, RXD2 (P1.0) of the MCU, TX (P1.1) of the MCU, and RX (P1.0) of the MCU are connected to the VIA of the digital isolator and the VIB pin of the digital isolator, and then the VOA of the digital isolator and the VOB pin of the digital isolator are connected to the RO of the 485 chip and the DO pin of the 485 chip one by one. By digitally isolating the 485 transceiver, interference during signal transmission can be effectively reduced, ensuring the stability and reliability of communication.

[0059] In summary, an intelligent instrument of the present invention can measure voltage, current, and battery temperature. The voltage and current sampling circuit of the present invention obtains a sampled voltage value with a small difference from the actual voltage value and a sampled current value with a small difference from the actual current value through multiple filterings and quantizations of the sampled value, thereby improving the measurement accuracy and the detection accuracy of voltage and current.

[0060] The temperature sensing module of the present invention improves the detection accuracy of battery temperature through multiple filterings and quantizations of the sampled value and by using the look-up table method for the final temperature conversion. Through the user input module, the user inputs corresponding parameters to modify and set the working mode, communication address, operation mode, CT ratio, baud rate, user password, etc. of the instrument to meet the needs of different users.

[0061] The above is only the preferred embodiment of the present invention, and it does not limit the patent scope of the present invention accordingly. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied to other related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. A smart meter, comprising an MCU, characterized in that: It also includes a voltage and current sampling circuit electrically connected to the MCU and used to collect voltage signals and current signals; The voltage and current sampling circuit includes five CON interfaces, multiple resistors, multiple capacitors and a current and voltage sampling chip U7; The CON interface includes interface J1, interface J2, interface J3, interface J4, and interface J5; The plurality of capacitors include capacitor C59, capacitor C60, capacitor C64, capacitor C61, capacitor C62, capacitor C63 and capacitor C64; The multiple resistors include resistor R140, resistor R141, resistor R142, resistor R143, resistor R144, resistor R145, resistor R146, resistor R147, resistor R148, and resistor R149, wherein the resistor R140, resistor R141, resistor R142, and resistor R143 are connected in series to form a first step-down circuit, a first end of the first step-down circuit is connected to the interface J1, a second end of the first step-down circuit is respectively connected to a first end of the resistor R144 and pin 5 VP of the current and voltage sampling chip U7, a second end of the resistor R144 is connected to the interface J2 and grounded, and the capacitor C59 is connected in parallel with the resistor R144; A capacitor C60 is connected between the interface J3 and the interface J4, and the interface J3 is connected to the 7-pin GND of the current and voltage sampling chip U7; The resistors R146, R147 and R148 are connected in series to form a second step-down circuit, the capacitor C64 and the resistor R148 are connected in parallel, the first end of the second step-down circuit is connected to the interface J4, and the second end of the second step-down circuit is connected to the 4th pin IN1 of the current and voltage sampling chip U7; The 4th pin IN1 of the current and voltage sampling chip U7 is connected to the 6th pin VN of the current and voltage sampling chip U7 and connected to the 7th pin GND of the current and voltage sampling chip U7; The interface J5 is connected to the first end of the resistor R149, the second end of the resistor R149 is connected to the first end of the capacitor C64, and the second end of the capacitor C64 is connected to the 4th pin IN1 of the current and voltage sampling chip U7; Pin 3 IP1 of the current and voltage sampling chip U7 is connected to the circuit node between the resistor R149 and the capacitor C64; The first end of the capacitor C61 and the capacitor C62 connected in parallel is connected to the GND ground, and the second end of the capacitor C61 and the capacitor C62 connected in parallel is connected to the pin 1 VDD of the current and voltage sampling chip U7, and the pin 1 VDD of the current and voltage sampling chip U7 is connected to the power supply VCC; Pin 13 DO-2 of the current and voltage sampling chip U7 is connected to the first end of the resistor R145, the second end of the resistor R145 is connected to pin 10 SEL of the current and voltage sampling chip U7 and the first end of the capacitor C63, the second end of the capacitor C63 is connected to the GND ground, and pin 10 SEL of the current and voltage sampling chip U7 is also connected to the power supply VCC.

2. The smart meter according to claim 1, characterized in that: The smart meter also includes: A temperature sensing module electrically connected to the MCU and used to use a temperature signal; A communication module electrically connected to the MCU and used to implement data transmission between the instrument and an external device; A digital tube display module electrically connected to the MCU and used to display the operating status and measurement results of the instrument; A user input module electrically connected to the MCU and used for the user to set and modify the instrument; A memory electrically connected to the MCU and used to store operating parameters and historical data of the instrument.

3. The smart meter according to claim 1, characterized in that: The MCU is an 8-bit single-chip microcomputer based on the 8051 core, has flash memory and RAM, and supports ISP programming and IAP programming.

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