CN101542298B - Electronic watthour meter - Google Patents

Electronic watthour meter Download PDF

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Publication number
CN101542298B
CN101542298B CN2006800561508A CN200680056150A CN101542298B CN 101542298 B CN101542298 B CN 101542298B CN 2006800561508 A CN2006800561508 A CN 2006800561508A CN 200680056150 A CN200680056150 A CN 200680056150A CN 101542298 B CN101542298 B CN 101542298B
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CN
China
Prior art keywords
output
voltage
potential
current
sensor
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CN2006800561508A
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Chinese (zh)
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CN101542298A (en
Inventor
吴一宪
吉川法子
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大崎电气工业株式会社
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Priority to PCT/JP2006/320773 priority Critical patent/WO2008047428A1/en
Publication of CN101542298A publication Critical patent/CN101542298A/en
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Publication of CN101542298B publication Critical patent/CN101542298B/en

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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R21/00Arrangements for measuring electric power or power factor
    • G01R21/133Arrangements for measuring electric power or power factor by using digital technique

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 Delta-Sigma 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 electric meter
Technical field
The present invention relates to calculate the electronic electric meter of the use electric flux of measurand according to the digital signal that obtains through the conversion of modulus (A/D) converting means.
Background technology
The measuring accuracy of electronic electric meter guarantee range usually for voltage be ratings ± about 10%, and be 6 times to 1/40 times wide-range of ratings for electric current.Therefore, in order in measuring accuracy guarantees range, to measure electric current with ± 1% precision, requiring resolution is 1/240 * 1%=1/24,000, promptly 1/24000, and be about 15 bits thereby require the resolution of A/D transducer.Yet the A/D transducer that is included in the microcomputer that is used as calculation process equipment usually only has the resolution of 10 bits or maximum 12 bits usually, thereby in the electronic electric meter that uses such mini-computer, resolution is just not enough.Therefore, for the deficiency of the resolution that remedies the A/D transducer that is included in the microcomputer, conventional electronic electric meter is just used with the corresponding amplification factor of the amplitude of measured electric current tested electric current is amplified.For example; In the electronic electric meter of the routine described in the patent documentation 1; Amplification factor is according to adjusting through the level of rectification and average tested electric current and the nominal level of multiplying arrangement automatically, in multiplying arrangement according to the output of current sensor being amplified through the amplification factor of adjustment.In addition, a kind of conventional electrical watt-hour meter is arranged, a plurality of amplifiers are configured in a plurality of levels, as shown in Figure 1, so that can amplify tested electric current with different amplification factors according to the amplitude of tested electric current.
This electronic electric meter is configured to comprise mini-computer 1.Microcomputer 1 is furnished with successive approximation A/D transducer 2 and carries out the software processes portion 3 of computing according to the numerical data that draws in 2 inner conversions of A/D transducer.The amplifier 9,10,11 and 12 of 5 times of input signal amplifications is connected into 4 levels, receive on the A/D transducer 2 through SS 7.Voltage sensor 13 is received on the amplifier 9 in the first order through SS 8 with current sensor 14.SS 8 can be selected ground switching and be connected to the arbitrary terminal among terminal 8a, 8b and the 8c.When switching was connected to terminal 8a, selected was the voltage signal from voltage sensor 13 with what measure; When switching was connected to terminal 8b, selected was the current signal from current sensor 14 with what measure; And when switching was connected to terminal 8c, selected was the reference potential that the detection of sensor 13 and 14 is exported with what measure.SS 7 can be selected a ground and switch and to be connected to the arbitrary terminal among terminal 7a, 7b, 7c and the 7d, so that select to be used for the progression of amplifier of the current signal that amplified current sensor 14 detected.When switching was connected to terminal 7a, selected was the amplifier 9 of one-level, made input signal amplify 5 times.In addition, when switching was connected to terminal 7b, selected was the amplifier 9 and 10 of secondary; When switching was connected to terminal 7c, selected was three grades amplifier 9 to 11; And when switching was connected to terminal 7d, selected was the amplifier 9 to 12 of level Four; Thereby input signal is amplified 5 respectively 2Doubly, 5 3Doubly with 5 4Doubly.
The LCD driver (lcd driver) 5 of control LED (light emitting diode) 15 and liquid crystal display (LCD) portion 6 is received in the software processes portion 3.Software processes portion 3 will become the magnitude of voltage of numerical data and current value to multiply each other in 2 inner conversions of A/D transducer, calculate electric power, with the electric power accumulation, calculate electric flux again.The electric flux that calculates shows on liquid crystal display part 6, and produces the pulse signal that is directly proportional with the use electric flux according to the electric flux that calculates, to switch on and off LED 15.
Fig. 2 is the process flow diagram that is illustrated in the above-mentioned software processes portion 3 summary of the computing of electric flux.
In the computing of electric flux, at first carry out the pseudo-A/D conversion process of electric current (see step among Fig. 2 (below be shown S) 1).In this is handled, with SS 8 switch be connected to terminal 8b after, give up the numerical data of the current value that obtains by the 2 initial conversion of A/D transducer, with raising current measurement precision.Then, carry out the preparatory A/D conversion process of electric current (S2).In this is handled, carry out and confirm to be used in the amplifier 9 to 12 measurement processing of best progression of amplifier of amplified current signal.Then, carry out the real A/D conversion process (S3) of electric current.In this is handled; Through switching selection switch 7; Be chosen in the amplifier of the progression that S2 confirms, and at the detection signal of current sensor 14 outputs after selected these amplifiers amplify, carry out the processing that detection signal is transformed into numerical data by A/D transducer 2.Then, carry out the pseudo-A/D conversion process (S4) of voltage.In this is handled, as such in the pseudo-A/D conversion process of the electric current of S1, with SS 8 switch be connected to terminal 8a after, give up the numerical data of the magnitude of voltage that obtains by the 2 initial conversion of A/D transducer, so that raising voltage measurement precision.Then, carry out the real A/D conversion process (S5) of voltage.In this is handled, through switching selection switch 7, select one-stage amplifier 9, the detection signal of voltage sensor 13 outputs is carried out the processing that detection signal is transformed into numerical data by A/D transducer 2 after amplifier 9 amplifies.
Then, from the current value that among S3, obtains and the processing (will after a while explain) of deduction through the S13 of last time obtains in the magnitude of voltage that S5 obtains amount of bias, calculate electric power (instantaneous power) again (S6).This amount of bias is the voltage of A/D transducer 2 outputs when in amplifier 9 each amplifier in 12, being input as zero, is (magnitude of voltage-amount of bias) * (current value-amount of bias) and calculate formulate in the electric power of S6.
Then, carry out the gain adjustment and handle (S7).Say a bit that specifically will be in S6 resulting electric power is calculated the result and increased the consistent prearranged multiple of amplification factor with the amplifier of determined progression in S2, adjusts thereby carry out to gain.Subsequently, carry out gain error correction and handle (S8).Specifically say a bit, carry out to eliminate electric power and calculate among the result because the processing of the error that the error of the internal resistance of the amplification factor of definite each amplifier 9 to 12 causes.Then, carry out the processing (S9) of calculating electric flux through with the resulting electric power data accumulation of the processing of S6 to S8 (accumulative total).According to the electric flux that the electric power accumulated process calculates, will export to LED 15 (S10) with the pulse signal that uses electric flux to be directly proportional, and on liquid crystal display part 6, show the electric flux that calculates.
Then, carry out the pseudo-A/D conversion process (S11) of amount of bias.In this is handled, with SS 8 switch be connected to terminal 8c after, give up the amount of bias data that A/D transducer 2 draws at first, to improve the amount of bias measuring accuracy of each amplifier 9 to 12.Then, carry out the real A/D conversion process (S12) of amount of bias.In this was handled, through switching selection switch 7, the amount of bias at different levels of measuring amplifier 9 to 12 was transformed into numerical data by A/D transducer 2 with the amount of bias that records again according to the order of sequence.Amount of bias is carried out measurement several times, calculate the mean value (S13) of amount of bias again according to measurement result.According to the amount of bias that therefore obtains, carry out the electric power of next time and calculate processing (S6), as stated.
Patent documentation 1: the open No.2004-177228 (paragraph [0025] is to [0031]) of Jap.P.
Summary of the invention
Yet; In conventional electrical watt-hour meter shown in Figure 1 discussed above; Because amplifier 9 to 12 connects into a plurality of grades configuration; Must confirm the best progression of amplifier through the preparatory A/D conversion process of the electric current of S2, the pseudo-A/D conversion process of essential amount of bias through S11 is measured the amount of bias of the amplifier 9 to 12 of each grade, and the biasing value of the several times that record of the essential amount of bias reality A/D conversion process of each grade storage through S12 to amplifier 9 to 12.In addition, need to handle each amplifier 9 to 12 execution gain adjustment, and need to proofread and correct the resistance error of each amplifier 9 to 12 of each grade through the gain error correction processing of S8 to each grade through the gain adjustment of S7.Therefore, in conventional electrical watt-hour meter shown in Figure 1 discussed above, need many processing, software size is big, needs big data storage capacity, thereby need have the microcomputer of large memories capacity.
In addition, because treatment capacity increases, must improve processing speed through the operational clock frequency that improves microcomputer 1, thereby the current drain of microcomputer 1 is big.In addition, because amplifier 9 to 12 connects into a plurality of grades configuration, the scale of artificial circuit part is big, thereby increases sizes of substrate, and the current drain of artificial circuit part is also big.Therefore, in conventional electrical watt-hour meter shown in Figure 1, can not use Miniature Power Unit.In addition, along with the increase of current drain, it is big that the fluctuating scope of electric power output voltage becomes, and therefore, in conventional electrical watt-hour meter shown in Figure 1, need be used for the circuit unit of output voltage of stabilized power source, thereby cost is increased.In addition, when the operational clock frequency of microcomputer 1 improved, it is big that the influence of the radiated electric field intensity of the electromagnetic noise that microcomputer 1 is produced becomes.Therefore, in conventional electrical watt-hour meter shown in Figure 1, need to strengthen the countermeasure such as electromagnetic screen of noise robustness (EMC), cost is increased.
Therefore, in conventional electrical watt-hour meter shown in Figure 1, there is not fully to reach the purpose that reduces product size and reduce cost.
The present invention has proposed a kind of electronic electric meter in order to overcome the above problems, and this electronic electric meter comprises:
Detect the voltage sensor of the voltage of measurand;
Detect the current sensor of the electric current of measurand;
Repeat according to the order of sequence to select that a ground is selected and the SS of the reference potential of the detection output of the detection output of output voltage sensor, current sensor or circuit ground,
The differential amplifying device of the current potential of the output signal of difference amplification SS and the reference potential of said circuit ground, and
Calculation process equipment, the simulating signal that contains differential amplifying device output is transformed into the A/D converting means of digital signal and the arithmetic unit that the use electric flux of measurand is carried out computing according to the digital signal of A/D converting means output,
Said electronic electric meter is characterised in that:
When SS was switched, the A/D converting means was carried out the A/D conversion through the modulation of Δ ∑, and shut-down operation after this conversion is accomplished; And
The use electric flux of the resulting digital signal calculating of the output measurand of A/D converting means when deducting at SS selection reference current potential in the output of A/D converting means when the arithmetic unit basis is passed through at least one detection from the detection output of the detection output of selecting voltage sensor at SS and current sensor.
According to this configuration, the detection output of voltage sensor, the detection of current sensor output and these reference potentials that detects output are transformed into digital signal through the modulation of the Δ ∑ in the A/D converting means from simulating signal.At least one from the detection output of the voltage sensor that is transformed into digital signal and current sensor of arithmetic unit detects that deduction is transformed into the reference potential of digital signal in the output, thereby from detecting separately of voltage sensor and current sensor exported, deducted the amount of bias of differential amplifying device and A/D converting means.The use electric flux of measurand calculates with the output of detection separately of the voltage sensor of having deducted amount of bias and current sensor.
Thereby in the A/D converting means, when the Δ ∑ is modulated, carry out meticulous sampling high resolving power ground simulating signal is transformed into digital signal, so multiplying arrangement need not be configured to have a plurality of levels for the lack of resolution that remedies the A/D converting means with over-sampling.Therefore, even multiplying arrangement is not configured to have a plurality of levels, also can on whole wide-range, need wide measuring accuracy to guarantee the detection output of the current sensor of range with high-acruracy survey.In addition because multiplying arrangement need not be configured to have a plurality of level, therefore also just needn't confirm amplifier best progression, measurement each amplifiers at different levels amount of bias and the amplifier biasing value at different levels that several times record is stored in the RAM.In addition, also just needn't handle the resistance error of proofreading and correct each amplifier to each Amplifier Gain adjustment at different levels with through gain error correction through gain adjustment processing execution.So treatment capacity reduces, thereby reduced the scale of software, and data storage capacity reduces also.Therefore, the calculation process device just is wanted the storer of low capacity.In addition, because treatment capacity reduces, calculation process operation of equipment clock frequency can be forced down, thereby its current drain can reduce.In addition, because multiplying arrangement need not be configured to have a plurality of levels, so the scale of artificial circuit part diminishes the current drain that this can reduce sizes of substrate and reduce artificial circuit part.So, can use the power supply of Miniature Power Unit as electronic electric meter.In addition, thus because current drain reduces to make the fluctuating range of the output voltage of power supply to reduce, therefore just do not need circuit unit, thereby cost can force down like the output voltage that is used for stabilized power source in the conventional electrical watt-hour meter.In addition, owing to can force down calculation process operation of equipment clock frequency, the influence of the radiated electric field intensity that therefore can reduce to cause owing to electromagnetic noise that calculation process equipment is produced, thus can practice thrift and realize anti-noise measure cost related.As a result, according to electronic electric meter of the present invention, can fully reach the purpose that reduces product size and reduce cost.
In addition,, can bias voltage be added to from the detection signal from current sensor at least of multiplying arrangement output as multiplying arrangement with differential amplifying device.Therefore; Even the detection signal of current sensor changes in negative scope; Also can detection signal become in positive scope change through applying bias voltage, the detection signal of current sensor can be transformed into digital signal by the A/D converting means after multiplying arrangement amplifies.In addition since with differential amplifying device as multiplying arrangement, even so have noise to be added on the input end, this noise also is cancelled, thereby can eliminate The noise.Therefore, input signal can obtain high-precision amplification.
In addition, when accomplishing each conversion of the reference potentials that detection output and these detections of voltage sensor and current sensor are exported, the operation of A/D converting means just stops, and performs the preparation that the A/D converting means starts next conversion.Therefore, each conversion just can be carried out rapidly from the state that the A/D converting means stops by the A/D converting means.So; When the operation that does not stop the A/D converting means is carried out conversion continuously; When starting conversion, accomplish last map function and so on and postpone next conversion of startup through wait A/D converting means; Thereby each conversion can not be carried out by regular time at interval, but according to this configuration, the startup of each conversion can be carried out by regular time at interval.As a result, the measurement of the measurement of the voltage and current of measurand timing and amount of bias is regularly carried out by regular time at interval, thereby can accurately carry out the computing of the use electric flux of measurand.
In addition, the invention is characterized in: arithmetic unit multiply by prearranged multiple or proofreaies and correct the absolute error of using electric flux through adjustment and the threshold value of using the corresponding pulse output of electric flux through using electric flux.
According to this configuration, multiply by the prearranged multiple consistent through the use electric flux that will calculate, the absolute error of the use electric flux that correction calculation goes out with the amplification factor of multiplying arrangement.In addition, through the threshold value of the corresponding pulse output of adjustment and the use electric flux that calculates, the timing of adjustment pulse output is used electric flux output pulse according to reality, thus the absolute error of the use electric flux that correction calculation goes out.Therefore, can multiply by prearranged multiple through the use electric flux that will calculate or come the absolute error of the use electric flux that correction calculation goes out, thereby increase the degree of freedom of design electronic electric meter through the threshold value of adjustment pulse output.
In addition; The invention is characterized in: when the reference potential of the detection of voltage sensor output was set at the reference potential different potential with the detection output of current sensor, arithmetic unit was according to the use electric flux of the resulting digital signal calculating of the output measurand of A/D converting means when only deduction is at SS selection reference current potential in the output of A/D converting means during the detection output of any from the detection output of the detection output of selecting voltage sensor at SS and current sensor.
According to this configuration; The performance number that detection output separately calculates according to sensor is a DC component; And the amount of bias of multiplying arrangement that in that detection output of not deducting reference potential, occurs and A/D converting means becomes the AC compounent of the positive and negative equalization appearance of voltage, can in the accumulative total processing procedure of using electric flux, remove through integral processing.So, only the reference potential of deduction through the conversion of A/D converting means, the amount of bias that just can from the use electric flux that calculates, remove multiplying arrangement and A/D converting means are carried out in one of the detection output of current sensor and detection output of voltage sensor.Therefore, simplify the computing of the use electric flux of measurand, reduced the scale of software, reduced the memory span of calculation process equipment, and reduced operational clock frequency, thereby can further reduce current drain.
In addition; The invention is characterized in: after the A/D converting means is accomplished the conversion that the detection output of voltage sensor and current sensor and these is detected in the reference potential of exporting any; Calculation process equipment switches to SS immediately and makes it carry out next selection; After a period of time, calculation process equipment makes the A/D converting means carry out next conversion.
According to this configuration; Accomplish when the detection output of voltage sensor and current sensor and these are detected in the reference potential of exporting the conversion of any at the A/D converting means; SS is switched immediately; After a period of time, the signal of just by the A/D converting means SS that is switched by warp being imported is carried out conversion.Therefore, the state startup down of the signal stabilization of certain hour input A/D converting means has all been crossed in each conversion of A/D converting means after switching at SS.Therefore, eliminated the factor that causes measuring error, thereby the A/D converting means can accurately be carried out each conversion.
In addition, the invention is characterized in: the reference voltage of A/D converting means is set at the current potential identical with the WV of calculation process equipment.
According to this configuration, can provide the power supply of WV to make a public power with the power supply that reference voltage is provided to the A/D converting means with to calculation process equipment.Therefore, the power supply that reference voltage is provided to the A/D converting means be needn't be equipped with separately, product size and the purpose that reduces cost further reduced thereby can reach.
According to the present invention, as stated, can provide fully to reach the electronic electric meter that reduces product size and the purpose that reduces cost.
Description of drawings
Fig. 1 is the block diagram of summary that the circuit arrangement of conventional electrical watt-hour meter is shown;
Fig. 2 is the process flow diagram that the summary of electric flux computing in the watt-hour meter shown in Figure 1 is shown;
Fig. 3 is the block diagram that illustrates according to the summary of the circuit arrangement of the electronic electric meter of one embodiment of the present of invention;
Fig. 4 is the part detailed circuit diagram of block diagram shown in Figure 3;
Fig. 5 is the process flow diagram that the summary of electric flux computing in the watt-hour meter shown in Figure 3 is shown;
Fig. 6 is the process flow diagram that the details of electric flux computing shown in Figure 5 is shown;
Fig. 7 is the block diagram that illustrates according to the summary of the circuit arrangement of the electronic electric meter of the present invention's first modification;
Fig. 8 is the block diagram that illustrates according to the summary of the circuit arrangement of the electronic electric meter of the present invention's second modification;
Fig. 9 is the block diagram that illustrates according to the summary of the circuit arrangement of the electronic electric meter of the present invention's the 3rd modification;
Figure 10 is the figure that the relation of use electric flux of in electronic electric meter, being accumulated according to the present invention's the 4th modification and the pulse signal that is produced is shown; And
Figure 11 is for being used for the internal circuit diagram of the A/D transducer of electronic electric meter according to the present invention's the 5th modification.
Embodiment
Below, will the best mode of embodiment of the present invention be described.
Fig. 3 is the block diagram that illustrates according to the summary of the circuit arrangement of the single-phase two-wire system electronic electric meter of present embodiment.In addition, Fig. 4 is the part detailed circuit diagram of block diagram shown in Figure 3.In Fig. 3 and 4, will use identical reference numbers and character to indicate with the identical or corresponding component among Fig. 1.
Be configured to comprise voltage sensor 13, current sensor 14, mini-computer 21 and liquid crystal display part 6 according to electronic electric meter of the present invention.The microcomputer 21 that is configured to calculation process equipment comprises SS 22, differential amplifier 23, A/D transducer 24, software processes portion 25, LCD driver 5 and LED 15, and circuit ground (GND) is connected to the reference potential V into 0V SSOn.
Voltage sensor 13 is configured to bleeder circuit, to the input voltage Vsin ω t dividing potential drop between power supply terminal P0 and the P1, detects and export the voltage E through dividing potential drop that appears at resistor 13c two ends with resistor 13a, 13b and 13c again VSin ω t is as the voltage of measurand.The signal ground that resistor 13c is connected is set to have bias voltage V COMCurrent potential (1.8V), bias voltage V COMFor being added to reference potential V SSOn the WV V of microcomputer 21 DD(3.6V) 1/2nd, as shown in Figure 4.Current sensor 14 is configured to bypassed resistor 14a, detects and exports because the voltage E that between load end 1S and 1L, occurs between the two ends of bypassed resistor 14a through load current Isin ω t ISin ω t is as the electric current of measurand.Power supply terminal P1 receives on the 0V identical with the reference potential of microcomputer 21 with load end 1S, and 0V also is the reference potential of the detection output of current sensor 14.Therefore, in the present embodiment, the reference potential of the detection output of the reference potential of the detection of current sensor 14 output and voltage sensor 13 is set to 0V and 1.8V respectively, and is different each other.
SS 22 can be selected ground switching and be connected among terminal 22a, 22b and the 22c any.When switching is connected to terminal 22a, select the detection output of voltage sensor, when switching is connected to terminal 22b, selects the detection output of current sensor 14, and when switching is connected to terminal 22c, select the reference potential of current sensor 14.Therefore, SS 22 is selected the detection output of the selection of ground, a ground and output voltage sensor 13 or current sensor 14 or is detected the reference potential of exporting.
Differential amplifier 23 is received on above-mentioned each sensor 13 and 14 through SS 22, to its amplification output of A/D transducer 24 outputs.Differential amplifier 23 has band with A/D transducer 24 and is added to the bias voltage V that the power supply 26 on the circuit ground (0V) is produced COMCurrent potential (1.8V), as reference potential, they are all by the WV V of microcomputer 21 DD(3.6V) work is carried out in power supply.
As shown in Figure 4; The inverting terminal (-) of differential amplifier 23 is received on the output terminal of SS 22 through resistor 23a, thereby SS 22 selected detection output or its reference potentials from sensor 13 or 14 are transfused to inverting terminal (-).In addition, non-inverting input terminal (+) through resistor 23b receive current sensor 14 on the reference potential of 0V, and receive on the power supply 26 through resistor 23c.In addition, resistor 23d is configured between the inverting terminal (-) and output terminal of differential amplifier 23, so that negative feedback is provided.Differential amplifier 23 is configured to the multiplying arrangement that amplifies is exported in the detection of SS 22 selected current sensors at least 14, and is configured to the input signal of input inverting terminal (-) and non-inverting input terminal (+) is carried out the differential amplifying device that difference is amplified.
A/D transducer 24 is received on the output terminal of differential amplifier 23.Microcomputer 21 makes A/D transducer 24 carry out each conversion of the detection of voltage sensor 13 and current sensor 14 being exported and detected the reference potential of exporting by Fixed Time Interval by regular time interval switching selection switch 22.A/D transducer 24 reference data voltage V RefTo become digital signal from the signal from analog signal transformation of differential amplifier 23 inputs through the modulation of Δ ∑.A/D transducer 24 is configured to through Δ ∑ modulation the reference potential of the detection output of voltage sensor 13 and current sensor 14 and current sensor 14 is transformed into from simulating signal the A/D converting means of digital signal.
Software processes portion 25 receives on the output terminal of A/D transducer 24.Receive in the software processes portion 25 with the LCD driver 5 of the demonstration of control liquid crystal display part 6 with the LED that pulse signal was added to that uses electric flux to be directly proportional 15.Software processes portion 25 will be through calculating electric power through detection output and the detection output multiplication of current sensor 14 that A/D transducer 24 is transformed into the voltage sensor 13 of digital signal; With the electric power accumulation that calculates, calculate the use electric flux of measurand again.Through the control of LCD driver 5, the use electric flux that calculates is shown on liquid crystal display part 6.In addition, software processes portion 25 also produces the pulse signal that is directly proportional with the use electric flux that calculates.When the pulse signal output that is produced, electric current flows into LED 15, thereby LED 15 is luminous.The light that LED 15 is launched is detected by optical receiving sensor, carries out the detection processing to the electric flux measuring accuracy through using with the pulse signal that uses electric flux to be directly proportional.Software processes portion 25 is configured to the arithmetic unit according to the use electric flux of the digital signal computing measurand that obtains through 24 conversion of A/D transducer.
Fig. 5 illustrates 25 pairs of process flow diagrams that use electric flux to carry out the summary of computing of above-mentioned software processes portion.
In the use electric flux computing of present embodiment, at first carry out electric current A/D conversion process (seeing the S21 among Fig. 5).In this was handled, SS 22 is switched was connected to terminal 22b, thereby will be transformed into digital signal from simulating signal through the detection output of differential amplifier 23 amplified current sensors 14 through the Δ ∑ modulation of A/D transducer 24.Subsequently, carry out voltage A/D conversion process (S22).In this was handled, SS 22 is switched was connected to terminal 22a, thereby the detection output of the voltage sensor 13 that the Δ ∑ modulation through A/D transducer 24 will be amplified through differential amplifier 23 is transformed into digital signal from simulating signal.
Then; Be transformed into deduction the magnitude of voltage of digital signal is transformed into digital signal in the processing of the S27 of last time (this will in explanation after a while) amount of bias from the current value that is transformed into digital signal at S21 with at S22, calculate electric power (S23) according to the current value of having deducted amount of bias and magnitude of voltage again.Amount of bias is the voltage that when being input as of differential amplifier 23 is zero, on the output terminal of A/D transducer 24, occurs, and rating formula is shown (magnitude of voltage-amount of bias) * (current value-amount of bias) in the processing of above-mentioned S23.
Then, carry out the gain adjustment and handle (S24).In this is handled, proofread and correct according to the absolute error of the definite factor pair instantaneous power of the amplification factor of differential amplifier 23 through multiply by in the electric power data that S23 calculates in advance.Then, will handle the electric power data accumulation that obtains, and calculate and use electric flux (S25), and the use electric flux that calculates show on liquid crystal display part 6 through S23 and S24.In addition, also produce the pulse signal that is directly proportional with the use electric flux that calculates, and the pulse signal that is produced is exported to LED 15 (S26).
Then, carry out offset A/D conversion process (S27).In this was handled, SS 22 is switched was connected to terminal 22c, thereby will be the reference potential input difference amplifier 23 of 0V, receives difference and amplifies.Subsequently, modulate and to be transformed into digital signal through the reference potential that difference is amplified, calculate the amount of bias of differential amplifier 23 and A/D transducer 24 again through the Δ ∑ of A/D transducer 24.In the power calculation of the S23 of next time is handled, from magnitude of voltage and current value, deduct the amount of bias that offset A/the D conversion process obtains as stated through S27, calculate electric power again.
Fig. 6 is the process flow diagram that the details of above-mentioned use electric flux computing is shown.Use the electric flux computing to carry out as the timer Interrupt Process of microcomputer 21.
Between institute's timing, reach T to the timer of the interrupt timing timing of timer Interrupt Process SSWhen (=500 μ s), the timer Interrupt Process starts.In the timer Interrupt Process, microcomputer 21 is at first confirmed T S2Whether sign is provided with (seeing the S31 among Fig. 6).T S2Sign is provided with in S39 when carrying out voltage A/D conversion process (seeing the S22 among Fig. 5), as will explaining after a while.When definite result was " denying ", microcomputer 21 was confirmed V subsequently OFFWhether sign is provided with in carrying out, and that is to say, determines whether to carry out the measurement (S32) to the amount of bias of differential amplifier 23 and A/D transducer 24.V OFFGetting the bid is provided with in S45 when aiming at carrying out offset A/D conversion process (seeing the S27 among Fig. 5), as will explaining after a while.When definite result of S32 was for " denying " not carrying out offset A/D conversion process, microcomputer 21 was provided with time T in timer S1(=93 μ s) (S33) makes timer T start-up time S1Regularly.At execution time T S1In the time of regularly, carry out to a series of processing of S39 as follows.In addition, because T is being crossed in the timer setting of S33 S1Time next timer just occurs and interrupt, start the voltage Δ ∑ A/D conversion of S41.Then, microcomputer 21 starting current A/D conversion process (seeing the S21 among Fig. 5) (S34).At this moment, be connected to terminal 22b because SS 22 has switched in the processing of the S56 that will explain after a while, so A/D transducer 24 is just exported in the detection of current sensor 14 output.Then, microcomputer 21 confirms whether accomplish (S35) in the electric current A/D conversion process that S34 starts, and when definite result was " being ", microcomputer 21 stopped the operation (S36) of A/D transducer 24 immediately.Subsequently, microcomputer 21 is connected to terminal 22a with SS 22 switchings, is imported into differential amplifier 23 (S37) with the detection output that state is configured such that voltage sensor 13, and gets ready for starting next voltage Δ ∑ A/D conversion (seeing S41).
Then, will in the S55 that will explain after a while, be transformed into the biasing value (V of digital signal through deduction the detection output valve (AD value) that is transformed into the current sensor of digital signal from processing at S34 and S35 OFFValue) resulting value (current value-amount of bias) sets into the service data memory block that does not illustrate of the RAM (RAS) that microcomputer 21 contained, and calculates the current value (S38) that uses as output power.Then, microcomputer 21 is with T S2Sign is provided with (S39), thereby finishes this timer Interrupt Process.
In addition, thereby the definite result who S31 has been set at TS2 sign is during for " being ", and microcomputer 21 is provided with time T in timer S2(=T SS-T S1=500-93=407 μ s) (S40), make timer T start-up time S2Regularly.At execution time T S2In the time of regularly, carry out to a series of processing of S49 as follows.Because T is being crossed in the timer setting of S40 S2Time next timer just occurs and interrupt, thereby start the V of S52 OFFΔ ∑ A/D conversion.Then, microcomputer 21 trigger voltage A/D conversion process (seeing the S22 among Fig. 5) (S41).At this moment, be connected to terminal 22a because SS 22 has switched in the processing of S37, so A/D transducer 24 is just exported in the detection of voltage sensor 13 output.Then, microcomputer 21 confirms whether accomplish (S42) in the voltage A/D conversion process that S41 starts, and when definite result was " being ", microcomputer 21 stopped the operation (S43) of A/D transducer 24 immediately.Microcomputer 21 is connected to terminal 22c with SS 22 switchings, is imported into differential amplifier 23 (S44) with the reference potential that state is configured such that current sensor 14, with V OFFSign is provided with (S45) in carrying out, and for starting next V OFFΔ ∑ A/D conversion (seeing S52) is got ready.
Then, microcomputer 21 will be transformed into the biasing value (V of digital signal through deduction from the detection output valve (AD value) of the voltage sensor 13 that the processing of S41 and S42, is transformed into digital signal in the S55 that will explain after a while OFFValue) resulting value (magnitude of voltage-amount of bias) sets into the interior service data storage area that does not illustrate of RAM that microcomputer 21 is contained, as the magnitude of voltage (S46) that supplies in electric power is calculated, to use.Then, microcomputer 21 T that will be provided with at S39 S2Sign is removed (S47), will multiply each other with the magnitude of voltage that sets into the service data storage area at the current value that S38 sets into the service data storage area subsequently, calculates electric power (S48).For the electric power data that in S48, calculate, carry out above-mentioned gain adjustment (seeing the S24 among Fig. 5) and electric power accumulated process (seeing the S25 among Fig. 5), thereby calculate the use electric flux, simultaneously its absolute error is proofreaied and correct.Then,, produce and the pulse signal (S49) that uses electric flux to be directly proportional, finish this timer Interrupt Process according to the use electric flux that calculates.The pulse signal that is produced is exported to LED 15, (sees the S26 among Fig. 5) as stated.
In addition, at V OFFDefinite result that thereby sign has been provided with S32 in carrying out is during for " being ", and microcomputer is provided with time T in timer SS(=500 μ s) (S51) makes timer T start-up time SSRegularly.At execution time T SSIn the time of regularly, carry out a series of processing to S57 as follows.Because T is being crossed in the timer setting of S51 SSTime next timer just occurs and interrupt, thereby start the electric current Δ ∑ A/D conversion of S34.Then, microcomputer 21 starts offset A/D conversion process (seeing the S27 among Fig. 5) (S52).At this moment, be connected to terminal 22c because SS 22 has been switched by the processing of S44, so the reference potential of current sensor 14 is just exported to A/D transducer 24.Then, microcomputer 21 confirms whether accomplish (S53) in offset A/D conversion process that S52 starts, and when definite result was " being ", microcomputer 21 stopped the operation (S54) of A/D transducer 24 immediately.Subsequently, microcomputer 21 will be transformed into the biasing value (V of digital signal in the processing of S52 and S53 OFFValue) sets into the service data storage area (S55) of the RAM that microcomputer 21 contained.Subsequently, microcomputer 21 is connected to terminal 22b with SS 22 switchings, is imported into differential amplifier 23 (S56) with the detection output that state is configured such that current sensor 14, and gets ready for starting next electric current Δ ∑ A/D conversion (seeing S34).Then, microcomputer 21 V that will be provided with at S45 OFFSign is removed (S57) in carrying out, and stop timing device Interrupt Process.
Electronic electric meter according to present embodiment; The reference potential that kind as explained above that the detection output of voltage sensor 13, the detection of current sensor 14 output and these detect output is transformed into digital signal (see S21, S22 and S27 Fig. 5, and the S34 among Fig. 6, S41 and S52) through the modulation of the Δ ∑s in the A/D transducer 24 from simulating signal.Through the computing in the software processes portion 25; Deduct the reference potential (seeing S38 and S46 among Fig. 6) that is transformed into digital signal the output from the voltage sensor 13 and the detecting separately of current sensor 14 that are transformed into digital signal, thereby from the output of detection separately of voltage sensor 13 and current sensor 14, deducted the amount of bias of differential amplifier 23 and A/D transducer 24.The use electric flux of measurand calculates (see S23 and S25 among Fig. 5, and the S48 among Fig. 6) with the output of detection separately of the voltage sensor of having deducted amount of bias 13 and current sensor 14.
Thereby in A/D transducer 24, when the Δ ∑ is modulated, digital signal is carried out meticulous sampling high resolving power ground simulating signal is transformed into digital signal, so multiplying arrangement does not need as in the conventional electrical watt-hour meter, being configured to have a plurality of levels for the resolution that remedies the A/D transducer with over-sampling.Therefore, need wide measuring accuracy guarantee the detection output of the current sensor 14 of range can be on whole wide-range high-acruracy survey, and need multiplying arrangement be configured to have a plurality of levels.In addition, because multiplying arrangement need not be configured to have a plurality of levels, just needn't confirm also that therefore the best progression of amplifier, the amount of bias of measuring amplifiers at different levels and the amplifiers at different levels biasing value several times that will record are stored in the RAM.In addition, also needn't proofread and correct amplifier execution resistance error at different levels to each amplifier execution gain adjustment at different levels with through the gain error correction processing through gain adjustment processing.So, reduced treatment capacity, thereby can reduce the software size in the software processes portion 25, and can reduce to be included in the data storage capacity of the RAM in the microcomputer 21.Therefore, can reduce the memory size of the required RAM of microcomputer 21.In addition, owing to reduced treatment capacity, therefore can reduce the operational clock frequency of microcomputer 21, thereby can reduce current drain.In addition,, therefore can reduce the scale of artificial circuit part, thereby can reduce to be included in the electronic circuit substrate in the electronic electric meter, and can reduce the current drain of artificial circuit part because multiplying arrangement need not be configured to have a plurality of levels.So, can use the power supply of Miniature Power Unit as electronic electric meter.In addition,, therefore do not need circuit unit like the stabilized power source output voltage in the conventional electrical watt-hour meter owing to reduce the fluctuating scope that current drain also just can reduce electric power output voltage, thus can cost squeeze.Owing to can reduce the operational clock frequency of microcomputer 21, therefore can reduce the influence of the radiated electric field intensity that electromagnetic noise that microcomputer 21 produced causes, thereby can force down and realize the measure cost related of anti-noise.As a result, according to the electronic electric meter of present embodiment, can fully reach the purpose that reduces product size and reduce cost.
In addition since with differential amplifier 23 as multiplying arrangement, can be with bias voltage V COMBe added on the detection signal of voltage sensor 13 and current sensor 14 of differential amplifier 23 output.Therefore, even the detection signal of voltage sensor 13 and current sensor 14 changes in negative voltage range, through applying bias voltage V COMAlso can make detection signal become the signal that in positive scope, changes, the detection signal of voltage sensor 13 and current sensor 14 can be transformed into digital signal with A/D transducer 24 after differential amplifier 23 amplifies.In addition since with differential amplifier 23 as multiplying arrangement, even there is noise to be added on its inverting terminal (-) and non-inverting input terminal (+), this noise also can be cancelled, thereby can eliminate The noise.Therefore, sensor 13 and 14 detection signal separately can obtain high-precision amplification.
In addition, in the present embodiment, press T S1+ T S2+ T SSThe electric current Δ ∑ A/D that the Fixed Time Interval of (=1000 μ s) is carried out S34 respectively starts, the voltage Δ ∑ A/D of S41 starts and the V of S52 OFFΔ ∑ A/D starts.When the conversion of the reference potentials of exporting with these detections is exported in the detection of any voltage sensor 13 and current sensor 14 with 24 completion of A/D transducer; Switching selection switch 22 (seeing S37, S44 and S56 among Fig. 6) is just carried out conversion (seeing S34, S41 and S52 among Fig. 6) with 24 pairs of signals by SSes 22 inputs of warp switching of A/D transducer after a period of time immediately.Therefore, each conversion of carrying out with A/D transducer 24 all starts under the state of the signal stabilization of having been crossed certain hour input A/D transducer 24 after the SS 22 quilt switchings.Therefore, eliminated and produced the factor of measuring error, thereby can use A/D transducer 24 accurately to carry out each conversion.
In addition; In the present embodiment; When each conversion of accomplishing the reference potential of the detection output of voltage sensor 13 and current sensor 14 and these detections; The operation of A/D transducer 24 stops (seeing S36, S43 and S54 among Fig. 6) immediately, is implemented as to start the preparation of the next one with the conversion of A/D transducer 24 execution.Therefore, each conversion of carrying out with A/D transducer 24 just can realize rapidly from the state that A/D transducer 24 stops.So; When the operation that does not stop A/D transducer 24 is carried out conversion continuously; When starting conversion, accomplish and so on the startup of postponing next conversion through the last map function of waiting for A/D transducer 24; The startup of each conversion can not be carried out by Fixed Time Interval, but according to present embodiment, the startup of each conversion can be by 1000 (=93+407+500) the Fixed Time Interval execution (seeing S34, S41 and S52 among Fig. 6) of μ s.As a result, the measurement of the measurement of the voltage and current of measurand timing and amount of bias is regularly carried out by preset time at interval, thereby the computing of the use electric flux of measurand can accurately be carried out.
In embodiment discussed above, explained with formula (magnitude of voltage-amount of bias) * (current value-amount of bias) and carried out the situation that electric power is calculated (seeing S23 and the S38 among Fig. 6, S46 and S48 among Fig. 5), but the present invention is not limited to this situation.As in embodiment discussed above, computing software processes portion 25 in is only had from through the detection output of the current sensor 14 of A/D transducer 24 conversion, deducting the configuration of the reference potential of exporting through the detection of the current sensor 14 of A/D transducer 24 conversion (amount of bias elimination) at the reference potential (1.8V) of the reference potential (0V) of the detection of current sensor 14 output and the detection output of voltage sensor 13.
Specifically, in this configuration, the not processing of from the magnitude of voltage that voltage sensor 13 is detected, deducting amount of bias of the S46 in the execution graph 6, and electric power is calculated with formula (magnitude of voltage) * (current value-amount of bias).Eliminate and do not carry out amount of bias and eliminate even only carry out amount of bias, also can accurate Calculation use electric flux in voltage side in the electric current side, as follows.
The signal ground that power supply terminal P0 in Fig. 4 and the voltage between the P1 are made as Vsin ω t, voltage sensor 13 is made as V COM, differential amplifier 23 and A/D transducer 24 amount of bias be made as V OFF, resistor 13a, 13b and 13c resistance value be made as R respectively 1, R 2And R 3And α=R 3/ (R 1+ R 2+ R 3) time, voltage sensor 13 is according to the voltage E that appears at resistor 13c two ends VThe A/D transformation results of the voltage that sin ω t records does
E v·sin?ωt+V OFF
=(V·sinωt-V COM)×α+V OFF
In addition, because electric current I sin ω t flows through, at the two ends of bypassed resistor 14a voltage E appears between load end 1L and 1S ISin ω t, so the A/D transformation results of the electric current that records of current sensor 14 does
E I·sinωt+V OFF
Therefore, can be by calculating electric power as follows.
Electric power
=(magnitude of voltage) * (current value-amount of bias)
=(E V·sinωt+V OFF)×(E I·sinωt+V OFF-V OFF)
={(V·sinωt-V COM)×α+V OFF}×(E I·sinωt+V OFF-V OFF)
=(α·V·sinωt-α·V COM+V OFF)×E I·sinωt
=α·V·E I·sin 2ωt-E I(α·V COM-V OFF)sinωt
In this case, export DC component (the α VE that the electric power value that calculates has first according to detecting separately of sensor 13 and 14 ISin 2ω t), the differential amplifier 23 that still in the detection output of the voltage sensor of not deducting reference potential 13, occurs and the amount of bias V of A/D transducer 24 OFFBecome the AC compounent E of second positive and negative variation I(α V COM-V OFF) sin ω t, in Fig. 5, become zero through integral processing in the electric power accumulated process of S25.Therefore, do not carry out in voltage side under the situation of amount of bias elimination, when electric power is calculated, eliminated V automatically OFFInfluence.Specifically, if in the formula of above explanation, satisfy α V=E V, just can use following formula 1:
∫ 0 t E V · E I · sin 2 ωtdt - ∫ 0 t E I ( α · V COM - V OFF ) sin ωtdt
= - E V · E I 2 ∫ 0 t ( cos 2 ωt - 1 ) dt - E I ( α · V COM - V OFF ) ∫ 0 t sin ωtdt
= - E V · E I 2 [ 1 2 ω · sin 2 ωt - t ] 0 t - E I ( α · V COM - V OFF ) × [ - 1 ω · cos ωt ] 0 t
= - E V · E I 2 ( 1 2 ω · sin 2 ωt - t ) - E I ( α · V COM - V OFF ) × ( - 1 ω · cos ωt + 1 ω )
= - E V · E I 2 { 1 2 ω · sin ( 2 ω · 2 π ω ) - t } - E I ( α · V COM - V OFF ) × { - 1 ω · cos ( ω · 2 π ω ) + 1 ω }
= - E V · E I 2 ( 1 2 ω · sin 4 π - t ) - E I ( α · V COM - V OFF ) × ( - 1 ω · cos 2 π + 1 ω )
= E V · E I · t 2
The use electric flux that calculating was calculated during the time 0 to t.Wherein, made sin 2The conversion of ω t=-(cos2 ω t-1)/2.In addition, because ω=2 π f=2 π/t have done the conversion of t=2 π/ω.
Here, because E VAnd E IAll be peak value, therefore when above-mentioned use electric flux is represented with effective value, satisfy following formula 2:
2 E V · 2 E I · t 2
= E V · E I · t
Therefore, do not eliminate, when electric power is calculated, can eliminate V automatically yet even carry out amount of bias in voltage side OFFInfluence.
According to configuration discussed above, only the reference potential of deduction through 24 conversion of A/D transducer carried out in the detection output of current sensor 14, thereby can from the use electric flux that calculates, be deducted the amount of bias of differential amplifier 23 and A/D transducer 24.Therefore, simplified the computing of the use electric flux of measurand, reduced the scale of software, thereby can reduce the memory size of microcomputer, and can reduce operational clock frequency, current drain is further reduced.
In addition; In configuration discussed above; Shown in 3 and 4, described situation is that the reference potential of the reference potential of the detection output of current sensor 14 and the detection output of voltage sensor 13 is set to 0V and 1.8V respectively; And only from deduction through the detection output of the current sensor 14 of A/D transducer 24 conversion through the reference potential of the detection output of the current sensor 14 of A/D transducer 24 conversion, but the present invention is not limited to this situation.For example, also can adopt such configuration: the reference potential of the detection output of current sensor 14 is set to the reference potential (for example, being 1.8V) of signal ground, and the reference potential of the detection output of voltage sensor 13 is set to the reference potential V of circuit ground SS(for example, being 0V) received the terminal 22c of SS 22 the reference potential V of circuit ground SSOn, thus only from deduction through the detection output of the voltage sensor 13 of A/D transducer 24 conversion through the reference potential of the detection output of the voltage sensor 13 of A/D transducer 24 conversion.
That kind as explained above; The electric power value that detection output separately calculates according to sensor 13 and 14 is presented as DC component; And appear at reference potential not the differential amplifier 23 in that the detection output of deduction and the amount of bias of A/D transducer 24 become the impartial AC compounent that occurs of positive and negative voltage, remove through the integral processing (seeing the S25 among Fig. 5) in the accumulative total processing procedure of using electric flux.So; Only the reference potential of deduction through 24 conversion of A/D transducer, the amount of bias that just can from the use electric flux that is calculated, remove differential amplifier 23 and A/D transducer 24 are carried out in one of the detection output of current sensor 14 and detection output of voltage sensor 13.Therefore, simplify the computing of the use electric flux of measurand, reduced the scale of software, reduced the memory span of microcomputer, and reduced operational clock frequency, thereby can further reduce current drain.
In addition; In embodiment discussed above; Described pair of electrical pressure sensor 13 and be configured to receive the situation on the differential amplifier 23, but also can adopt the configuration that comprises many multiple-unit electronic electric meters to voltage sensor and current sensor through SS 22 with current sensor 14.
Fig. 7 is the block diagram of summary that the circuit arrangement of the electronic electric meter that comprises three pairs of voltage sensors and current sensor is shown.In this drawing, be marked with identical reference numbers and character with identical or corresponding component among Fig. 3, and no longer they described.
In the multiple-unit electronic electric meter based on this configuration, voltage sensor 13A, 13B and 13C and current sensor 14A, 14B and 14C receive on the differential amplifier 23 that is included in the microcomputer 41 through SS 42.Current sensor 14A to 14C respectively is configured to current transformer or Rogowski coil, and is that every pair of unit is separately carried out electric power and calculated by the 25a of software processes portion.Some adopts and identical configuration in embodiment discussed above except this.In this configuration, provide and the electronic electric meter similar operation effect in embodiment discussed above.
In addition, in embodiment discussed above, described the situation that both detection output of voltage sensor 13 and current sensor 14 is all amplified by differential amplifier 23, but the present invention is not limited to this situation.Compare with electric current, guarantee that as the measuring accuracy of the voltage of measurand range is not wide range, and the amplitude of detection signal is big as measurand.Therefore, as shown in Figure 8, can adopt voltage sensor 13 directly to receive on the A/D transducer 24 and do not receive the configuration on the differential amplifier 23.In this drawing, be marked with identical reference numbers and character with identical or corresponding component among Fig. 3, and no longer they described.
In this configuration; Except voltage sensor 13 being received on the A/D transducer 24 and not being received processing and this configuration consistency on the differential amplifier, in the 25b of software processes portion and different these 2, adopt and identical configuration in embodiment discussed above with two SSes 22 and 52.
When the detection with voltage sensor 13 is input to A/D transducer 24 and is transformed into digital signal; SS 22 and 52 is as shown in Figure 8ly switched to respectively splicing ear 22a and 52a, thereby makes the detection output of voltage sensor 13 directly import A/D transducers 24 through SS 22 with 52.In addition; When the detection with current sensor 14 is input to A/D transducer 24 and is transformed into digital signal; SS 22 and 52 is switched is connected to terminal 22b and 52b, thereby makes detection output input A/D transducer 24 after differential amplifier 23 amplifies of current sensor 14.In addition; When the reference potential of current sensor 14 is imported A/D transducer 24 and is transformed into digital signal; SS 22 and 52 is switched to splicing ear 22c and 52b respectively, thereby makes reference potential input A/D transducer 24 after differential amplifier 23 amplifies of current sensor 14.So, in this configuration, also provide and the electronic electric meter similar operation effect in embodiment discussed above.
In addition, in embodiment discussed above, described the situation in the prime that differential amplifier 23 is included in the inner A/D transducer 24 of microcomputer 21, but the present invention is not limited to this situation.Differential amplifier 23 can be included in the microcomputer 21, perhaps can be configured in outside the microcomputer 21.
Fig. 9 is the block diagram that the summary of the circuit arrangement that is configured to the electronic electric meter of differential amplifier 23 outside microcomputer 21 is shown.In this drawing, be marked with identical reference numbers and character with identical or corresponding parts among Fig. 3, and no longer they described.
Microcomputer 61 in this configuration is the mini-computer that comprises amplifier 63, and amplifier 63 is received on the A/D transducer 24 through SS 62.In addition, current sensor 14 is received on the SS 22 in microcomputer 61 with differential amplifier 64 through being configured in microcomputer 61 outer SSes 65.This configuration except this some with in the 25c of software processes portion with this some corresponding to handle different this some configuration identical with embodiment discussed above.
Be input to A/D transducer 24 when being transformed into digital signal in the detection with voltage sensor 13, SS 22 and 62 is switched to splicing ear 22a and 62a respectively as shown in Figure 9.The detection output of voltage sensor 13 is directly imported the A/D transducer through SS 22 and 62.In addition, be input to A/D transducer 24 when being transformed into digital signal in the detection with current sensor 14, SS 65,22 and 62 is switched to splicing ear 65a, 22b and 62b respectively.The detection output of current sensor 14 is input A/D transducer 24 after differential amplifier 64 and amplifier 63 amplify.In addition, when the reference potential input A/D transducer 24 with current sensor 14 was transformed into digital signal, SS 65,22 and 62 was switched to splicing ear 65b, 22c and 62b respectively.The reference potential of current sensor 14 is input A/D transducer 24 after differential amplifier 64 and amplifier 63 amplify.So, in this configuration, also provide and the electronic electric meter similar operation effect in embodiment discussed above.
In addition, in embodiment discussed above, described the use electric flux and instantaneous electric power multiply by the situation that prearranged multiple is proofreaied and correct, but the present invention is not limited to this situation through handling in (seeing the S24 among Fig. 5) in the gain adjustment.
Figure 10 be the use electric flux (seeing the S25 among Fig. 5) accumulated is shown and pulse signal that software processes portion 25 exports to LED 15 between the figure of relation.(a) among Figure 10 shows according to the use electric flux of going through accumulated time, and (b) among Figure 10 shows the output timing of the pulse signal of corresponding output when using electric flux to reach the fixed value (threshold value) shown in (a) of Figure 10.At (a) of Figure 10 with (b), abscissa axis is a time shaft.
In the time need not proofreading and correct the absolute error of using electric flux, the threshold value of pulse output is arranged to shown in the solid line in Figure 10 (a).When the use electric flux of in software processes portion 25, being accumulated reaches α, export a pulse signal, shown in Figure 10 (b), and the use electric flux of being accumulated reset to " 0 ".After this, with the same manner, when having crossed time t and having used electric flux to reach threshold alpha, just export a pulse signal.Threshold alpha is adjusted to and when rated voltage and rated current are added on the electronic electric meter, makes time t become constant and pulse signal frequency becomes for example 6.4Hz.Yet the increment rate of the use electric flux that cumulative actual obtains is according to precision of each assembly and so on, such as separately internal resistance value of sensor 13 and 14, be added to the reference voltage V on the A/D transducer 24 RefValue and the gain error of differential amplifier 23, diminish and become big, dotted line in Figure 10 (a) and that kind of the zig-zag shown in the dot-and-dash line.When increment rate changed like this, the beat that uses electric flux to reach threshold alpha will change, and therefore through adjustment and the threshold value of using the corresponding pulse output of electric flux, the absolute error of using electric flux was proofreaied and correct.Specifically say a bit, when the increment rate of using electric flux diminishes, shown in the dotted line in Figure 10 (a), threshold value is changed into β (α>β) from α.In addition, when the increment rate of using electric flux becomes big, shown in dot-and-dash line, threshold value is changed into γ (α<γ) from α.Through such adjustment threshold value, the beat of pulse output obtains adjustment, then use the electric flux output pulse signal according to reality, thus the absolute error of having proofreaied and correct the use electric flux that calculates.
The absolute error of the use electric flux that calculates can will be used electric flux to multiply by the prearranged multiple consistent with the amplification factor of differential amplifier 23 through the gain adjustment of the S24 among Fig. 5 and proofread and correct, but also can proofread and correct through the threshold value of adjusting pulse output as stated.Therefore, increased the degree of freedom that designs this electronic electric meter.
In addition, in embodiment discussed above, described the detection signal of sensor 13 and 14 and the situation that reference potential is all amplified by differential amplifier 23, but the present invention is not limited to this situation.For example, in Fig. 3 and electronic electric meter shown in Figure 4, sensor 13 and 14 detection signal and reference potential separately can be according to the input capacitor of A/D transducer 24 rather than amplifier 23 than amplifying.Figure 11 illustrates the switch capacitance integrator circuit that is configured in the A/D transducer 24.
A/D transducer 24 is configured to comprise the operational amplifier 71 and comparer 72 on the outgoing side of receiving it.The input side of operational amplifier 71 is connected with 80 feedbacks through keeping capacitor 79 with outgoing side.In addition, respectively have capacitor C i the sampling capacitor 73 that input signal is sampled and 74 and the feedback condenser that feeds back 75 and 76 that respectively has a capacitor C r receive the input side of operational amplifier 71.Change-over switch 77 and 78 is received respectively on feedback condenser 75 and 76, and these two switches 77 and 78 are switched by the output of comparer 72, and reference voltage+V RefOr-V RefBe added on feedback condenser 75 and 76.On the SS 22 that sampling capacitor 73 is mentioned above receiving, sensor 13 with 14 detect separately export and reference potential according to the switching input sample capacitor 73 of SS 22.In addition, sampling capacitor 74 is received on the reference potential of current sensor 14, thereby is the reference potential input sample capacitor 74 of 0V.
In configuration discussed above, input sample capacitor 73 and 74 signal amplify than the amplification factor difference of Ci/Cr through input capacitance respectively and are transformed into digital signal from simulating signal after modulating with the Δ ∑.So, in this configuration, also provide and embodiment similar operation effect discussed above.
In addition; In embodiment discussed above; Described voltage sensor 13 to be configured to component voltage resistor 13a to 13c and current sensor 14 is configured to the situation of bypassed resistor 14a, but the suitably change of type of voltage sensor 13 and current sensor 14.For example, can use the current transformer shown in Fig. 7 (CT), Rogowski coil and so on as current sensor 14.
In addition; In embodiment discussed above; Described through switching selection switch 22 and in A/D transducer 24, the reference potential of the detection output of the detection output of current sensor 14, voltage sensor 13 and current sensor 14 has been carried out the situation of A/D conversion process (seeing S21, S22 and S27 among Fig. 5) by this order, but this is to the suitably change of order of the A/D conversion process of each signal.
In addition, in embodiment discussed above, the reference voltage V that is added on the A/D transducer 24 has been described RefBe WV V with microcomputer 21 DDSituation about separately being equipped with separately, but the present invention is not limited to this situation.For example, can be with the reference voltage V of A/D transducer 24 RefBe arranged on WV V with microcomputer 21 DDIdentical current potential, thus can be with reference voltage V being provided to A/D transducer 24 RefPower supply and to microcomputer 21 WV V is provided DDPower supply make a public power.According to this configuration, needn't be equipped with separately reference voltage V is provided to A/D transducer 24 RefPower supply, reduce product size and the purpose that reduces cost thereby can further reach.
In addition, in the timer Interrupt Process of embodiment discussed above, with time T S1, T S2And T SSBe set to 93 μ s, 407 μ s and 500 μ s respectively, and with the bias voltage V of microcomputer 21 COMWith WV V DDBe set to 1.8V and 3.6V respectively, but T S1, T S2And T SSAnd V COMAnd V DDBe not limited to these values, but suitably change.
In addition; In embodiment discussed above; The withstand voltage properties of having described in order to improve voltage sensor 13 in series is connected on the situation between power supply terminal P0 and the resistor 13c with resistor 13a and 13b; But the resistor that is connected between power supply terminal P0 and the resistor 13c can be one also, that is to say, the suitably change of the number of these resistors.
Industrial applicability
In embodiment discussed above; Described the situation that the present invention is applied to the single-phase two-wire system electronic electric meter, but the present invention also can be applied to the various electronic electric meters according to the single-phase three wire system, three-phase three-wire system of the use electric flux of measurand being carried out computing through the digital signal of A/D converting means conversion and so on.When the present invention is applied to so various electronic electric meter, also provide and embodiment similar operation effect discussed above.

Claims (5)

1. electronic electric meter comprises:
Detect the voltage sensor of the voltage of measurand;
Detect the current sensor of the electric current of measurand;
Repeat to select a ground according to the order of sequence and select and export the SS of reference potential of detection output or the circuit ground of the detection output of said voltage sensor, said current sensor;
Difference is amplified the differential amplifying device of reference potential of current potential and said circuit ground of the output signal of said SS; And
Calculation process equipment, the simulating signal that contains said differential amplifying device output is transformed into the A/D converting means of digital signal and the arithmetic unit that the use electric flux of measurand is carried out computing according to the digital signal of A/D converting means output,
Said electronic electric meter is characterised in that:
When said SS was switched, said A/D converting means was carried out the A/D conversion through the modulation of Δ ∑, and shut-down operation after this conversion is accomplished; And
Said arithmetic unit calculates the use electric flux of measurand according to digital signal, and this digital signal is to deduct in the output of said A/D converting means when detecting output through from the detection output of the detection output of selecting said voltage sensor at said SS and said current sensor at least one that the output of said A/D converting means obtains when said SS is selected said reference potential.
2. according to the described electronic electric meter of claim 1; It is characterized in that: the threshold value of said arithmetic unit through said use electric flux being multiply by prearranged multiple or exporting, the absolute error of proofreading and correct said use electric flux through the corresponding pulse of adjustment and said use electric flux.
3. according to the described electronic electric meter of claim 1, it is characterized in that:
When the reference potential of the detection of said voltage sensor output is set at the reference potential different potential with the detection output of said current sensor; Said arithmetic unit calculates the use electric flux of measurand according to digital signal, and this digital signal is to deduct in the output of said A/D converting means during through the arbitrary detection output from the detection output of the detection output of selecting said voltage sensor at said SS and said current sensor only that the output of said A/D converting means obtains when said SS is selected said reference potential.
4. according to the described electronic electric meter of claim 1; It is characterized in that: said calculation process equipment switches to said SS immediately after said A/D converting means is accomplished the detection output of said voltage sensor and said current sensor and any the conversion in these reference potentials that detects output and makes it carry out next selection; After a period of time, said calculation process equipment makes said A/D converting means carry out next conversion.
5. according to the described electronic electric meter of claim 1, it is characterized in that: the reference voltage of said A/D converting means is set at the current potential identical with the WV of said calculation process equipment.
CN2006800561508A 2006-10-18 2006-10-18 Electronic watthour meter CN101542298B (en)

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