WO2008047428A1

WO2008047428A1 - Electronic watthour meter

Info

Publication number: WO2008047428A1
Application number: PCT/JP2006/320773
Authority: WO
Inventors: Kazunori Go; Noriko Yoshikawa
Original assignee: Osaki Electric Co., Ltd.
Priority date: 2006-10-18
Filing date: 2006-10-18
Publication date: 2008-04-24
Also published as: CN101542298A; SK50302009A3; CN101542298B; JP4896150B2; JPWO2008047428A1

Abstract

A conventional electronic watthour meter cannot achieve sufficient miniaturization and cost reduction. In the inventive electronic watthour meter, the detection outputs of a voltage sensor (13) and a current sensor (14) and the reference potential of the current sensor (14) are amplified differentially by a differential amplifier (23) and then A/D converted by an A/D converter (24) through ΔΣ modulation under control of a software processing section (25). The A/D converted reference potential is then removed from the A/D converted detection outputs of the voltage sensor (13) and the current sensor (14), respectively, thus calculating the electric energy used by a measurement object. A correction processing for the absolute error of the electric energy used in performed by gain regulation processing only. The calculated electric energy used is displayed at a liquid crystal display section (6) under control of a liquid crystal driver (5), and delivered, as a pulse signal, to an LED (15).

Description

Electronic energy meter

Technical field

[0001] The present invention relates to an electronic watt-hour meter that calculates the power consumption of a measurement target based on a digital signal converted by an A / D (analog Z digital) conversion means. Background art

[0002] The measurement accuracy guarantee range of electronic watt-hour meters is generally wide, with the voltage being about ± 10% of the rated value, while the current is 6 to 1Z40 times the rated value. . Therefore, 1/240 X 1% = 1/24, 000, that is, a resolution of 1 / 24,000 is required to measure the current within the guaranteed accuracy range with an accuracy of ± 1%. Therefore, the A / D converter requires about 15-bit resolution. However, AZD converters built in microcomputers (hereinafter referred to as microcomputers) that are widely used as arithmetic processing units generally have a resolution of 10 bits and at most 12 bits. An electronic watt-hour meter using a general-purpose microcomputer will lack resolution. For this reason, conventional electronic watt-hour meters amplify the current to be measured with an amplification factor according to the magnitude of the AZD converter with a built-in microcomputer. For example, in the conventional electronic watt-hour meter disclosed in Patent Document 1, the amplification factor is automatically adjusted based on the level of the rectified and averaged measurement current and the rated level of the amplification means, and the amplification means Then, the output of the current sensor is amplified based on the adjusted amplification factor. There is also a conventional electronic watt-hour meter in which a plurality of amplifiers are provided in multiple stages as shown in FIG.

This electronic watt-hour meter is configured to include a general-purpose microcomputer 1. The microcomputer 1 is provided with a successive approximation type AZD converter 2 and a software processing unit 3 that performs an operation based on the digital data converted by the A / D converter 2. The AZD converter 2 is connected via a selection switch 7 to amplifiers 9, 10, 11 and 12 that amplify the input signal five times in four stages. A voltage sensor 13 and a current sensor 14 are connected to the amplifier 9 at the first stage via a selection switch 8. Selection switch 8 has terminals 8a, 8b, 8 The connection is selectively switched to one of the terminals in c. When switched to terminal 8a, the voltage signal from voltage sensor 13 is selected.When switched to terminal 8b, the current sensor has 14 power signals.When switched to terminal 8c, the reference potential of the detection output of each sensor 13, 14 is selected. Is measured. When the selection switch 7 selects the number of stages of amplifiers used to amplify the current signal detected by the current sensor 14, the selection switch 7 is selectively connected to one of the terminals 7a, 7b, 7c, 7d. Can be switched. When switched to terminal 7a, one-stage amplifier 9 is selected and the input signal is amplified five times. When switched to terminal 7b, two-stage amplifiers 9 and 10 are selected.When switched to terminal 7c, three-stage amplifiers 9 to 11 are selected, and when switched to terminal 7d, four-stage amplifiers 9 to 12 are selected and the input signal is selected. 5 ^twice, respectively, 5 ^three times and amplified in 5 ^four times.

[0004] The software processing unit 3 is connected to an LED (light emitting diode) 15 and a liquid crystal driver 5 for controlling the display of the liquid crystal display unit 6. The software processing unit 3 calculates power by multiplying the voltage value and current value converted into digital data by the AZD converter 2 and cumulatively adds this power to calculate the power amount. The calculated power amount is displayed on the liquid crystal display unit 6, and based on the calculated power amount, a nors signal proportional to the used power amount is generated and the LED 15 blinks.

FIG. 2 is a flowchart showing an outline of the calculation process of the electric energy in the software processing unit 3 described above.

[0006] In this power amount calculation process, first, a current dummy AZD conversion process is performed (see FIG. 2, step (hereinafter referred to as S) 1). In this process, the digital data of the current value that is first converted by the AZD converter 2 after the selection switch 8 is switched to the terminal 8b is discarded to improve the current measurement accuracy. Next, a current pre-AZD conversion process is performed (S2). In this process, the measuring process for determining the optimum number of stages of the amplifiers used to amplify the current signal is also performed. Next, current production AZD conversion processing is performed (S3). In this process, the amplifier of the number of stages determined in S2 is selected by switching the selection switch 7, the detection signal output from the current sensor 14 is amplified by the selected amplifier, and then converted into digital data by the AZD converter 2. Is performed. Next, a voltage dummy AZD conversion process is performed (S4). In this process, the power of S1 Similar to the current dummy AZD conversion process, the selection switch 8 is switched to the terminal 8a and is discarded to increase the digital data power of the voltage value first converted by the AZD converter 2 to increase the voltage measurement accuracy. Next, voltage production AZD conversion processing is performed (S5). In this process, the selection switch 7 is switched to select the one-stage amplifier 9, and the amplifier 9 amplifies the detection signal output from the voltage sensor 13 and then converts it to digital data by the AZD converter 2. Done.

[0007] Next, the offset obtained in the process of S13 described later is removed from the current value obtained in S3 and the voltage value obtained in S5, and power (instantaneous power) is calculated (S6 ). The offset is the voltage output from the AZD converter 2 when the input of each amplifier 9 to 12 is zero, and the power calculation formula in S6 is expressed as (Voltage value offset) X (Current value-Offset). It is.

[0008] Next, a gain adjustment process (S7) is performed. That is, the gain adjustment is performed by multiplying the power calculation result obtained in S6 by a predetermined number according to the amplification factor of the amplifier having the number of stages determined in S2. Subsequently, gain error correction processing is performed (S8). In other words, a process for removing an error in the power calculation result due to an error of the internal resistance that determines the amplification factor in each of the amplifiers 9 to 12 is performed. Next, processing for calculating the amount of power by accumulating (integrating) the power data obtained by the processing of S6 to S8 is performed (S9). Based on the amount of power calculated in this power accumulation process, the pulse signal is output to the pulse signal power LED 15 proportional to the amount of power used (S10), and the calculated amount of power is displayed on the liquid crystal display unit 6.

Next, an offset dummy AZD conversion process is performed (Sll). In this process, the offset data first obtained by the A / D converter 2 when the selection switch 8 is switched to the terminal 8c is discarded to increase the offset measurement accuracy of each amplifier 9-12. Next, an offset production AZD conversion process is performed (S12). In this process, the offset of each stage of the amplifiers 9 to 12 is measured in turn by switching the selection switch 7, and the measured offset is converted into digital data by the AZD converter 2. The offset is measured several times, and the average value of the offset is calculated based on the measurement result (S13). Based on the offset obtained in this way, the next power calculation process (S6) is performed as described above. Patent Document 1: Japanese Patent Application Laid-Open No. 2004-177228 (paragraphs [0025] to [0031])

Disclosure of the invention

However, since the conventional electronic watt-hour meter shown in FIG. 1 has a configuration in which the amplifiers 9 to 12 are connected in multiple stages, the current pre-AZD conversion process of S2 optimizes the amplifier. Determine the number of stages, measure the offset of the amplifiers 9 to 12 at each stage by the offset dummy AZD conversion process of S11, or use the offset values of several times measured by the offset AZD conversion process of S 12 to amplifiers 9 to 12 Must be stored for each stage. Further, it is necessary to adjust the gain for each of the amplifiers 9 to 12 in each stage by the gain adjustment process of S7, or to correct the resistance error for the amplifiers 9 to 12 of each stage by the gain error correction process of S8. Therefore, the conventional electronic watt-hour meter shown in FIG. 1 requires a lot of processing, increases the scale of the software, and requires a large data storage capacity. Therefore, a microcomputer with a large memory size is required. It becomes.

[0011] Further, as the amount of processing increases, the operating clock frequency of the microcomputer 1 must be increased to improve the processing speed, and the current consumption of the microcomputer 1 increases. In addition, since the amplifiers 9 to 12 are connected in multiple stages, the analog circuit portion is increased in size and the board size is increased, and the current consumption in the analog circuit portion is increased. Therefore, the conventional electronic watt-hour meter shown in Fig. 1 cannot use a small power source. As the current consumption increases, the fluctuation range of the output voltage of the power supply also increases, so the conventional electronic energy meter shown in Fig. 1 requires circuit components to stabilize the output voltage of the power supply. Incurs an increase in cost. In addition, when the operation clock frequency of the microcomputer 1 is increased, the influence of the radiated field intensity due to electromagnetic noise generated from the microcomputer 1 increases. For this reason, the conventional electronic energy meter shown in Fig. 1 requires measures such as electromagnetic shielding to improve noise resistance (EMC).

V, but it costs too much.

As a result, the conventional electronic watt-hour meter shown in FIG. 1 has not been able to sufficiently reduce the size and cost of the product.

[0013] The present invention has been made to solve such a problem,

A voltage sensor for detecting a voltage to be measured; and A current sensor for detecting a current to be measured;

A selection switch that selectively selects and outputs either the detection output of the voltage sensor or current sensor or the reference potential of the detection output; and

Amplifying means for amplifying at least the detection output of the current sensor;

The detection output of the voltage sensor and current sensor output by the selection switch, the AZD conversion means for converting the reference potential into an analog signal force digital signal, and the use of the measurement target based on the digital signal converted by the AZD conversion means An arithmetic processing unit with a built-in arithmetic means for calculating electric energy,

In an electronic watt-hour meter with

The amplification means is composed of differential amplification means for differentially amplifying the input signal,

AZD conversion means converts the input signal to analog signal power digital signal by Δ∑ modulation,

The computing means is characterized by calculating the power consumption of the measurement target by respectively removing the reference potential converted by the AZD conversion means from the detection output of the voltage sensor and current sensor converted by the AZD conversion means. To do.

According to this configuration, the detection output of the voltage sensor, the detection output of the current sensor, and the reference potential of these detection outputs are converted from an analog signal to a digital signal by Δ∑ modulation in the AZD conversion means. The calculation means removes the reference potential converted into the digital signal from each detection output of the voltage sensor and the current sensor converted into the digital signal, so that the differential amplification means from the detection output of the voltage sensor and the current sensor. And the offset of the AZD conversion means is removed. The power consumption of the measurement target is calculated using the detection outputs of the voltage sensor and current sensor from which the offset has been removed.

[0015] Analog signal power in AZD conversion means Conversion to a digital signal is performed with high resolution by fine sampling by oversampling at the time of ΔΣ modulation, so that it is like a conventional electronic watt-hour meter. Therefore, it is not necessary to configure the amplification means in multiple stages to supplement the resolution of the AZD conversion means. For this reason, the detection output of a current sensor that requires a wide range of guaranteed measurement accuracy is not required to be configured in multiple stages. Therefore, it becomes possible to measure with high accuracy. In addition, since it is not necessary to configure the amplification means in multiple stages, it is possible to determine the optimum number of amplifiers, measure the offsets of the amplifiers in each stage, and measure the number of times measured, as in conventional electronic watt-hour meters. It is not necessary to store the offset value for each stage of the amplifier. Furthermore, there is no need to adjust the gain for each stage of the amplifier by the gain adjustment process, or to correct the resistance error of the amplifier at each stage by the gain error correction process. Accordingly, as the amount of processing is reduced, the size of software is reduced and the data storage capacity is also reduced, so that the memory size required for the arithmetic processing unit can be reduced. Further, since the amount of processing is reduced, the operation clock frequency of the arithmetic processing unit can be kept low, and the current consumption can be reduced. In addition, since it is not necessary to configure the amplification means in multiple stages, the size of the analog circuit portion can be reduced, the board size can be reduced, and the current consumption in the analog circuit portion can also be reduced. Therefore, a small power source can be used as the power source of the electronic watt-hour meter. In addition, since the current consumption can be reduced and the fluctuation range of the output voltage can be reduced, there is no need for circuit components to stabilize the output voltage of the power supply, such as a conventional electronic watt-hour meter. , Can reduce costs. In addition, since the operation clock frequency of the arithmetic processing unit can be kept low, the influence of the radiation electric field intensity caused by the electromagnetic noise generated from the arithmetic processing unit can be reduced, and the cost for countermeasures against noise resistance can be suppressed. . As a result, the electronic watt-hour meter according to the present invention can sufficiently reduce the size and cost of the product.

[0016] Further, since the differential amplifying means is used as the amplifying means, it is possible to apply a bias voltage to the detection signal output from the amplifying means with at least a current sensor. For this reason, even if the detection signal of the current sensor fluctuates in the negative range, it is converted into a signal that fluctuates in the positive range by applying a bias voltage, and the detection signal of the current sensor is amplified by the amplification means. It can be amplified and converted to a digital signal by AZD conversion means. Further, since the differential amplifying means is used as the amplifying means, even if noise is applied to the input terminal, it is canceled and the influence of the noise can be eliminated, so that the input signal can be amplified with high accuracy.

[0017] Further, according to the present invention, the calculation means reduces the absolute error of the power consumption by multiplying the power consumption by a predetermined value or by adjusting the threshold value of the pulse output according to the power consumption. correction It is characterized by doing.

[0018] According to this configuration, the absolute error of the calculated power consumption is corrected by multiplying the calculated power consumption by a predetermined amount according to the amplification factor of the amplifying unit. In addition, by adjusting the threshold output threshold value corresponding to the calculated power consumption, the pulse output timing is adjusted so that the pulse is output according to the actual power consumption. Therefore, the absolute error of the calculated power consumption is corrected. This makes it possible to correct the absolute error of the calculated power consumption by multiplying it by a predetermined amount or by adjusting the pulse output threshold value, which frees the design of an electronic watt-hour meter. The degree increases.

[0019] Further, the present invention provides a method in which the reference potential converted by the AZD conversion means is converted into a current sensor when the calculation means makes the reference potential of the detection output of the current sensor different from the reference potential of the detection output of the voltage sensor. It is characterized in that it is removed from either the detection output of the sensor or the detection output of the voltage sensor.

[0020] According to this configuration, the power value calculated from the detection output of each sensor is a force that is a DC component force. The amplification means that appears in the detection output of the force without the removal of the reference potential

The offset of the AZD conversion means becomes an AC component that appears evenly in the positive and negative voltages, and is removed by the integration process in the process of integrating the amount of power used. Accordingly, the reference potential converted by the AZD conversion means is removed only for either the current sensor detection output or the voltage sensor detection output, and the calculated power consumption power amplification means and AZD The offset of the conversion means can be removed. This simplifies the process of calculating the power consumption of the measurement target, further reduces the memory size of the arithmetic processing unit as the software scale becomes smaller, and further lowers the operating clock frequency. Thus, the current consumption can be further reduced.

[0021] Further, according to the present invention, the arithmetic processing unit switches the selection switch immediately after completion of the conversion by the AZD conversion unit with respect to any of the detection output of the voltage sensor and the current sensor and the reference potential of the detection output. After the next selection is made, time is taken! / And the next conversion by the AZ D conversion means is performed.

[0022] According to this configuration, immediately after the conversion by the AZD conversion means with respect to any of the detection output of the voltage sensor and the current sensor and the reference potential of the detection output is completed, The selection switch is switched, and after that, the signal input by the switched selection switch is converted by the AZD conversion means. For this reason, each conversion by the AZD conversion means is started in a state in which the signal input to the AZD conversion means is stable after a certain amount of time has passed since the selection switch was switched. Therefore, the cause of the measurement error is removed, and each conversion by the AZD conversion means is performed accurately.

[0023] Further, the present invention provides that the arithmetic processing device stops the operation of the AZD conversion unit immediately after the completion of each conversion by the AZD conversion unit, and prepares to start the next conversion by the AZD conversion unit. Features.

[0024] According to this configuration, when each conversion of the detection output of the voltage sensor and the current sensor and the reference potential of the detection output is completed, the operation of the AZD conversion unit stops immediately, and the next conversion by the AZD conversion unit is performed. Preparation for starting is performed. For this reason, each conversion by the AZD conversion means is quickly executed when the AZD conversion means is stopped. Therefore, when converting continuously without stopping the operation of the AZD conversion means, the start of the next conversion is delayed by waiting for the completion of the conversion operation before the AZD conversion means at the start of conversion. Each conversion cannot be started at a constant cycle, but according to this configuration, it can be performed at a constant cycle. As a result, the measurement timing of the voltage and current to be measured and the measurement timing of the offset are performed at regular intervals, and the calculation process of the power consumption of the measurement target can be performed accurately.

[0025] Further, the present invention is characterized in that the reference voltage of the AZD conversion means is set to the same potential as the operating voltage of the arithmetic processing unit.

[0026] According to this configuration, the power source that supplies the reference voltage to the AZD conversion unit and the power source that supplies the operating voltage to the arithmetic processing unit can be shared. This eliminates the need for a separate power supply for supplying the reference voltage to the A / D conversion means, further reducing the size and cost of the product.

[0027] According to the present invention, as described above, it is possible to provide an electronic watt-hour meter that can sufficiently reduce the size and cost of a product.

Brief Description of Drawings FIG. 1 is a block diagram showing an outline of a circuit configuration of a conventional electronic watt-hour meter.

FIG. 2 is a flowchart showing an outline of calculation processing of electric energy in the electronic watt-hour meter shown in FIG.

FIG. 3 is a block diagram showing an outline of a circuit configuration of an electronic watt-hour meter according to one embodiment of the present invention.

4 is a partial detailed circuit diagram of the block diagram shown in FIG.

FIG. 5 is a flowchart showing an outline of calculation processing of electric energy in the electronic watt-hour meter shown in FIG.

6 is a flowchart showing details of the electric energy calculation process shown in FIG.

FIG. 7 is a block diagram showing an outline of a circuit configuration of an electronic watt-hour meter according to a first modification of the present invention.

FIG. 8 is a block diagram showing an outline of a circuit configuration of an electronic watt-hour meter according to a second modification of the present invention.

FIG. 9 is a block diagram showing an outline of a circuit configuration of an electronic watt-hour meter according to a third modification of the present invention.

[Fig. 10] Fig. 10 is a diagram showing a relationship between a cumulative amount of used electric power and a generated pulse signal in an electronic watt-hour meter according to a fourth modification of the present invention.

FIG. 11 is an internal circuit diagram of an AZD converter used in an electronic watt-hour meter according to a fifth modification of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, the best mode for carrying out the present invention will be described.

FIG. 3 is a block diagram showing an outline of the circuit configuration of the single-phase two-wire electronic watt-hour meter according to the present embodiment. FIG. 4 is a partial detailed circuit diagram of the block diagram shown in FIG. In FIG. 3 and FIG. 4, the same or corresponding parts as in FIG.

The electronic watt-hour meter according to the present embodiment includes a voltage sensor 13, a current sensor 14, a general-purpose microcomputer 21, and a liquid crystal display unit 6. The microcomputer 21 that constitutes the arithmetic processing unit includes a selection switch 22, a differential amplifier 23, an AZD converter 24, and software processing. It includes a logic unit 25, a liquid crystal driver 5, and an LED 15. The circuit ground (GND) is connected to the reference potential V of 0 [V].

ss

[0032] The voltage sensor 13 is composed of a voltage dividing circuit that divides the voltage V'sin cot input between the power supply terminals PO and P1 by the resistors 13a, 13b, and 13c, and the divided voltage that appears across the resistor 13c. The voltage E 'sin cot is detected and output as the voltage to be measured. Signal to which resistor 13c is connected

V

The ground is a bias voltage that is 1Z2 of the operating voltage V (3.6 [V]) of microcomputer 21.

DD

V (1.8 [V]) is set to the potential applied to the reference potential V as shown in Fig.4. Electric

COM SS

The current sensor 14 is composed of a shunt resistor 14a, and the voltage E · sin ωt that appears across the shunt resistor 14a due to the load current I · sin ωt flowing between the load terminals IS and 1L is measured.

I

Detect and output as current to be measured. The power supply terminal P1 and load terminal 1S are connected to 0 [V], which is the same as the reference potential V of the microcomputer 21. This 0 [V] is detected by the current sensor 14.

SS

This is the reference potential of force. Thus, in this embodiment, the reference potential of the detection output of the current sensor 14 and the reference potential of the detection output of the voltage sensor 13 are set to 0 [V] and 1.8 [V], respectively, and are different. .

[0033] The selection switch 22 is selectively switched to one of the terminals 22a, 22b, and 22c. When switched to terminal 22a, the detection output of voltage sensor 13 is selected, when switched to terminal 22b, the detection output of current sensor 14 is selected, and when switched to terminal 22c, the reference potential of current sensor 14 is selected. Therefore, the selection switch 22 selects and outputs either the detection output of the voltage sensor 13 or the current sensor 14 or the reference potential of this detection output.

The differential amplifier 23 is connected to the sensors 13 and 14 via the selection switch 22 and outputs the amplified output to the AZD converter 24. In the differential amplifier 23 and AZD converter 24, the bias voltage V (1.8 [V]) generated by the power supply 26 is circuit ground (0 [V]).

COM

The potential added to is the reference potential, and the operating voltage V (3.

DD

6 [V]) is supplied to operate.

As shown in FIG. 4, the inverting input terminal (−) of the differential amplifier 23 is connected to the output terminal of the selection switch 22 via the resistor 23a, and each sensor selected by the selection switch 22 is connected. The detection output from 13 and 14 and its reference potential are input. Non-inverting input terminal (+) Is connected to the reference potential of 0 [V] of the current sensor 14 via the resistor 23b and to the power source 26 via the resistor 23c. Further, a resistor 23d is provided between the inverting input terminal (one) and the output terminal of the differential amplifier 23 to apply negative feedback. The differential amplifier 23 constitutes an amplifying means for amplifying at least the detection output of the current sensor 14 selected by the selection switch 22, and is input to the inverting input terminal (one) and the non-inverting input terminal (+). It constitutes differential amplification means for differentially amplifying the input signal.

An AZD converter 24 is connected to the output terminal of the differential amplifier 23. The microcomputer 21 switches the selection switch 22 at regular time intervals, and performs conversion of the detection output of the voltage sensor 13 and the current sensor 14 and the reference potential of the detection output to the AZD comparator 24 at regular time intervals. Make it. The AZD converter 24 refers to the reference voltage V and converts the signal input from the differential amplifier 23 into analog signal power by ΔΔ modulation.

ref

Convert to digital signal. The AZD converter 24 constitutes AZD conversion means for converting the detection output of the voltage sensor 13 and the current sensor 14 and the reference potential of the current sensor 14 into an analog signal and a digital signal by Δ modulation.

A software processing unit 25 is connected to the output side of the AZD converter 24. Connected to the software processing unit 25 are an LED 15 that outputs a pulse signal proportional to the amount of power used, and a liquid crystal driver 5 that controls the display of the liquid crystal display unit 6. The software processing unit 25 calculates the power by multiplying the detection output of the voltage sensor 13 and the detection output of the current sensor 14 converted into a digital signal by the AZD converter 24, accumulates the calculated power, and applies the result. Calculate the power consumption to be measured. The calculated power consumption is displayed on the liquid crystal display unit 6 under the control of the liquid crystal driver 5. In addition, the software processing unit 25 generates a pulse signal proportional to the calculated power consumption. When this generated pulse signal is output, current flows through LED 15 and LED 15 emits light. The light emitted from the LED 15 is detected by a light receiving sensor, and a pulse signal proportional to the amount of power used is used to test the accuracy of power measurement. The software processing unit 25 constitutes a calculation unit that calculates the power consumption of the measurement target based on the digital signal converted by the AZD converter 24.

FIG. 5 is a flowchart showing an outline of the calculation processing of the electric energy used by the software processing unit 25 described above. It is a chart.

[0039] In the calculation process of power consumption in the present embodiment, first, a current AZD conversion process is performed (see FIG. 5, S21). In this process, the selection switch 22 is switched to the terminal 22b, and the analog signal force is also converted into a digital signal by the Δ 出力 modulation of the detection output force A / D converter 24 of the current sensor 14 amplified by the differential amplifier 23. The Subsequently, voltage A / D conversion processing is performed (S22). In this process, the selection switch 22 is switched to the terminal 22a, and the detection output of the voltage sensor 13 amplified by the differential amplifier 23 is also converted into a digital signal by the Δ∑ modulation of the AZD converter 24.

[0040] Next, the offset converted into the digital signal in the process of S27 described later is removed from the current value converted into the digital signal in S21 and the voltage value converted into the digital signal in S22. Current value and voltage value power with offset removed are calculated (S23). The offset is a voltage that appears at the output of the AZD converter 24 when the input of the differential amplifier 23 is zero, and the power calculation formula in the processing of S23 is expressed as (voltage value offset) X (current value offset).

Next, gain adjustment processing is performed (S24). In this process, the absolute error of the instantaneous power is corrected by multiplying the power data calculated in S23 by a predetermined factor according to the amplification factor of the differential amplifier 23. Next, the power data obtained by the processing of S23 and S24 is cumulatively added to calculate the power consumption (S25), and the calculated power consumption is displayed on the liquid crystal display unit 6. In addition, a pulse signal proportional to the calculated power consumption is generated, and the generated pulse signal is output to the LED 15 (S26).

Next, an offset AZD conversion process is performed (S27). In this process, the selection switch 22 is switched to the terminal 22c, and a reference potential of 0 [V] is input to the differential amplifier 23 for differential amplification. Then, the differentially amplified reference potential is converted into a digital signal by Δ∑ modulation of the AZD converter 24, and the offset of the differential amplifier 23 and the AZD converter 24 is calculated. In the next power calculation process of S23, the offset obtained by the offset AZD conversion process of S27 is removed from the voltage value and the current value as described above, and the power is calculated. FIG. 6 is a flowchart showing details of the above-described calculation process of the power consumption. The calculation process of the power consumption is performed as a timer interrupt process of the microcomputer 21.

[0044] The time measured by the timer that measures the interrupt timing of the timer interrupt processing is T (= 500 [^ ₅ ])

SS

When the value reaches, timer interrupt processing is started. In this timer interruption process, the microcomputer 21 first determines whether or not the T flag is set (see FIG. 6, S31). T hula

S2 S2 is set in S39 as described later while the voltage AZD conversion process (see FIG. 5, S22) is performed. If this determination is "No", then whether the V medium flag is set

OFF

In other words, it is determined whether or not the offset of the differential amplifier 23 and the AZD converter 24 is being measured (S32). V middle flag is offset AZD conversion processing (Fig. 5,

OFF

During S45), it is set at S45 as described later. If offset AZD conversion processing has not been performed and the determination of S32 is "No", microcomputer 21 sets the time of T (= 93 3]) to the timer (S33) and starts measuring time T Let This time T

While SI SI S1 is being measured, the following series of processing up to S39 is performed. Also, due to the timer set in S33, after the time T has elapsed, the next timer interrupt is generated and the voltage in S41

S1

Δ∑AZD conversion starts. Next, the microcomputer 21 starts current AZD conversion processing (see FIG. 5, S21) (S34). At this time, the selection switch 22 has already been switched to the terminal 22b for outputting the detection output of the current sensor 14 to the AZD converter 24 in the process of S56 described later. Next, the microcomputer 21 determines whether or not the current AZD conversion process started in S 34 is completed (S 35). When this determination is “Yes”, the operation of the AZD converter 24 is immediately stopped. (S36). Then, the selection switch 22 is switched to the terminal 22a to set the detection output of the voltage sensor 13 to be input to the differential amplifier 23 (S37), and preparation for starting the next voltage Δ∑AZD conversion (see S41). To do.

Next, an offset value (V value) that has already been converted into a digital signal in S55 described later from the detection output value (AD value) of the current sensor 14 converted into a digital signal in the processes of S34 and S35. The removed value (current value—offset) is used as the current value for power calculation.

OFF

Set to the work data storage area (not shown) of RAM (Random Access' Memory) built in computer 21 (S38). Next, the microcomputer 21 sets the T flag (S39) and timer allocation.

S2

Finish the process. [0046] If the T flag is set and the determination in S31 is "Yes", the microcomputer 21

S2

Set the time of T (= T — Τ = 500—93 = 407 [5]) to the timer (S40).

S2 SS S1

Start measuring time T. While the time T is being measured, the following S49

S2 S2

A series of processes up to are performed. Also, after the time T has elapsed, the timer set in S40

S2

Then, the next timer interrupt is generated and the V Δ∑AZD conversion of S52 is started. Next, Maiko

OFF

21 starts voltage AZD conversion processing (see FIG. 5, S22) (S41). At this time, the selection switch 22 has already been switched to the terminal 22a to which the detection output of the voltage sensor 13 is output to the AZD converter 24 in the process of S37. Next, the microcomputer 21 determines whether or not the voltage AZD conversion process started in S41 is completed (S42), and when this determination is “Yes”, the operation of the AZD converter 24 is immediately stopped ( S43) Then, the selection switch 22 is switched to the terminal 22c so that the reference potential of the current sensor 14 is input to the differential amplifier 23 (S44), and the V medium flag is set (S45). V Δ ΣΑ / D conversion (

OFF OFF

Prepare to start (see S52).

[0047] Next, an offset value (V value) that has already been converted into a digital signal in S55, which will be described later, from the detection output value (AD value) of the voltage sensor 13 converted into a digital signal in the processing of S41 and S42. The removed value (voltage value—offset) is

OFF

It is set in the work data storage area (not shown) of the RAM built in the computer 21 (S46). Next, the T flag set in S39 is cleared (S47), and then the work data is stored in S38.

S2

The power value is calculated by multiplying the current value set in the area by the voltage value set in the work data storage area in S46 (S48). The power data calculated in S48 is subjected to the above-described gain adjustment processing (see Fig. 5 and S24) and power accumulation processing (see Fig. 5 and S25) to calculate the amount of power used and Absolute error is corrected. Next, based on the calculated power consumption, a pulse signal proportional to the power consumption is generated (S49), and the timer interrupt process is terminated. The generated pulse signal is output to the LED 15 as described above (see FIG. 5, S26).

[0048] If the V medium flag is set and the determination of S32 is "Yes", the microcomputer 21

OFF

Sets the time of T (= 500 [3]) to the timer (S51) and starts measuring time T

SS SS

. While this time T is being measured, the following series of processing up to S57 is performed. Is called. Also, the next timer interrupt is generated after the time T has elapsed, due to the timer set in S51.

SS

S34 current Δ∑AZD conversion starts. Next, the microcomputer 21 starts offset AZD conversion processing (see FIG. 5, S27) (S52). At this time, the selection switch 22 has already been switched to the terminal 22c for outputting the reference potential of the current sensor 14 to the AZD converter 24 in the process of S44. Next, the microcomputer 21 determines whether or not the offset AZD conversion process started in S52 is complete (S53). When this determination is “Yes”, the operation of the AZD comparator 24 is immediately stopped. Next, the offset value (V value) converted into a digital signal by the processing of S52 and S53 is used to operate the RAM built in the microcomputer 21.

OFF

Set in the data storage area (S55). Then, the selection switch 22 is switched to the terminal 22b so that the detection output of the current sensor 14 is input to the differential amplifier 23 (S56), and preparation for starting the next current Δ∑AZD conversion (see S34) is made. Do. Next, the V medium flag set in S45 is cleared (S57), and the timer interrupt processing ends.

OFF

[0049] According to the electronic watt-hour meter of the present embodiment, as described above, the detection output of the voltage sensor 13, the detection output of the current sensor 14, and the reference potential of these detection outputs are the same in the AZD converter 24. Analog signal force is converted into a digital signal by Δ∑ modulation (see Fig. 5, S21, S22, S27, Fig. 6, S34, S41, S52). Then, the reference potential converted into the digital signal is removed from the detection outputs of the voltage sensor 13 and the current sensor 14 converted into the digital signal by the calculation in the software processing unit 25 (FIG. 6). , S38, and S46), the offset of the differential amplifier 23 and the AZD converter 24 is also removed from the detected output forces of the voltage sensor 13 and the current sensor 14. The amount of power used for the measurement target is calculated using the detection outputs of the voltage sensor 13 and the current sensor 14 from which the offset has been removed (see FIGS. 5, S23, S25, and FIGS. 6, S48).

[0050] Analog signal power in the AZD converter 24 Conversion to digital signals is performed with high resolution by oversampling by oversampling at the time of ΔΣ modulation, so that it is like a conventional electronic watt-hour meter. In addition, it is not necessary to configure the amplification means in multiple stages in order to supplement the resolution of the AZD converter 24. For this reason, the detection output of the current sensor 14 requiring a wide range of measurement accuracy guarantee can be measured with high accuracy over a wide range without configuring the amplification means in multiple stages. Also, the amplification means is multistage Since there is no need to configure, it is possible to determine the optimum number of amplifier stages, measure the offset of the amplifier at each stage, and measure the measured offset value for the amplifier like a conventional electronic watt-hour meter. There is no need to store the data in RAM for each stage. Furthermore, it is not necessary to adjust the gain for each stage of the amplifier by the gain adjustment process, or to correct the resistance error for the amplifier of each stage by the gain error correction process. Therefore, as the amount of processing decreases, the size of the software in the software processing unit 25 decreases, and the data storage capacity of the RAM built into the microcomputer 21 also decreases, so the memory size of RAM required for the microcomputer 21 Can be small. Further, since the amount of processing is reduced, the operation clock frequency of the microcomputer 21 can be kept low, and the current consumption can be reduced. In addition, since it is not necessary to configure the amplification means in multiple stages, the analog circuit portion is reduced in size, the electronic circuit board incorporated in the electronic watt-hour meter is reduced in size, and the current consumption in the analog circuit portion is reduced. Can also be reduced. Therefore, a small power source can be used as the power source for the electronic watt-hour meter. In addition, since the current consumption can be reduced and the fluctuation range of the output voltage from the power supply can be reduced, a circuit component for stabilizing the output voltage of the power supply such as a conventional electronic watt-hour meter is not required, and the cost is reduced. Can be suppressed. Further, since the operation clock frequency of the microcomputer 21 can be kept low, the influence of the radiation electric field intensity due to the electromagnetic noise generated from the microcomputer 21 can be reduced, and the cost for measures against noise resistance can be suppressed. As a result, the electronic watt-hour meter according to the present embodiment can sufficiently reduce the size and cost of the product.

In addition, since the differential amplifier 23 is used as the amplifying means, the bias voltage V is applied to the detection signal of the voltage sensor 13 and the current sensor 14 output from the differential amplifier 23.

COM

be able to. For this reason, even if the detection signals of the voltage sensor 13 and the current sensor 14 fluctuate in the negative voltage range, applying the bias voltage V causes the positive range.

COM

The signal detected by the voltage sensor 13 and the current sensor 14 can be amplified by the differential amplifier 23 and converted into a digital signal by the AZD converter 24. Further, since the differential amplifier 23 is used as the amplifying means, even if noise is applied to the inverting input terminal (one) and the non-inverting input terminal (+), it is canceled and the influence of the noise can be eliminated. The detection signals of sensors 13 and 14 can be amplified with high accuracy. In this embodiment, the current ΔΣ 電流 / D start of S34, the voltage ΔΣΑ / D start of S41, and the V Δ∑AZD start of S52 are T + T + T (= 1000 [

OFF SI S2 SS μ s]). When the conversion by the AZD converter 24 is completed for either the detection output of the voltage sensor 13 or the current sensor 14 and the reference potential of this detection output, the selection switch 22 is immediately switched (FIGS. 6, S37, S44, S56). (See Fig. 6, S34, S41, S52) After that, after that, the signal inputted by the switched selection switch 22 is converted by the AZD converter 24 (see Fig. 6, S34, S41, S52). For this reason, each conversion by the AZD converter 24 is started in a state where the signal input to the AZD converter 24 is stable after a certain amount of time has passed since the selection switch 22 was switched. Therefore, the cause of the measurement error is removed, and each conversion by the A ZD converter 24 is performed accurately.

Further, in this embodiment, when the conversion of the detection output of the voltage sensor 13 and the current sensor 14 and the reference potential of the detection output is completed, the operation of the AZD converter 24 is immediately stopped (FIG. 6, S36). , S43, S54), preparation for starting the next conversion by the AZD converter 24 is performed. Therefore, each conversion by the AZD converter 24 is quickly executed even when the AZD converter 24 is stopped. Therefore, when converting continuously without stopping the operation of the AZD converter 24, the start of the next conversion is delayed by waiting for the completion of the previous conversion operation of the AZD converter 24 at the start of conversion. Thus, although the start of each conversion cannot be performed at a constant cycle, according to the present embodiment, the force S can be performed at a constant cycle of 1000 (= 93 + 407 + 500) [/ zs] (FIG. 6, (See S34, S41, S52). As a result, the measurement timing of the voltage and current of the measurement target and the offset measurement timing are performed at a constant period, and the calculation process of the power consumption of the measurement target can be performed accurately.

In the above embodiment, the force S (FIG. 5, S23, FIG. 6, S38, S46, S48) has been described in the case where the power calculation is performed by the equation (voltage value offset) X (current value offset). The present invention is not limited to this. When the reference potential (0 [V]) of the detection output of the current sensor 14 is different from the reference potential (1.8 [V]) of the detection output of the voltage sensor 13 as in the above embodiment, software processing Computational power in section 25 With A / D converter 24 The reference potential of the detection output of the converted current sensor 14 may be removed (offset cancellation) only from the detection output of the current sensor 14 converted by the AZD converter 24.

[0055] That is, in this configuration, the voltage value force detected by the voltage sensor 13 also removes the offset. The processing of FIG. 6, S46 is not performed, and the power is given by the equation (voltage value) X (current value offset). Calculated. As described below, the power consumption is accurately calculated without performing only offset cancellation on the current side and offset cancellation on the voltage side.

[0056] In FIG. 4, the voltage between the power terminals PO and P1 is V'sincot, the signal ground of the voltage sensor 13 is V, the offset by the differential amplifier 23 and the AZD converter 24 is V, and the resistance 13

COM OFF

If the resistance values of a, 13b, and 13c are R, R, R, and a = R Z (R + R + R), respectively,

1 2 3 3 1 2 3

The voltage measured by the voltage sensor 13 based on the voltage E'sinc t

V

The AZD conversion result is

E 'sinc t + V

V OFF

= (V'sincot-V) X α + V

COM OFF

It becomes. Also, voltage E'sin cot appears across shunt resistor 14a due to current I'sincot flowing between load terminal 1L and IS, so AZD conversion of the current measured by current sensor 14

I

Result is,

E 'sinc t + V

I OFF

It becomes. Accordingly, power is calculated as shown below.

Electric power

= (Voltage value) X (Current value offset)

= (E 'sinc t + V) X (E ^ ίηωΐ + V-V)

V OFF I OFF OFF

= ((V'sino> t-V) X α + V} X (Ε ^ ίηωΐ + V-V)

COM OFF I OFF OFF

= (a • V'sinc t ― a ⁹ V + V) XE 'sinc t

COM OFF I

= a · ν · Ε ^e sin ωΐ ― E (a ^e V ― V) sin cot

I I COM OFF

[0057] In this case, the power value calculated from the detection outputs of the sensors 13 and 14 is the force that is the DC component of the first term · ν · Ε 'sin ² cot) force The force without the removal of the reference potential Voltage sensor 1

I The offset V of differential amplifier 23 and AZD converter 24 appearing at the detection output of 3 is

OFF

, AC component E 'V-V) sin cot that swings positive and negative in the second term.

I COM OFF

It becomes zero by the integration process in the power accumulation process. Therefore, the effect of V is automatically removed in the power calculation without performing voltage-side offset cancellation.

OFF

The In other words, if α · ν = で in the above formula, the power consumption calculated between time 0 and t

V

Is calculated by the following equation. Where sin ² cot = — (cos2cot— 1) / 2. In addition, since ω = 2πf = 2πZt, it is converted to t = 2ππω.

[Number 1]

tv-Ei 't

~~

F ^ j "ί'Λ ti

2 I-in 2uJt ― t S) i 2)

.

― El (0-VCOM. 27L — I

This + 'ώ

2

Here, since E and E are peak values, the above power consumption is expressed as an effective value as follows.

V I

This is the formula.

[Equation 2]

Two £ v · Ei-t

[0059] As described above, the influence of V is not affected by the offset cancellation on the voltage side.

OFF

It is automatically removed when calculating.

[0060] According to the above configuration, the power to be used for calculating the power of the differential amplifier 23 and the A / A can be calculated only for the detection output of the current sensor 14 by removing the reference potential converted by the AZD converter 24. The offset of the D converter 24 can be removed. This simplifies the process of calculating the amount of power used for the measurement target, further reducing the size of the software, further reducing the memory size of the microcomputer 21, and further reducing the operating clock frequency. Thus, the current consumption can be further reduced.

[0061] In the above configuration, as shown in FIGS. 3 and 4, the reference potential of the detection output of the current sensor 14 and the reference potential of the detection output of the voltage sensor 13 are 0 [V] and 1. Although the reference potential of the detection output of the current sensor 14 that is set to 8 [V] and converted by the AZD converter 24 is removed only from the detection output of the current sensor 14 converted by the A ZD converter 24, The present invention is not limited to this. For example, the reference potential of the detection output of the current sensor 14 is the reference potential of the signal ground (for example, 1.8 [V]), and the reference potential of the detection output of the voltage sensor 13 is the reference potential V of the circuit ground (for example, 0 [V]). And select

SS

Connect the terminal 22c of the selector switch 22 to the reference potential V of this circuit ground,

SS

The reference potential of the detection output of the voltage sensor 13 converted by the barter 24 may be removed only from the detection output of the voltage sensor 13 converted by the AZD converter 24.

[0062] As described above, the power value calculated from the detection output of each of the sensors 13 and 14 is composed of a DC component, but the differential amplifier 23 and the output appearing in the detected output without the reference potential being removed. The offset of the AZD converter 24 becomes an alternating current component that appears evenly in voltage positive and negative, and is removed by integration processing (see FIG. 5, S25) in the process of integrating power consumption. Therefore, the removal power of the reference potential converted by the AZD converter 24 Detection of the current sensor 14 Only by either the output or the detection output of the voltage sensor 13, the offset of the differential amplifier 23 and the AZD converter 24 can be removed from the calculated power consumption amount. This simplifies the process of calculating the power consumption of the measurement target, further reducing the size of the software, further reducing the memory size of the microcomputer 21, and lowering the operating clock frequency. The current consumption can be further reduced.

Further, in the above-described embodiment, a case has been described in which one set of the voltage sensor 13 and the current sensor 14 is configured to be connected to the differential amplifier 23 via the selection switch 22. It is also possible to adopt a multi-element instrument configuration equipped with a voltage sensor and a current sensor.

FIG. 7 is a block diagram showing an outline of a circuit configuration of an electronic watt-hour meter including three sets of voltage sensors and current sensors. In the figure, the same or corresponding parts as in FIG. 3 are denoted by the same reference numerals, and the description thereof is omitted.

[0065] In the multi-element electronic watt-hour meter according to this configuration, the voltage sensor 13A, 13B, 13C, and the current sensor 14A, 14B, 14C is connected. Each of the current sensors 14A to 14C is composed of a current transformer or a mouth gosky key, and power calculation by the software processing unit 25a is performed for each element of each set. Except for these points, the configuration is the same as that of the above embodiment. Even in this configuration, the same operational effects as the electronic watt-hour meter in the above-described embodiment can be obtained.

[0066] In the above embodiment, the case where the detection outputs of the sensors of both the voltage sensor 13 and the current sensor 14 are amplified by the differential amplifier 23 has been described, but the present invention is not limited to this. is not. The voltage to be measured has a wider measurement accuracy guarantee range than the current to be measured, and the amplitude of the detection signal is larger than the current to be measured. Therefore, as shown in FIG. 8, the voltage sensor 13 can be directly connected to the AZD converter 24 without using the differential amplifier 23. In the figure, the same or corresponding parts as in FIG. 3 are denoted by the same reference numerals, and the description thereof is omitted. [0067] In this configuration, the voltage sensor 13 is connected to the AZD converter 24 without using the differential amplifier 23 using the two selection switches 22 and 52, and the software processing unit 25b according to these configurations. The configuration is the same as that of the above embodiment except that the processing in is different.

[0068] When the detection output of the voltage sensor 13 is input to the AZD converter 24 and converted into a digital signal, the selection switches 22 and 52 are respectively switched to terminals 22a and 52a as shown in FIG. The detection output of the voltage sensor 13 is directly input to the A / D converter 24 via the selection switches 22 and 52. When the detection output of the current sensor 14 is input to the A / D converter 24 and converted into a digital signal, the selection switches 22 and 52 are switched to the terminals 22 b and 52 b, and the detection output of the current sensor 14 Is amplified by the differential amplifier 23 and then input to the AZD converter 24. When the reference potential of the current sensor 14 is input to the AZD converter 24 and converted into a digital signal, the selection switches 22 and 52 are switched to the terminals 22c and 52b, respectively, and the reference potential of the current sensor 14 is Then, after being differentially amplified by the differential amplifier 23, it is input to the AZD converter 24. Therefore, also in this configuration, the same operational effects as the electronic watt-hour meter in the above embodiment are exhibited.

[0069] In the above embodiment, the case where the differential amplifier 23 is built in the front stage of the AZD converter 24 inside the microcomputer 21 has been described, but the present invention is not limited to this. Absent. The differential amplifier 23 may be built in the microcomputer 21 or provided outside the microcomputer 21.

FIG. 9 is a block diagram showing an outline of a circuit configuration of an electronic watt-hour meter configured with the differential amplifier 23 provided outside the microcomputer 21. In the figure, the same or corresponding parts as in FIG. 3 are denoted by the same reference numerals, and the description thereof is omitted.

The microcomputer 61 in this configuration is a general-purpose microcomputer provided with an amplifier 63, and the amplifier 63 is connected to the AZD converter 24 via a selection switch 62. The current sensor 14 is connected to a selection switch 22 inside the microcomputer 61 via a selection switch 65 and a differential amplifier 64 provided outside the microcomputer 61. Except for these points and the point that the processing in the software processing unit 25c differs depending on these configurations, the configuration is the same as that of the above embodiment. When the detection output of the voltage sensor 13 is input to the AZD converter 24 and converted into a digital signal, the selection switches 22 and 62 are switched to terminals 22a and 62a, respectively, as shown in FIG. The detection output of the voltage sensor 13 is directly input to the AZD converter 24 via the selection switches 22 and 62. Further, when the detection output of the current sensor 14 is input to the AZD comparator 24 and converted into a digital signal, the selection switches 65, 22, and 62 are switched to terminals 65a, 22b, and 62b, respectively. The detection output of the current sensor 14 is amplified by the differential amplifier 23 and the amplifier 63 and then input to the AZD converter 24. Further, when the reference potential of the current sensor 14 is input to the AZD converter 24 and converted into a digital signal, the selection switches 65, 22, and 62 are switched to the terminals 65b, 22c, and 62b, respectively. The reference potential of the current sensor 14 is amplified by the differential amplifier 23 and the amplifier 63, and the force is also input to the AZD converter 24. Therefore, even in this configuration, the same effects as those of the electronic watt-hour meter in the above embodiment can be obtained.

In the above embodiment, the case where the absolute error of the used power amount is corrected by multiplying the instantaneous power by a predetermined value in the gain adjustment process (see FIG. 5, S 24) has been described. It is not limited to this.

FIG. 10 is a diagram showing the relationship between the accumulated power consumption (see FIG. 5, S 25) and the pulse signal output from the software processing unit 25 to the LED 15. Figure (a) shows the amount of power used cumulatively added over time. Figure (b) shows the output when the power consumption shown in Figure (a) reaches a certain value (threshold). The output timing of each pulse signal is shown. In FIGS. 4A and 4B, the horizontal axis represents the time axis.

[0075] When it is not necessary to correct the absolute error in the amount of power used, the pulse output threshold is set to a as shown by the solid line in FIG. When the cumulative amount of power used in the software processing unit 25 reaches oc, a pulse signal is output as shown in Fig. 5 (b), and the cumulative amount of power used is reset to "0". The Similarly, a pulse signal is output each time the time t has elapsed and the amount of power used reaches the threshold value α. The threshold value α is adjusted so that the time t becomes constant and the pulse signal frequency becomes 6.4 [Hz], for example, when the rated voltage and current are applied to the electronic watt-hour meter. However, the rate of increase in the amount of power used that is actually cumulatively added depends on the sensitivity and internal sensitivity of each sensor 13, 14. Resistance value, reference voltage V applied to AZD converter 24, differential amplifier 23 〖

ref

Depending on the accuracy of each component, such as gain error, the waveform changes as it becomes smaller or larger like the sawtooth waveform shown by the dotted line and the alternate long and short dash line in Fig. 9 (a). When the rate of increase changes in this way, the timing at which the amount of power used reaches the threshold value a also changes.Therefore, by adjusting the pulse output threshold according to the amount of power used, the absolute amount of power used Correct the error. Specifically, when the rate of increase in the amount of power used decreases as shown by the dotted line in Fig. 9 (a), the threshold value is changed from a force to β (α〉 β). When the rate of increase in the amount of power used increases as shown by the alternate long and short dash line, the threshold value is changed from α to γ (αγγ). In this way, the pulse output timing is adjusted by adjusting the threshold value, so the pulse signal is output according to the actual power consumption, and the absolute error in the calculated power consumption Is corrected.

The absolute error of the calculated power consumption is corrected by multiplying the gain of S24 by a predetermined amount according to the amplification factor of the differential amplifier 23 by the gain adjustment of S24, as described above. It is also corrected by adjusting the negative value. This increases the degree of freedom in designing electronic watt-hour meters.

In the above embodiment, the case where the differential signals 23 are used to amplify the detection signals and reference potentials of the sensors 13 and 14 has been described. However, the present invention is not limited to this. For example, in the electronic watt-hour meter shown in FIGS. 3 and 4, the detection signals and reference potentials of the sensors 13 and 14 may be amplified by the input capacitor ratio of the AZD converter 24 instead of the differential amplifier 23. Good. FIG. 11 is a circuit diagram showing a switched capacitor integrating circuit configured inside the AZD converter 24.

The AZD converter 24 includes an operational amplifier 71 and a comparator 72 connected to the output side thereof. The input side and the output side of the operational amplifier 71 are connected in feedback by hold capacitors 79 and 80. On the input side of the operational amplifier 71, sampling capacitors 73 and 74 having a capacity Ci for sampling an input signal and feedback capacitors 75 and 76 having a capacity Cr for performing feedback are connected. Switching capacitors 77 and 78 are connected to the feedback capacitors 75 and 76, respectively, and these switches 77 and 78 are switched by the output of the comparator 72 to provide feedback. The reference voltage + V or 1 V is applied to the capacitor 75 and 76. Sampling controller ref ref

The densityr 73 is connected to the selection switch 22 described above, and the detection output of each of the sensors 13 and 14 and the reference potential are input to the sampling capacitor 73 in accordance with the switching of the selection switch 22. The sampling capacitor 74 is connected to the reference potential of the current sensor 14, and a reference potential of 0 [V] is input to the sampling capacitor 74.

[0079] In the above configuration, the signals input to the sampling capacitors 73 and 74 are differentially amplified and Δ-modulated with an amplification factor of the input capacitor ratio CiZCr, and converted into an analog signal and a digital signal. Therefore, even in this configuration, the same effects as those of the above-described embodiment are achieved.

Further, in the above embodiment, the force voltage sensor 13 and the current sensor 14 have been described in the case where the voltage sensor 13 is composed of the voltage dividing resistors 13a to 13c and the current sensor 14 is composed of the shunt resistor 14a. The type of can be changed as appropriate. For example, the current sensor 14 may be a current transformer (CT), a Rogowski coil, or the like shown in FIG.

In the above embodiment, the AZD conversion process is performed in the AZD converter 24 in the order of the detection output of the current sensor 14, the detection output of the voltage sensor 13, and the reference potential of the current sensor 14 by switching the selection switch 22. The case where the AZD conversion process is performed has been described (see FIGS. 5, S21, S22, and S27), but the order of the AZD conversion processing for these signals can be changed as appropriate.

In the above embodiment, the case where the reference voltage V applied to the AZD converter 24 is prepared separately from the operating voltage V of the ref microcomputer 21 has been described.

DD

It is not limited. For example, the reference voltage V of the AZD converter 24 is

Set to the same potential as the operating voltage V and supply the reference voltage V to the AZD converter 24.

DD ref

The power source and the power source that supplies the operating voltage V to the microcomputer 21 can be shared. This structure

DD

According to the configuration, prepare a separate power supply for supplying the reference voltage V to the AZD converter 24 ref

This eliminates the need for further reduction in product size and cost.

[0083] In the timer interrupt process of the above embodiment, the time of Τ, Τ, T is

SI S2 SS

93 [s], 407 [μ s], and 500 [s], as well as the bias voltage V and microcontroller 21

COM

,,, T, and T, which are described as 1.8 [V] and 3.6 [V] respectively.

DD SI S2 SS V and V are not limited to these values and can be changed as appropriate.

COM DD

Further, in the above embodiment, the case where two resistors 13a and 13b are connected in series between the power supply terminal PO and the resistor 13c has been described in order to improve the withstand voltage performance of the voltage sensor 13. A single resistor may be connected between the power supply terminal P0 and the resistor 13c, and the number thereof can be changed as appropriate.

Industrial applicability

[0085] In the above embodiment, the case where the present invention is applied to a single-phase two-wire electronic watt-hour meter has been described. However, the measurement target is based on the digital signal converted by the AZD conversion means. It can also be applied to various electronic watt-hour meters such as single-phase three-wire and three-phase three-wire systems that calculate the amount of power used. Even when the present invention is applied to such various electronic watt-hour meters, the same effects as those of the above-described embodiment can be obtained.

Claims

The scope of the claims

[1] A voltage sensor that detects the voltage of the measurement target;

A current sensor for detecting a current to be measured;

A selection switch that selectively selects and outputs either the detection output of the voltage sensor or the current sensor or the reference potential of the detection output;

Based on the detection output of the voltage sensor and the current sensor output by the selection switch, the AZD conversion means for converting the reference potential into an analog signal force digital signal, and the digital signal converted by the AZD conversion means. An arithmetic processing unit with a built-in arithmetic means for calculating the power consumption of the measurement target;

In an electronic watt-hour meter with

The amplification means is composed of differential amplification means for differentially amplifying an input signal, and the AZD conversion means converts the input signal into an analog signal power digital signal by Δ∑ modulation,

The calculation means removes the reference potential converted by the AZD conversion means from the detection outputs of the voltage sensor and the current sensor converted by the AZD conversion means, respectively, and reduces the power consumption of the measurement target. An electronic watt-hour meter characterized by being calculated.

[2] The calculation means corrects the absolute error of the power consumption by multiplying the power consumption by a predetermined value or by adjusting a threshold value of a pulse output corresponding to the power consumption. The electronic watt-hour meter according to claim 1, wherein:

[3] When the reference potential of the detection output of the current sensor is different from the reference potential of the detection output of the voltage sensor, the calculation means converts the reference potential converted by the AZD conversion means into the reference potential. The electronic watt-hour meter according to claim 1 or 2, wherein the electronic watt-hour meter is removed from only one of a detection output of a current sensor and a detection output of the voltage sensor.

[4] The arithmetic processing unit converts the detection output of the voltage sensor and the current sensor and the reference potential of the detection output by the AZD conversion means. 4. The method according to any one of claims 1 to 3, wherein the selection switch is switched immediately after completion to perform the next selection, and then the next conversion by the AZD conversion means is performed over time. The electronic watt-hour meter according to item 1.

[5] The arithmetic processing unit performs the processing immediately after the completion of each conversion by the AZD conversion means.

5. The electronic watt-hour meter according to claim 4, wherein the operation of the ZD conversion unit is stopped to prepare for the start of the next conversion by the AZD conversion unit.

6. The electronic energy according to claim 1, wherein the reference voltage of the AZD conversion means is set to the same potential as the operating voltage of the arithmetic processing unit. Total.