MONITOR AND RESULTS COMPUTER SYSTEM

• US 3,855,456 A
• Filed: 11/22/1972
• Issued: 12/17/1974
• Est. Priority Date: 11/22/1972
• Status: Expired due to Term

• Current Assignee: Betty L. Christy, Joseph V. Sweeney, William A. Summers
• Original Assignee: Betty L. Christy, Joseph V. Sweeney, William A. Summers
• Inventors: Summers, William A., Christy, Betty L., Sweeney, Joseph V.
• Primary Examiner(s): Gruber, Felix D.
• Assistant Examiner(s): Dildine, Jr., R. Stephen
• Application Number:
  US05/308,770
• Time in Patent Office: 755 Days
• Field of Search: 235/151.1,151.2,151.3,152,151.35 324/181,188,285E 444/1 340/213Q,415,223
• US Class Current: 700/286
• CPC Class Codes: G05B 23/0262 Confirmation of fault detection, e.g. extra checks to confirm that a failure has indeed occurred
• CPC Class Codes: G05B 23/0264 Control of logging system, e.g. decision on which data to store; time-stamping measurements

Abstract

System used for aiding the operation of processes occurring in a power generation plant is disclosed which includes a logging technique for transforming input data from various pickup points into a universal, named system variable format usable by all system functions. Specified changes in time or in any system variable can cause a given log to be triggered into a storing state, or an outputting state wherein the stored data is outputted by a printer in a page oriented log print-out format. Also included in the system is a sequence of events interrupt technique wherein the detection devices located within the protective circuits are corrected for their respective time delays between the sensing time of a measured condition and the actuation time of the associated switching contacts. The correction is achieved by storing the predetermined values of the time delays associated with each of the detection devices, and subtracting such stored time delay values from the system detected times of actuation of the respective switching contacts, thereby deriving a corrected sequence of events indicating the correct order of occurrence of the events at the detection devices and, consequently, the initial cause of the event. The system also includes an alarming technique wherein alarm limit values are assigned for a measured system variable at a given point in the system, and realarm values are calculated so that realarming occurs when the measured system variable departs from the last alarmed value by a significant amount of change, thereby employing system discretion in selecting only the most important alarm conditions to be outputted. A CRT device is used for displaying the alarm information and operates with a reduced line format for those alarms acknowledged by the operator. Entry, removal and presentation of alarm data on the CRT screen is designed to present the data in a simple and easily understandable manner while maximizing the amount of data presented.

Claims

1. A method of producing at least one log of datA containing at least one line having provision for at least one value representing a bit of data to be logged in a monitoring and operations display system, the method comprising:

a. receiving signals for monitoring devices corresponding to bits of data to be logged;

b. providing a format for storing representations of the signals in memory means, each portion of the format corresponding to a different log;

c. allocating at least one portion of the format for storing therein representations of the signals corresponding to a predetermined log;

d. storing representations of the signals in the allocated portion of the format;

e. requesting a predetermined log to be produced;

f. retrieving representations stored in a selected portion for the format, the representations corresponding to the predetermined log to be produced; and

g. presenting on an output display means the data of the retrieved representations in the form of a log.

2. A method of producing at least one log of data in accordance with claim 1 in which said step of receiving signals corresponding to bits of data to be logged further comprises the step of scanning the outputs of a plurality of sources of the signals corresponding to the bits of data to be logged.

3. A method of producing at least one log of data in accordance with claim 2 in which the step of scanning the outputs of a plurality of sources of the signals corresponding to the bits of data to be logged further comprises the step of controlling the frequency of the scanning of the outputs of each of the plurality of sources.

4. A method of producing at least one log of data in accordance with claim 1 and further comprising transforming the received signals into representations thereof in accordance with a universal format which is usable for substantially all functions related to the method.

5. A method of producing at least one log of data in accordance with claim 4 in which the step of transforming the received signals into representations thereof in accordance with a universal format includes introducing the name identification of the variable of the bit of data to be logged and providing the value of the variable of the bit of data to be logged.

6. A method of producing at least one log of data in accordance with claim 4 in which the step of transforming the received signals into representations thereof in accordance with a universal format includes additionally introducing the quality of the data to be logged.

7. A method of producing at least one log of data in accordance with claim 4 in which the step of transforming the received signals into representations thereof in accordance with a universal format includes providing the time at which the data to be logged is obtained.

8. A method of producing at least one log of data in accordance with claim 4 in which the step of transforming the received signals into representations thereof in accordance with a universal format includes providing the name of the variable to be logged.

9. A method of producing at least one log of data in accordance with claim 1 and further comprising selecting one of a plurality of different states for each log in response to a triggering.

10. A method of producing at least one log of data in accordance with claim 9 in which the step of selecting one of a plurality of different states for each log in response to a triggering comprises selecting a free and undefined log state representing the log number without additional information concerning the log.

11. A method of producing at least one log of data in accordance with claim 9 in which the step of selecting one of a plurality of diifferent states for each log in response to a triggering comprises selecting a defined and inactive log state in which the log has some system variables assigned to it without the gathering and printing of signals corresponding to bits of data to be logged.

12. A method of producing at least one log of data in accordance with clAim 9 in which the step of selecting one of a plurality of different stages for each log in response to a triggering comprises selecting an active log state in which values are collected.

13. A method of producing at least one log in accordance with claim 9 in which the step of selecting one of a plurality of different states of the log comprise selecting an outputting log state in which information is applied to the log.

14. A method of producing at least one log in accordance with claim 13 in which the changes to different states include changing from the free and undefined log state to a defined and active log state in which the log has some variables assigned thereto without the gathering and presenting of the log, from the defined and inactive log state to the active log state in which the values associated with the variables of the log are collected, and from the active log state to the outputting log state in which the presentation of the log is made available.

15. A method of producing at least one log of data in accordance with claim 1 and further comprising selecting one of a predetermined number of different states for each log in the format for storing representations of the signal, the predetermined number of different states of each log in the format including a free and undefined log state representing the log number without additional information concerning the log, a defined and inactive log state in which the log has some system variables assigned to it without the gathering and printing of signals corresponding to bits of data to be logged, an active log state in which values to be logged are collected, and an outputting log state in which information is applied to the log.

16. A method of producing at least one log of data in accordance with claim 15 and further comprising changing the state of a log in response to a predetermined triggering condition.

17. A method of producing at least one log of data in accordance with claim 16 in which the changing of a state of a log in response to a predetermined triggering condition comprises a triggering condition which is at least one of a specified change of a condition.

18. A method of producing at least one log of data in accordance with claim 17 in which the predetermined triggering condition is a specified change in a variable in the format.

19. A method of producing at least one log of data in accordance with claim 17 in which the predetermined triggering condition is a change induced by human operator.

20. A method of producing at least one log of data in accordance with claim 17 in which the predetermined triggering condition is a specified change in time.

21. A method of producing at least one log of data in accordance with claim 1 and further comprising the step of initiating in response to a command the requesting of a predetermined log to be produced.

22. A method of producing at least one log of data in accordance with claim 21 in which the step of initiating in response to a command the requesting of a predetermined log to be produced comprises responding to a command which is one of that caused by the occurrence of a predetermined condition and that caused by a manual direction.

23. A method of producing at least one log of data in accordance with claim 1 in which the step of providing a format for storing representations of the signals includes a format by which representations of the signals are stored and replaced in a sequential manner.

24. A method of producing at least one log of data in accordance with claim 1 in which the step of providing a format for storing representations of the signals includes a format for storing a plurality of representations of the same signal with each of the pluralities of representations of the same signal being displaced in order of occurrence from one another.

25. A method of producing at least one log of data in accordance with claim 1 in which the retrieving of stored representations is initiated in response to a command.

26. A method of producing at least one log of data in accordance with claim 25 in which the retrieving of stored representations corresponding to the selected log in response to a command includes response to one of a predetermined condition and a manual direction.

27. A method of producing at least one log of data in a monitoring and operations display system, each log being divided into at least one page, each page containing at least one line having provision for at least one record representing a bit of data to be logged, the method comprising the steps of:

a. receiving signals from monitoring devices corresponding to each bit of data to be logged;

b. providing a format for the storing of representations of the signals, the format being organized into portions each of which corresponds to a different one of the pages, selecting at least one portion of the format for storing therein representations of the signals corresponding to a given page;

c. storing in memory means the representations of the signals in accordance with the format;

d. providing a directory of the pages into which each log is divided;

e. selecting a predetermined log to be produced;

f. determining from the directory the identity of at least one page into which the predetermined log is divided;

g. retrieving stored representations corresponding to the page identified by the directory; and

h. presenting on an output display means the retrieved representations in the form of a page of the log.

28. A method of producing at least one log of data in accordance with claim 27 in which the retrievig of stored representations corresponding to an identified page is initiated in response to a command.

29. A method of producing at least one log of data in accordance with claim 28 in which the retrieving of stored representations corresponding to an identified page and initiated in response to a command includes response to one of a predetermined condition and a manual direction.

30. A method of producing at least one log of data in accordance with claim 27 in which the step of retrieving stored representations corresponding to the page identified by the directory comprises retrieving each page in a predetermined order determined by the format.

31. A method of producing at least one log of data in accordance with claim 30 in which the step of presenting the retrieved representations in the form of a page of the log comprises presenting each page of the log successively with respect to another.

32. In a method of producing at least one log of data containing at least one line having provision for at least one value representing a bit of data to be logged in a monitoring and operations display system receiving signals from monitoring devices corresponding to bits of data to be logged, providing a format for storing representations of the signals, each portion of the format corresponding to a different log, allocating at least one portion of the format for storing therein representations of the signals corresponding to a predetermined log, storing representations of the signals in memory means in the allocated portion of the format, requesting a predetermined log to be produced, retrieving representations stored in a selected portion of the format, the representations corresponding to the predetermined log to be produced, and presenting on an output display means the data of the retrieved representations in the form of a log, the improvement comprising triggering the occurrence of one of a plurality of different log states, the log states including:

a. a free undefined log state, having a log number, b. a defined inactive log state having names of variables related thereto, c. or active log state having names and values being collected, and d. or outputting state in which an indicator of the log is made.

33. Method of logging data in a monitoring and operations display system, comprising:

presenting analog and digital input data to the computeR system from monitoring devices, such as transducers and thermocouples located at various pickup points external to the computer system;

scanning said input data with scanning devices;

transforming said scanned input data into a universal, named system variable format usable by all system functions;

defining triggering conditions for the system such that specified changes in time or specified changes in a variable in the format cause triggering of a given log into one of two active states;

storing the log data of said system variable format in a log page field in a memory means; and

visually presenting said stored log data on a page oriented output display device.

34. Method as in claim 33 wherein said transforming of scanned input data into a universal, named system variable format includes the defining in said format of a name identification of the system variable, the value of the system variable, the quality of the data measured representing said system variable, and the time at which said data is obtained.

35. Method as recited in claim 33 wherein triggering conditions are defined for the system to cause a given log to be triggered into either an active and storing state or an active and outputting state.

36. Method as in claim 35 wherein said two log states are active in that they include both names and values correlated with times or time intervals, and said active outputting log state further includes, in addition to said names, values and times, a demand for the visual presenting of a log.

37. Method as in claim 33 wherein log data of said system variable format is stored in a log page field at a proper index location upon changing or triggering a given log into an active and storing state.

38. Method as in claim 37 wherein said log data is stored in the system memory in a log page field having a format which is similar to a log page format used by an output printer.

39. Method as in claim 33 wherein said stored log data is presented visually by a device in a log page format comprising a plurality of columns associated with said pickup points, set forth in heading across the top of the log page, a listing extending down said first column at the lefthand side of the page, which defines a common variable in the log page for all of the pickup points on the respective lines extending to the right of said common variable, each of said columns having a plurality of lines running down the page along the respective columns for displaying information associated with said columns.

40. Method as in claim 39 wherein the heading for said output format includes a listing of each of the columns, a name identification of the pickup points associated with each of said columns, and a description of each of said pickup points.

41. Method as in claim 39 wherein a given log page contains data for a single log, together with the page number of the log.

42. Method as in claim 41 wherein a plurality of said log pages associated with a single log are arranged in series in a strip manner wherein a first page contains a first number of defined columns in said log, said second page contains a second number of defined columns in said log, and so on.

43. A method of determining the initiation of an event in a control system having a plurality of devices responsive to the event, each of the responsive devices having a time delay characteristic representing the time duration extending between the time in which a given responsive device is subjected to the event and the time to which the given responsive device provides an output in response to the event, the method comprising the steps of:

a. storing in memory means the time delay characteristics of each of the responsive devices, b. sensing the time of the output from each of the plurality of responsive devices, c. subtracting from the time of the sensed output of each of the plurality of responsive devices the stored time delay related thereto, and d. providing from the Subtracting operation and corrected reading for each of the responsive devices indicating the actual time at which the responsive device was subjected to the event, whereby the corrected readings determine the actual initiation of the event.

44. A method in accordance with claim 43 and further comprising the step of selecting the plurality of devices responsive to an event as a function of at least one of their direct response to the event and their indirect response to the event by way of response to the output of at least one other responsive device.

45. A method of determining the initiation of an event in accordance with claim 43 and further comprising the step of compiling a list of the responsive devices in the order of the occurrence of their respective corrected readings indicating the actual times at which the responsive devices were subjected to the event, the list providing a corrected sequence of events of the responsive devices.

46. A method of determining the initiation of an event in accordance with claim 45 and further comprising deriving from the compiled list of the responsive devices in the order of the occurrence of their respective corrected readings the identity of the responsive device which was initially subjected to the event.

47. A method of determining the cause of an event in a control system having a plurality of devices responsive to the event, each of the responsive devices having a time delay characteristic representing the time duration extending between the time at which a given responsive device is subjected to the event and the time at which the responsive device provides an output in response to the event, the method comprising:

a. storing in memory means the time delay characteristic of each of the responsive devices, b. receiving signals from each of the responsive devices in response to the occurrence of the event, c. sensing the time of each of the received signals, d. identifying each of the received signals with its respective responsive device, e. subtracting the respective stored time delay characteristics from the sensed time of each of the received signals as related to each of the responsive devices, and f. providing from the subtracting operation a corrected output of the initiation time of the event for each of the responsive devices.

48. A method in accordance with claim 47 and further comprising the step of compiling a list of the responsive devices in the order of the occurrence of their initiation times to provide a corrected sequence of events by the responsive devices.

49. Method of deriving the ordered sequence of events sensed by detection devices connected with a protective control circuit wherein such devices are characterized by a time delay between the sensing of a predetermined condition and the actuation of their associated switching contacts, comprising:

a. detecting the switching operation of the respective switching contacts;

b. storing in memory means the values of the time delays associated with each of said detection devices, said time delays representing the known delay for a particular contact between its switching time and the actual time of occurrence of the event at the associated detection device; and

c. subtracting the stored time delay values from the detected times of actuation of said switching contacts of the respective devices to produce a corrected time of initiation of the event at the respective devices, whereby a corrected sequence of events is derived indicating the correct order of occurrence of the events at said devices and, consequently, the initial cause of the event.

50. A method of producing a presentation of data which shows the trend of the data comprising the steps of:

a. scanning an output providing a signal representing a value;

b. storing representations of the scanned values in a predetermined log format assigned to respective scanned output points, each representation being stored For a predetermined time duration; and

c. causing, by means of operator command controls, the presentation of at least a portion of the stored values, whereby the trend of data past in time can be presented on display means.

51. A method in accordance with claim 50 in which the step of causing the presentation of at least a portion of the stored values comprises relating the values to their sequence in past time.

52. A method in accordance with claim 50 and further including the step of providing a plurality of output signals corresponding to a plurality of different values to be presented and selecting one of the plurality of output signals to be selected.

53. A method in accordance with claim 50 in which the step of scanning an output providing a signal representing a value comprises scanning each output at a predetermined frequency.

54. A method in accordance with claim 53 in which the step of scanning each output at a predetermined frequency comprises a frequency which is dependent upon the output selected to be scanned.

55. A method in accordance with claim 50 in which the step of storing representations of the scanned values each for a predetermined time duration comprises the storing of new values and concurrently removing from storage values which have been stored for the predetermined length of time in order to update the values being stored.

56. A method in accordance with claim 50 in which the step of causing the presentation of at least a portion of the stored values comprises triggering the presentation of the stored values in response to a predetermined triggering condition.

57. A method in accordance with claim 56 in which the predetermined triggering condition represents one of the command of a human operator and of a command responsive to the occurence of a predetermined level for the value to be presented.

58. A method in accordance with claim 50 in which the causing of the presentation of at least a portion of the stored values comprises the display of the values corresponding to a predetermined period of time in a visual numerical form.

59. A method in accordance with claim 50 in which the causing of the presentation of at least a portion of the stored values comprises the displaying of the values in a graphical form.

60. A method in accordance with claim 50 in which the causing of the presentation of at least a portion of the stored vlaues, the presentation having an axis representative of time comprises the displaying of the values by the trace of a CRT display.

61. A method in accordance with claim 50 and further comprising the step of additionally causing the presentation of values representing the condition after the initiation of the step of the causing of the presentation of the values.

62. A method in accordance with claim 61 and further comprising the step of additionally causing the presentation of values representing the condition after the initiation of the step of the causing of the presentation of the values, whereby the presentation includes representatives of the past and present values of the condition.

63. Method of detecting and displaying alarm conditions in an monitor and results computer system having monitoring devices located at various pickup points external to said computer system comprising:

a. assigning of an alarm limit value for a measured system variable at a given point in said system;

b. scanning said point for the measured system variable even after such an alarm value is detected;

c. calculating and applying a second alarm value representing a significant change (a delta) in the measured system variable from the last alarm value; and

d. outputtting the system variable information existing at each of such realarm values.

64. Method as in claim 63, further comprising the setting of a fixed significant change (a delta) associated with the measured system variable of a point whereby the second alarm and any subsequent realarms would ordinarily be set off when the measured system variable departs from the last alarmed value by this fixed amount.

65. Method as in claim 64, further comprising changing said delta for a given point by selecting a multiplier which is applied to the fixed delta to produce a different delta which then represents the current value of the significant change in the measured system variable, said current delta value requiring the next alarming of the measured system variable value.

66. Method of outputting alarm messages associated with a plurality of measuring points in an alarm measuring system, comprising:

assigning a wide format for displaying new alarm messages on a plurality of lines on the screen of a CRT, each of said lines being used to display alarm messages for individual alarm points in the system;

assigning a reduced format for displaying further alarm messages on a line after said new alarm messages have been acknowledged by an operator, said acknowledgement serving to automatically change an alarm message from said wide format to said reduced format;

inserting the oldest alarm message at the bottom of said screen and the relatively newer alarm messages at line positions above the relatively older alarm message;

inserting the newest alarm message on the line above the last alarm message to be entered on said screen;

detecting when the top line of said screen is filled with alarm information and compacting tha alarm messages downwards to fill in any unused lines on said screen, thereby permitting entry of the newest alarm message at the first free line above the displayed alarm messages.

67. A system for producing at least one log of data containing at least one line having provision for at least one value representing a bit of data to be logged comprising:

a. means for receiving signals corresponding to bits of data to be logged, b. means for providing a format for storing representations of the signals, each portion of the format corresponding to a different log, c. means for allocating at least one portion of the format for storing therein representations of the signals corresponding to a predetermined log, d. means for storing representations of the signals in the allocated portion of the format, e. means for requesting a predetermined log to be produced, f. means for retrieving representations stored in a selected portion of the format, the representations corresponding to the predetermined log to be produced, and g. means for presenting the data of the retrieved representations in the form of a log.

68. A system for producing at least one log of data, each log being divided into at least one page, each page containing at least one line having provision for at least one record representing a bit of data to be logged, comprising:

a. means for receiving signals corresponding to each bit of data to be logged, b. means for providing a format for the storing of representations of the signals, the format being organized into portions each of which corresponds to a different one of the pages, means for selecting at least one portion of the format for storing therein representations of the signals corresponding to a given page, c. means for storing the representations of the signals in accordance with the format, d. means for providing a directory of the pages into which each log is divided, e. means for selecting a predetermined log to be produced, f. means for determining from the directory the identity of at least one page into which the predetermined log is divided, g. means for retrieving stored representations corresponding to the page identified by the directory, and h. means for presenting the retrieved representations in the form of a page on the log.

69. In a system for producing at least one log of data containing at least one stored having provision for at least one value representing a bit of data to be logged by receiving signals corresponding to bits of data to be logged, the system including means for providing a format for storing representations of the signals, each portion of the format corresponding to a different log, means for allocating at least one portion of the format for storing therein representations of the signals corresponding to a predetermined log, means for storing representations of the signals in the allocated portion of the format, means for requesting a predetermined log to be produced, means for retrieving representations sotred in a selected portion of the format, the representations corresponding to the predetermined log to be produced, and means for presenting the data of the retrieved representations in the form of a log, the improvement comprising means for triggering the occurrence of one of a plurality of different log states, the log states including:

a. a free undefined log state, having a log number, b. a defined inactive log state having names of variables related thereto, c. or active log state having names and values being collected, and d. or outputtting state in which an indicator of the log is made.

70. A system for logging data in a monitor and results computer system, comprising:

a. means for presenting analog and digital input data to the system from monitoring devices, such as transducers and thermocouples located at various pickup points external to the computer system;

b. means for scanning said input data;

c. means for transforming said scanned input data into a universal, named system variable format usable by all system functions;

d. means for defining triggering conditions for the system such that specified changes in time or specified changes in a variable in the format cause triggering of a given log into one of two active states;

e. means for storing the log data of said system variable format in a log page field; and

f. means for visually presenting said stored log data on a page oriented device.

71. System as recited in claim 70, wherein said means for visually presenting said stored log data on a page oriented device includes a printer.

72. System as recited in claim 71, wherein said printer provides a page oriented print-out wherein each of said logs is identified by a unique number and the data print-out for said identified log is included under a log heading.

73. System as recited in claim 72, wherein each of said logs is constituted by one or more pages of data produced by said printer, with each of said pages containing a multiplicity of system variables.

74. System as recited in claim 70, wherein said means for visually presenting said stored log data on a page oriented device includes graphic display means for providing trends of selectable log data on a screen.

75. System as recited in claim 74, further comprising an operator demand panel for selecting display trend information which is to be presented by said graphic display means.

76. System as recited in claim 70, wherein said means for visually presenting said stored log data on a page oriented device includes a log page printer wherein each page print-out comprises a given log content in a full page of information with several points of information located on one line for a given log time, whereby a given log content is provided on a full page of information.

77. System as recited in claim 70, wherein said means for transforming said scanned input data into a universal, named system variable format includes memory means for providing named data, calculating means for providing quality data and variable data, and timing means for providing time data, whereby said named system variable format is constituted by the name, the variable, the quality and the time defining a given log.

78. System as recited in claim 70, further comprising means for assigning a specified named system variable to a particular log column of a log page.

79. System as recited in claim 70, further comprising means for removing a named system variablE from a specified column in said log page.

80. System as recited in claim 70, further comprising means for activating any selected log on demand.

81. A system for determining the initiation of an event in a system having a plurality of devices responsive to the event, each of the responsive devices having a time delay characteristic representing the time duration extending between the time in which a given responsive device is subjected to the event and the time to which the given responsive device provides an output in response to the event, the system comprising:

a. means for storing the time delay characteristics of each of the responsive devices, b. means for sensing the time of the output from each of the plurality of responsive devices, c. means for subtracting from the time of the output of each of the plurality of responsive devices the stored time delay related thereto, and d. means for providing from the subtracting a corrected reading for each of the responsive devices indicating the actual time at which the responsive device was subjected to the event, whereby the corrected readings determine the initiation of the event.

82. A system for determining the cause of an event in a system having a plurality of devices responsive to the event, each of the responsive devices having a time delay characteristic representing the time duration extending between the time at which a given responsive device is subjected to the event and the time at which the responsive device provides an output in response to the event, comprising:

a. means for storing the time delay characteristic of each of the responsive devices, b. means for receiving signals from each of the responsive devices in response to the occurrence of the event, c. means for sensing the time of each of the received signals, d. means for identifying each of the received signals with its respective responsive deivce, e. means for subtracting the respective time delay characteristics from the time of each of the received signals as related to each of the responsive devices, and f. means for providing a corrected output of the initiation time of the event for each of the responsive devices.

83. A system for deriving the ordered sequence of events sensed by detection devices connected with a protective circuit wherein such devices are characterized by a time delay between the sensing of a predetermined condition and the actuation of their associated switching contacts, comprising:

a. means for detecting the switching operation of the respective switching contacts;

b. means for storing values of the time delays associated with each of said detection devices, said time delays representing the known delay for a particular contact between its switching time and the acutal time of occurrence of the event at the associated detection device; and

c. means for subtracting the stored time delay values from the detected times of actuation of said switching contacts of the respective devices to produce a corrected time of initiation of the event at the respective devices, whereby a corrected sequence of events is derived indicating the correct order of occurrence of the events at said devices and, consequently, the initial cause of the event.

84. System as recited in claim 83, wherein said subtracting means includes logic means for compiling a list of said detection devices in the order of the occurrence of their respective correct readings indicating the acutal times at which such detection devices where subjected to the event.

85. System as recited in claim 83, wherein said subtracting means includes a logic circuit for deriving the identity of the detection device which was initially subjected to the event.

86. A display device for outputting alarm information associated with a plurality of measuring points in an alarm measuring system, comprising:

a screen upon which said alarm information is displayed;

first means For assigning a wide format for displaying new alarm information on a plurality of lines on said screen, each of said lines being used to display alarm information for individual alarm points in the system;

second means for assigning a reduced format for displaying alarm information on a line after said new alarm information has been acknowledged by an operator, said acknowledgement serving to automatically change an alarm message from said wide format to said reduced format;

arranging means for inserting the oldest alarm message at the bottom of said screen and the relatively newer alarm messages at line positions above the relatively older alarm message;

inserting means for inserting the newest alarm message on the line above the last alarm message to be entered on said screen;

means for detecting when the top line of said screen is filled with alarm information; and

compacting means, responsive to said detecting means for compacting the alarm information downwards to fill in any unused lines on said screen, thereby permitting entry of the newest alarm information at the first free line above the displayed alarm messages.

87. A display device as recited in claim 86, further comprising control means for removing alarm information from said screen, and memory means responsive to said control means for storing said removed alarm information in memory as alarm backlog information.

88. A display device as recited in claim 87, wherein said control means includes means for returning alarm backlog information from said memory means to said screen.

89. A display device as recited in claim 87, further comprising a visual information means connected to said memory means for providing a video presentation of alarm data stored in said memory means.

90. A display device as recited in claim 89, further comprising an operator keyboard comsole connected to said control means for requesting a video readout on said visual information means of specified alarm data stored in said memory means.

91. A display device as recited in claim 89, wherein said visual information means includes a display area for presenting a memory of what alarm information the operator was previously using, whereby the operator is able to visualize the previous information and operations so that he can modify his present operations.

92. A display device as recited in claim 89, further comprising a local memory connected to said visual information means for storing information previously provided by said visual information means.

93. A subsystem for detecting and displaying alarm conditions in a monitoring and display system having monitoring devices located at various pickup points external to said computer system, comprising:

a. means for assigning an alarm limit value for a measured system variable at a given point in said system;

b. means for scanning said point for the measured system variable even after such an alarm value is detected;

c. logic means for calculating and applying a second value representing a significant change (a delta) in the measured system variable from the last alarm value; and

d. display means for outputting the system variable information existing at each of such realarm values.

94. A subsystem as recited in claim 93, further comprising memory means associated with said logic means for storing the setting of a fixed significant change (a delta) associated with the measured system variable of a point, whereby the second alarm and any subsequent realarms would ordinarily be set off when the measured system variable departs from the last alarm value by this fixed amount.

95. A subsystem as recited in claim 94, wherein said logic means includes means associated with asid memory means for changing said delta for a given point by the selection of a multiplier which is applied to the fixed delta to produce a different delta which then represents the current value of the significant change in the measured system variable, said current Delta value requiring the next alarming of the measured system variable value.