Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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1 The present invention relates to a method and
apparatus for monitoring an area for a disaster.
~ leretofore, since the prior art loop line
system relating to disaster prevention handled only
alarm contact outputs of the detectors arranged in
the area to be monitored, it could detect an abnormal
condition but could not determine actual status of the
area to be monitored in analog fashion because the data
transmitted were restricted to ON/OFF signals. Accord-
ingly, the prior art loop line system has suffered asignificant limitation with respect to the function
of the monitor and alarm apparatus.
The prior art system had also a significant
i drawback in that it was not capable of predicting the -~
occurrence of the abnormal condition and monitoring
status and variables derived from a plurality of data
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~'~ because it could not handle analog data representing-~ the status of the area to be monitored.
In order to resolve the above inconvenience,
the present invention is characterized in that terminal
control units are provided in the area to be monitored, and
analog signals from deteotors) which are grouped with eaoh
group comprising several detectors, are converted into
~; digital signals by multiplexers and analog-to-digital
converters incorporated in the terminal control units
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~ and carried over the loop line.
`~ According to one aspect of the present invention
~l a method for monitoring and alarming a disaster in an
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area, which comprises the steps of: generating a -~
` 30 plurality of analog signals by measuring the status
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1083;~42
of the disaster at a plurality of detecting points distributed in the area
to be monitored with respect to a disaster by means of detecting means at
said detecting points; forming said plurality of analog signals into a
plurality of groups each corresponding to a respective group of said detect-
ing means, each group of said plurality of groups of analog signals includ-
ing at least two kinds of signals indicative of two different parameters
relating to said disaster; combining and converting each of said plurality
of groups of analog signals into digital signals separately to form a series
of digital signals for each of said groups at a plurality of terminal control
units each connected to a corresponding one of said groups of detecting
means; transmitting said series of digital slgnals from said plurality of
terminalcontrol units to a data transmission control unit through a loop line
sequentially in response to a request from said data transmission control
unit, said loop line connecting said plurality of terminal control units
and said data transmission control unit in a loop; transferring properly
received digital signals at said data transmission control unit to a central
monitor and alarm apparatus connected to the data transmission control units;
and comparing said transferred digital signals with a predetermined monitor
level, and then generating an alarm signal at said central monitor and
alarm apparatus.
According to another aspect of the present invention there is
provided a monitor and alarm apparatus for a disaster comprising: a
plurality of detectors disposed in an area to be monitored with respect to
the disaster, said plurality of detectors being formed into groups and being
adapted to generate an analog signal by measuring the status of the disaster,
each group of said groups of detectors including at least two types of
detectors which sense at least two different parameters relating to said
disaster; a plurality of terminal control units each connected to a corres-
ponding one of said groups of detectors, each of said plurality of terminal
control units being operable to convert the analog signals of a respective
group of detectors into a series of digital signals; a loop line for connect-
` ing said plurality of terminal control units in a loop; a data transmission
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control unit inserted in said loop line to form a loop line system, said
data transmission control unit being adapted to receive said series of
digital signals from said plurality of terminal control units and allow a
properly received digital signal to be transferred therethrough; and a central
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monitor and alarm apparatus connected to said data transmission control unit
for comparing said transferred digital signals with a predetermined monitor
level and for generating an alarm signal.
A preferred embodiment of the present invention is now described
in conjunction with the accompanying drawings, in which:
Fig. 1 is a block diagram of one embodiment of the present
monitor and alarm apparatus in the loop line system.
Fig. 2 is a detailed block diagram of N-th terminal control unit
in Fig. 1 and detectors associated therewith.
In the preferred embodiment, since a micro-computer having a word
length of 12 bits is used, an analog signal is converted into an 8-bit
digital signal. For a proper function of the monitor and alarm apparatus,
a digital signal of 8 to 12 bits may be appropriate.
Fig. 1 shows a block diagram of the preferred embodiment in which
11, 12 .... lN designate terminal control units respectively arranged in
sectors or sub-areas in the area to be monitored, 111, 112, .... 115; 121;
122 .... 125; ....; and lNl, lN2 .... lN5 designate detectors located at
ff detecting points and connected to the terminal control units, 2 designate
' a loop line, 3 a data transmission control unit, and 4 a central monitor
and alarm apparatus, and where 41 designates a data processing unit, 42 an
alarm data display unit, 43 a typewriting unit, 44 a memory unit
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1 and 45 an input/output console. The data processing
unit 41 used in the present embodiment performs data
transmission processing function (data transmission
check and collection) and data processing function in
accordance with a program stored in the memory unit
44. The functions of the data processing unit 41 and
the memory unit 44 may be performed by a usual micro-
computer. ~nalog signals detected by the detectors
111, 112, ...... lN5 are periodically converted into
8-bit data signals in the terminal control units 11,
12, .... 1~. Whenever requested by the data transmission
control unit 3 at a given time interval, the data from
the five detectors associated with respective terminal ~
control units are each consolidated to a block of data, ~ -'
which is then transferred to the data transmission control
unit through the loop line, following an address signal
for the terminal control unit. ~
~;~ The data transmission control unit compares ~ ~ -
the received address signal with the transmitted address `~
signal, and if the comparison shows a coincidence it
determines that a proper reception has been made and
transfers the block of data transmitted following the -
address signal to the central monitor and alarm apparatus
as a detected signal for that address.
The data processing unit 41 decomposes the
transferred block of data into 8-bit signals and
simultaneously checks whether or not the data trans-
mission has been properly made by information representing
the characteristic of the data.
In the preferred embodiment, a double-transmission
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1 check system is used, in which data are normally read
out twice for the same address and these data are
compared with each other to determine whether they
are correct data only when the comparison shows the
coincidence.
If the data do not coincide with each other
in the comparison, the data transmission control unit
is instructed to read the same address again. This
procedure is repeated up to three times, and if the
readout of correct data is not attained within three
repetitions, it is regarded that there is a failure in
the data transmission control unit and the location of
- the fault is displayed and printed out.
The faults in the data transmission may be -
generally classified into the following two categories:
(1) Faults in the loop line
(2) Faults in the data transmission control
unit and/or the data transmission terminal
~ control circuit.
;~ 20 For the former faults, a loop line switching
circuit for detecting the fault in the loop line and
switching the direction of transmission in the loop line
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from clockwise to counterclockwise or vice versa is
additionally provided to permit the use of the loop
line in an essentially dual mode as a countermeasure
i for the fault in the loop line.
For the latter faults, the double-transfer
check system described above may be used.
~he data processing unit 41 performs three
~0 types of monitor (prediction, caution and alarm) for
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1 the detected signals from the respective detectors
by comparing the detected signals with a signal
representative of a predetermined monitor level stored
in the memory unit 44. In order to detect an abnormal
condition at an early stage, the data processing unit
41 is provided with a special data processing function
to derive a particular status variable (for example,
an overall heat transfer coefficient, U = f(Tl, T2 .....
Tn)~ is obtained from temperatures T1, T2 ...... Tn detected
by thermal sensors or thermocouples) from detected data
or a changing rate of a particular variable (for example,
a change rate of temperature ~ = dT) to enhance ~: :
the monitoring density in accordance with a program
stored in the memory unit 44. :
: 15 When the abnormal condition is detected, it
. is informed to an operator through the alarm data display ~ ~-
: unit 42 and the typewriting unit 43, and the data at~ :
the time of the abnormal condition is maintained in the ::.
memory unit 44. When the system is constructed such
that the operator verifies present value of the address
from the input/output console 45, the detected data
may be displayed in the alarm data display unit 42.
Fig. 2 shows a construction of the terminal
~ control unit lN, in which 5N designates a station for :
i 25 the loop line, 6N a data transmission terminal control
.~ . circuit, 7N an 8-bit analog-to-digital converter circuit,
~N a multiplexer circuit for switching detected signals
from the respective detectors, 9N a program control
circuit, lONl, lON2 ...... lON5 measuring circuits for
30 the respective detectors, and lNl, lN2, ....... lN5
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1 detectors associated with the terminal control unit.
~ ach of the detectors detects independently
from others and includes its own adjuster to permit
zero and span (range) adjustments for each detecting
point.
The program control circuit 9N causes the
multiplexer 8N to sequentially scan the analog signals
from the respective detectors, the analog-to-digital
converter 7N to convert them into 8-bit data signals t
and the buffer memory to store them. When an address
signal for addressing the terminal control unit lN is
received from the central data transmission control unit
over the loop line, the data transmission terminal control
circuit 6N compare the received address signal with the
preset address signal assigned to the terminal control
unit lN, and if the comprison shows the coincidence the -
,~ ~ data transmission terminal control circuit 6N instructs
the interruption of the analog-to-digital conversion to
the program control circuit in order to allow the trans- -
!~ ~ 20 mission of a predetermined data to the central data
transmission control unit, and the last five data which
have been converted to digital form are transferred as
a data block following to the address code assigned
to the terminal control unit lN, to the central data
~ 25 transmission control unit via the loop line.
: In order to prevent an error from being
introduced during the data transmission, the data
signal transmitted to the central station includes a
parity bit and a total bit in addition to start and
' 30 stop codes, which bits are used in error checking for
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1 the data transmission.
The construction and the operation of the
present apparatus have been fully discussed. An object
of the present apparatus is to reduce the cost of wiring
required in gathering the detected signals from a number
of detectors distributed in the area to be monitored as
well as to expand the capability of monitoring of the
- detected data. The present apparatus can be applied
to monitor and alarm apparatus in a tankyard, high pressure .
reaction facilities, a compressor and a plant, and it
allows the assembling of the apparatus at a cheaper
cost than required in the prior art apparatus.
The detector may be a temperature measuring
element such as a thermocouple or a temperature sensitive
resistor, a pressure transmitter by a ~ourdon's tube
system or a strain gauge system, a flow rate and level
'~ transmitter by a differential pressure system or a
static capacitance type level transmitter, for the
measurement of temperature, pressure, flow rate or
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~ 20 level. These different kinds of sensors may be
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formed as a group of sensors which are connected to
each of the terminal control units depending upon the
event to be monitored.
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; It should be understood that the data processing
unit used with the present apparatus need not be provided
~ with the specific data processing function in order to
i~ function as the monitor and alarm apparatus.
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