Note: Descriptions are shown in the official language in which they were submitted.
--r + ~ _
1 11 ~E 17
FREEZING ITEMS FOR DISPLAY
IN ELECTRONIC WATTHOUR REGISTER
BACKGROUND OF THE INVENTION
The pr~sent invention relates to electrio
. 5 watthour metering systems and, more particularly, to
watthour.m~tering systems including an electronic
register containing a plurality o~ items to be
- displayed.
Electxic watthour metering systems
conventionally employ means for measuring
instantaneous power consumption by a load and means
for accumulating the insta~taneous power consumption
to provide a measurement of electric energy consumed
by the load.
The most familiar type of power-measurement
: ~ device includes a metallic disk driven at a speed
; proportional to the product of the line voltage and
the load current, that is, the power consumed by the
load. Each revolution of the metallic disk
signifies the consumption of a predetermined quantum
of electric energy. In some equipment, a pulse
initiator converts the revolutions of the disk into
electrical output pulses, each signifying the
consumption of a predetermined quantum of electric
,
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2 11~ 178
energy.
More recently, fully electronic power-
measurement devices are disclosed which directly
measure consumption of electric power without the
- 5 intermediate step of rotating a disk. Thes~
electronic devices produce an output pulse upon
sensing the consumption of a predetermined quantum
of electric energy.
Xn either type of power~measurement equipment,
10 an electronic register conventionally sums the
pulses to produce a total of energy consumption.
~ Utilities generally consider that the cost o~
electric energy can be attributed to two factors: 1)
the out-of-pocket cost ~or generatiny the energy
15 (fuel, operating and ~aintenance personnel and
eguipment, etc.~ and 2~ the capital cost of the
generating equipment which ~ust be installed to
generate the electric energy.
Electric energy consumptiDn is far from
20 constant over a day, month or year. In some seasons
such as, for example, the air-conditioning season,
power demand is much greater than at other seasons.
In order to provide aQequate service, the utility
must provide generating e~uipment capable of
2~ satisfying the maximum demand which it may
experience. Thus, the utility must bear the capital
cost of installing sufficient generating capacity to
satisfy the peak demand. It must do this while
knowing that, except at peak times, a substantial
30 portion of its generating capacity remains idle.
- According to this analysis, the capital component ~f
the total energy cost is governed by the peak demand
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3 11-ME~178
in the peak season.
Some rate-setting bodies have recognized the
importance ~f peak demand and have established
tariffs in a manner designed t~ encourage energy
consumers to limit peaks in their energy usage and
to shift energy consumption from peak to ofE-peak
times. ~ne of such tariffs permits the utility to
measure the am~unt of energy consumed in a ~equence
of demand intervals. At the end of each demand
interval, the demand in the just-completed demand
interval is compared with a stored value
representing the highest demand in any demand
interval since the register was last reset. If the
demand in the just-completed demand interval is
higher than the previous high demand value, then the
-- value of the demand in the just-completed demand
interval is stored and the previously-stored value
is deleted. The value of the maximum demand
existing at the time the meter is read determines
the rate the consumer must pay for all of its
electric energy. Thus, the consumer receives a
powerful econo~ic incentive to limit the peak load
- placed on the utility system.
An electronic register including demand
metering and time-of-use metering requires
constantly updated time and date information for
setting the lengths of the demand intervals and Eor
switching between the permitted rates at different
times and seasons.
The data in an electronic register is displayed
on a human-readable display device for providing
access to the data stored therein. Conventional
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4 ll-ME-178
display device~ include, for example, light-emitting
diodes and liquid-crystal displays. In order to
limit cost, and to conser~e ~pace, ~uch display
devices are capable of displaying far less than the
total amount o~ information contained in the
electronic register. It is thus conventional to
display the data sequentially, one or two lines at a
time, holding each displayed line on the display for
~ long enough for a person to ~ee,~ possibly to
write down, the relevant in~ormation. Each item may
remain displayed for several ~econds. In some
operations for electr~nic registers, a large number
of 6eparate items require seq~ential occupancy on
the display wherein each occupancy requires several
seconds to complete. The complete display sequence,
- sometimes called a scroll, may take up to several
minutes.
The extended time for running a complete
display scroll produces a problem in interpreting
the data. In conventional systems, each displayed
item represents the value of the displayed data at
the time that it is displayed. In a scroll lasting
- for several minutes, the later-displayed data may
not relate to the earlier-displayed data. For
example, during the scroll, the electronic register
may have passed from one demand interval to another,
and may have recorded a new maximum demand, and have
zeroed the data in the current-demand period. One
examining the scrolled display may find it difficult
to understand the relationship between present, very
small, amount of energy accumulated in the current-
demand period and the previously-displayed data of
f..~
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11-ME-178
the timing of the demand interval itself which
showed that the end of the demand interval was being
approached. As a further example, during the
scroll, the time of day may ha~e passed from one
time-of-use accumulation to another, Combining
earlier- and later-displayed data o~ this type may
be misleading,
03JECTS AND SUMMARY OF THE INVENTION
Accordingly, it an object of the invention to
provide an electronic resister for electric watthour
metering system which overcomes the drawbacks of the
: prior art.
It i5 a further object o~ the invention to
provide ~n electronic register for an electric
watthour metering system wherein all elements in
scrolled display data relate to each other.
It is a further object of the invention to
provide an electronic register for an electric
; watthour metering system including a display buffer
into which all data to be displayed is stored, and
~rom which, desired items of data are scrolled for
display. The display buffer ensures that all
displayed items in a display scroll relate to the
same time and to consistent conditions of the data
in the electronic register,
Briefly stated, the present invention provides
an electronic register for an electric watthour
metering system. The electronic register includes a
- display buffer for receiving, at substantially the
6 11-ME-178
same time, all data items to be displayed. The data
items in the display bu~fer are scrolled to a
display in sets appropriate for the capacity of the
display. Each set is maintained on the display for
as long as required for human reading. The
displayed items, having heen taken into the display
~ buffer at the same instant, are consistent with each
other regardless of the length of time required to
complete the display sequence.
According to an embodiment of the invention,
there is provided an electronic register for a
- electric watthour metering system, the electric
watthour metering system including a power
measurement device e~fective for producing signals
each signifying consumption o~ a predetermined
- quantum of electricity by a load, comprising: a
central processing unit effective for accumulating
the signals, a display for displaying data in the
central processing unit, a display buffer, means for
transferring all data to be displayed to the display
buf~er at substantially the same instant, and means
for displaying data in the display buffer without
the display reflecting changes in data in the
central processing unit.
According to a feature of the invention, there
is provided a method for displaying data in an
electronic register for a electric watthour metering
system, the electric watthour metering system
including a power measurement device effectiYe for
producing signals each signifying consumption of a
predetermined quantum of electricity by a load,
comprising: accumulating the signals in a central
7 11-ME-178
processing unit, kransferring all data to be
displayed to a display buffer at substantially the
same instant, and displaying data in the display
buffer without the display reflecting changes in
data in thQ central processing unit.
The above, and other objects, features and
advantages of the present invention will become
apparent from the following description read in
conjunction with the accompanying drawings, in which
- 10 like reference numerals designate the same elements.
BRIEF DESCRIPTION O~ THE DRAWINGS
Fig. 1 is a simplified block diagram of an
electric watthour metering system accordin~ to the
prior art.
Fig. 2 is a simplified block diagram of an
electric watthour metering system according to an
embodiment of the invention.
DE~AILED DESCRIPTION OF THE PREFE~RED E~BODIMæNT
Referring to Fig. 1, there is shown, generally
at 10, an electric watthour metering system
according to the teaching of the p_ior art. A
power- measurement device 12 which may be, for
example, an electro-mechanical or an all-electronic
device, produces signals, each signifying the
consumption of a predetermined quantum of electric
energy, for application on a line 14 to a central
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processing unit 16 of an electronic registPr 18. A
clock/calendar circuit 2a applies ~ignals indicating
the current date and time of day on a line 22 to
central pr~cessing unit 16.
A display 24 pr3duces human-readable indicia
indicating the present contents of data registers in
central processing unit 16. Such contents ~ay
include, ~or example, the date, time of day, the
current demand intervall the amount of energy
accumulated in the current demand interval, the
maximum demand experienced in any demand intexval
- since the register was last reset, the time of-use
rate currently being applied. In addition to the
- preceding, various test and troubleshcoting
functions may ~xpand the data to be displayed, and
.-- the consequent time to aocomplish the display, by an
order of magnitude.
A display controller 26 applies control sisnals
on a line 28 to central processing unit 16 for
controlling the data to be displayed and the manner
in which the display is to be accomplished. It is
conventional for display controller 26 to provide a
normal-operation mode in which a small nu~ber of the
data items of interest to the energy consumer are
displayed, either constantly, or in a scroll of
relatively brief length. Display controller 26 may
: also be capable of receiving manual or electronic
commands for changing the amount and type of data
displayed. For example, an externally actuatable
switch (not shown) such as disclosed, for example,
in U.S. Patent 4,602,211 issued July 22, 1986, Losapio et
al, may be provided. The switch may be actuated from the
9 11-ME-178
normal position to a reading positi.on by a meter
reader to enable display of the data of interest to
the meter reader. The switch may also include means
for resetting a demand register upon completion of
reading. The switch may also ha~e a test position
accessible to a service technician for providing
display of more detailed data o~ interest t~ the
service technician in verifying correct performance
of electronic register 18, or in isolzting a fault
to a replaceable unit.
Display modes other than the normal display can
~ contain enough items for sequential display that a
relationship between earlier- and later-displayed
items i~ lost.
Referring now to Fig. 2, there is shown,
generally at3electric watthour metering system, a
electric watthour metering sy~tem according to an
embodiment of the invention. Elements ha~ing
identical reference numerals to ~hose in ~ig. 1 are
identical in structure and function in the
embodiment in Fig. 2. Elements in Fig. 2 which have
substantially similar functions to those described
in connection with Fig. 1 are primed. A full
discussion of the identical items is properly
omitted herefrom.
A display buffer 32 is interposed between
central processing unit 16' and display 24. One
output of display controller 26' on line 28 enables
output of all items to be displayed from central
processing unit 16' on a line 34 to display buffer
32. The transfer of data to be displayed into
display buffer 32 is so fast as to be substantially
~ ~5q~'~
10 11-ME-178
instantaneous. Thus, the data in display buffer 32
represents a snapshot at a ~ingle time of the data
in central processing unit 16'. Display controller
26' applies a display-scrolling command signal on a
line 36 to display buffer 32. Display buffer 32
then outputs the sequence of data items on a line 3
to display 24 in a sequence, and for times required
for human use of the data.
The data items displayed on display 24 are all
lo from the ins ant that the full set of data was
transferred into display buffer 32. While the
display is proceeding, the contents of central
processing unit 16' are proceeding in their normal
functions wherein ~ome of the data items are
changed. Such change~ do not provide inconsistencies
-- to the one observing the display.
Any convenient devices may be employed for
realizing the invention in Fig. 2. As previously
noted, power measurement device 12 may be electronic
or electro mechanical. Central pro_essing unit 16'
is preferably a digital device and, most preferably,
a microprocessor. Display buffer 32 may be an area
of random-access memory or may be an storage element
such, for example, an electronically eraseable read
2~ only memory. Cl~ck/cale~dar circuit 20 may be a
conventional integrated circuit, preCerably
including a battery backup for providing continued
operation during a power outage.
Having described preferred embodiments of the
invention with reference to the accompanying
drawings, it is to be understood that the invention
is not limited to those precise embodiments, and
11 11-ME-178
that various changes and modifications may be
effected therein by one skilled in the art without
departing from the scope or spirit of the invention
as defined in the appended
claims.
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