FC 48 - Analog Exception Report with High / Low Alarm Deadband

The analog exception report with high/low alarm deadband function code allows an analog value to be sent on the communication highway if the value changes outside a configured deadband. This function also generates an alarm if the high or low limit values are reached. The analog exception report is transmitted after a time limit that is configured in the module’s executive or segment control block.

 

This function does not perform any conversion of its input. Specifications S3 and S4 (zero and span of input) are used internally, and significant change (S7) is used to report to other Harmony control units (HCUs) or operator interface devices.

 

Specification S2 (engineering units) is used for reporting to these higher level devices.

 

To insure that the signal is successfully transferred, the analog signal generates a point quality flag. To test the quality of the signal, include a function code 31 in the configuration. The quality of the point cannot be used as an input to any other type of block. The analog output value can be used as an input to any analog processing block.   Refer to Appendix H, for a definition of point quality.  

 

Use function code 69 to test the alarm associated with the analog exception report with high/low alarm deadband function

block.

 

Outputs:

Blk

Type

Description

N

R

Analog Output Value and Quality

 

 

Specifications:

Spec

Tune

Default

Type

Range

Description

S1

N

5

I

Note 1

Block address of input

S2

N

0

I

0 - 255

Engineering unit identifier

S3

N

0.000

R

Full

Zero of <S1> in engineering units

S4

N

100.000

R

Full

Span of <S1> in engineering units

S5

Y2

100.000

R

Full

High Alarm point limit value in engineering units

S6

Y2

0.000

R

Full

Low Alarm point limit value in engineering units

S7

N

1.000

R

Full

Significant change in engineering units

S8

Y

1.000

R

Full

High Alarm Deadband in engineering units

S9

Y

1.000

R

Full

Low Alarm Deadband in engineering units

 

NOTES:

  1. Maximum values are: 9,998 for the BRC-100, IMMFP11/12 and31,998 for the HAC

  2. All alarm limits are tunable, but not adaptable. Function code 24 cannot be used to adapt the values of alarm limits.

 

 

48.1  Explanation

 

Exception Reports

 

An exception report is returned to the bus interface module or network processing module following a report poll message if a report enable message has been received for the block number. This requires that an analog input block (function code 26 or 121) be configured in some other HCU, or as a point from a network interface unit, or as a tag defined in a console, referencing the output of the analog exception report block. An exception report will occur when:

 

 

 

Alarm Reports

 

An alarm report is returned to the bus interface or network processing module following a report poll message if:

 

1. A report enable message has been received for the block number.

and

2. The low or high alarm set point is exceeded.

 

An alarm report occurs when:

 

1. <S1> > S5, and current status not equal high alarm.

 

2. <S1> < S6, and current status not equal low alarm.

 

3. (S6 + S9) < <S1> < (S5 – S8), and current status not equal normal.

where:

<S1> = Current value of input.

S5      = Value of high alarm limit.

S6      = Value of low alarm limit.

S8      = High alarm deadband in engineering units

S9      = Low alarm deadband in engineering units

 

4. Time limit (Tmax) generates an exception report after a time interval configured in the executive or segment control block.

 

A sample input, with alarm and exception reports identified, is plotted in Figure 48-1.