JP2017049142A - Device for detecting state change of weighting meter, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To more reduce misdetection of state change of a weighting meter than conventional ones, by referring to a time series change of a used amount of an object.SOLUTION: A state change detection device 10 includes: a used amount calculation unit 12 configured to calculate a used amount of an object and a cumulative value of the used amount at every predetermined time, based on a pulse signal transmitted from a weighting meter 2; a feature amount calculation unit 13 configured to calculate an increment of the cumulative value at every predetermined time and a ratio of the increment to a previous increment as feature amounts; and an abnormality detection unit 14 configured to detect abnormality of the weighting meter 2 by referring to time series change of the feature amounts.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an apparatus for detecting exchange and disconnection (hereinafter referred to as “state change”) of a metering meter represented by electricity, gas, water supply, heat quantity (hereinafter referred to as “object”).

  Analog metering meters are widely used for metering the amount of objects used. The meter can output an electrical signal of one pulse per unit usage amount, and a monitoring device such as a building monitoring system (hereinafter referred to as “BAS”) receives the pulse signal. Thus, the meter value can be monitored by BAS or the like without visually checking the value (hereinafter referred to as “meter value”) indicated by the meter at the place where the meter is installed. The number of pulses per unit usage is defined as a pulse constant for each meter, for example, “pulse / kWh” in the case of electricity.

  If the connection line connecting the meter and the monitoring device such as BAS is disconnected due to deterioration over time, or is replaced without permission with another meter with a different pulse constant, the number of pulse signals received by the BAS changes. . Using this, the disconnection or replacement of the meter may be detected by analyzing the amount of use of the object, that is, the time-series change in the number of received pulses.

  As a prior example relating to the present invention, Patent Document 1 discloses an apparatus for distinguishing instantaneous measurement error (noise) of a metering meter from instantaneous use amount. Patent Document 2 discloses a system that detects an abnormality of a flow control valve of a water meter.

JP 2010-96539 A JP 2008-269055 A

  Originally, the number of pulse signals of the metering meter depends on the operating conditions of the equipment using the object. For example, the number of pulse signals transmitted from the metering meter to the BAS changes when the equipment is stopped or the equipment is increased. Therefore, if an attempt is made to detect disconnection or replacement of the meter from the increase / decrease in the number of pulse signals, that is, the time-series change in the amount of the object used, Disconnection or replacement may be detected erroneously.

  In order to reduce such false detection, an average value of the usage amount over a certain period may be used. Since the time series change of the average value is slower than the time series change of the usage amount, using the average value reduces false detection of a change in the meter state due to a temporary usage change. be able to. However, since the change becomes slow, it takes time to detect the state change that should be detected originally, and thus it is not possible to use the average value for a longer period than necessary. As a result, there is a limit to the false detection reduction effect, so another method is expected.

  Patent Document 1 discloses an apparatus for distinguishing instantaneous noise of a metering meter from instantaneous usage. The usage amount erroneously measured by noise is sufficiently small compared with the usage amount that is originally intended to be measured, so that when the usage amount exceeds a specified threshold value, it is distinguished from noise. However, when the metering meter is disconnected and when the equipment is suspended, the amount of use is almost zero, so it is difficult to distinguish between the amount of use.

  Patent Document 2 discloses a system for detecting an abnormality of a flow control valve installed upstream of a water meter. However, there is no mention of reducing false detection of abnormalities.

  The present invention has been made to solve the above-described problems, and aims to reduce erroneous detection of changes in the state of a meter as compared with the prior art with reference to time-series changes in the amount of object used. .

  The state change detection device for a meter according to the present invention is based on a pulse signal transmitted from a meter of an object, and an increase amount per unit time of a cumulative value of the amount used of the object and within a unit time immediately before Feature amount calculation means for calculating a ratio of the increase amount to the increase amount as a feature amount that represents a time-series change in the usage amount of the target object, a time series change of the feature amount calculated by the feature amount calculation means, and its feature amount Detecting means for detecting a change in the state of the weighing meter based on the magnitude relationship between the threshold value and the threshold value. The detecting means has a first threshold value of 1 + α (α is a positive value) and 1−α as a threshold value. When the ratio is equal to or higher than the first threshold value or equal to or lower than the second threshold value as a detection candidate for the change in state of the meter, the ratio is equal to or higher than the first threshold value. Or when It said ratio within a predetermined time period in the past or future when there is a time equal to or lower than the second threshold value is one that does not detect a state change of the weighing meter.

  Further, when the detection means detects a change in the state of the weighing meter from the relationship between the ratio and the threshold value, but the increase amount may be zero within a predetermined period in the past from the time of the detection. Is not detected as a change in state of the meter.

  The program according to the present invention is based on a pulse signal transmitted from a metering meter of an object, and increases the amount of accumulated usage of the object per unit time and the amount of increase within the immediately preceding unit time. Feature amount calculation means for calculating a ratio of the increase amount as a feature amount representing a time-series change in the usage amount of the target object, a time-series change of the feature amount calculated by the feature amount calculation means, and the feature amount and a threshold value It functions as a detection unit that detects a change in the state of the meter based on the magnitude relationship, and the detection unit includes a first threshold value of 1 + α (α is a positive value) and a second threshold value of 1-α as threshold values. When the ratio is greater than or equal to the first threshold or less than or equal to the second threshold when the ratio is set as a detection candidate for the change in state of the meter, but the ratio is greater than or equal to the first threshold Et if the ratio within a predetermined time period in the past or future is when: the second threshold value is one that does not detect a state change of the weighing meter.

  ADVANTAGE OF THE INVENTION According to this invention, the misdetection of the state change of a measuring meter can be reduced rather than before with reference to the time-sequential change of the usage-amount of a target object.

It is the block block diagram which showed one Embodiment of the state change detection apparatus of the metering meter which concerns on this invention. It is a hardware block diagram of the state change detection apparatus in this Embodiment. It is the figure which showed an example of the data structure of the meter information memorize | stored in the meter information storage part in this Embodiment. It is the flowchart which showed the state change detection process in this Embodiment. It is a graph used in order to demonstrate operation | movement of the feature-value calculation part in this Embodiment. It is a graph used in order to demonstrate operation | movement of the abnormality detection part in this Embodiment. It is another graph figure used in order to demonstrate operation | movement of the abnormality detection part in this Embodiment. It is another graph figure used in order to demonstrate operation | movement of the abnormality detection part in this Embodiment. It is another graph figure used in order to demonstrate operation | movement of the threshold value setting part in this Embodiment.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
Embodiment 1 FIG.

  FIG. 1 is a block diagram showing an embodiment of a state change detection device for a metering meter according to the present invention. FIG. 1 shows a meter change detection device (hereinafter simply referred to as “state change detection device”) 10 and a meter 2. As described above, the objects include electricity, gas, water, and heat. The state change detection device 10 in the present embodiment is a device that is electrically connected to the metering meter 2 and detects a state change of the metering meter 2 based on a pulse signal transmitted from the metering meter 2. Although two weighing meters 2 are illustrated in FIG. 1, the state change detection device 10 may detect a state change of the other number of weighing meters 2.

  FIG. 2 is a hardware configuration diagram of a computer forming the state change detection device 10 according to the present embodiment. The computer forming the state change detection apparatus 10 in the present embodiment can be realized by a general-purpose hardware configuration that has existed in the past, such as a personal computer (PC). That is, as shown in FIG. 2, the computer connects the CPU 21, ROM 22, RAM 23, hard disk drive (HDD) 24, mouse 25 and keyboard 26 provided as input means, and display 27 provided as a display device. An input / output controller 28 and a network controller 29 provided as communication means are connected to an internal bus 30.

  Returning to FIG. 1, the state change detection device 10 according to the present exemplary embodiment includes a pulse signal reception unit 11, a usage amount calculation unit 12, a feature amount calculation unit 13, an abnormality detection unit 14, an output unit 15, a threshold setting unit 16, a meter. An information storage unit 17 and a ratio storage unit 18 are included. In FIG. 1, components not used in the description of the present embodiment are omitted from FIG. The pulse signal receiving unit 11 receives a pulse signal transmitted from the weighing meter 2.

  The usage amount calculation unit 12 receives the pulse signal received by the pulse signal reception unit 11 and calculates the usage amount of the object. For example, when a pulse unit receives 1 pulse from a 1 pulse / kWh electric meter, it is calculated that 1 kWh is consumed. Further, the usage amount calculation unit 12 calculates the cumulative value of the object by calculation and records it in the meter information storage unit 17. For example, it is assumed that 10 pulses have been received in the past from an electric meter with a pulse unit of 1 pulse / kWh, and 10 kWh has been recorded as a cumulative value. In this state, when a new pulse is received, the accumulated value is updated to 11 kWh. Further, the usage amount calculation unit 12 may record the time-series change of the accumulated value in the meter information storage unit 17. For example, the cumulative value is recorded every hour, the cumulative value at 12:00 is recorded in the meter information storage unit 17, and when the current time is 13:00, the usage amount calculation unit 12 The current cumulative value is recorded in the meter information storage unit 17 as the cumulative value at the time. The current time is obtained from time measuring means (not shown). Here, the recording interval of the time series change is described as one hour, but any interval may be used. It is assumed that the recording interval is preset in the usage amount calculation unit 12.

  The feature amount calculation unit 13 obtains a feature amount representing a time series change of the usage amount of the target object from the time series change of the accumulated value calculated by the usage amount calculation unit 12 based on the pulse signal received by the pulse signal reception unit 11. calculate. The abnormality detection unit 14 detects the state change of the meter 2 based on the time-series change of the feature amount calculated by the feature amount calculation unit 13 and the magnitude relationship between the feature amount and the threshold value.

  In the present embodiment, the exchange and disconnection of the metering meter are defined as “state change” as described above. However, in the case of replacement with a correct weighing meter, no problem occurs, so this case does not correspond to a state change. On the other hand, the disconnection between the meter 2 and the monitoring device such as BAS may not be an abnormality of the meter 2 itself, but causes a problem that the pulse signal transmitted from the meter 2 cannot be received. It was handled as a change in the state of the meter 2. That is, the “state change” of the weighing meter 2 that is detected by the state change detection device 10 according to the present embodiment and is the output target of the detection result is synonymous with “abnormality detection”.

  When the abnormality detection unit 14 detects a change in the state of the metering meter 2, the output unit 15 outputs the detected change in the state of the metering meter 2 and the estimated time when the state change has occurred in a prescribed manner. . The feature amount calculation unit 13 in the present embodiment calculates, as the feature amount, the increase amount per unit time of the accumulated value of the usage amount of the object and the ratio of the increase amount to the immediately previous increase amount. The ratio calculated by the feature amount calculation unit 13 is stored. Based on the accumulated ratio, the threshold setting unit 16 sets a threshold to be used when detecting a change in the state of the weighing meter 2 by calculation.

FIG. 3 is a diagram showing an example of a data configuration of meter information stored in the meter information storage unit 17 in the present embodiment. The meter information is associated with the following information for each weighing meter 2. The serial number is an identifier of the weighing meter 2 and is an arbitrary numerical value. The object is information for specifying an object to be measured by the metering meter 2, and corresponds to electricity, gas, water supply, heat quantity, and the like. Instead of recording as electricity, gas, water, or heat, it may be recorded with a corresponding symbol such as A or B. Units and is a unit of the measurement object, for example, if the electric kWh, etc. kWs and m ³ If gas, such as m ³ if water, if the amount of heat J, MJ is recorded. The pulse unit represents the number of pulses per unit usage and is recorded as a numerical value. The consumption facility name is the name of the facility that consumes the measurement target of the metering meter 2, and air conditioning / cooling equipment, lighting, and the like are recorded therein. In addition, it may record with applicable symbols, such as A and B, instead of recording with air-conditioning cold / heat and illumination. The above item values need to be set in advance before the operation of the present embodiment.

  Among the fields for storing the accumulated value, the current accumulated value is set to the accumulated value of the latest usage amount of the object. In the accumulated value (i = 1, 2, 3,...), The accumulated value of the usage amount of the object at each date is set. The usage amount calculation unit 12 writes the accumulated value of the usage amount of the metering meter 2 in the meter information storage unit 17 every time it calculates. The current cumulative value is updated with the latest cumulative value, but the past cumulative value is recorded without being deleted.

  Each component 11-15 in the state change detection apparatus 10 is implement | achieved by cooperation operation | movement of the computer which forms the state change detection apparatus 10, and the program which operate | moves by CPU21 mounted in the computer. Each storage unit 17, 18 is realized by the HDD 24 mounted in the state change detection device 10. Alternatively, the RAM 23 or an external storage means may be used via a network.

  Further, the program used in this embodiment can be provided not only by communication means but also by storing it in a computer-readable recording medium such as a CD-ROM or USB memory. A program provided from a communication unit or a recording medium is installed in a computer, and various processes are realized by the CPU 21 of the computer sequentially executing the program.

  Next, the state change detection process performed by the state change detection device 10 in the present embodiment will be described with reference to the flowchart shown in FIG.

  In step 101, the pulse signal receiving unit 11 receives a pulse signal from the weighing meter 2. In the present embodiment, the processing described below is equally performed on the pulse signals from the respective metering meters 2 regardless of the difference in the object, and therefore attention is paid to the pulse signals from one weighing meter 2 here. To explain.

  When the pulse signal is received, in step 102, the usage amount calculation unit 12 obtains the pulse unit and unit of the metering meter 2 that has transmitted the pulse from the meter information storage unit 17, and calculates the usage amount. For example, when the pulse unit is 10 and the unit is kWh, it is calculated that the electric energy of 10 kWh is used by receiving the pulse. The calculated usage amount is added to the current cumulative value stored in the meter information storage unit 17 to update the current cumulative value.

  In step 103, when a predetermined time has elapsed since the last update of the current cumulative value and the specified time has come, the stored current cumulative value is stored as a past history. For example, when the time is 10:00 on January 1 and the time is a predetermined time, the current accumulated value is left in the meter information as the accumulated value on 1 January 1st. This process may be performed by a meter information management unit or the like (not shown).

  In step 104, the feature amount calculation unit 13 calculates a feature amount for detecting a state change from the time series change of the accumulated value stored in the meter information storage unit 17. For example, the ratio y of the increase amount of the cumulative value is calculated. As shown in FIG. 5A, the value of the accumulated value at a certain time i is defined as f (i). Let f (i−N) be the cumulative value of N (N ≠ 0) past from i. In this case, as shown in FIG. 5B, the increment g (i) of the cumulative value can be calculated as g (i) = f (i) −f (i−N). In this case, as shown in FIG. 5C, the ratio y of the increase amount of the cumulative value can be calculated as y (i) = g (i) / g (i−N). For example, when N = 1, the increase amount of the accumulated value at the immediately preceding time (i−1) is g (i−1) = f (i−1) −f (i−2), and the accumulated value at the current time i. The increase amount of the value can be calculated as g (i) = f (i) −f (i−1), respectively, but the ratio y of the increase amount of the accumulated value that can be calculated at the current time i is y (i). = G (i) / g (i-1), that is, the cumulative value increase amount g (i) at the current time i with respect to the cumulative value increase amount g (i-1) at the immediately preceding time (i-1). it can.

  When the most recent increase value g (i) is close to the past increase value g (i−N), the ratio y (i) is close to 1. On the other hand, when the most recent cumulative value increase amount g (i) and the past cumulative value increase amount g (i−N) are significantly different, the ratio y (i) is a value relatively far from 1. Show. For example, when disconnection occurs, the ratio y (i) becomes zero. Further, when only one line is disconnected in the three-wire measuring meter 2, the number of pulses received from the measuring meter is halved, and thus the ratio y (i) is likely to be a value of 0.5 or less. In many cases, the pulse unit of the metering meter 2 is defined by an integer multiple, for example, a numerical value such as 1 or 10. Therefore, when it changes to another metering meter 2 from which a pulse unit differs, the number of pulses which state change detection device 10 receives becomes an integral multiple, for example, 10 times or more, or becomes 1/10 or less. In this case, the ratio y (i) is likely to be a value relatively far from 1, such as 10 or more, or 0.1 or less. Accordingly, since the ratio y (i) shows a value relatively far from 1, it is possible to detect a change in the state of the metering meter 2.

  In step 105, the abnormality detection unit 14 detects a change in the state of the meter 2 using the feature amount calculated by the feature amount calculation unit 13 as follows.

First, the abnormality detection unit 14 compares the ratio y (i) calculated by the feature amount calculation unit 13 with the prescribed threshold values (1 + α) and (1-α),
(Y (i))
A case where the condition is satisfied is set as a detection candidate 1 for a change in the state of the weighing meter 2. Α is a positive value.

  When the increase amount of the object temporarily increases during a short period (T) as shown in FIG. 6 (a), the ratio y is a positive threshold (1 + α) as shown in FIG. 6 (b). ) (Hereinafter “first threshold value”) or more, and then becomes the minus threshold value (1-α) (hereinafter “second threshold value”) or less. When the state change of the weighing meter 2 occurs, it is unlikely that the increase amount will return to the same level as the original value after the increase amount of the object increases. Is also unlikely. Therefore, when the ratio y indicates a time series change including both a value greater than or equal to the first threshold and a value less than or equal to the second threshold during the period T, it is not detected as a state change of the metering meter 2. That is, it is not detected as an abnormality.

  Similarly, when the increase amount of the object temporarily decreases during the short period (T) as shown in FIG. 7 (a), the ratio y becomes the second value as shown in FIG. 7 (b). After becoming below the threshold, it becomes above the first threshold. When the change in the state of the meter 2 occurs, it is unlikely that the amount of increase will return to the same level as the original value after the amount of increase in the object has decreased. Is also unlikely. Therefore, when the ratio y indicates a time series change including both a value less than or equal to the second threshold value and a value greater than or equal to the first threshold value during the period T, it is detected as a state change of the metering meter 2, that is, an abnormality do not do.

That is, for x [i−T, i + T]
y (x)> 1-α
Or y (x) <1 + α
When the condition is satisfied, it is set as the detection candidate 2 for the state change of the weighing meter 2.

  When the increase amount of the object increases from 0 as shown in FIG. 8 (a), the ratio y is the first regardless of the change in the state of the meter 2 as shown in FIG. 8 (b). The threshold is exceeded. Therefore, when the increase amount indicates 0 during the predetermined period S, it is not detected as a state change of the metering meter 2. Alternatively, since the ratio y is calculated as y (i) = g (i) / g (i−N), the ratio y cannot be calculated when the past increase amount g (i−N) indicates 0. Therefore, if the ratio y cannot be calculated during the period S, it is not detected as a change in the state of the weighing meter 2, that is, an abnormality.

That is, if x is a real number, x [i−S, i]
y (x) / 0
When the condition is satisfied, it is set as the detection candidate 3 for the state change of the weighing meter 2.

  The abnormality detection unit 14 detects the change in state of the meter 2 when y (i) corresponding to all or a part of the detection candidates 1, 2, 3 of the state change is detected. In addition, i at this time is an estimated time when the state change occurs.

  Additional facilities may be temporarily operated depending on the operation in the building. Thereby, the increase amount of a target object may show a time-sequential change like FIG. 6 irrespective of replacement | exchange of the measurement meter 2, or a disconnection. In addition, when the calendar is a holiday such as New Year, Bon Festival, Golden Week, etc., each facility in the building will be suspended. Since each facility is restarted after the holiday, the amount of increase in the object may show a time-series change as shown in FIGS. 7 and 8 regardless of the exchange of the metering meter 2 or disconnection. The abnormality detection unit 14 in the present embodiment prevents detection of a change in the state of the meter 2 when the time-series change of the feature quantity does not satisfy a predetermined condition. Detection can be reduced.

として演算できる。ここで、数１におけるＭはｙ（ｉ）の総サンプル数である。閾値設定部１６は、比率ｙ（ｉ）を比率蓄積部１８から読み出し取得する。 In step 106, the threshold setting unit 16 updates the variable α included in the threshold used by the abnormality detection unit 14. As shown in FIG. 9, the ratio y (i) calculated by the feature amount calculation unit 13 is Poisson distributed around the average value 1. In this case, the standard deviation σ of the ratio y (i) is

Can be calculated as Here, M in Equation 1 is the total number of samples of y (i). The threshold setting unit 16 reads and acquires the ratio y (i) from the ratio storage unit 18.

  The Poisson distribution is known to be an excellent approximation of the normal distribution. In the case of the normal distribution, it is known that the average value ± σ range includes about 68% of the whole, the average value ± 2σ range of about 95% of the whole, and the average value ± 3σ of about 99% of the whole. ing. Therefore, when the threshold value setting unit 16 updates the variable α to α = 3σ, the abnormality detection unit 14 sets the ratio y (i) that does not fall within about 99% of the normal Poisson distribution as the state change of the meter 2. It becomes possible to detect appropriately. Note that the variable α is not necessarily 3σ, and may be a constant multiple of σ.

  In step 107, the output unit 15 outputs the detection of the state change by a prescribed method when the abnormality detection unit 14 detects the state change of the metering meter 2. For example, the state change detection is displayed on the display 27. Specifically, the serial number of the weighing meter 2 in which the state change is detected is displayed. Sound / announcement is output from a speaker or the like (not shown) in order for the administrator of the state change detection device 10 to notice that the state change detection device 10 detects the state change and displays the detection result on the display 27. May be. Alternatively, when the network controller 29 is connected to the public line network, the output unit 15 may transmit the state change detection result to a preset transmission destination. Moreover, the output part 15 may output simultaneously the time estimated that the state of the measurement meter 2 changed. The time when the state of the metering meter 2 is estimated to be changed is the time when the abnormality detection unit 14 detects the state change.

  In FIG. 4, a series of state change detection processes are illustrated to end after the end of step 107, but the process may be repeated by returning to step 101 and receiving the next pulse signal. .

  According to the present embodiment, focusing on the time-series change in the usage amount of the object, even when a change in the state of the metering meter 2 is detected, the state is found when a certain rule can be derived from the content of the time-series change in the usage amount Since the change is not regarded as a change, it is possible to reduce erroneous detection of the abnormality of the metering meter 2.

  In the first embodiment, the state change detection device 10 is configured as shown in FIG. 1, but it is not necessary for the state change detection device 10 to have all the components shown in FIG. For example, the weighing meter 2 may be connected to the BAS and the accumulated value may be held and managed by the BAS. In this case, the pulse signal reception unit 11, the usage amount calculation unit 12, and the meter information storage unit 17 may be provided outside the state change detection device 10 such as BAS. And the state change detection apparatus 10 should just acquire the information which needs the process mentioned above from the exterior.

  2 Metering meter, 10 State change detection device, 11 Pulse signal receiving unit, 12 Usage amount calculating unit, 13 Feature amount calculating unit, 14 Abnormality detecting unit, 15 Output unit, 16 Threshold setting unit, 17 Meter information storage unit, 18 Ratio Storage unit, 21 CPU, 22 ROM, 23 RAM, 24 hard disk drive (HDD), 25 mouse, 26 keyboard, 27 display, 28 I / O controller, 29 network controller, 30 internal bus.

Claims (3)

Based on the pulse signal transmitted from the weighing meter of the object, the amount of increase in the accumulated amount of the object used per unit time and the ratio of the increase to the increase in the unit time immediately before are used for the object. A feature amount calculating means for calculating as a feature amount representing a time-series change of the amount;
Detecting means for detecting a change in state of the meter based on a time-series change of the feature quantity calculated by the feature quantity calculating means and a magnitude relationship between the feature quantity and a threshold;
Have
In the case where a first threshold value of 1 + α (α is a positive value) and a second threshold value of 1-α are set as the threshold value, the detection means has the ratio equal to or higher than the first threshold value or lower than the second threshold value. If the ratio is less than or equal to the second threshold within a predetermined period in the past or future from when the ratio is greater than or equal to the first threshold, 2. A meter change detection device that does not detect a change in the state of the meter.   If the detection means detects a change in the state of the meter from the relationship between the ratio and the threshold value, but the increase amount is sometimes zero within a predetermined period in the past after the detection, the detection means 2. The state change detecting device for a meter according to claim 1, wherein the device is not detected as a state change of the meter. Computer
Based on the pulse signal transmitted from the weighing meter of the object, the amount of increase in the accumulated amount of the object used per unit time and the ratio of the increase to the increase in the unit time immediately before are used for the object. A feature amount calculating means for calculating a feature amount representing a time-series change of the amount,
Detecting means for detecting a change in the state of the meter based on a time-series change of the feature quantity calculated by the feature quantity calculating means and a magnitude relationship between the feature quantity and a threshold;
Function as
In the case where a first threshold value of 1 + α (α is a positive value) and a second threshold value of 1-α are set as the threshold value, the detection means has the ratio equal to or higher than the first threshold value or lower than the second threshold value. If the ratio is less than or equal to the second threshold within a predetermined period in the past or future from when the ratio is greater than or equal to the first threshold, A program which is not detected as a change in state of the meter.

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