GB2088601A - Recording energy use - Google Patents

Abstract

Pulses are generated as a function of the instantaneous rate of energy use, and such pulses are counted during succeeding discrete time intervals to determine the electrical energy used the counts being recorded in digital form at respective discrete locations in a memory (43), which may be in a removable cartridge 41. The counts are summed to provide a grand total energy use value which is stored at another discrete location in the EPROM memory (43) at the end of a recording period composed of a multiple of such succeeding discrete time intervals. The counts are also successively compared and the count for that interval having the greatest energy usage within the period is also recorded on the EPROM (43). At the conclusion of the recording period the cartridge is removed and read to establish the electrical energy consumed at the particular location. The respective times of beginning and end of the particular total time period may also be recorded, as well as the location of the energy use. <IMAGE>

Description

SPECIIFICATION Method and apparatus for recording energy use This invention relates to the recording of data on interval, total and peak use of electrical energy, and more particularly to a method and an apparatus for recording such data in a memory storage device.

For purposes of this application terms use, utilisation, usage, and consumption are used synonymously and interchangeably in the sense that energy or power is inputted to a consumer or user.

Electric utility companies use a unit called peak demand to charge their customers for the increased capacity of power generation that they have to provide in order to supply the peak demand of their customers. A device called a peak demand recorder is used for large customers to record information from which this peak demand as well as the total power usage by the customer can be derived, and from this recorded information the utility company computes the charges for a particular customer for a given period of electrical energy use.

The peak demand recorder and method of energy use recording which has been conveniently and widely used takes the form of a conventional mechanical-type tape recorder using a magnetic tape cassette or magnetic tape data cartridge, and the electrical pulses that come from the utility meter in the form of contact closures are recorded on an energy consumption channel of the magnetic tape.

In addition, a time indexing tick is recorded on a separate channel every fifteen minutes, or at other suitable intervals. The indexing ticks serve to provide a subsequent translator device with time intervals from which to derive the peak energy figure to be applied for the particular given overall energy use period. These translators generally operate by simply counting and integrating the total pulse count values and retaining the highest individual interval (typically fifteen minute length) pulse count value which has occurred over the total time frame.

However, unfortunately, human editing and guessing is required, since these mechanical tape recorders are very unreliable in that they vary in speed, and this has the effect of compressing or expanding the data on the tape, and the operator at the translator has to guess and fill in any missing blanks, etc., in attempting to determine the best estimate of what the consumption curve actually was. After this raw information has been "edited' the operator conventionally generates a nine-level IBM-type computer tape which is then put into a separate computerto generate the customer billing.

Significant problems are encountered with these prior devices in failure or variation in rate of their drive motors, and the recorders are also very susceptible to temperature changes, and in general have encountered many varied mechanical problems, with resulting beak-downs, inaccuracies and/ or at the least, questionable recordings and consequent billings.

According to a first aspect of this invention a method of recording the amount of energy used at a particular location comprises the steps of transmitting discrete count signals varying in rate as a function of the rate of energy use; counting the quantity of the discrete count signals during succeeding discrete time intervals to produce succeeding interval summation count value digital signals; recording the succeeding interval summation digital count values in digital signal form at discrete individual locations in a record medium for subsequent read out, comparing the succeeding interval summation count value digital signals with previous of the interval summation count value digital signals to determine which of the succeeding interval summation count value digital signals is the highest; recording, in digital signal form, at a discrete location in the record medium, the highest of the interval summation count value digital signals that occurs during a given total recording period composed of a plurality of the succeeding time intervals, the highest of the interval summation count value digital signals representing peak interval summation digital count values; summing the interval summation digital count values represented by the interval summation count value digital signals over the given total recording period to thereby provide a grand total energy use digital value signal for the given total recording period; and recording the grand total energy use digital value signal as a digital signal at a discrete location in the record medium.

According to a second aspect of this invention an apparatus for recording electrical energy use at a particular location and for use with pulse generating means for generating electrical pulses at a variable frequency varying as a function of instant electrical energy use, to enable recording of signals indicative of interval peak power use and total energy use, the apparatus comprises a removable cartridge solid state read only memory; means for converting the total number of pulses emitted by a pulse generating means in each of a plurality of sequential time intervals into a succession of respective interval summation digital signals each of which is representative of the total pulses occurring in each respective successive time period; temporary memory storage means for storing the first of the respective interval summation digital signals; comparator means for comparing each succeeding interval summation digital signal with the presently stored interval summation signal; logic means responsive to the occurrence of a succeeding interval summation digital signal larger in value than the presently stored interval summation digital signal to effect substitution of the larger value interval summation digital signal in the temporary memory means instead of the presently stored digital signal against which the larger interval summation digital signal has been compared; means for feeding each successive one of the interval summation digital signals to and for recording such at respective discrete open memory locations on the readable memory; means for recording in the readable memory after the termination of a plurality of the time intervals, a digital signal equal in value to the interval summation digital signal then stored in the temporary memory and representing the peak energy used for the total of the recorded time intervals, the recording being effected at a selected open memory location in the removable cartridge read only memory; means for summing in a total energy utilisation temporary memory the running composite total of the electrical pulses between the respective times of commencement and termination of the recording of signals as a function of the pulses; means for recording in the readable memory at a selected open memory iocation a digital signal corresponding to the signal value then in the total energy utilisation temporary memory at the termination time; and, means for recording in digital form on the readable memory at respective open memory locations both the time of commencement and the time of termination of the time intervals.

This invention thus replaces the prior method and apparatus in which a tape recorder system is used for recording energy use by a system in which peak power and total power use are recorded in digital form at two respective memory locations in a digital memory, and preferably in a read only memory which may be removed and which may be erased for re-use.

This invention has the advantage that the digital summation count value signals corresponding to respective succeeding time intervals are recorded as are the digital total summation signal corresponding to the total of all of the time interval signal values, and a peak power digital signal corresponding to the largest single quantity value of the succeeding time interval digital summation signals, all without aid of operator computation, and this enables subsequent machine reading, processing and/or print out, or other use to be made of the data.

A particular example of a method and apparatus in accordance with this invention will now be described with reference to the accompanying drawings; in which Figure lisa block diagram of an example of the apparatus; and, Figure 2 is a diagram illustrating the format of recorded data used in the example.

Referring now in detail to the figures of the drawings, a solid state electronic digital recorder 10 is connected to an energy source such as a conventional EMF power source 11 which connects in energy feeding relation to an energy utilisation location through an energy flow responsive variable frequency pulse generator 15 which may be of any conventional or other suitable construction and which yields electrical output pulses at a frequency proportional to the rate of energy flow therethrough to the energy utilization location or facility 13. The generator 15 is shown outside the recorder 10, (but may if desired be within the recorder), as when employing a power flow sensing variable frequency generator as is presently in use at user locations for present tape recording of energy usage.

The electrical pulse output of generator 15 is fed into interval pulse counter 17 which may suitably take the form of a binary digital output counter started, outputted, and reset by a timing clock 19, and appropriate control signals from control logic unit 31, which counter 17 outputs at the end of each interval period of, for instance, 15 minutes, a digital signal indicative of the total pulse count for each respective interval period. This interval pulse sum mation signal is fed to each of gate 21, comparator 23, adder 18, and the input of buffer memory 25 for storage at a desired discrete memory location, which latter buffer memory may suitably be a random access memory.

The output of gate 21 is also connected to the input of buffer memory 25 for storage at a selected discrete memory location. This memory location will have stored therein a signal representative of the updated interval peak power utilization for all interval periods to date within the overall total particular recording period.This is effected by connecting an output from this memory location in buffer memory 25 to one comparison input of comparator 23 while connecting the output of interval pulse counter 17 to another comparison input to comparator 23, with the output from comparator 23 connected to the control input to gate 21, such that if the value of the output signal from interval pulse counter 17 exceeds the value of the interval pulse summation signal fed to comparator 23 from buffer memory 25, the gate 21 will be opened and permit the instant signal from interval pulse counter 17 to pass and be stored in the interval peak power memory location in memory 25 in replacement of the previousiy stored value. In this manner, the interval summation peak power utilization value will be stored on a continuously updated basis in the respective memory location in buffer memory 25.

The digital output signal from interval pulse counter 17 is also fed into a total power adder 18 which may take the form of a conventional or other desired adder of successive digital input values thereto, and the output from adder 18 may be successively, or only as finally sum mend if desired, fed into a selected memory location in buffer memory 25 for subsequent transfer into a corresponding or other desired memory location in cartridge memory unit 43. Alternatively the pulses from generator 15 may be fed to a total pulse counter (not shown) and the final count at the time of record termination, and representative of total power consumed or utilized, may be caused by control logic unit 31 to be fed into a memory location for total power consumption in buffer memory 25 as well as EPROM 43.

Control logic unit 31 is provided for controlling the address register 27, buffer memory 25, and the solid state cartridge memory 43 contained within and forming a part of removable cartridge 41. A suitable EMF source 33 for recorder 10 and cartridge memory 43 is connected to and feeds through the control logic unit 31.Control logic unit 31 serves not only to provide electrical power and control signals to the address register 27, buffer memory 25 and cartridge memory 43, but also serves to transmit signals from a digital signal means 35, which may suitably be a hand holdable pendant keyboard terminai input unit, for generation of digital signals representative of the times of starting and termination of recording for a given period, as well as customer and/or location or facility identification number or the like, and if desired the identification of the recorder may also be inputted through this signal unit 35.

Control logic unit 31 also has a running clock input from clock 19 for overall timed control of the various units 27,25 and 43.

In addition to the control signal outputs from control logic unit 31 to address register 27, memory 25 and memory 43, the identification and time indication signals from signal unit 35 are fed through control unit 31 and inputted at selected memory locations in buffer memory 25 for subsequent transfez to and final storage in respective selected memory locations in cartridge memory 43.

Address register 27 and buffer memory 25 may be of conventional or other desired connectibly compatible construction, as may buffer 30 connecting between address register 27 and the address inputs of cartridge memory unit 43 on the one hand, and buffer 29 connecting between buffer memory 25 and the input/output pins of memory unit 43, which latter pins will in the highly preferred embodiment serve solely as one-shot inputs for the purpose of recording data therethrough as will be subsequently further described, and will thereafter serve solely as nonrecordable output pins after removal from the recorder 10, until such time as positive steps are taken to effect erasure of the recorded information on cartridge memory 43.

Cartridge memory 43 takes the form in the highly preferred illustrative embodiment of an ultraviolet light-erasable programmable read-only memory now conventionally referred to as a UV EPROM. This EPROM memory unit 43 is mounted within a plastic or other suitable cartridge case which is substantially opaque to UV light, and with only an electrical pin connector exposed at an edge or face of the cartridge for plug-in in a suitable pin-connection socket on the solid state recorder 10.

The opaque plastic case of cartridge 41 may be suitably openable, as by being separable into two halves or the like, on one of which the EPROM and any associated circuit connections may be mounted, with the UV-sensitive data storage section of the EPROM exposed for erasure after completion of use and upon opening of the case. Suitable tamper prevention seal means 45 may be provided on the cartridge case to aid in enhancing the security of the recorded data on the EPROM memory unit 43.

The respective recorder output pins or pin groups are designated as EMF for EPROM memory chip power output, CE for chip enable signal outputs, DATA for data output, and ADDRESS for address outputs, and the corresponding input pins or pin groups of EPROM memory unit 43 are V for chip DC power input, CE for chip enable, I/O for input/output pins, and A for address pins. The output enable pin OE of EPROM 43 is not connected to the recorder 10, as no read-out is necessary, unless as an option some form of checking is desired, as when an operator removes or is preparing to remove the cartridge 41 from the recorder 10.

The entire solid state electronic recorder 10 and removable solid state memory cartridge 41 are preferably enclosed within a security cabinet, which may have a suitable access door 53 and which door may be suitably sealed as indicated at 55 upon closing and locking by the operator after inserting a fresh cartridge 41 and recording the location and start time information through manually keyed or other suitable input from signal means 35 which is desirably near to the door 53 within cabinet 51, or such unit 35 may be an operator-carried plug-in unit for economy purposes.Upon subsequent return and removal after a suitable desired time period of, for instance, 30-35 days, the door 53 is reopened, after checking the seal 55, and the time of termination of recording is entered by the operator by keying or otherwise actuating signal means 35, whereupon cartridge 41 is removed for subsequent read-out and processing of its stored data. In each instance, the outputs from signals means 35 may be generated in suitably binary digital form for insertion in the respective memories 25 and 43. While it is possible to insert the outputs from signal means 35, as well as the output from counter 17 directly into the cartridge EPROM memory, the better practice for reliable entry is to employ a buffer memory 25 and buffers 29, whereby input recycling of the input signals to the memory 43 can be effected to ensure entry.Such successive step memory entries may be readily and simply effected by control logic unit 31, as will be readily apparent.

After inserting the fresh fully erased cartridge 41 in the recorder 10 connection socket, the recorder will begin its recording cycle, recording on buffer memory 25 each succeeding interval pulse count summation signal value from internal pulse counter 17, as well as recording the instant updated peak energy utilization signal value for all time intervals to date after the start time. If desired the commencement of recording may be begun only after and upon completion of entry of the start time, or as an automation alternative the starting of recording may be initiated by the insertion of the cartridge into the recorder socket, or other suitable start routine may be employed.The successive interval pulse count summation digital signals from counter 17 may be sent from buffer memory 25 to cartridge EPROM 41 directly after entry into memory 25 in order to economize on data transfer and operator time at the time of termination of the recording period, although, if desired, such data may be transferred at the end of the recording period. In any event, the final peak power signal value stored in buffer memory 25 is not transferred to cartridge memory EPROM 43 until the end of the recording period. This transfer may suitably be initiated by the control logic unit 31 as a function of either a direct command from the operator signal means 35 after or at the time of entering the stop recording time, or such data transfer may be initiated through control unit 31 automatically in response to the entry of the stop recording time through or from operator signal means 35. While signal means 35 is shown and described as operator controlled, such may be automated as by interlocking with door 53 and/or the cartridge socket of recorder 10 to initiate and terminate recording and initiate entry of data for times of starting and stopping of recording.

As has been generally indicated above, the solid state electronic memory unit of removable cartridge 41 takes the form of an ultraviolet light-erasable programmable read-only memory in the illustrated and highly desirably preferred mode of practice and embodiment of the invention. While other memory units may be employed within the broad ambit of the overall invention, this preferred mode of practice and embodiment aspect of the invention offers substantial advantages which materially enhance the invention from both practical and commercial standpoints.Ordinary PROMs are not erasable and thus may not be reused, while electrically erasable PROMs permit the spurious electrical erasure at individual memory locations and subsequent entry of alternate data in lieu of the correct recorded data, thereby rendering the recording less secure and more open to suspicion and falsification or spurious unintended alteration. On the other hand, the UV EPROMs are erasable essentially only by UV light exposure for general practical purposes, and erasure is effected at all memory locations without any ability to selectively erase and rewrite a selected given memory location. In addition, once data is entered, no rewrite thereover with different data is possible without first effecting erasure which by its nature is effected as a totality by UV exposure.

Accordingly, the employment of a solid state electronic data cartridge 41 with its UV EPROM in practicing the method and apparatus invention offers major advantages in reliability and security of data and cost of use.

Figure 2 illustrates schematically or diagrammatically a preferred format mode of practice for recording locations for the foregoing described and discussed data on the cartridge EPROM 43. Desirably, the successive interval power summation value signals are stored in a plurality of successive contiguous memory locations on the EPROM, and the data indicating location of the energy utilization facility, the commencement or begin record time, the termination or stop record time, are stored together at the initial memory locations for ease of subsequent read-out acquisition. Likewise, the signals indicating interval peak power utilization and total ower utilization (which is indicated as the sum of all recorded successive interval power accumulation values) are desirably also accessible adjacent the time and location header information on the EPROM.Accordinly the interval peak power and total power utilization data are preferably stored immediately afterthe location and time start/stop record date.

However, other data memory locations and modes of arrangement of the data might of course be used if so desired, within the broad ambit of my invention.

While the invention has been illustrated and described with respect to its preferred practice through employment of an illustrative preferred physical apparatus embodiment, it will be apparent that various modifications and improvements may be made without departing from the scope and spirit of the invention. For instance, while the invention is shown as practical through use of an overall generally hardware system, with an optionally hardware and/or software control logic unit, the invention in both its method and apparatus aspects may be practiced by use of a recorder which may to a substantial degree be embodied in software. Accordingly, it is to be understood that the invention is not to be limited by the particular illustrative embodiment, but only by the scope of the appended Ciaims.

Claims (30)

1. A method of recording the amount of energy used at a particular location, comprising the steps of: transmitting discrete count signals varying in rate as a function of the rate of energy use; counting the quantity of the disctete count signals during succeeding discrete time intervals to produce succeeding interval summation count value digital signals; recording the succeeding interval summation digital count values in digital signal form at discrete individual locations in a record medium for subsequent read-out, comparing the succeeding interval summation count value digital signals with previous of the interval summation count value digital signals to determine which of the succeeding interval summation count value digital signals is the highest; recording, in digital signal form, at a discrete location in the record medium, the highest of the interval summation count value digital signals that occurs during a given total recording period composed of a plurality of the succeeding time intervals, the highest of the interval summation count value digital signals representing peak interval summation digital count values; summing the interval summation digital count values represented by the interval summation countvaue digital signals over the given total recording period to thereby provide a grand total energy use digital value signal for the given total recording period; and recording the grand total energy use digital value signal as a digital signal at a discrete location in the record medium.

2. A method according to claim 1, in which the discrete count signals are transmitted as electrical pulses.

3. A method according to claim 1 or 2, which includes the further step of effecting an entry in the record medium which identifies the particular location at which the energy is used.

4. A method according to claim 3, in which the location entry is encoded in digital signal form and recorded at a discrete location on the record medium.

5. A method according to any one of the preceding claims, which includes the further step of: forming and recording signals on the record medium indicative of the start and conclusion of the given total recording period.

6. A method according to claim 5, in which the start and conclusion signals are in digital signal form, and in which the start and conclusion digital signals are recorded at discrete locations in the record medium.

7. A method according to any one of the preceding claims, in which the recording is carried out on a removable solid state read-only memory unit.

8. A method according to any one of the preceding claims, in which the recording is carried out on an erasable programmable read-only memory.

9. A method according to claim 7 or 8, in which the recording is carried out by application to the record medium of energy in one form for data entry recording, and employing a record medium which is not erasable by further application of energy in said one form but which is grossly erasable, but not discretely erasable as to individual discrete record locations, by application of energy in another form.

10. A method according to claim 9, in which the recording is carried out on a UV erasable EPROM.

11. A method according to claim 9 or 10, in which the recorded energy use information stored in the record medium for the total time period is subsequently read and then the record energy use information is grossly erased from the record medium by application to the record medium of energy in another form from said one form employed for data entry recording.

12. A method according to any one of the preceding claims, in which the comparing step is effected by: storing in an updatable storage medium the first of the interval summation count value signals as the current interval summation peakvalue for the given total recording period; comparing each succeeding interval summation count value signal with the interval summation count value signal stored as represeting the current interval peak value; and, substituting any one of the succeeding summation count value signals for the current peak value summation count value signal presently in the storage medium, when such succeeding interval summation count value is larger in value than the presently stored interval summation count value, thereby continually maintaining in the storage medium the highest interval summation peak value for the given recording period.

13. A method according to claim 12, in which the recording in digital signal form, of the digital signal representing the final peak interval summation digital count value during a given total recording period, is effected after the conclusion of the last of the succeeding time intervals and is effected by recording on the record medium a digital signal corresponding to the value of the last interval summation count value signal appearing in the storage medium after the conclusion of the last of the succeding time intervals and after effecting the count value comparison and count value substitution steps.

14. A method according to claim 12 or 13, further comprising after each succeeding time interval, summing the summations of all preceeding time intervals and storing the resulting summed value as a digital signal in a storage medium; and recording the final instant updated total summation as the grand total energy use value at the conclusion of the given total recording period.

15. A method according to claim 14, further comprising storing, at respective individual discrete locations in a storage medium, a respective digital signal representing respectively each of the succeeding individual interval summation count values after the conclusion of each such individual interval summation; and, recording the stored succeeding interval summation count values as digital signals at respective discrete locations in the record medium after the conclusion of the final time interval in the given total recording period.

16. A method according to any one of the preceding claims, including the further steps of: storing updated summations of the discrete time intervals in an updatable storage medium; and, recording in the record medium, the final updated summation present in the updatable storage medium, as the grand total energy use value at the conclusion of the given total recording period.

17. A method according to claim 12, in which the recording as a peak interval summation count value of the highest of the interval summation values occurring during a given total recording period, is effected at the conclusion of the last of the succeeding time intervals, and is effected by recording, on the record medium, of a digital signal corresponding to the value of the final updated interval summation count signal appearing in the storage medium after the conclusion of the last of the succeeding time intervals and after effecting the count value comparison and count value substitution steps; and, which further comprises storing the instant updated summation of all preceding time intervals in a storage medium, and recording on the record medium the final instant updated summation as a digital signal representing the grand total energy use value at the conclusion of the given total recording period.

18. A method according to claim 17, in which the storing of the various count value signals are effected in a buffer storage memory, and in which the recording is effected from the signals in the buffer storage memory.

19. A method according to claim 1, substantially as described with reference to the accompanying drawings.

20. An apparatus for recording electrical energy use at a particular location and for use with pulse generating means for generating electrical pulses at a variable frequency varying as a function of instant electrical energy use, to enable recording of signals indicative of interval peak power use and total energy use, the apparatus comprising: means for converting the total number of pulses emitted by a pulse generating means in each of a plurality of sequential time intervals into a succession of respective interval summation digital signals each of which is representaive of the total pulses occurring in each respective successive time period; temporary memory storage means for storing the first of the respective interval summation digital signals; comparator means for comparing each succeeding interval summation digital signal with the presently stored interval summation signal; logic means responsive to the occurrence of a succeeding interval summation digital signal larger in value than the presently stored interval summation digital signal to effect substution of the larger value interval summation digital signal in the temporary memory means instead of the presently stored digital signal against which the larger interval summation digital signal has been compared; means for feeding each successive one of the interval summation digital signals to and for recording such at respective discrete open memory locations on a readable memory; means for recording in a readable memory after the termina tion of a plurality of the time intervals, a digital signal equal in value to the interval summation digital signal then stored in the temporary memory and representing the peak energy used for the toal of the recorded time intervals; means for summing in a total-energy-utilisation temporary memory the running composite total of the temporary memory the running composite total of the electrical pulses between the respective times of commencement and termination of the recording of signals as a function of the pulses; means for recording in a readable memory a digital signal corresponding to the signal value then in the total energy utilisation temporary memory at the termination time; and, means for recording in digital form on a readable memory both the time of commencement and the time of termination of the time intervals.

21. An apparatus according to claim 20, further comprising a solid state electronic readable memory unit operatively connectableto each of the means for recording.

22. An apparatus for recording electrical energy use at a particular location and for use with pulse generating means for generating electrical pulses at a variable frequency varying as a function of instant electrical energy use, to enable recording of signals indicative of interval peak power use and total energy use, the apparatus comprising: a removable cartridge solid state read only memory; means for converting the total number of pulses emitted by a pulse generating means in each of a plurality of sequential time intervals into a succession of respective interval summation digital signals each of which is representative of the total pulses occurring in each respective successive time period; temporary memory storage means for storing the first of the respective interval summation digital signals; comparator means for comparing each succeeding interval summation digital signal with the presently stored interval summation signal; logic means responsive to the occurrence of a succeeding interval summation digital signal larger in value than the presently stored interval summation digital signal to effect substitution of the larger value interval summation digital signal in the temporary memory means instead of the presently stored digital signal against which the larger interval summation digital signal has been compared; means for feeding each successive one of the interval summation digital signals to and for recording such at respective discrete open memory locations on the readable memory; means for recording in the readable memory after the termination of a plurality of the time intervals, a digital signal equal in value to the interval summation digital signal then stored in the temporary memory and representing the peak ener gyusedforthetotal of the recorded time intervals, the recording being effected at a selected open memory location in the removable cartridge read only memory; means for summing in a total energy utilisation temporary memory the running composite total of the electrical pulses between the respective times of commencement and termination of the recording of signals as a function of the pulses; means for recording in the readable memory at a preselected open memory location a digital signal corresponding to the signal value then in the total energy utilisation temporary memory at the termination time; and, means for recording in digital form on the readable memory at respective open memory locations both the time of commencement and the time of termination of the time intervals.

23. An apparatus according to claim 21 or 22, in which the solid state electronic recording memory unit comprises a removable solid state electronic recording cartridge having a memory unit therein.

24. An apparatus according to claim 23, in which the cartridge comprises a protective cartridge case having a programmable read only solid state electronic digital memory unit contained therewithin.

25. An apparatus according to claim 24, in which the programmable read only memory unit is an erasable programmable read only memory unit.

26. An apparatus according to claim 25, in which the erasable programmable read only memory unit is recordable in memory by electrical impulses and is erasable by ultraviolet light, the cartridge case being substantially opaque to ultraviolet light in the region of its ultraviolet light-sensitive erase zone.

27. An apparatus according to any one of claims 21 to 26, further including fixed program logic means effective to record the commencement and termination time signals, the final stored interval summation digital signal, and the total energy utilisation signal on the readable memory at respective successive memory locations at the beginning memory locations of the memory so that such signals can be easily read out and used separately without the necessity of reading the entire memory with its successive time interval value signals, or alternatively, entirely together with such successive time interval value signals.

28. An apparatus according to any one of claims 20 to 27, in which the means for summing the running composite total includes means for adding togetherthevalues represented by all of the interval summation digital signals within the given period of forming and for recording such interval summation signals.

29. An apparatus according to any one of claims 20 to 28, in which the apparatus also includes the pulse generating means for generating electrical impulses at a variable frequency varying as a function of instant electrical energy use at the particular location.

30. An apparatus accordng to claim 20 or 22, constructed substantially as described with reference to the accompanying drawings.