FC 177 - Data Acquisition Analog

The data acquisition analog (DAANG) function code provides a number of unique data selection, conditioning and monitoring functions. These include support for enhanced alarm management capabilities at the module level of a Symphony system.

 

The default specifications allow single level alarming and exception reporting of the real input.

 

 

Outputs:

Blk

Type

Description

N

R

Current value, quality/status

N+1

R

Current extended status

 

Spec

Tune

Default

Type

Range

Description

S1

N

100.000

R

Full

Engineering unit high display reference

S2

N

0.000

R

Full

Engineering unit center display reference

S3

N

0.000

R

Full

Engineering unit low display reference

S4

N

9.2E18

R

Full

Engineering unit high constraint limit

S5

N

-9.2E18

R

Full

Engineering unit low constraint limit

S6

N

0

I

0 - 255

Engineering unit identifier

S7

N

5

I

Note 1

Spare real input

S8

N

5

I

Note 1

Block address of quality state override

S9

N

5

I

Note 1

Block address of input select control

S10

N

5

I

Note 1

Block address of real value input

S11

N

5

I

Note 1

Block address of input shaping algorithm

S12

N

5

I

Note 1

Block address of calculated value input

S13

N

0.000

R

Full

Engineering unit selected inserted value

S14

N

0

I

Note 1

Block address of permit input selection

S15

N

0

I

Note 1

Block address of request exception report

S16

N

0

I

Note 1

Block address of activate alarm suppression

S17

N

5

I

Note 1

Block address of variable high 1 alarm limit

S18

N

5

I

Note 1

Block address of variable low 1 alarm limit

S19

N

5

I

Note 1

Block address of deviation alarm reference value

S20

Y

0.000

R

Full

Alarm control

S21

Y2

2.000

R

Full

Engineering unit high alarm dead band

S22

Y2

0.000

R

Full

Engineering unit high 3 alarm difference

S23

Y2

0.000

R

Full

Engineering unit high 2 alarm difference

S24

Y2

9.2E18

R

Full

Engineering unit high 1 fixed alarm value

S25

Y2

-9.2E18

R

Full

Engineering unit low 1 fixed alarm value

S26

Y2

0.000

R

Full

Engineering unit low 2 alarm difference

S27

Y2

0.000

R

Full

Engineering unit low 3 alarm difference

S28

Y2

2.000

R

Full

Engineering unit low alarm dead band

S29

Y2

9.2E18

R

Full

Engineering unit deviation alarm limit

S30

Y

2.000

R

Full

Engineering unit significant change to force

exception report

S31

Y

100.000

R

Full

Period for time based alarms in seconds

S32

Y

9.2E18

R

Full

Engineering unit high rate of change

S33

Y

0.000

R

Full

Engineering unit low rate of change

S34

Y

2.000

R

Full

Time sequence alarm count

 

 

 

NOTES:

1. Maximum values are:9,998 for the BRC-100, IMMFP11/12 and 31,998 for the HAC

2. Specification is tunable but not adaptable. Adapted specification values are invalid.

 

 

177.1   Explanation

 

 

177.1.1  Specifications

 

S1

Engineering units high display reference. A numeric or graphical display element can use this value as the maximum positive reference of the monitored value.

 

S2

Engineering units center display reference. This specification allows bidirectional bar chart elements on consoles by defining a positive and negative segment for the display (i.e., upward movement when the input is greater than S2 and downward movement when the input is less than S2). Specifications S2 and S3 define the lower segment. Specifications S1 and S2 define the upper segment. To disable the center display reference, set S2 equal to S3.

 

S3

Engineering units low display reference. Numerical or graphical display elements use this value as the maximum negative reference of the monitored value.

 

S4

Engineering units high constraint limit. The input select control <S9> enables this limit. Enabled constraint limits cause the selected input value to report as less than or equal to the high constraint limit. The input will be constrained when it exceeds this configured value. When the real (constrained) input is selected (by a value of 4.0 or 5.0 at <S9>), the constraining action is the resultant value of the input characterization algorithm defined by <S11> (if used).

 

NOTE: S4 must be greater than S5.

 

S5

Engineering units low constraint limit. The input select control <S9> enables this limit. An enabled constraint limit makes the selected input value always greater than or equal to this low limit. The input is constrained when below this configured value. When the real (constrained) input is selected (by a value of 4.0 or 5.0 at <S9>), the constraining action is the resultant value of the input characterization algorithm defined by <S11>.

 

NOTE: S4 must be greater than S5.

 

S6

Engineering unit identifier. It is used by display systems to select an engineering unit descriptor.

 

S7

Spare real input.

 

S8

Block address of the quality state override. It allows an external source to override the quality and status of the reported value. The override value converts to a truncated integer and the bits are shown in Table 177-1.

 

 

The quality state override does not affect the processing of the DAANG function code. The override state specified is logically ORed with the internally derived state. This permits the selective use of the internal functions or special external functions.

 

NOTE: If an external function generates any of these control bits, the internal features that correspond to the defined functions must be inhibited. This prevents a possible conflict between the externally driven status and the internal status.

 

Quality is normally derived from the selected input unless:

 

A real <S10> or calculated <S12> input with bad quality from any block (except one containing function code 178) sets the hardware failure bit in the DAANG exception report (status and extended status fields). Normally, the quality associated with an exception report (alarm field) is set by the communication system to indicate a communication failure. Therefore, the quality state in the exception report alarm field is actually the communication status for function code 177 exception reports and is never set by the function code 177 itself. Neither bad input quality or overridden/forced bad quality will affect this bit.  In the DAANG function code the hardware failure bit in the exception report extended status field, exception report status field, and extended status output N+1 is set to propagate the bad quality of the input. The state of the hardware failure bit sets the quality of the block output N.

 

S9

Block address of the input control. This specification gives an external source the ability to control the input selection when enabled by the permit input selection <S14>. The real input value is converted into a truncated integer and the bits are mapped as in Tables 177-2 and 177-3.

 

 

 

 

When a transition takes place on bit zero or one, the new input source and status are selected. The console can also select the input source. A transition on the input control bit cancels any pending console request.

 

Input select and console requests are disabled during module startup. The block maintains the saved mode and initializes the input select during startup to prevent a transition being detected when startup is complete. When adding the block to a module configuration, the default mode is input select equals real value, on report, unconstrained (<S9> equals zero).

 

The constrain input high/low limit (bit two) controls limiting for the selected input. Specification S4 defines the upper constraint limit and S5 defines the lower constraint limit.

 

The report mode (bit seven) controls the exception reporting mode. No report disables exception report updates. Enabling no report causes one exception report to generate which shows that no report is enabled. The block continues to execute and its outputs update, but no exception reports generate.

 

The console can control the exception reporting mode. When a point is no report, the console can issue a force exception report update command to cause the point to update. This feature allows updating of the point value without putting it back on report. The block outputs (local block outputs N and N+1) continue to update when a new exception report normally generates. The current report mode of an input is stored in NVRAM and is stored upon a reset or mode change. All report mode change requests (logic and console) are locked out during module startup.

 

S10

Block address of the real input value. The real input value can be the block output value of any block in the module addressed by this vector. It is selected when <S9> equals zero, one, four or five. The console can also select this input value in auto mode. Changes to the selected mode are disabled when the block addressed by S14 equals zero.

 

S11

Block address of the input shaping algorithm. This function allows additional linearization on the real input value for unique characterization or scaling. This specification can point to either a function generator (function code 1) or polynomial (function code 167) block. Multiple blocks can point to the same function generator or polynomial block. This permits a single block to provide common input characterization or scaling data for many DAANG inputs. When either <S9> equals zero, one, four or five, or a console command selects the real input, <S10> will be the input value to the function code configured at the block addressed by this specification. The output of the algorithm is the actual real input value. The case of <S11> equals two disables this feature and causes <S10> to be used as received.

 

S12

Block address of the calculated value. The calculated value is an alternate input value selected when <S9> equals three or seven. The console can select the calculated input from auto mode. Changes to the selected mode are disabled when the block addressed by S14 equals zero.

 

S13

Engineering units selected inserted value. The selected inserted value is an alternate input value selected when <S9> equals two or six. The console can ramp or set this value after selecting manual mode. Changes to the selected mode are disabled when the block addressed by S14 equals zero.

 

S14

Block address of the permit input selection. When the input value of this block is a logic 1, changes at the <S9> input or the console commands will change the input select mode. If the input is logic 0, then requests for input select mode changes are ignored.

 

S15

Block address of the send exception report request. When there is a zero to one transition on this block address, an exception report of the current data and status is generated. This input can link to a timer that expires on the scan period for the implementation of a fixed scan type system. When the point is off scan this input effectively disables. The console can force an exception report update that reports the current value even when the point is off scan. The point remains off scan after sending one update if it was previously off report.

 

S16

Block address of the activate alarm suppression. Alarm suppression functions specified in S20 enable when this input equals logic 1. The console also can control alarm suppression.

 

High alarms suppressed:

High alarm and level.

High deviation.

High rate.

Low alarms suppressed:

Low alarm and level.

Low deviation.

Low rate.

 

The current alarm suppression state (on/off) is stored in NVRAM upon a reset or mode change. All alarm suppression requests (console and logic) lock during module initialization.

 

S17 and S18

Block addresses of the variable high one and low one alarms respectively. These inputs are active only when variable mode alarms are selected with the alarm control S20. Effectively, these dynamic values substitute for the high one alarm value S24 and low one alarm value S26 when using this feature.

 

S19

Block address of the deviation alarm reference. This specification combined with the deviation alarm limit S29 determines when the monitored input value has a high or low deviation alarm.

High deviation alarm limit = <S19> + S29

Low deviation alarm limit = <S19> - S29

 

S20

Alarm control. The input value converts to a truncated integer and the bit map as in Table 177-4.

 

 

Bit zero selects the mode for the high one alarm level. Logic 0 selects the fixed value of S24 and logic 1 selects the dynamic input of the block addressed by S17.

 

Bit one selects the mode for the low one alarm level. Logic 0 selects the fixed value of S25 and logic 1 selects the dynamic input of the block addressed by S18.

 

Bit two selects single level high one and low one alarms when false (logic 0). Bit two selects multilevel high three, high two, high one, low one, low two, and low three when true (logic 1).

 

Bit three and bit four control alarm suppression for all low or all high alarms based on the logic state of <S16>.

 

Bits five and six enable the de-alarm and return alarm functions.

The de-alarm and return alarm control the alarms:

 

De-alarm (bit five) suppresses alarms when the timer expires. The timer resets any time the input value exits the alarm state. The alarms must remain present for the entire timer period (S31) before they can be de-alarmed. The alarms remain suppressed until the input value exits the alarm state. The de-alarm, when active, is identical to alarm suppression when both the high and low alarm suppression is selected by S20, bits three and four and enabled by <S16>.

 

Return alarm (bit six) causes the console to reinstate the alarm by changing the state of the return alarm bit in the extended status output and exception report if an alarm state is still present since the last alarm report. Until the input value exits the alarm state, the timer automatically starts after each return alarm message and a new return alarm issues after each S31 time period.

 

If both the de-alarm and return alarm bits are selected, the return alarm function overrides the de-alarm function.  Specification S31 defines the time period (in seconds) to de-alarm or return alarm the input.  Bit seven enables the rate of change alarm feature. Specification S31 defines the sample time interval (specified in seconds). The rate of change is the absolute (EU) value of the difference between the previous sampled input value and the current sampled input value. The configured time interval (S31) defines the sampling time between the two values. Thep previous input value initializes during startup to the current selected input value. Refer to S32 and S33 for details.  Bit eight enables the digital alarm count filter. The time period in S31 (specified in seconds) defines the sequential count time interval. The value in S34 defines the number of transitions that activate the alarm count filter. Refer to S34 for details.  Bit nine allows mode configuration of the alarm suppression indication at the extended status output (N+1, bit one). When this bit is logic 0, the alarm suppression indication sets when alarm suppression is selected (through S20, bits three and four) and enabled (through <S16>). When this bit equals logic 1, the alarm suppression indication is set when an alarm is suppressed.

 

S21

High alarm dead band. This is the dead band compensation value, in engineering units, that subtracts from each high alarm threshold value to determine the value at which the existing alarm level will be reduced.

 

S22

High three alarm difference. With multilevel alarming selected, this value adds to S23. The result adds to the value used for high one level to determine the high three alarm threshold value. If the monitored variable becomes greater than this value, a high three alarm state exists.

 

S23

High two alarm difference. With multilevel alarming selected, this value adds to the value used for high one level to determine the high two alarm threshold value. If the monitored variable becomes greater than this value, a high two alarm state exists.

 

S24

High one fixed alarm value. When fixed alarm levels are selected, and the monitored input value becomes greater than this value, a high one alarm status exists.

 

S25

Low one fixed alarm value. When fixed alarm levels are selected, and the monitored input value becomes less than this value, a low one alarm status exists.

 

S26

Low two alarm difference. With multilevel alarming selected, this value subtracts from the value used for low one alarm level to determine the low two alarm threshold value. If the monitored variable becomes less than this value, a low two alarm state exists.

 

S27

Low three alarm difference. With multilevel alarming selected, this value adds to the value of S26. The resultant total subtracts from the value used for the low one alarm level to determine the low three alarm threshold value. If the monitored variable becomes less than this value, a low three alarm state exists.

 

S28

Low alarm dead band. This is the dead band compensation value that adds to each low alarm threshold value to determine the value at which the existing alarm level will be reduced. Table 177-5 shows alarm thresholds.

 

 

Figure 177-1 shows relationships of S21, S22, S23, S26, S27 and S28 to actual alarm thresholds when using <S17> and <S18>.

 

The striped line in Figure 177-1 illustrates the monitored variable. The arrowhead shows the relative movement of this dynamic variable away from the quiescent (left side) and in the direction of nominal (right side).

 

High Alarm Values:

<S17> (variable high alarm value) = 600

S24 (fixed high alarm value) = 600

S23 (high 2 alarm delta) = 100

S22 (high 3 alarm delta) = 50

S21 (high alarm dead band) = 5

 

Low Alarm Values:

<S18> (variable low alarm value) = 400

S25 (fixed low alarm value) = 400

S26 (low 2 alarm delta) = 100

S27 (low 3 alarm delta) = 50

S28 (low alarm dead band) = 10

 

S29

Deviation alarm limit. The high deviation alarm is violated when the selected input <S10>, <S11> or <S12> as selected by <S9> is greater than or equal to the sum of the deviation alarm reference <S19> and the deviation alarm limit S29.

 

The low deviation alarm is violated when the selected input <S10>, <S11> or <S12> as selected by <S9> is less than or equal to the difference between the deviation alarm reference <S19> and the deviation alarm limit S29.

 

 

Deviation Alarm Levels:

High deviation = <S19> + S29

Low deviation = <S19> - S29

 

Deviation dead band Levels:

High deviation dead band = <S19> + S29 - S21

Low deviation dead band = <S19> - S29 + S28

 

S30

Significant change in engineering units input. A new exception report generates when the selected input change is greater than the level defined by this input, and the exception report minimum time has been exceeded (as defined by the segment control block).

 

S31

Period for time based alarms. This time period is in seconds. Refer to S20.

 

S32 and S33

Define the rate of change in engineering units. Specification S20 enables this function. Specification S31 determines the time period to sample input. The rate of change is the absolute value of the difference between the previous sampled input value and the current sampled input value. The configured time interval defines the sampling time between the two values.  The previous input value initializes during startup to the current selected input value.

 

A high rate of change is present when the absolute value of the difference between the new sample value and the previous sample value is greater than the high rate of change S32.

 

A low rate of change is present when the absolute value of the difference between the new sample value and the previous sample value is less than the low rate of change S33.

 

S34

Alarm count limit for the time sequence alarm filter. Specification S20 enables this alarm function. The time period defined by S31 is the time interval. This feature, when enabled by S20, maintains an alarm level if the monitored variable is moving into and out of that alarm level X times (defined by S34) during period Y (defined by S31).

 

Each crossing of an individual alarm level increments an internal counter in the function code. This counter resets to zero at the end of the time specified in S31. When the counter value is equal to or greater than the value of S34, the existing alarm level maintains through the next count period. This filtered alarm level maintains as long as the internal sequential count per time period (S31) equals or exceeds (S34), or the monitor variable is in violation of the posted alarm threshold.

 

The filtered alarm level cancels if any other alarm level is violated or if a time period (S31) occurs without (S34) alarm level crossings.

 

NOTE: Normal dead band action is included in the determination of return from each alarm level violation used by the time sequence alarm filter.

 

The hold state automatically cancels when the next alarm level is violated or exited. The internal alarm state is used before performing alarm suppression. Thus, alarm suppression does not affect the processing of the sequential alarm count limit.

 

 

 

177.1.2   Outputs

 

N

Current value and status. The current value and status output provides the current output value and the status bits. Table 177-6 shows the status bits for output N.

 

 

 

Refer to Figure 177-2 for an example of the module access to status. The test quality block (function code 31) can retrieve the quality status bit. The quality state is bad when the hardware failure status is bad. The test alarm block (function code 69) can retrieve the alarm status (bits three through six). Set S2 (function code 69) to zero to test the high and low alarms.

 

Set S2 (function code 69) to one to test the alarm level.

 

N+1

Current extended status. Figure 177-2 shows an example of the module access to status. The extended status output converts to a real output as an integer. Table 177-7 shows the bit map for output N+1.

 

 

 

 

177.2   Applications

 

Figure 177-3 illustrates a typical application using the data acquisition analog block. In this application, the value of the S20 block is 24 decimal (18 hex).

 

 

 

 

This configuration:

 

 

Figure 177-4 shows the data acquisition analog block used in normal, variable and deviation alarm situations.