IE45755B1 - Electrical meter apparatus - Google Patents

Abstract

This electronic maximum-demand meter which consists of a kilowatt hour meter and a maximum-demand mechanism exhibits a microcomputer with non-volatile memory in the maximum-demand mechanism. To save the various values of the maximum demands of the month and of the state of the counting mechanism in the event of mains failure, regular refreshing of the memory contents is provided, the interruption of the current consumption metering and transmission of the data into the non-volatile memory being initiated by a subroutine. In addition to the current data in each case, the user-specific values are also entered in the memory.

Description

This invention relates to electrical meter apparatus.

In Patent Specification No. 44654 . in respect of which this an application for a patent of addition, there is disclosed an electrical maximum-demand energy meter apparatus which comprir.es a digital microcomputer for receiving an input signal representative of an energy demand and providing an output signal representative of the maximum energy demand over a preceding predetermined measuring period, the microcomputer comprising a non-volatile store.

Such an apparatus will be hereinafter referred to as an apparatus of the type specified.

According to the present invention, there is provided an apparatus of'the type specified, including means for refreshing the Content of the non-volatile store periodically.

The apparatus may optionally be in accordance also with any one of claims 2 to 24 of Patent Specification No. 44654 In an advantageous embodiment, the apparatus is such that, both at the end of each one of successive predetermined measuring periods and upon a power failure occurring, the microcomputer is arranged to write into the non-volatile store the value of the maximum energy demand during the immediately preceding said period, provided that said value is greater than the last stored maximum demand value.

Advantageously, the non-volatile store contains useroriented programming of the computer, and the or each useroriented program is formed by assembling individual program -2457SS portions which are stored in a program store of the computer, and the or each whole program is assembled by means of an assembly code which is stored in the non-volatile store and is read out by the computer to assemble said program portions in the correct order.

The computer may be arranged to store in the non-volatile store a plurality pf maximum demand values with associated status bits, corresponding to a respective plurality of maximum-demand tariffs.

In Patent Specification No. 44654 , there is disclosed an electronic maximum-demand meter which comprises a single-chip microcomputer having an associated non-volatile store, for the evaluatioh of input signals representing energy demand, which signals may be presented in pulse form, for example, from a Ferraris measuring instrument.

This microcomputer outputs numerical values in digital and/or analog form. In the case of a maximum-demand meter these values can be s momentary maximum, monthly maximum^ cumulative monthly maxima and the number of resets effected. In addition , the computer may be capable of computing a large number of further values from the input signals available to it (demandproportional pulses, mains frequency, and in some cases processed centralised-control pulses, control orders for turning the maximum demand measurement on and off, tariff changeover orders, etc.) and of thus making available a considerably greater output than is possible in the case of mechanical maximum-3demand meters.

In the parent Application, the computer uses a non-volatile store ' which is either externally situated or integrated on the same chip. This non-volatile store desirably has the S properties of an electrically variable read-only store(EafiOM, electrically alterable read-only memory), that is to say, it should behave as a random access write-read store (RAM), but should retain its £jtore content on failure of the power supply. Hon-volatile stores in the form of magnetic core stores are known, but these are not preferred in the present application for many reasons. MHOS and MAS semiconductor stores have been known for some years. They differ from one another basically in the composition Of the gate dielectric. In the MNOS store, a two-layer dielectric consisting of silicon nitride and silicon oxide is used, while in the MAS store, a dielectric consisting of aluminium oxide and silicon oxide is used. In both cases, a charge is stored in the boundary layer of the two dielectrics by application of high voltages, and passes through the thin silicon oxide. In order that the tunnel effect of relatively low voltages may he initiated, the silicon oxide should have a thickness of only a few atomic layers, hut should at the same time be uniformly distributed over the whole area of the gate without pores. Apart from the difficulties in manufacturing such semiconductor stores in large quantities with good yield, there exists the practical disadvantage of a limited storage -445755 time, whitffi depends upon the combination of voltage level and pulse width -and (amounts typically to one year at room temperature. A further feature of these semiconductor stores is the limited number of permissible writing cycles , which is typically Z- Q between 10°·end 10 . The number ofreading cycles is also limited, oecause a low voltage must be applied to the gate for reading.

This low voltage acts as a weak writing voltage, so that typically the store content can no longer be reliably observed Ί Ί i after about 10 reading operations, ^or these reasons, it is ' not possible to operate the available electrically alterable read-only stores (EaROM) as normal write-read stores (MAM), because they would become unservicable after a short time at the high data processing rates currently employed. Further, a normal write-read storage operation is also possible only in rare cases, oecause an erasing action lasting about 1 s must initially be carried out in the MNOS store before a writing operation typically lasting 1 ms becomes possible. Therefore, in the Parent Application, an electrically alterable read-only store (EaROM) will desirably be activated only 2o when the supply voltage fails or after it has returned. For this purpose, the failure of the supply voltage should be recognised in such time that, for example, storage capacitors of the system can still make available sufficient energy to write reliably i-hto the read-only store (EaROM) data which ia to be saved. -545755 ' It has already been described in the Parent Application how the user (customer)-oriented programming of the apparatus can be effected by writing into storage locations intended therefor in the non-volatile store. However, a disadvantage here can be the aforesaid limited storage time of only about one year.

The present invention is concerned with the provision of an improved meter apparatus, in so far as the content of the non-volatile store is refreshed periodically, as is described further in the following, by way of example.

There may be employed store refreshment methods known per se, in which the store content is regularly read out and rewritten as a whole or in partidular parts. If this refreshment is effected at intervals which are short in relation to the minimum guaranteed storage time, an item of information once written in can thereby be kept as long as desired, provided that the unit which contains the described non-volatile store never remains without current supply for a time which is longer than the minimum guaranteed storage time. Also it is desirable that it is possible for stored data to be tested at any time, 2o that is to say, to be able to display appropriately even that part of the store content which serves only for user-oriented programming.

The user-oriented, programming is desirably effected either in a manufacturer's testing station or in a user's testing department. Thus, for example, it can be possible at any time to readily re-programme a meter for another place of use, -6Λ5755 ίο IS whilst in the case of known mechanical instruments, time-consuming and costly modifications must usually be carried out by skilled personnel. For the purpose of the user-oriented programming, there is desirably produced for a particular type of meter a programming unit which is connected to the electronic part of the maximum-demand meter, for example by way of plug-in connection* The values to be fed in can then be manually set at this programming unit and then written by means of a storage order into the non-volatile store of the maximum-demand meter. Of course, frequently recurring programmings can also be stored on suitable known data carriers (punched tapes, magnetic tape, magnetic card or the like) and fed-in in a correspondingly shorter time. After the programming, either the maximum-demand meter returns the values just introduced into the store to the programming unit for checking on the basis of a corresponding computer programme and sets up an alarm signal in the event of non-agreement, or the programmed values are successively reproduced also on an indicator device of the maximum-demand meter and optically checked as to their accuracy.

As disclosed in the Parent Application, the computer may start at a predetermined program point at each return of power after a power failure, and first read out the content of the non-volatile stohe, either partially or entirely, and transfer or copy it into its own write-read store (RAM) if it requires it. -745755 In the application of the method of regular refreshment of the non-volatile store as proposed here, it is possible for all data which is to be saved in the event of a power failure to be written-in, not just at the moment of a power failure, is but before such a failure occurs, as soon as the data/available or has been computed. For example, in a maximum-demand meter, the existing state of a monthly maximum is rewritten at the end of each measuring period (i.e. eachmsnth). Despite the possibly limited number of writing cycles, this method is practicable especially since it is most unlikely in practice that the monthly maximum is raised each month, so that the actual number of writing operations to be carried out is considerably smaller than would theoretically be the case.

When each writing operation must be preceded by an erasing operation, it is immaterial in principle whether only individual values are written in the writing-in, or the whole store content. This depends upon the design of the non-volatile store.

In known MNOS stores, for example, it is possible to address individual blocks each formed of 4 words of 4 bits each, that is to say to read and erase them and to write them.

When a mechanical cumulative counter is used as a visual display in a maximum-demand meter, into which counter a respective monthly maximum can be counted at the end of the month only with a particular maximum counting frequency, the transfer of the corresponding maximum-demand value from the non-volatile store to the counter may take a few minutes. If the power supply fails during the transfer, it should be recorded how many pulses, -84575S for example, have already been counted in to the counter. It is desirable then to use the non-volatile store for this purpose, with a continuous decrement of pulses from the stored monthly maximum value simultaneously with the counting of pulses in the counter. Since in this case the danger is increased that · a permissible number of writing cycles may be reached or even exceeded in the non-volatile store, the computer program can be SO carried out that, for example, only each tenth counting pulse into the counter is substracted from the non-volatile store, so that the number of necessary erasing and writing operations is reduced to a tenth. An additional status character (bit) is set in the non-volatile store at the beginning of the transfer and erased after completion. On restoration of the power supply after a failure, the status bit informs the computer of the state of operation which existed before the failure.

In the Parent Application, it is disclosed that the maximum demand meter can be automatically reset, that is to say, there can be preset by means of user oriented programming a period of time after which the maximum -demand meter is reset to zero. In this case, reset intervals of between JO days and one year are conventional. The computer then advantageously comprises a time counter, which generally counts days, and the existing state of which should also be stored in the non-volatile store either periodically or in the event of a power failure, in order that the electronic maximum-demand counter may also behave in the same way as known mechanical meters. The meter can then recommence counting from the stored counter reading after the - 9 457 55 ; · ί ' · restoration of power.

The computer present in the maximum-demand meter may be used for computing centralised-control orders, in which case the user-oriented programming can he contained in the non-volatile store. Since there are various centralised-control systems and the possibilities of combination for centralised-control orders are numerous, it is desirable to use the method of indirect addressing, that is to say, to provide many possible program portions in the program store of the computer and to select by 10 an addressing code stored in the non-volatile store only particular portions of the 'program which are specifically related to the user. In this case, therefore, only one encoding need be stored for the type of centralised-control system and one en’coding for the centralised-control order itself.

Claims (13)

1. CLAIMS:1. An electrical meter apparatus of the type specified, including means for refreshing the content of the non-volatile store periodically.

2. An apparatus according to claim 1, wherein, both at the end of each one of successive predetermined measuring periods and upon a power failure occurring, the microcomputer is arranged to write into the nonvolatile store the value of the maximum energy demand during the immediately preceding said period, provided that said value is greater than the last stored maximum demand value.

3. An apparatus according to claim 1 or 2, wherein the computer is arranged to reset a measured maximumdemand energy value to zero at predetermined intervals, and includes a time counter the reading of which is arranged to be written into the non-volatile store either periodically or upon a power failure occurring.

4. An apparatus according to claim 3, wherein the time counter reading is arranged to be written into ι the non-volatile store every 24 hours.

5. An apparatus according to any one of the preceding claims, wherein the computer is arranged to restart, after restoration of power following a power failure,' at a predetermined program point, at which firstly the content of the non-volatile store is read out. 11 43755

6. An apparatus according to any one of the preceding claims, wherein the non-volatile store contains user-oriented programming of the computer.

7. An apparatus according to claim 6, wherein the or each user-oriented program is formed by assembling individual program portions which are stored in a program store of the computer, and the or each whole program is assembled by means of an assembly code which, is stored in the non-volatile store and is read out by the computer to assemble said program portions in the correct ,ordqr.

8. An apparatus according to any one of the preceding claims, including a mechanical cumulative counter which'is arranged to visually display a maximum demand value and to be updated periodically by transfer of a maximum demand value from the non-volatile •J store to the counter, which transfer is effected by counting transfer pulses into the counter whilst simultaneously subtracting pulses from the maximum demand value in the non-volatile store.

9. An apparatus according to claim 8, wherein not every transfer pulse into the counter is accompanied by a corresponding subtraction pulse from the nonvolatile store.

10. An apparatus according to claim 9, wherein there is a corresponding subtraction pulse from the non-volatile store for each tenth transfer pulse.

11. An apparatus according to claim 8, 9 or 10, wherein, during each transfer of a maximum demand value into the counter, a corresponding status bit is written into the non-volatile store to inform the 5 computer, in the event of power restoration following a power failure, that a transfer operation is in progress.

12. An apparatus according to any one of the preceding claims, wherein the computer is arranged to store in 10 the non-volatile store a plurality of maximum demand values with associated status bits, corresponding to a respective plurality of maximum-demand tariffs.

13. An electrical meter apparatus according to claim 1 and substantially as described herein.