The present invention relates to a method and apparatus for displaying
metered electrical energy.
Techniques and devices for metering the various forms of electrical
energy are well known. Meters, such as utility power meters, can be of two types,
namely, electro-mechanical based meters whose output is generated by a rotating
disk and electronic based meters whose output component is generated electronically.
A hybrid meter also exists, wherein an electronic register for providing an electronically
generated display of metered electrical energy has been combined, usually optically,
to a rotating disk. Pulses generated by the rotating disk, for example by light
reflected from a spot painted on the disk, are utilized to generate an electronic
It will be appreciated that electronic meters have gained considerable
acceptance due to their increasing reliability and extended ambient temperature
ranges of operation. Consequently, various forms of electronic based meters have
been proposed which are virtually free of any moving parts. In the last ten years
several meters have been proposed which include a microprocessor.
Testing of electronic meters has always been a problem. A special
mode of register operation known in the industry as the test mode has been available
to ease register testing, however, little has been done to improve overall meter
testing. Electronic meters have the potential of providing faster test times, multiple
metering functions and calibration of the meter through software adjustment. However,
implementing such functions can be expensive and complicated.
Presently, electric utility companies can test mechanical meters
with a piece of test equipment which can reflect light off a metered disk to detect
a painted spot as the disk rotates. An alternative form of testing mechanical
meters is disclosed in U.S. Patent Number 4,600,881 which describes the formation
of a hole in the disk. A light sensitive device is placed in a fixed position
on one side of the disk. As the disk rotates, and the hole passes over the light
sensitive device, a pulse is provided indicating disk movement.
Since electronic meters preferably do not contain rotating disks,
such simple testing techniques cannot be used.
US Patent Specification 4,884,021, corresponding to the pre-characterising
part of claim 1, discloses an energy meter comprising a first processor for generating
pulsed energy signals and a second processor responsive to the energy signals
for driving a display. However, the specification is primarily concerned with the
determination of the electrical energy units. Meter testing is not specifically
addressed, and the nature of the displayed signals is not described.
Consequently, a need exists for an electronic meter having a relatively
simple means of testing the meter.
This object is achieved by the invention claimed in claim 1.
UK Patent Specification 2,177,805 and US Patent Specification 4,881,027
both disclose metering apparatus in which flashing outputs are provided. However,
neither uses two processors as specified in the pre-characterising part of claim
1, and in neither case does the displayed information correspond to that specified
in the characterising part of claim 1.
An embodiment of the invention will now be described, by way of example,
with reference to the accompanying drawings, in which:
- Fig. 1 is a block diagram of an electronic meter embodying the present invention;
- Figs. 2A-2E combine to provide a flow chart of the primary program utilized
by the microcontroller shown in Fig. 1;
- Fig. 3 is a front elevation of the liquid crystal display shown in Fig. 1;
- Fig. 4 is a diagrammatic view of selected annunciators of the liquid crystal
display shown in Fig. 3;
- Fig. 5 is a schematic diagram of the optical port shown in Fig. 1; and
- Fig. 6 is a schematic diagram of certain command buttons contained in the meter.
A meter for metering electrical energy is shown in Fig. 1 and generally
designated 10. It is noted at the outset that this meter is constructed so that
the future implementation of higher level metering functions can be supported.
Meter 10 is shown to include three resistive voltage divider networks
12A, 12B, 12C; a first processor - an ADC/DSP (analog-to-digital converter/digital
signal processor) integrated circuit chip 14; a second processor - a microcontroller
16 which in the preferred embodiment is a Mitsubishi Model 50428 microcontroller;
three current sensors 18A, 18B, 18C; a 12V switching power supply 20 that is capable
of receiving inputs in the range of 96-528V; a 5V linear power supply 22; a non-volatile
power supply 24 that switches to a battery 26 when 5V supply 22 is inoperative;
a 2.5V precision voltage reference 28; a liquid crystal display (LCD) 30; a 32.768
kHz oscillator 32; a 6.2208 MHz oscillator 34 that provides timing signals to
chip 14 and whose signal is divided by 1.5 to provide a 4.1472 MHz clock signal
to microcontroller 16; a 2 kbyte EEPROM 35; a serial communications line 36; an
option connector 38; and an optical communications port 40 that may be used to
read the meter. The inter-relationship and specific details of each of these components
is set out more fully below.
It will be appreciated that electrical energy has both voltage and
current characteristics. In relation to meter 10 voltage signals are provided to
resistive dividers 12A-12C and current signals are induced in a current transformer
(CT) and shunted. The output of CT/shunt combinations 18A-18C is used to determine
First processor 14 is connected to receive the voltage and current
signals provided by dividers 12A-12C and shunts 18A-18C. As will be explained in
greater detail below, processor 14 converts the voltage and current signals to
voltage and current digital signals, determines electrical energy from the voltage
and current digital signals and generates an energy signal representative of the
electrical energy determination. Processor 14 will always generate watthour delivered
(Whr Del) and watthour received (Whr Rec) signals, and depending on the type of
energy being metered, will generate either volt amp reactive hour delivered (VARhr
Del)/volt amp reactive hour received (VARhr Rec) signals or volt amp hour delivered
(VAhr Del)/volt amp hour received (VAhr Rec) signals. In the preferred embodiment,
each transition on conductors 42-48 (each transition from logic low to logic high
and vice versa) is representative of the measurement of a unit of energy. Second
processor 16 is connected to first processor 14. As will be explained in greater
detail below, processor 16 receives the energy signal(s) and generates an indication
signal representative of the energy signal(s).
In relation to the preferred embodiment of meter 10, currents and
voltages are sensed using conventional current transformers (CT's) and resistive
voltage dividers, respectively. The appropriate multiplication is accomplished
in an integrated circuit, i.e. processor 14. Although described in greater detail
in relation to Fig. 1, processor 14 is essentially a programmable digital signal
processor (DSP) with built in analog to digital (A/D) converters. The converters
are capable of sampling three input channels simultaneously at 2400 Hz each with
a resolution of 21 bits and then the integral DSP performs various calculations
on the results.
Meter 10 can be operated as either a demand meter or as a so-called
time of use (TOU) meter. It will be recognized that TOU meters are becoming increasingly
popular due to the greater differentiation by which electrical energy is billed.
For example, electrical energy metered during peak hours will be billed differently
than electrical energy billed during non-peak hours. As will be explained in greater
detail below, first processor 14 determines units of electrical energy while processor
16, in the TOU mode, qualifies such energy units in relation to the time such units
were determined, i.e. the season as well as the time of day.
All indicators and test features are brought out through the face
of meter 10, either on LCD 30 or through optical communications port 40. Power
supply 20 for the electronics is a switching power supply feeding low voltage
linear supply 22. Such an approach allows a wide operating voltage range for meter
In the preferred embodiment of the present invention, the so-called
standard meter components and register electronics are for the first time all located
on a single printed circuit board (not shown) defined as an electronics assembly.
This electronics assembly houses power supplies 20, 22, 24 and 28, resistive dividers
12A-12C for all three phases, the shunt resistor portion of 18A-18C, oscillator
34, processor 14, processor 16, reset circuitry (not shown), EEPROM 35, oscillator
32, optical port components 40, LCD 30, and an option board interface 38. When
this assembly is used for demand metering, the billing data is stored in EEPROM
35. This same assembly is used for TOU metering applications by merely utilizing
battery 26 and reprogramming the configuration data in EEPROM 35.
Consider now the various components of meter 10 in greater detail.
Primary current being metered is sensed using conventional current transformers.
It is preferred for the current transformer portion of devices 18A-18C have tight
ratio error and phase shift specifications in order to limit the factors affecting
the calibration of the meter to the electronics assembly itself. Such a limitation
tends to enhance the ease with which meter 10 may be programmed. The shunt resistor
portion of devices 18A-18C are located on the electronics assembly described above
and are preferably metal film resistors with a maximum temperature coefficient
of 25 ppm/°C.
The phase voltages are brought directly to the electronic assembly
where resistive dividers 12A-12C scale these inputs to processor 14. In the preferred
embodiment, the electronic components are referenced to the vector sum of each
line voltage for three wire delta systems and to earth ground for all other services.
Resistive division is used to divide the input voltage so that a very linear voltage
with minimal phase shift over a wide dynamic range can be obtained. This in combination
with a switching power supply allows the wide voltage operating range to be implemented.
It will be appreciated that energy units are calculated primarily
from multiplication of voltage and current. The specific formulae utilized in the
preferred embodiment, are described in greater detail in co-pending European Application
No. 92925121.3 (PCT/US92/09631). However, for purposes'of Fig. 1, such formulae
are performed in processor 14.
The M37428 microcontroller 16 is a 6502 (a traditional 8 bit microprocessor)
derivative with an expanded instruction set for bit test and manipulation. This
microcontroller includes substantial functionality including internal LCD drivers
(128 quadraplexed segments), 8 kbytes of ROM, 384 bytes of RAM, a full duplex hardware
UART, 5 timers, dual clock inputs (32.768 kHz and up to 8 MHz), and a low power
During normal operation, processor 16 receives the 4.1472 MHz clock
from processor 14 as described above. Such a clock signal translates to a 1.0368
MHz cycle time. Upon power fail, processor 16 shifts to the 32.768 KHz crystal
oscillator 32. This allows low power operation with a cycle time of 16.384 kHz.
During a power failure, processor 16 keeps track of time by counting seconds and
rippling the time forward. Once processor 16 has rippled the time forward, a WIT
instruction is executed which places the unit in a mode where only the 32.768 kHz
oscillator and the timers are operational. While in this mode a timer is setup
to "wake up" processor 16 every 32,768 cycles to count a second.
While power supply 20 can be any known power supply for providing
the required direct current power, a preferred form of power supply 20 is described
in detail in copending application ABB-0010, filed concurrently herewith and which
is incorporated herein by reference.
Consider now the main operation of processor 16 in relation to Figs.
2A-2E and Fig. 3. At step 1000 a reset signal is provided to microcontroller 16.
A reset cycle occurs whenever the voltage level Vdd rises through approximately
2.8 volts. Such a condition occurs when the meter is powered up.
At step 1002, microcontroller 16 performs an initialize operation,
wherein the stack pointer is initialized, the internal ram is initialized, the
type of liquid crystal display is entered into the display driver portion of microcontroller
16 and timers which requires initialization at power up are initialized. It will
be noted that the operation of step 1002 does not need to be performed for each
power failure occurrence. Following a power failure, microcontroller 16 at step
1004 returns to the main program at the point indicated when the power returns.
Upon initial power up or the return of power after a power failure,
microcontroller 16 performs a restore function. At step 1006, microcontroller 16
disables pulses transmitted by processor 14. These pulses are disabled by providing
the appropriate signal restore bit. The presence of this bit indicates that a restore
operation is occurring and that pulses generated during that time should be ignored.
Having set the signal restore bit, microcontroller 16 determines at step 1008
whether the power fail signal is present. If the power fail signal is present,
microcontroller 16 jumps to the power fail routine at 1010. In the power fail
routine, the output ports of microcontroller 16 are written low unless the restore
bit has not been set. If the restore bit has not been set, data in the microcontroller
16 is written to memory.
If the power fail signal is not present, microcontroller 16 displays
segments at step 1012. At this time, the segments of the display are illuminated
using the phase A potential. It will be recalled that phase A potential is provided
to microcontroller 16 from processor 14. At 1014, the UART port and other ports
are initialized at 1016, the power fail interrupts are enabled such that if a falling
edge is sensed from output A of processor 14, an interrupt will occur indicating
power failure. It will be recalled that processor 14 compares the reference voltage
VREF to a divided voltage generated by the power supply 20. Whenever the power
supply voltage falls below the reference voltage a power fail condition is occurring.
At step 1018, the downloading of the metering integrated circuit
is performed. It will be appreciated that certain tasks performed by microcontroller
16 are time dependent. Such tasks will require a timer interrupt when the time
for performing such tasks has arrived.
At 1022, the self-test subroutines are performed. Although no particular
self-tests subroutine is necessary in order to practice the present invention,
such subroutines can include a check to determine if proper display data is present.
It is noted that data is stored in relation to class designation and that a value
is assigned to each class such that the sum of the class values equals a specified
number. If any display data is missing, the condition of the class values for
data which is present will not equal the specified sum and an error message will
be displayed. Similarly, microcontroller 16 compares the clock signal generated
by processor 14 with the clock signal generated by watch crystal 32 in order to
determine whether the appropriate relationship exists.
Having completed the self-test subroutines, the ram is re-initialized
at 1024. In this re-initialization, certain load constants are cleared from memory.
At 1026, various items are scheduled. For example, the display update is scheduled
so that as soon as the restore routine is completed, data is retrieved and the
display is updated. Similarly, optical communications are scheduled wherein microcontroller
16 determines whether any device is present at optical port desired to communicate.
Finally, at 1028 a signal is given indicating that the restore routine has been
completed. Such a signal can include disabling the signal restore bit. Upon such
an occurrence, pulses previously disabled will now be considered valid. Microcontroller
16 now moves into the main routine.
At 1030, microcontroller 16 calls the time of day processing routine.
In this routine, microcontroller 16 looks at the one second bit of its internal
and determines whether the clock needs to be changed. For example, at the beginning
and end of Daylight Savings Time, the clock is moved forward and back one hour,
respectively. In addition, the time of day processing routine sets the minute change
flags and date change flags. As will be appreciated hereinafter, such flags are
periodically checked and processes occur if such flags are present.
It will be noted that there are two real time interrupts scheduled
in microcontroller 16 which are not shown in Fig. 2, namely the roll minute interrupt
and the day interrupt. At the beginning of every minute, certain minute tasks
occur. Similarly, at the beginning of every day, certain day tasks occur. Since
such tasks are not necessary to the practice of the presently claimed invention,
no further details need be provided.
At 1032, microcontroller 16 determines whether a self-reprogram routine
is scheduled. If the self-reprogram routine is scheduled, such routine is called
at 1034. The self-reprogram typically programs in new utility rates which are
stored in advance. Since new rates have been incorporated, it will be necessary
to also restart the display. After operation of the self-reprogram routine, microcontroller
16 returns to the main program. If it is determined at 1032 that the self-reprogram
routine is not scheduled, microcontroller 16 determines at 1036 whether any day
boundary tasks are scheduled. Such a determination is made by determining the time
and day and searching to see whether any day tasks are scheduled for that day.
If day tasks are scheduled, such tasks are called at 1038. If no day tasks are
scheduled, microcontroller 16 next determines at 1040 whether any minute boundary
tasks have been scheduled. It will be understood that since time of use switch
points occur at minute boundaries, for example, switching from one use period
to another, it will be necessary to change data storage locations at such a point.
If minute tasks are scheduled, such tasks are called at 1042. If minute boundary
tasks have not been scheduled, microcontroller 16 determines at 1044 whether any
self-test have been scheduled. The self-tests are typically scheduled to occur
on the day boundary. As indicated previously, such self-tests can include checking
the accumulative display data class value to determine whether the sum is equal
to a prescribed value. If self-tests are scheduled, such tests are called at 1046.
If no self-tests are scheduled, microcontroller 16 determines at 1048 whether
any season change billing data copy is scheduled. It will be appreciated that as
season changes billing data changes. Consequently, it will be necessary for microcontroller
16 to store energy metered for one season and begin accumulating energy metered
for the following season. If season change billing data copy is scheduled, such
routine is called at 1050. If no season change routine is scheduled, microcontroller
16 determines at 1052 whether the self-redemand reset has been scheduled. If the
self-redemand reset is scheduled, such routine is called at 1054. This routine
requires microcontroller 16 to in effect read itself and store the read value
in memory. The self-redemand is then reset. If self-redemand reset has not been
scheduled, microcontroller 16 determines at 1056 whether a season change demand
reset has been scheduled. If a season change demand reset is scheduled, such a
routine is called at 1058. In such a routine, microcontroller 16 reads itself and
resets the demand.
At 1060, microcontroller 16 determines whether button sampling has
been scheduled. Button sampling will occur every eight milliseconds. Reference
is made to Fig. 6 for a more detailed description of an arrangement of buttons
to be positioned on the face of meter 10. Consequently, if an eight millisecond
period has passed, microcontroller 16 will determine that button sampling is scheduled
and the button sampling routine will be called at 1062. If button sampling is
not scheduled, microcontroller 16 determines at 1064 whether a display update has
been scheduled. This routine causes a new quantity to be displayed on LCD 30. As
determined by the soft switch settings, display updates are scheduled generally
for every three-six seconds. If the display is updated more frequently, it may
not be possible to read the display accurately. If the display update has been
scheduled, the display update routine is called at 1066. If a display update has
not been scheduled, microcontroller 16 determines at 1068 whether an annunciator
flash is scheduled. It will be recalled that certain annunciators on the display
are made to flash. Such flashing typically occurs every half second. If an annunciator
flash is scheduled, such a routine is called at 1070. It is noted in the preferred
embodiment that a directional annunciator will flash at the same rate at which
energy determination pulses are transmitted from processor 14 to processor 16.
Another feature of the embodiment is that other annunciators (not indicative of
energy direction) will flash at a rate approximately equal to the rate of disk
rotation in an electro-mechanical meter used in a similar application.
If no annunciator flash is scheduled, microcontroller 16 determines
at 1072 whether optical communication has been scheduled. It will be recalled that
every half second microcontroller 16 determines whether any signal has been generated
at optical port. If a signal has been generated indicating that optical communications
is desired, the optical communication routine will be scheduled. If the optical
communication routine is scheduled, such routine is called at 1074. This routine
causes microcontroller 16 to sample optical port 40 for communications activity.
If no optical routine is scheduled, microcontroller 16 determines at 1076 whether
processor 14 is signaling an error. If processor 14 is signaling an error, microcontroller
16 at 1078 disables the pulse detection, calls the download routine and after performance
of that routine, re-enables the pulse detection. If processor 14 is not signaling
any error, microcontroller 16 determines at 1080 whether the download program is
scheduled. If the download program is scheduled, the main routine returns to 1078
and thereafter back to the main program.
If the download program has not been scheduled or after the pulse
detect has been re-enabled, microcontroller 16 determines at 1082 whether a warmstart
is in progress. If a warmstart is in progress, the power fail interrupts are disabled
at 1084. The pulse computation routine is called after which the power fail interrupts
are re-enabled. It will be noted that in the warmstart data is zeroed out in order
to provide a fresh start for the meter. Consequently, the pulse computation routine
performs the necessary calculations for energy previously metered in places that
computation in the appropriate point in memory. If a warmstart is not in progress,
microcontroller 16 at 1084 updates the remote relays. Typically, the remote relays
are contained on a board other than the electronics assembly board.
All data that is considered non-volatile for meter 10, is stored
in a 2 kbytes EEPROM 35. This includes configuration data (including the data for
memory 76 and memory 80), total kWh, maximum and cumulative demands (Rate A demands
in TOU), historic TOU data, cumulative number of demand resets, cumulative number
of power outages and the cumulative number of data altering communications. The
present billing period TOU data is stored in the RAM contained within processor
16. As long as the microcontroller 16 has adequate power, the RAM contents and
real time are maintained and the microcontroller 16 will not be reset (even in
a demand register).
LCD 30 allows viewing of the billing and other metering data and
statuses. Temperature compensation for LCD 30 is provided in the electronics. Even
with this compensation, the meter's operating temperature range and the LCD's
5 volt fluid limits LCD 30 to being triplexed. Hence, the maximum number of segments
supported in this design is 96. The display response time will also slow noticeably
at temperatures below -30 degrees celsius. For a more complete description of
the generation of a display signal for display 30, reference is made to co-pending
European Application No. 92925121.3 (PCT/US92/09631).
The 96 available LCD segments, shown in Fig. 3, are used as follows.
Six digits (.375 high) are used for data display and three smaller digits (.25
high) for numeric identifiers. In addition to the numeric identifiers, there are
seventeen alpha annunciators that are used for identification. These are: PREV,
SEAS, RATE, A, B, C, D, CONT, CUM, RESETS, MAX, TOTAL, KV, /, \, -\, R, and h.
The last six annunciators 220 can be combined to produce: KW, KWh, KVA, KVAh, KVAR,
or KVARh, as shown. Three potential indicators are provided on the LCD and appear
as light bulbs. These indicators operate individually and are on continuously
when the corresponding phase's potential is greater than 57.6 Vrms, and flash when
the potential falls below 38.4 Vrms. "TEST", "ALTO", and "EOI" annunciators are
provided to give an indication of when the unit is in test mode, alternate scroll
mode, or an end of a demand interval has occurred. Six (6) pulse indicators 200-210
are also provided on LCD 30 for watt-hours and an alternate quantity (VA-hours
Pulse indicators 200-210 are configured as two sets of three, one
set for indicating watts and another set for indicating VARhours. Each set has
a left arrow, a solid square, and a right arrow. During any test, one of the arrows
will be made to blink at the rate microcontoller 16 receives pulses from processor
14 while the square will blink at a lower rate representative of a disk rotation
rate and in a fashion which mimics disk rotation. It will be noted that signals
necessary to flash indicators 200-210 are generated by processor 16 in energy pulse
interrupt routines. The left arrow 200 blinks when energy is received from the
metered site and the right arrow 204 blinks when energy is delivered to the metered
site. The solid square 202 blinks at a Kh rate equivalent to an electromechanical
meter of the same form, test amperes, and test voltage. Square 202 blinks regardless
of the direction of energy flow. The rate at which square 202 blinks can be generated
by dividing the rate at which pulses are provided to processor 16. Consequently,
testing can occur at traditional rates (indicative of disk rotation) or can occur
at faster rates, thereby reducing test time. Indicators 206-210 operate in a similar
fashion, except in relation to apparent or reactive energy flow.
These pulse indicators can be detected through the meter cover using
the reflective assemblies (such as the Skan-A-Matic C42100) of existing test equipment.
As indicated above, the second set of three indicators indicate apparent or reactive
energy flow and have the tips of arrows 206 and 210 open so that they will not
be confused with the watt-hour indicators.
Referring to Fig. 4, it will be seen that annunciators 200-204 are
positioned along a line, wherein annunciator 202 is positioned between annunciators
200 and 204. As time progresses, processor 16 generates display signals so that,
when energy is flowing in the forward direction, annunciator 204 always flashes.
However, annunciators 200 and 202 can be made to flash selectively, to create the
impression that energy is flowing from left to right. When energy is flowing in
the reverse direction, the reverse is true. Annunciator 200 flashes continuously,
and annunciators 202 and 204 flash selectively to mimic energy flowing from right
Meter 10 interfaces to the outside world via liquid crystal display
30, optical port 40, or option connector 38. It is envisioned that most utility
customers will interface to LCD 30 for testing of the meter, some utilities will
desire an infrared LED, such as LED 112, to test the meter calibration. Traditionally,
electronic meters have provided a single light emitting diode (LED) in addition
to an optical port to output a watt-hour pulse. Such designs add cost, decrease
reliability and limit test capabilities. The present embodiment overcomes these
limitations by multiplexing the various metering function output signals and pulse
rates over optical port 40 alone. Meter 10 echoes the kh value watthour test output
on optical port 40 anytime the meter has been manually placed in the test mode
(the TEST command button in Fig. 6 has been pressed) or alternate scroll mode (the
ALT command button in Fig. 6 has been pressed). While in these manually initiated
modes, communication into processor 16 through optical port 40 is prevented. It
is noted that in the preferred embodiment, the ALT button is capable of being
enabled without removal of the meter cover (not shown). To this end a small movable
shaft (not shown) is provided in the meter cover so that when the shaft is moved
the ALT component is enabled. Consequently, removal of the meter cover is not
necessary in order to test the meter.
Referring now to Fig. 5, optical port 40 and reset circuitry 108
are shown in greater detail. Optical port 40 provides electronic access to metering
information. The transmitter and receiver (transistors 110 and 112) are 850 nanometer
infrared components and are contained in the electronics assembly (as opposed to
being mounted in the cover). Transistors 110 and led 112 are tied to UART include
within microcontroller 16 and the communications rate (9600 baud) is limited by
the response time of the optical components. The optical port can also be disabled
from the UART (as described below), allowing the UART to be used for other future
communications without concern about ambient light. During test mode, optical port
40 will echo the watthour pulses received by the microcontroller over the transmitting
LED 112 to conform to traditional testing practices without the necessity of an
Meter 10 also provides the ability to be placed in the test mode
and exit from the test mode via an optical port function, preferably with a data
command. When in a test mode initiated via optical port 40, the meter will echo
metering pulses as defined by the command transmitted on the optical port transmitter.
This allows the multiplexing of metering functions or pulse rates over a single
LED. In the preferred embodiment, such a multiplexing scheme is a time based multiplexing
operation. The meter will listen for further communications commands. Additional
commands can change the rate or measured quantity of the test output over optical
port 40. The meter will "ACK" any command sent while it is in the test mode and
it will "ACK" the exit test mode command. While in an optically initiated test
mode, commands other than those mentioned above are processed normally. Because
there is the possibility of an echoed pulse confusing the programmer-readers receiver,
a command to stop the pulse echo may be desired so communications can proceed uninterrupted.
If left in test mode, the usual test mode time out of three demand intervals applies.
The data command identified above is called "Enter Test Mode" and
is followed by 1 data byte defined below. The command is acknowledged by processor
16 the same as other communications commands. The command places meter 10 into
the standard test mode. While in this mode, communications inter-command timeouts
do not apply. Hence, the communications session does not end unless a terminate
session command is transmitted or test mode is terminated by any of the normal
ways of exiting test mode (pressing the test button, power failure, etc.), including
the no activity timeout. Display 30 cycles through the normal test mode display
sequence (see the main program at 1044, 1060 and 1064) and button presses perform
their normal test mode functions. Transmitting this command multiple times causes
the test mode, and its associated timeout counter, to restart after each transmission.
The data byte defines what input pulse line(s) to processor 16 should
be multiplexed and echoed over optical port 40. Multiple lines can be set to perform
a totalizing function. The definition of each bit in the data byte is as follows:
- bit0 = alternate test pulses,
- bitl = alternate delivered pulses,
- bit2 = alternate received pulses,
- bit3 = whr test pulses,
- bit4 = whr delivered pulses,
- bit5 = whr received pulses,
- bits 6 and 7 are unused.
If no bits are set, the meter stops echoing pulses. This can be used
to allow other communications commands to be sent without fear of data collision
with the output pulses. While in this mode, other communications commands can be
accepted. The test data can be read, the meter can be reprogrammed, the billing
data can be reset or a warmstart can be initiated. Since the Total KWH and Maximum
Demand information is stored to EEPROM 35, test data is being processed in memory
areas and functions such as demand reset and warmstart will operate on the Test
Mode data and not the actual billing data. Any subsequent "Enter Test Mode Command"
resets the test mode data just as a manual demand reset would in the test mode.
This command also provides the utility with a way to enter the test
mode without having to remove the meter cover. This will be beneficial to some