Apparatus for counting rotation frequency of numeral wheel of meter for remote meter reading system

Disclosed is an apparatus for counting the rotation frequency of a numeral wheel of a meter to be used for a remote metering system. A light reflection tape is coated on one of low placed numeral wheels. A light sensor unit has an opaque case formed with first and second holes in which an infrared ray emitter and an infrared ray sensor are located, respectively. The light sensor unit is fixedly mounted on the ceiling of a rectangular shaped housing which is detachably coupled with a meter to cover the front of the meter. A portion of the housing over numeral wheels and a front plate of the meter is transparent. The transparent portion of the housing has an infrared ray rejection function to prevent infrared rays from entering into the housing. In place of employing such housing, a light shield may be used to shield a space between the light sensor unit and the light reflection tape coated numeral wheel from outer light. A microprocessor counts the rotation frequency of the light reflection tape coated numeral wheel by counting the number of output pulses from the infrared ray sensor to measure an amount of a supply, for example, gas used, A power supply portion using batteries supplies the light sensor unit and the microprocessor with necessary power. Particularly, for the minimum consumption of the battery power, an input signal for the infrared ray emitter is made in a pulse form signal of which duty ratio is under 1/100.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a remote meter reading system for a meter, and more particularly, to an apparatus for counting the rotation frequency of a numeral wheel of a meter which counts the rotation times of the numeral wheel of a predetermined digit in existing meters by a light sensing method, so that the used amount of a supply such as gas can be monitored from a remote place.

2. Description of the Prior Art

The amount of usage of supplies, such as electricity, gas, or water, is metered when the supplies pass through a meter. The amount of usage is expressed by a number value of a numeral wheel counter disposed on the front side of a meter. The charge for supply usage is determined with respect to the amount of usage. A manual meter reading method, by which in order to read a meter for the amount of the supply used, a meter-reading person visits each consumer's house and reads a meter, needs a lot of time and efforts and also causes much inconvenience.

In order to solve the problems of this manual meter reading method, a system enabling remote automatic meter reading of a meter is strongly demanded. Among remote automatic meter reading systems of a meter there is a digital meter. This is a meter formed for a digital method, not for a mechanical method, and outputs the amount of the supply used as a digital electric signal such that a remote automatic meter reading system can be easily built. However, since this needs to replace existing mechanical type meters, the expense is high, and the economic efficiency is low. Accordingly, it is difficult to practically apply this to ordinary household use. Alternatively, there is a meter which embeds a magnetic type lead switch or a hole sensor in a mechanical meter and produces electric pulses as a means to count the rotation frequency of a numeral wheel of a meter. However, the meter also has the problem that an existing mechanical meter cannot be used as is, and it is highly probable that a metering error by a magnet occurs. Due to these problems, a light sensing type apparatus for counting the rotation frequency of a numeral wheel of a meter is greatly attracting attention because it can utilize an existing meter while minimizing the effect to the performance of a meter or safety.

As prior art related to an apparatus for counting the rotation frequency of a numeral wheel of a meter using a light sensing method, there are Korean Patent Registration No. 10-0287540 entitled “Apparatus for generating signal of usage amount of meter by light sensing”, Korean Patent Application Laid-open No. 2000-0066245 entitled “Apparatus for counting rotation frequency of numeral wheel of meter”, and Korean Utility Model Registration No. 20-0273026 entitled “Apparatus for counting rotation frequency of numeral wheel of meter”. In constructing an apparatus for counting the rotation frequency of a numeral wheel of a meter in a light sensing method, forming a light sensor by means of an infrared ray emitter and an infrared ray sensor is the most practical and competitive way, considering requirements such as economic efficiency, stability of operations, the life span, and low power consumption.

FIGS. 1aand1bshow the structure of an apparatus disclosed in the Korean Utility Model Registration No. 20-0273026. According to this apparatus, a reflection sheet20is attached to the outer surface of a predetermined numeral wheel11aof a meter5. In addition, an optical sensor unit22is formed with a light emitter22aemitting light to the numeral wheel11aand an optical sensor22bdetecting the light reflected by the reflection sheet and outputting the detected light as an electric signal. This optical sensor unit22is mounted on the inner surface of a housing21and then this housing21is detachably coupled with the cover12on the front of the meter5by covering the cover12. The optical sensor unit22is formed by means of an infrared ray emitter22aand an infrared ray sensor22b. The optical sensor unit22and the reflection sheet20are installed only over the lowest digit numeral wheel. A part of the housing21on which the optical sensor unit22is mounted should be made to be opaque or translucent, while a part of the housing facing the numeral wheel counter formed with the remaining numeral wheels and a metal plat on the front of the meter, on which meter product information (the proper number of the meter, class, maximum usage amount per hour, maximum use pressure, an authentication institute, authentication number, etc.) is written, should be transparent. This is to enable a consumer or a meter reading person to read with the naked eye, to confirm that the amount of use measured by remote automatic meter reading matches the amount of use measured by manual meter reading, and also to confirm meter product information such as the proper number of the meter, the class of the meter, maximum allowable quantity of use per hour.

To the infrared ray emitter22a, driving pulses as shown inFIG. 2aare provided as power such that infrared ray emission is intermittently repeated during the time when the driving pulses are provided. If the consumer uses a supply, for example, gas, the predetermined numeral wheel11ato which the reflection sheet20is attached begins to rotate. If the reflection sheet20rotating together with the predetermined numeral wheel11acomes just below the optical sensor unit22of the meter5, an infrared ray emitted from the infrared ray emitter22ais reflected by the reflection sheet20to the light sensor22b. If the remaining section of the numeral wheel11aon which the reflection sheet20is not attached comes below the light sensor22, the reflection as such hardly occurs. As the predetermined numeral wheel11arotates, the section on which the reflection sheet20is attached and the remaining section on which the reflection sheet20is not attached pass alternately below the light sensor22. As a result, a sensing signal obtained from the light sensor22bhas a shape in which there are pulses in a predetermined section, that is, in a reflection section, while there are no pulses in a predetermined section after a predetermined point, that is, in a non-reflection section, as shown inFIG. 2b. A means capable of counting pulses is connected to the output terminal of the light sensor22band by counting the frequency of repetition of the reflection section and non-reflection section, calculates the rotation frequency of the predetermined numeral wheel11a.

However, a meter may be installed outdoors or indoors and there is natural light or artificial light where the meter is installed. Generally, this external light includes an infrared ray having a wavelength that can be detected by the light sensor22b. If the housing21is constructed as described above, though external light would not be incident directly on the light sensor22b, external light penetrates into the transparent part on the front side of the housing21cand is incident indirectly on the light sensor22b, through complex multiple reflections between the numeral wheel counter, an inner surface of the housing21cand the front surface part of the meter on which meter product information is written, and along the narrow space of the numeral wheels11bon which the optical sensor unit22is not disposed, as shown inFIG. 1b. In other words, external light is incident on the numeral wheels11bon which the optical sensor unit22is not disposed (particularly on the numeral wheels neighboring the numeral wheel11aon which the optical sensor unit22is disposed), and diffusedly reflected by the numeral wheels. Part of the reflected light is incident on the numeral wheel11aand is reflected by it to be mixed with the infrared ray emitted by the infrared ray emitter22b, and is ultimately incident on the light sensor22b, too. Particularly, since the front surface part of the meter on which meter product information is written is usually made of a metal plate with a very high reflection rate, for example, an aluminum plate14, a considerable portion of external natural light or artificial light, which is incident on this part at a low angle, is strongly introduced into to the light sensor part. When this external light is introduced and mixed, the level of the output sensing signal from the light sensor22bis raised both in the reflection section and the non-reflection section and the amplitude difference between the two sections is relatively reduced such that discrimination between the reflection section and the non-reflection section becomes difficult, as shown inFIG. 2c. Particularly, when the meter5is installed outdoors and exposed to sunlight, the strength of an external infrared ray which is mixed with the infrared ray originated from the light sensor22bbecomes very high. In this case, it is very difficult to distinguish the reflection section from the non-reflection section, which may result in a great deal of error in automatic meter reading.

As an alternative method to reduce this error, it can be considered to further raise the amplitude of a driving pulse of the light emitter22awith taking the maximum level of an expected noise signal into consideration. However, this method increases power consumption and reduces a replacement cycle for battery which is used as a power source. Accordingly, it is difficult to employ this method. In addition, since there is a limit to the increase of the amplitude of the driving pulse of the light emitter22adue to the intrinsic characteristic of the device, the amplitude increase should be limited under a predetermined value, which makes it difficult to solve the problem.

Meanwhile, in addition to the apparatus for counting the rotation frequency of a numeral wheel of a meter as described above, the entire optical remote meter reading system further comprises a pulse generator30which provides a driving pulse signal (Pin) to the light emitter22a; an amplifier32which amplifies the output signal of the light sensor22b; a micom34which by recognizing changes of ‘non-reflection→reflection→non-reflection’ through comparison of levels of the output pulses (Pout) from the light emitter22b, counts the rotation frequency of the numeral wheel11a; a transmitter36which wirelessly transmits usage amount data counted by the micom34together with consumer information; and a battery38which provides needed power to these elements.

Using commercial electric power source instead of a battery is not appropriate because the commercial electric power cannot be used as is due to a lot of noise. In addition, it imposes an additional burden on consumers and additional cabling works for power supply are needed. Accordingly, it is practically difficult to employ the method. There may be a compulsory examination for the effective period of a meter in each country. In Republic of Korea's case, the examination period for effective period of a meter is 5 years. The life span of a battery needs to be longer than this period. Accordingly, a remote meter reading system needs to be designed as an optimized energy saving type one which can minimize power consumption in operation. However, the prior art technologies described above only mention that a pulse signal is used as a driving signal, but fail to suggest a specific solution required for the energy saving design.

SUMMARY OF THE INVENTION

To solve the above problems, it is an object of the present invention to provide an apparatus for counting the rotation frequency of a numeral wheel of a meter which even when installed in a place where there is a huge amount of infrared ray, can prevent occurrence of measuring error due to the external infrared ray.

It is another object of the present invention to provide an apparatus for counting the rotation frequency of a numeral wheel of a meter which makes a battery replacement cycle longer than an examination cycle for an effective period of a meter through minimizing power consumption in order to remove inefficiency and inconvenience of replacement of a battery before expiration of an examination period for an effective period of a meter.

According to an aspect of the present invention, there is provided an apparatus for counting the rotation frequency of a numeral wheel of a meter for a remote meter reading system, which is applied to a meter in which the numeral value of a numeral wheel counter formed with a plurality of numeral wheels accumulatively increases in proportion to the usage amount of a supply, the apparatus comprising: a light reflection means which is attached on part of the outer surface of any one numeral wheel of the numeral wheel counter so that a surface of the light reflection means having a high reflection rate is directed to the outside, and which reflects an incident infrared ray while rotating with the numeral wheel; a light sensor unit in which two independent holes are formed on one side of a case made of an opaque material, and an infrared ray emitter, which receives a driving pulse signal and intermittently emits an infrared ray, is disposed inside a first hole and an infrared ray sensor, which outputs an electric signal in proportion to the light amount of an infrared ray flowing into a second hole, is disposed inside the second hole; a light sensor fixing housing which has a structure in which the housing is detachably coupled with the meter while the light sensor unit is mounted and fixed inside the housing, and in an assembled state of the housing, the first hole and the second holes are located above a rotation path of the numeral wheel, on which the light reflection means is attached, and at least a part of the housing, covering the numeral wheel counter and a part on which meter product information is written, is transparent so as to be read from the outside, and has an infrared ray blocking function to block external infrared rays flowing into the inside; a micom which calculates the usage amount of the supply by counting the output electric signal from the infrared ray sensor to recognize the rotation frequency of the numeral wheel; and a power supply means which supplies power needed for the light sensor unit and the micom by using a battery power source, and in particular, provides the infrared ray emitter with the driving pulse signal. Since the light sensor fixing housing prevents an infrared ray in the wavelength for operation of the light sensor unit from flowing into its inside, metering error of the amount of supply usage that may occur by optical noise does not occur.

According to another aspect of the present invention, there is provided an apparatus for counting the rotation frequency of a numeral wheel of a meter for a remote meter reading system, which is applied to a meter in which the number value of a numeral wheel counter formed with a plurality of numeral wheels accumulatively increases in proportion to the usage amount of a supply, the apparatus comprising: a light reflection means which is attached on part of the outer surface of a predetermined numeral wheel of the numeral wheel counter so that a surface of the light reflection means having a high reflection rate is directed to the outside, and which reflects an incident infrared ray while rotating with the numeral wheel; a light sensor unit in which two independent holes are formed on one side of a case made of an opaque material, and an infrared ray emitter, which receives a driving pulse signal and intermittently emits an infrared ray, is disposed inside a first hole and an infrared ray sensor, which outputs an electric signal in proportion to the light amount of an infrared ray flowing into a second hole, is disposed inside the second hole, and the light sensor unit is inserted into an aperture formed on a part on the top side surface or the bottom side surface of a meter cover, said part corresponding to the location of the numeral wheel, on which the light reflection means is attached; a light blocking cover which prevents external light from entering into a space between the light sensor unit and the numeral wheel on which the light reflection means is attached; a micom which calculates the usage amount of the supply by counting the output electric signal from the infrared ray sensor to recognize the rotation frequency of the numeral wheel; and a power supply means which supplies power needed for the light sensor unit and the micom by using a battery power source, and in particular, provides the infrared ray emitter with the driving pulse signal. Also, in this case, the space between the light sensor unit and the numeral wheel on which the light reflection means is attached is surrounded by the light blocking cover and external light cannot flow into the space such that metering error of the amount of supply usage that may occur by optical noise does not occur.

In order to more clearly remove possibility of occurrence of metering error due to external optical noise, it is preferable that a light filter means which allows only infrared rays in a wavelength output by the light emitter to pass through is further disposed at the entrance of the second hole, in which the infrared ray sensor is disposed. In addition, it is preferable that an infrared ray absorption material is coated or an infrared ray film is attached on at least the remaining section, on which the light reflection unit is not attached, of the numeral wheel, on which the light reflection means is attached.

Also, in order to provide an infrared ray prevention function to this apparatus, it is preferable that by using molding materials obtained by mixing a transparent plastic resin with infrared ray blocking powder, the housing is made by injection molding. As another method, the housing is made of a transparent plastic resin and on the outer surface or inner surface of the housing, an infrared ray blocking material is coated, or an infrared ray film is attached. As still another method, one of two polarization films whose polarization directions are perpendicular to each other, is attached on the surface of the transparent part of the housing (or the cover of the meter) and the other is attached on the entrance of the second hole, in which the infrared ray sensor is disposed. If these methods are used, it can effectively prevent light noise causing metering error from inputting into the infrared ray sensor.

Meanwhile, according to the feature of the present to achieve the second object, it is preferable that the duty ratio of the driving pulse signal is 1/100 or less. In addition, it is preferable that the cycle of the driving pulse signal does not exceed 250 ms, the duration time is longer than the response time of the infrared ray sensor, and the duty ratio of the driving pulse signal is determined as a value not exceeding 1/100.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

First, a numeral wheel counter110of an existing mechanical-type meter to which the apparatus according to the present invention is applied will now be explained briefly. A numeral wheel counter of a meter indicating the amount of supply usage is formed by closely arranging a plurality of numeral wheels to show roughly 4˜5 integer digits and 1˜3 decimal digits. Each numeral wheel has a drum shape and numbers from 0 to 9 expressed on the outer surface of it. If a supply such as gas, water, or electricity is used, the lowest numeral wheel of the numeral wheel counter110in the meter rotates at the fastest speed in proportion to the amount of the supply usage, and the ratio of the rotation speed of a first numeral wheel to that of a second numeral wheel which is one-digit higher than the first numeral wheel is 10 to 1.

FIGS. 3aand3bare diagrams of the structure of an apparatus for counting the rotation frequency of a numeral wheel of a meter according to a preferred embodiment of the present invention, andFIG. 4is a cross-sectional view of the apparatus shown along cutting line B-B′ ofFIG. 3b. In addition,FIG. 6is a conceptual diagram of the structure of a wireless remote automatic meter reading system for remote meter reading in a unit area (a local area). In order to construct a remote automatic meter reading system, an apparatus for counting the rotation frequency of a numeral wheel is installed in each consumer's meter. The apparatus100for counting the rotation frequency of the present invention comprises a light reflection sheet120, a light sensor unit130, a light sensor fixing housing140, a micom152, and a power supply portion156including a battery, as means to count the usage amount of a supply, for example, gas. There are a variety of methods for collecting counted usage amount information to a computer system of a supply providing company. In order to wirelessly transmit the information, the apparatus100for counting the rotation frequency of a numeral wheel should further comprise a wireless communication portion154. It is preferred that the apparatus100further comprises a wireless repeater160in each unit area. Also in the structure, the wireless repeaters in respective unit areas should be connected to a central computer162of the supply providing company through a wireless and/or wire communication network. Preferably, the micom152, the wireless communication portion154, and the power supply portion156are mounted together on a printed circuit board (not shown) to form a single wireless communications unit150. The light sensor unit130and the wireless communications unit150are connected through a cable151.

The light reflection sheet120is attached on a part of the outer surface of a low digit numeral wheel, preferably, the lowest digit numeral wheel. Though one number digit is inevitably covered by the light reflection sheet120, it is not desirable that two or more digits are covered. Accordingly, it is preferred that the length of the light reflection sheet120is made to not exceed approximately a {fraction (15/100)} of the circumference of the numeral wheel100a. One rotation of the numeral wheel110a, on which the light reflection sheet120is attached, corresponds with that a section of the outer surface of the numeral wheel110aon which the light reflection sheet120is attached (hereinafter referred to as a ‘reflection section’) and a section on which the light reflection sheet120is not attached (hereinafter referred to as a ‘non-reflection section’) pass through below the light sensor unit130once. Clear distinction and recognition of the reflection section and the non-reflection section directly relates to the accuracy of counting the rotation frequency. Accordingly, in order to clearly distinguish the reflection section from the non-reflection section, it is preferable that the light reflection sheet120is made of a material having a high light reflection rate and the non-reflection section, by contrast, is made to well absorb infrared light to prevent reflection. In order to provide an infrared ray absorption function to the non-reflection section, an infrared ray absorbing material may be applied to the outer surface of the numeral wheel110a, or an infrared ray absorbing film may be attached by pressure bonding and then the light reflection sheet120is attached on that. When the light reflection sheet120is detached, it will interrupt the rotation of the numeral wheel110a. Accordingly, it should be solidly attached and, for example, it is preferable that an aluminum thin film tape is attached on the outer surface of the numeral wheel110aby thermo-compression bonding. It will be more economical if the light reflection sheet120is attached when an examination of a newly produced meter or an examination for an effective period expiration of a meter is performed.

The light sensor unit130comprises an infrared ray emitter132and an infrared ray sensor134. The light sensor unit130is constructed so that light from the infrared ray emitter132is incident on the infrared ray sensor134not directly, but by reflection. For this, by using an opaque material a case135is made such that two independent holes138aand138bare formed on one side of the case135and the infrared ray emitter132and the infrared ray sensor134are installed inside the first hole138aand the second hole138b, respectively. In order for the infrared ray of the infrared ray emitter132reflected by the light reflection sheet120to be incident on the infrared ray sensor134to the maximum, it is preferable that the first hole138aand the second hole138bare formed to be slanted so that the light reflection sheet120becomes a vertex as shown in FIG.4. To reduce transmission loss of an infrared ray, the inside walls of the first hole138aand the second hole138bare coated preferably by light reflection films (not shown).

In actually constructing the light sensor unit130, for example, an infrared ray emitting diode may be used as the infrared ray emitter132, and a photodiode or phototransistor may be used as the infrared ray sensor134. It is preferred that the infrared ray emitter132outputting near infrared rays in the wavelength range of 700 nm˜1100 nm and the infrared ray sensor134receiving these rays are used. In particular, it is more preferred that the infrared ray emitter and infrared ray sensor having substantially identical peak wavelengths and spectrum bandwidths need to be used.

The housing140having an infrared ray blocking function to be described later can prevent a considerable portion of near infrared rays (approximately over 80%) but allows the wavelength in the visible light range to pass through. Particularly in sunlight, including ultraviolet ray, visible light, and infrared ray, the wavelength distribution is high and rays other than the near infrared ray wavelength band, including a little portion of the near infrared ray wavelength band, may flow inside the housing140, and through complicated reflection processes, some of the rays may be incident on the infrared ray sensor134in the second hole138b. In this case it is highly probable that the rays may cause light interference with an infrared ray emitted from the infrared ray emitter132such that sensing error occurs in the sensor134. In order to solve this sensing error problem caused by light interference, it is preferable that a near infrared ray filter136which selectively allows infrared rays in wavelength bands that can be sensed by the infrared ray sensor134, to pass through, and prevents light in the remaining wavelength bands from passing through is disposed at the entrance of the second hole138bin which the infrared ray sensor134is installed.

As shown inFIGS. 3aand3b, while the light sensor unit130is fixed on the inside of the housing140, the housing is detachably coupled with a flange112, covering a cover116which covers a metal plate114on the front side, on which the numeral wheel counter110is disposed, and side surfaces of the meter. In the housing140, a part142afor fixing the light sensor unit130and a part142bfor covering the numeral wheel counter110of the meter form a stepped shape, and a plurality of locking members146enabling the housing140to be detachably coupled with the flange112of the meter are formed along the rim of the mouth of the housing140. A light sensor fixing unit148into which the light sensor unit130can be inserted and fixed is formed inside the part142afor fixing the light sensor unit130.

Since the counted numeral value of the numeral wheel counter110should be able to be read even when the housing140is mounted on the meter, it is needed to make the housing140entirely transparent or at least the part144of the housing140facing the numeral wheel counter110transparent. In the latter case, it is preferable that the parts other than the part144facing the numeral wheel counter110are made to be opaque so that external light cannot pass through. However, if at least the part144facing the numeral wheel counter110is transparent, as described above as the problem of the prior art, an infrared ray passes into the housing through this transparent part144from the outside so that it works as noise causing a count error. If the noise level is high, it becomes very difficult to distinguish the reflection section and the non-reflection section in the output signal of the infrared ray sensor134as shown inFIG. 2c. Accordingly, it is necessary to provide the housing140with a function to block influx of external infrared rays that cause errors. Even though the infrared ray blocking function is provided to the housing, the numeral wheel counter110and meter product information part on the front surface of the meter should be able to be read by naked eye. Accordingly, visible light should be allowed to pass through the transparent part144but near infrared rays that are the wavelength band used by the light sensor unit130should be blocked.

In order to provide the housing with an infrared ray blocking function, there are a method attaching an infrared ray blocking film on the housing140, a method coating an infrared ray blocking material on the housing140, a method making the housing140with a material obtained by mixing an infrared ray blocking material with an injection molding material for the housing140. Also, there is a method using the principle of polarization. That is, in the method with two polarization films whose polarization directions are perpendicular to each other, that is, 90 degree different, one film is attached to the entire surface of the transparent part144of the housing140, while the other film is disposed at the entrance of the second hole138bin which the infrared ray sensor134is inserted. Except the part144covering the numeral wheel counter110, the housing is made to be opaque. By using this method, inflow of unnecessary light noise into the infrared ray sensor134can be blocked.

FIG. 5arelates to the first method and shows the case where when only the part facing the numeral wheel counter110and meter product information part on the front surface of the meter is made to be a transparent window144and the remaining part is made to be opaque in the housing, a film200ahaving an infrared ray blocking function is attached on at least one side of the transparent window144.FIG. 5brelates to the second method and shows the case where infrared ray blocking material200bis coated on at least one side of the transparent window144.

There are many commercialized products of an infrared ray blocking material having an infrared ray blocking function, by which visible light is allowed to pass through, while an infrared ray is reflected, or an infrared ray blocking film using the material. There are commercial products with over 80% of an infrared ray blocking rate, and these products may prevent most errors caused by influx of external infrared rays. Only applying theses products to the apparatus of the present invention is needed. Detailed explanations on the products will be omitted.

In the apparatus for counting the rotation frequency of the present invention, the infrared ray emitter132, the infrared ray sensor134, the micom152, and the wireless communication portion154are power-consuming elements, and batteries are used as the power source. The source voltage for the wireless communication portion154may be the same as those of other elements or may not be. In order to improve the performance of wireless communications, a separate battery for wireless communications may be used in addition to batteries for other elements. It is most preferable that the power source, including that for the wireless communication portion154, can be formed by means of one AA size battery. That is, when the goal is to construct the power supply portion with one AA size battery so that the power supply portion operates during at least an examination cycle for expiration of an effective period of a meter (5 years in Republic of Korea), special considerations should be needed for power saving. The power consumption of the infrared ray sensor134is very small such that it can be neglected. In addition, the micom152has no special method for saving power except using sleep mode and wakeup mode that are generally used. Accordingly, there is room for saving power only in the infrared ray emitter132and which driving method for this will be employed has a great influence on the amount of power consumption.

A method to reduce power consumption in the infrared ray emitter132is providing driving power as in a form of pulse signal with a very low duty ratio. The current capacity of the AA size battery is approximately 2700 mAh. Broadly speaking, half of the entire current capacity is consumed in the micom152and the remaining half is consumed in the infrared ray emitter132. Considering a margin by natural discharge of the battery and the like, it can be assumed that for five years that is an examination cycle for expiration of an effective period of a meter in Republic of Korea, the current capacity allocated to the infrared ray emitter132is 1000 mAh. Then, 200 mAh is available for the infrared ray emitter132every year, and approximately 0.55 mAh is allowed to be consumed every day. In order to satisfy this requirement, the driving power source of the infrared ray emitter132should be a pulse signal as shown inFIG. 2aand in particular, the duty ratio and amplitude of the pulse signal need to be minimized. Only when the current value of the driving signal is at least approximately 2 mA or over, the infrared ray emitter132can outputs an amount of light that can be sensed by the infrared ray sensor134. When the driving signal of the infrared ray emitter132is not a pulse signal, at least 48 mAh is consumed everyday. The allowed current capacity is 0.55 mAh. Accordingly, the duty ratio of the driving pulse signal of the infrared ray emitter132should be lower than approximately 1/100. In response to the duration time of this pulse signal, the infrared ray emitter132emits light intermittently. For stable operation, it is preferable that the amplitude of the driving signal is greater than 2 mA, and in this case, the duty ratio should be reduced in proportion to the amplitude change.

Next, the power supply portion156comprises a battery (not shown) and a supply circuit (not shown) providing the battery power to the elements that needs the power, that is, the light sensor unit130, the micom152, and the wireless communication portion154. In particular, since the infrared ray emitter132needs the pulse signal, as shown inFIG. 2a, the battery power is converted into a desired pulse signal (Pin) by using an oscillator and a counter, which generates a pulse signal with a desired cycle (T) and duty ratio (Td/T) which can be obtained by frequency dividing the oscillation signal from the oscillator, and provides the pulse signal (Pin) to the infrared ray emitter132. The circuit may be constructed so that the micom152adjusts the cycle (T) and duty ratio (Td/T) of the driving pulse signal. Preferably, the cycle (T) of the driving pulse signal (Pin) is selected appropriately within a range not exceeding 250 ms, and the duration time (Td) is selected as short as possible, but as a value longer than the response time of the infrared ray sensor134.

While a consumer uses the supply, when there is no external light noise, optical-detection signals output from the infrared ray sensor134may have a waveform as shown inFIG. 2b. The micom152receives the output signal of the infrared ray sensor134, and counts the frequency of repetition of the reflection section and the non-reflection section of the numeral wheel110a. By doing so, the micom152detects the usage amount of the supply, and provides the detected result to the wireless communication portion154. Of course, instead of the micom152, a central processing unit (CPU) can be used. The optical-detection signal of the infrared ray sensor134may be amplified to a voltage level appropriate to be processed by the micom152and then provided to the micom152. For this, an amplifier (not shown) is disposed between the infrared ray sensor134and the micom152.

The operation principle of the apparatus100for counting the rotation frequency of a numeral wheel will now be explained briefly. If a consumer uses the supply, the light reflection sheet120attached to a part of the outer surface of a predetermined numeral wheel of the meter begins to rotate. In this rotation process, while the light reflection sheet120passes below the light sensor unit130, an infrared ray emitted from the infrared ray emitter132is reflected to the infrared ray sensor134. Then, with receiving the reflected light as an input signal, the infrared ray sensor134outputs a optical-detection signal as shown inFIG. 2b. The output signal of the infrared ray sensor134is provided to the micom152. By sampling the output signal provided by the light sensor unit130and comparing with a reference signal, the micom152can count the rotation frequency of the numeral wheel. More specifically, for example, when the infrared ray sensor134is formed with a phototransistor, an infrared ray incident on the sensor134works as a driving source to a base of it and with respect to the received amount of light, the current amount flowing between the collector and the emitter varies. The change in the amount of the flowing current is converted into a voltage of a resistor connected to the emitter and by using this voltage it is determined whether or not an infrared ray is incident. Since the voltage sensed by the phototransistor is an analogue signal having a high level and a low level with respect to the amount of light, the micom152performs sampling of the voltage signal and comparison with a reference voltage to convert the voltage signal into digital signals in order to distinguish the reflection section and the non-reflection section. When the output voltage of the phototransistor is 0˜1.2[V], it is recognized as a “low (0)” logic level, and when 3.7˜5[V], as a “high (1)” logic level. Then, the rotation frequency is counted in a manner that if a digital value, for example, a “high (1)” logic level, continues twice or more and a “low (0)” logic level continues 8 times or more, it is recognized that the reflection section and the non-reflection section of the numeral wheel110apass once below the light sensor unit130, that is, one rotation of the numeral wheel110ais recognized. The rotation frequency of the numeral wheel counted in this manner in the apparatus for counting of each consumer, that is, the information on the usage amount of the supply, is transmitted to the local wireless repeater160. Information collected by each local wireless repeater160is again transferred to the central computer162of the supply providing company through wireless and/or wire communications networks. Thus, the remote meter reading is fully automated.

Meanwhile, the initial value of the numeral wheel counter110of a meter is generally not ‘0000.000’ when the meter is installed in a consumer's house. Generally, a newly produced meter may be tested in the factory or when production examination is performed, and after the numeral wheels rotate tens of times for tests, it is installed in a consumer's house. In the case of an already installed meter, it is reused after examination for expiration of an effective period, or after repair examination, and therefore it is highly probable that the numeral wheels may presents a particular initial value larger than ‘0000.000’. When a meter is installed, the already existing initial value of the numeral wheel counter110should be reflected when the usage amount of a supply is counted. As methods to reflect this initial value, there are a method reflecting this value on the central computer162of the supply providing company and a method reflecting on the micom152mounted on each meter.

In the former method, the initial value of each meter is separately written down by an installer when the meter is installed, and then input to the central computer. In this case, the micom152needs to calculate only an accumulated rotation frequency, that is, the accumulated usage amount, and transfer it to the central computer162. The central computer162calculates the usage amount by adding the received accumulate usage amount to the corresponding initial value.

In the latter method, in order to reflect the initial value, when a meter is installed, the initial value of the meter is input to the micom152of the apparatus by the installer. In order to reflect the initial value, the value may be input by wire communication or by using a dedicated wireless input device. In this case, the wireless communication portion154always transmits the same value with the current value of the numeral wheel counter110.

In the former method, the numeral value of the micom152of the apparatus for counting the rotation frequency of a numeral wheel is not equal to the numeral value of the meter. Accordingly, when the meter is examined on the spot, there is a problem that only after the initial value of the meter stored in the central computer162is referred to and then the value is combined with the accumulated usage amount of the micom152, it can be confirmed whether the apparatus for counting the rotation frequency of a numeral wheel is under normal operation. Also, there is inconvenience that when sensing error occurs, or when the sensing value of the micom is initialized, the initial value of the central computer162also should be modified.

Compared to this, the latter method is convenient because there is no need to input the initial value of each meter in the central computer162, and therefore there is no possibility of occurrence of input errors. Also, if the value of the numeral wheel counter110is not equal to the accumulated usage amount value of the micom152, it indicates an abnormal state, and therefore, whether or not the meter operates normally can be confirmed immediately. Even when the single wireless communications unit150is replaced, the initial value of the central computer162does not need to be modified.

Any of the two methods may be employed, but when advantages and disadvantages are compared, the latter method is more preferable.

Next, referring toFIGS. 7aand7b, another preferred embodiment of an apparatus for counting the rotation frequency of meter of the present invention will now be explained. This embodiment is obtained by partially modifying the structure of the light sensor unit130of the previous embodiment such that the apparatus does not need the housing140and is directly installed on the cover116of the meter.

More specifically, as shown inFIG. 7a, on the top side surface or the bottom side surface of the meter cover116corresponding to the location on which the lowest numeral wheel110ais disposed, an aperture into which a light sensor unit130-1can be inserted is formed. Into the aperture, the light sensor unit130-1is inserted. Of course, in order that dust or water does not inflow from the outside, after the light sensor unit130-1is inserted, the aperture is finished with a sealing material.

Since at least the front surface of the meter cover116or the entire meter cover116is transparent, an additional means which makes light inflowing from the outside not affect the light sensing is needed. In order to minimize the effect of external light, as shown inFIG. 7b, a space between the front surface of the light sensor unit130-1and the lowest numeral wheel110ais surrounded by a light blocking cover so that external light cannot flow into the space.

As a method for this, the light sensor unit130-1is constructed to further have a light blocking cover137which extends from the rim of the front surface, on which holes138aand138bare formed, to a predetermined length in the direction of light emission of the infrared ray emitter132. In another method, the light blocking cover is not fixed on the light sensor unit130-1, and instead, the aperture part formed on the bottom side surface or the top side surface of the meter is extended in the form of a tunnel so that part of the numeral wheel110ais surrounded. In any methods, the light blocking cover137needs to cover the front surface of the light sensor unit130-1and the side surface of the numeral wheel110aso that external light is not allowed to enter into the space.

In order to more completely block the entrance of light into the space between the light sensor unit130-1and the numeral wheel110a, it is necessary to provide the infrared ray blocking function to the transparent part of the cover116by using the methods applied to the housing140in the previous embodiment, that is, by coating an infrared ray blocking material, by attaching an infrared ray blocking film, or by injection molding of the cover after mixing the raw material of the cover with an infrared ray blocking material.

If the light blocking cover with one of those structures is employed, the housing for installing a light sensor unit is not needed.

The prior art optical-type apparatus for counting the rotation frequency cannot be commercialized because when it is installed in a place where natural light or artificial light is strong, metering error due to light noise occurs. However, the present invention uses a housing having an infrared ray blocking function such that it prevents the occurrence of metering error due to light noise in a meter located even in a place where natural light or artificial light is strong. In addition, the present invention complementarily provides an infrared ray absorption function to the remaining section of the numeral wheel110aexcept the section, on which the light reflection sheet120is attached, or an infrared ray filtering function which, among the lights directed to the infrared ray sensor134, allows only near infrared rays to pass through. By doing so, metering error due to light noise can be removed almost completely.

Further, the present invention minimizes power consumption so that a battery does not need to be replaced within an examination cycle for expiration of an effective period of a meter. In addition, the apparatus of the present invention can be used for the existing mechanical-type meters without change and when an examination for expiration of an effective period is performed, only the light reflection sheet120needs to be attached on the numeral wheel by pressurized bonding. Accordingly, installation of the apparatus of the present invention hardly causes inconvenience to the consumers.

The facts described above mean that the apparatus of the present invention can successfully satisfy commercialization requirements of a remote automatic meter reading system.

Optimum embodiments have been explained above. However, it is apparent that variations and modifications by those skilled in the art can be effected within the spirit and scope of the present invention defined in the appended claims. Therefore, all variations and modifications equivalent to the appended claims are within the scope of the present invention.