JP5944820B2 - AC signal level / DC signal level conversion device and AC signal level / frequency conversion device using the value - Google Patents

Description

  The present invention relates to an AC signal level / DC signal level conversion apparatus and an AC signal level / frequency conversion apparatus using the apparatus. More specifically, the present invention relates to an apparatus for converting an alternating current (AC) signal input level to a direct current (DC) signal level corresponding to the level, and converting an AC signal input level to a frequency corresponding to the level. The present invention relates to an AC signal level / frequency conversion device. The present invention also relates to a watt hour meter using such an AC signal level / frequency converter.

FIG. 1 shows a watt-hour meter having a device for converting the level of power, which is an alternating current (AC) input, into a frequency according to a conventional example, the watt-hour meter being an AC voltage of power supplied from a power line. V and AC current I are sampled at predetermined frequencies (for example, 2 MHz) in analog / digital (A / D) converters 101 and 102, respectively, and the sampled voltage value V and current value I are respectively filtered ( The instantaneous power value W (for example, a sampling frequency of about 7.8 kHz) is output by multiplication by the multiplier 103 via a low-pass filter (LPF) 104. The integrated value Wh <b> 1 obtained as a result of the input to the device 105 is output via the pulse circuit 106. The pulsing circuit 106 outputs a pulse when the integrated value Wh1 from the integrator 105 reaches a predetermined threshold value, outputs the pulse to a counter (not shown) connected to the subsequent stage, and integrates with the output pulse. The device 105 is configured to be reset.
In this way, the amount of electric power can be measured by outputting a pulse train from the pulsing circuit 106 and monitoring the output frequency (or period) of the pulse train.

  FIG. 2 is a waveform diagram schematically showing the output of each component in the watt-hour meter shown in FIG. As shown in FIG. 1, the watt hour meter is normally configured to remove the frequency component of the power value W by the LPF 104, but in the graph of FIG. 2, the pattern A does not include the LPF 104. In this case, the output waveform of the integrator 105 (that is, the integrated value Wh1) when the output includes a ripple component even if the LPF 104 is provided is shown schematically. The output waveform of the integrator 105 (that is, the integrated value Wh2) when the minute is not included is shown.

As shown by the pattern A in FIG. 2, the integrated value Wh1 of the integrator 105 includes a ripple component that depends on the instantaneous power value W, and therefore exceeds the threshold value particularly when the instantaneous power value W is large. Time will be early. For this reason, when the pulse from the pulsing circuit 106 is output earlier, the interval between the sequentially output pulses does not become constant, and the pulse interval becomes coarse and dense in the series of output pulse trains. On the other hand, in the integrated value Wh2 of the pattern B that does not include the ripple, pulses are output at equal intervals.
As described above, when the integrated value Wh1 includes a ripple, the period between pulses is different, and the pulse train is coarse. As a result, the frequency of the pulse train varies, which affects the measurement accuracy of the power value.

  In FIG. 2, for ease of explanation, the output of the integrator 105 and the threshold value set in the pulsing circuit 106 are shown to increase sequentially step by step. The threshold value set in the pulsing circuit 106 is one, and every time the threshold value is reached, the integrator 105 is reset by the output pulse from the pulsing circuit 106. Therefore, the output of the accumulator 105 is represented by a waveform having one cycle of a waveform that increases from the zero value toward the threshold every time an output pulse is generated.

  As shown in FIG. 1, in the conventional example, the watt hour meter is provided with an LPF 104 so as to suppress the ripples in the harmonic to commercial power frequency band included in the instantaneous power value W. However, in order to reliably remove the AC component generated by the multiplication of the voltage V and current I of the commercial power supply, it is necessary to use a low-pass filter with a large circuit scale. Not practical.

  This coarse and dense pulse interval is due to the fact that the increment of the integrated value Wh1 resulting from integrating the instantaneous power value W of the AC power waveform as it is is not constant. It becomes an obstacle when performing short-time measurement such as verification of watt-hour meter. For example, before shipping the watt hour meter, whether or not a 1000 Hz pulse is output from the pulsing circuit 106 at the rated power (100 V, 30 A) is tested in a short time. The effect is particularly large near the rated power. Further, the variation in the frequency of the pulse train can be averaged to some extent in the case of a relatively long time measurement, but in the short time measurement, the variation appears in the measurement result as it is. In addition, high-accuracy watt-hour meters are required to have extremely small variations in the frequency of output pulse trains even in a short time. It becomes a problem.

Also, as shown in FIG. 3, in the case of a power waveform in which the phases of the voltage V and the current I are out of phase, the periods t1 to t1 in which the sign of the instantaneous power value W is switched from positive to negative in one cycle and become negative power. There is t2. In this case, in the apparatus according to the conventional example shown in FIG. 1, the integrator 105 performs positive integration during the positive power period and performs negative integration during the negative power period. In such a case, depending on the magnitude of the negative power, the negative power integrated value exceeds a predetermined threshold value, so that a pulse resulting from integrating the negative power is output. When detecting the active power value, it is necessary to cancel the positive power and the negative power to calculate the original power value, and thus a process for canceling the positive and negative pulses and outputting them is necessary. For this reason, in the conventional example, a circuit for canceling the positive and negative pulses is provided at the subsequent stage of the pulse forming circuit 106.
However, canceling the positive and negative pulses leads to a period in which no pulse is output, and eventually, the pulse train becomes coarse.

Furthermore, in order to solve the problem of the density of the output pulse train, a watt hour meter having a function of performing an averaging process of the pulse interval in the subsequent stage (or in the circuit) of the pulse circuit 106 shown in FIG. 1 has been proposed. ing. FIG. 4 shows a conventional example in which a circuit for averaging the pulse interval is arranged at the subsequent stage of the pulsing circuit 106. In the averaging processing circuit, the pulse train from the pulsing circuit 106 is counted by the counter 107, the count value is divided by the dividing means 108 by the period of the AC input measured by the period measuring means 108, and the obtained division is obtained. The pulse generator 110 is configured to output a pulse train having a period corresponding to the value and having a constant period. As a result, the pulse intervals can be averaged, and a pulse train of equal intervals is output instead of the coarse / fine cycle.
However, in order to perform a pulse train averaging process and output a pulse train having a fixed period, it is necessary to include a counter, a period measuring means, a dividing means, and a pulse generating means as shown in FIG. However, there is a problem that the processing time is increased as the processing time becomes complicated.

  Thus, there is a strong desire to solve the above-described problems, and this is a common desire not only for watt hour meters but also in the technical field of meters. The object of the present invention is to solve such problems and to output a DC level corresponding to the AC signal input level with high accuracy without using a ripple removal filter and a pulse train interval averaging circuit. It is to provide an AC signal level / frequency conversion device that can be used. Another object of the present invention is to provide an watt-hour meter equipped with such an AC signal level / frequency conversion device and an AC signal level / frequency conversion device for converting an AC signal input level into a DC level. A signal level / DC signal level conversion apparatus is provided.

In order to achieve the above-mentioned object, the present invention converts an AC (alternating current) signal input level sampled at a predetermined frequency into a DC (direct current) signal level corresponding to the level and outputs it from an output terminal. Because
An average value calculation / holding means for calculating an average value of each cycle of AC signal input and outputting an average value of one cycle before during the current cycle;
A comparison means for applying a signal output from the average value calculation / holding means to one input terminal and comparing the signal to a signal applied to the other input terminal;
Switching means that is switched by the output of the comparison means and selectively outputs a signal applied to one input terminal of the comparison means and a signal applied to the other input terminal, the signal having the smaller value Switching means for outputting
Subtracting means for subtracting the signal output from the switching means from the signal applied to the other input terminal of the comparing means;
Storing the signal obtained by the subtracting means and outputting the signal obtained by the subtraction before one sampling;
An AC characterized by comprising an addition means for adding the signal from the previous value holding means and the current sampling AC signal input and supplying the obtained value to the other input terminal of the comparator and the switching means. A signal level / DC signal level conversion device is provided.

  In the above AC signal level / DC signal level conversion device, the average value calculating / holding means detects the maximum value and the minimum value of the AC signal input, and calculates the average value by calculating a half of the sum. Is preferably calculated. Further, the average value calculating / holding means further adds the previous value stored in the previous value holding means to the calculated average value before one cycle, and the previous value of the last sampling before the one cycle for one cycle. It is preferable that a value obtained by adding the values divided by the number of samplings is output as an average value during the current period. Further, the AC signal level / DC signal level conversion device further detects a time point when the sign of the AC signal input is inverted, and forcibly sets the output from the switching means to zero level for at least one period from the time point. Preferably means are provided. Still further, there is provided means for monitoring the average value calculated by the average value calculation / holding means and forcibly outputting the average value as a zero value when the average value is outside a predetermined range. preferable.

The present invention is also an AC signal level / frequency conversion device for converting the level of the AC signal input supplied to the input terminal into a frequency corresponding to the level and outputting the frequency from the output terminal. A signal level conversion device, an integration means for integrating the outputs of the AC signal level / DC signal level conversion device, and a means for outputting a pulse each time the output of the integration means reaches a predetermined value. An AC signal level / frequency conversion device comprising pulse generation means for generating a pulse train having a frequency corresponding to the level of the AC signal input by resetting.
The present invention further provides a watt-hour meter including the above-described AC signal level / frequency converter.

It is a circuit diagram which shows the structure of the watt-hour meter of a prior art example. It is a wave form diagram for demonstrating the problem in the watt-hour meter of a prior art example. It is a wave form diagram for demonstrating the problem in the watt-hour meter of a prior art example. It is a circuit diagram which shows the circuit structure which averages the space | interval of the pulse train in the watt-hour meter of a prior art example. It is a circuit diagram which shows the structure of one Example of the AC signal level / frequency converter of this invention. FIG. 6 is a waveform diagram for explaining a basic operation of the AC signal level / frequency converter shown in FIG. 5. FIG. 6 is a waveform diagram for explaining an operation when the sign of the AC signal input level is inverted in the AC signal level / frequency conversion device shown in FIG. 5. FIG. 6 is a waveform diagram for explaining an operation in the case where the AC signal input level sequentially increases in the AC signal level / frequency conversion apparatus shown in FIG. 5. It is a circuit diagram which shows the structure of the other Example of the AC signal level / frequency converter of this invention.

FIG. 5 shows a first embodiment of an AC signal level / frequency conversion apparatus for converting the level of an AC signal input into a frequency corresponding to the level according to the present invention. In FIG. 5, the same components as those in FIG. 1 are denoted by the same reference numerals. Reference numeral 10 denotes a circuit that outputs an output of a DC signal level corresponding to an AC signal input level, which is a feature of the present invention, that is, an AC signal level / DC signal level conversion device. , A latch circuit 12, an adder 13, a comparator 14, a switching circuit 15, an adder (subtracter) 16, and a previous value holding circuit (Z ⁻ ) 17.

Before describing the specific configuration of this embodiment in detail, the principle of the present invention will be described.
As described above, in the conventional example, since the AC (alternating current) component is included in the instantaneous power W, the ripple value is included in the integrated value Wh1, so that the period of the pulse train becomes coarse and dense. It was. The above-described problem of the pulse interval in the pulse train is caused by the fact that the increment of the integrated value Wh1 is not constant because the instantaneous power value W of the AC power waveform is integrated as it is, that is, the ripple component is included. Has occurred. Therefore, the present inventor has arrived at the present invention by paying attention to the fact that the coarse / fine cycle can be prevented if the integrated instantaneous power value Wh1 is uniform.

More specifically, the output for one period of the AC (alternating current) waveform can be handled in a direct current manner by calculating an average value, that is, a constant value. Therefore, as shown in the following expression, by integrating one period, an upper limit value W _UP of values to be integrated in the next one period is obtained as an average value.
W _UP = (W ₍₁₎ + W ₍₂₎ + W ₍₃₎ + W ₍₄₎ +… + W _(N) ) / N
= ΣW _(i) / N
In the above equation, i represents a sampling number within one period, N represents the number of samples in one period (for example, a frequency of about 7.8 kHz), and Σ represents i = 1, 2,. _Represents the addition of W _(i) for.

When determining the output value W _OUT (that is, the output value for integration that is the value integrated by the integrator), the following case classification is performed with respect to the average value W _UP . In this description, it is assumed that the sign of the input value remains positive. W _REST is an output of the adder (subtracter) 16 and is a value obtained by subtracting the output W _OUT of the switching circuit 15 from the output W _SUM of the adder 13, and W _SUM is an input power value. This is a value obtained by adding W _REST before one sampling to W.
(B) When W _SUM is less than or equal to W _UP (W _SUM ≤ W _UP )
W _OUT = W _SUM
W _REST = W _SUM −W _OUT = 0
(B) When W _SUM is greater than W _UP (W _SUM > W _UP ),
W _OUT = W _UP
W _REST = W _SUM −W _OUT

When the integration output value W _OUT is determined by dividing the cases as described above, W _OUT becomes equal to W _UP , whereby the integration value is increased by a certain amount. However, in the initial state, W ₍₁₎ , W ₍₂₎ , ..., W _(i) , ..., W _(N) must be output as they are for the first period until W _UP is determined. become. In the first period, it may be set to output a zero level as W _OUT .

FIG. 6 is a schematic waveform diagram for explaining that W _OUT = W _UP by performing the above case classification. (A), (B), and (C) are instantaneous powers, respectively. The values W, W _SUM (= W + (W _REST before one sampling)), and W _OUT are represented.
As described above, in the first cycle of the power value W, an average value of W is obtained and stored as W _UP . Therefore, in the first first cycle, the input W is output as the output W _OUT , and W _SUM is zero.
In the second period, when the input W is below the average value W _UP , W = W _SUM , so W _SUM ≤ W _UP (in the case of (A)), and W _SUM (= W) is W _OUT Is output. When W _SUM > W _UP at time t ₁ (in the case of (B)), W _UP, that is, an average value is output as W _OUT , and W _SUM ≦ W _UP ((I) again at time t ₂ . ), W _SUM is output as W _OUT .
In the third and subsequent cycles, since W _SUM > W _UP is always satisfied (in the case of (B)), W _UP is output as W _OUT .

As a result, as shown in FIG. 6 (C), in the third period or more, W _{OUT as} an input to the integrator is constant regardless of whether the value of W is greater than or less than the average value W _UP . The output from the accumulator becomes a certain amount of increase, that is, linear, and the above-described problem of pulse train density can be prevented.
In addition, since the average value for one period is set as the upper limit value W _UP , if out-of-phase power W is input and the upper limit value and the sign of W are different, W _OUT is forced by detecting it. Can be zero. Therefore, it is not necessary to provide the canceling circuit provided in the conventional example.

Returning to FIG. 5, the configuration and operation of an embodiment of the AC / frequency converter of the present invention based on the above principle will be described in detail.
The average value calculation unit 11 receives the signal W indicating the power value output from the multiplier 103, and calculates the average value of the power of the commercial power source for each period j. The calculated average value is latched by the latch circuit 12, used as the upper limit value W _UP in the period j + 1, and supplied to one input terminal of the comparator 14 and one input terminal of the switching circuit 15.
As described above, the average value calculated in the period j of the power W is latched, supplied to the comparator 14 and the switching circuit 15 in the period j + 1, and used as the upper limit value of the output from the switching circuit 15.

The calculation of the average value of W in the average value calculation unit 11 can be obtained by integrating the sample values for one cycle of W and dividing the integrated value by the number of samples for one cycle as described above. . Further, when W phase of the current and voltage in a sine wave is coincident, in order to calculate the average value of one period of the power from the electric energy _{W = (V P I P /} 2) cosθ is the maximum value Since it can be calculated if the minimum value is known, it can also be calculated by detecting the maximum value W _MAX and the minimum value W _MIN within one period and dividing these added values by 2.
W _UP = (W _MAX + W _MIN ) / 2
At this time, if the period of the waveform is already known, the timing at which the maximum value W _MAX and the minimum value W _MIN can be sampled with reference to the zero cross timing is detected by detecting the zero cross timing. And the end point are set to detect the maximum value W _MAX and the minimum value W _MIN and calculate the average value.

After the calculation of the upper limit value W _UP , substantial measurement of the electric energy is started in the second period and thereafter. As described above, the power signal supplied during one period of substantial measurement is Let i be the sampling number and represent W _(i) (i = 1, 2,..., N).
The switching circuit 15 is switched when the output of the comparator 14 is applied as a control signal. When W _{SUM (i)} ≦ W _UP (in the case of (A)), the output W _{SUM (i)} of the adder 13 is changed. When W _UP <W _SUM (in the case of (B)), the output W _UP of the latch circuit 12 is supplied to the integrator 105 as the output signal W _{OUT (i)} . The state of the switching circuit 15 in FIG. 5 represents the case of W _UP <W _SUM .
The adder 16 adds the output W _{SUM (i)} of the adder 13 and the inverted signal of the output W _{OUT (i)} of the switching circuit 15, that is, subtracts W _{OUT (i)} from W _{SUM (i)} Output signal W _{REST (i)} . The signal W _{REST (i)} is held in the previous value holding circuit 17. The previous value holding circuit 17 outputs W _{REST (i−1)} inputted last time at the timing of sampling i, and this output is supplied to the other input terminal of the adder 13.

The output W _{SUM (i)} of the adder 13 is a value obtained by adding the output W _{REST (i−1)} of the previous value holding circuit 17 to the power W _(i) , and can be expressed as follows.
W _{SUM (i)} = W _(i) + W _{REST (i-1)}
Also, the output W _{REST (i)} of the adder 6 is obtained by subtracting W _{OUT (i)} from the output W _{SUM (i)} of the adder 13 and can be expressed as follows.
W _{RESET (i-1)} = W _{SUM (i-1)} -W _{OUT (i-1)}
From these two equations,
W _{SUN (i)} = W _(i) + W _{SUM (i-1)} -W _{OUT (i-1)}
= W _(i) + (W _(i-1) + W _{SUM (i-2)} -W _{OUT (i-2)} ) -W _{OUT (i-1)}
= ΣW _(i) + W _{SUM (0)} −ΣW _{OUT (i-1)}
Is obtained.

As is apparent from the above equation, W _SUM output from the adder 13 in the apparatus of FIG. 5 is as shown in FIG. In particular, in the second cycle, W _{SUM (0)} corresponds to W _{SUM (N)} of the last sample number N in the first cycle, and is 0 and can be ignored, and W (1) = because it is _{0, W SUN (1) =} 0, W SUN (2) = W (2), a _{W SUN (3) = W (} 3), W SUN (4) is a W ₍₄₎ ( W ₍₃₎ -W _{OUT (2)} -W _{OUT (3)} ) is added. Furthermore, W _{SUM (0)} in the third cycle corresponds to W _{SUM (N)} of the last sample number N in the second cycle, and since W _{SUM (N)} is larger than W _UP , the switching circuit 15 The output W _UP of the latch circuit 12 is output as W _{OUT (i)} . The fourth and subsequent cycles are the same as the third cycle.
Thus, it can be seen that the W _SUM and W _OUT waveforms shown in FIG. 6 can be obtained by the AC signal level / DC signal level conversion apparatus 10 shown in FIG.

As described above, when the input waveform is a sine wave, W _UP is always output as W _OUT after the third period. Thereafter, if the middle power cycle is interrupted, because the W _SUM is W _SUM ≦ W _UP and lower than W _UP latched, so that the switching circuit outputs the W _SUM. Then, W _SUM decreases depending on W, and W _OUT is subtracted by the adder 16, so that W _OUT = W _SUM rapidly becomes zero level. Therefore, W _UP is not continuously output even when the power supply is cut off. As a result, an output accurately corresponding to the actual power W can be obtained.

By the way, as shown in FIG. 7, the power value Wj-1 of the previous cycle j-1 may be positive, and the sign of the power value may be negative in the cycle after the current cycle j. For example, when the load on the current side is not determined due to the influence of line noise when the load is light (the amount of power used is small), it is assumed that the sign of the power in the previous period and the current period is reversed. In such a case, in the AC signal level / DC signal level conversion apparatus 10 shown in FIG. 5, the input power Wj in the current period j is equal to or less than the average value, so that the power value Wj-1 including the AC component remains as it is. Will be output.
As described above, when the sign of the average value and the input value W is different, a sign inversion detection unit (not shown) for detecting the sign is provided, and the output W _OUT for one cycle immediately after the sign inversion is held at zero. Then, by using the average value detected in the cycle j + 1 as W _UP , it is possible to obtain a constant output that does not include an AC component.

In addition, for example, the amplitude of the input power W may be gradually increased instead of being constant, as in the case of detecting darkness with a sensor and automatically increasing the intensity of illumination accordingly. FIG. 8 shows a waveform diagram when the input power W gradually increases and the average value gradually increases. In this case, the input power value Wj of the current cycle j is the preceding period j-1 of the mean = will have a larger average value than the upper limit value Wj _UP, W _SUM will cause an overflow. For example, the adder 13 as a reference to 32 bit integrating counter, assuming Wj than the period of the previous one by 128 increases, W _SUM at about 5 hours (33554432 samples) overflows.
In order to prevent this, W _UP may be increased gradually by adding 128 / (number of samples in one cycle) to the average value W _UP .

That is,
Wj _UP = Calculated average value Wj-1 _UP + (Wj-1 _REST (remaining power) / number of samples in one cycle)
In the above formula, the calculated average value itself calculated by the average value calculating circuit 11 increases as the input power increases, but in addition to the calculated average value (Wj-1 _REST / number of samples in one cycle) by adding, before it is possible to cycle j-1 of Wj-1 _REST output in the current cycle j, Thus, since there is no carry over the remainder fraction to the next cycle j + 1, the overflow of the adder 13 Can be prevented.

Furthermore, the power measurement range may be determined when the load is light. For example, there is a device whose starting current value is defined by JIS standards, and since the starting current is defined in such a device, the user sets the measurement range of the watt-hour meter to a predetermined range. . When the power measurement range is determined in this way, it may be configured such that zero is output as W _OUT when it is outside the measurement range.
FIG. 9 shows another embodiment of the present invention configured to output zero as W _OUT when it is outside the measurement range. In this embodiment, as shown in FIG. 9, range setting means 18 and a switch 19 are added to the AC signal level / DC signal level conversion apparatus 10 shown in FIG. Then, the user sets the measurement range in the range setting unit 18, and the range setting unit 18 monitors whether or not the calculated average value calculated in the average value calculation circuit 11 is within the set range, and the light load For example, when the predetermined range is not entered, the switch 19 is switched by the output of the range setting means 18 to forcibly make the input to the comparator 14 zero. Thereby, the average value, that is, the upper limit value W _UP can be prevented from being output. Further, the output of the switching circuit 15 may be forced to zero in conjunction with the switching of the switch 19.

  Since the present invention is configured as described above, a DC signal level corresponding to an AC signal input level can be output without using a large LPF, and an AC signal can be output using the DC signal level. When generating a pulse train having a frequency corresponding to the input level, the pulse train does not become coarse or dense. Furthermore, when the present invention is applied to a watt-hour meter, a relatively simple and small-sized watt-hour meter can be provided, and when a power fluctuation occurs, a DC signal level that immediately follows it is output. Therefore, an output that follows the power supply fluctuation with high accuracy can be generated from the watt-hour meter.

  In the above description, the power value is described as an AC signal input. However, the AC signal level / DC signal level conversion device and the AC signal level / frequency conversion device of the present invention are not limited to the power value. It will be apparent that the present invention can be applied to the measurement of the level.

Claims (7)

An apparatus for converting an alternating current (AC) signal input level sampled at a predetermined frequency into a direct current (DC) signal level corresponding to the level and outputting the same from an output terminal,
An average value calculating / holding means for calculating an average value of each cycle of AC signal input and outputting an average value of one cycle before during the current cycle;
A comparison means for applying a signal output from the average value calculation / holding means to one input terminal and comparing the signal to a signal applied to the other input terminal;
Switching means that is switched by the output of the comparison means and selectively outputs a signal applied to one input terminal of the comparison means and a signal applied to the other input terminal, the signal having the smaller value Switching means for outputting
Subtracting means for subtracting the signal output from the switching means from the signal applied to the other input terminal of the comparing means;
Storing the signal obtained by the subtracting means and outputting the signal obtained by the subtraction before one sampling;
An AC characterized by comprising an addition means for adding the signal from the previous value holding means and the current sampling AC signal input and supplying the obtained value to the other input terminal of the comparator and the switching means. Signal level / DC signal level converter. In the AC signal level / DC signal level conversion device according to claim 1, the average value calculation / holding means detects the maximum value and the minimum value of the AC input, and calculates 1/2 of the sum of them. An AC signal level / DC signal level conversion device configured to calculate an average value. 3. The AC signal level / DC signal level conversion apparatus according to claim 1 or 2, wherein the average value calculating / holding means further includes a previous value stored in the previous value holding means in the calculated average value of one cycle before. And an AC signal configured to output a value obtained by adding a value obtained by dividing the previous value of the last sampling of the previous cycle by the number of samplings of one cycle as an average value during the current cycle. Level / DC signal level converter. The AC signal level / DC signal level conversion apparatus according to any one of claims 1 to 3, wherein the apparatus further includes:
AC signal level / DC characterized by comprising means for detecting the time when the sign of AC input is inverted and forcibly setting the output from the switching means to zero level for at least one period from that time Signal level conversion device. 5. The AC signal level / DC signal level conversion device according to claim 1, wherein the device further comprises:
Means is provided for monitoring the average value calculated by the average value calculation / holding means, and forcibly outputting the average value as a zero value when the average value is outside a predetermined range. AC signal level / DC signal level converter. An AC signal level / frequency conversion device that converts an alternating current (AC) signal input level supplied to an input end into a frequency corresponding to the level and outputs the frequency from the output end,
AC signal level / DC signal level conversion device according to any one of claims 1 to 5,
Integration means for integrating the output of the AC signal level / DC signal level conversion device;
A means for outputting a pulse each time the output of the integrating means reaches a predetermined value, and a pulse generating means for generating a pulse train having a frequency corresponding to the level of the AC signal input by resetting the integrator by the pulse; An AC signal level / frequency conversion device characterized by comprising: An watt-hour meter for measuring the amount of power of an alternating current (AC) power source to be input, comprising the AC signal level / frequency conversion device according to claim 6.