Reference Manual

00809-0100-4697, Rev EA October 2011

Rosemount 848T

Appendix D Function Blocks

ANALOG INPUT (AI) FUNCTION BLOCK

OUT_D

AI

OUT

 

Out = The block output value and status Out_D = Discrete output that signals a selected alarm condition

Analog Input (AI) Function Block . . . . . . . . . . . . . . . . . . . page D-1 Multiple Analog Input (MAI) Function Block . . . . . . . . . . page D-9 Input Selector Function Block . . . . . . . . . . . . . . . . . . . . . . page D-15

The Analog Input (AI) function block processes field device measurements and makes them available to other function blocks. The output value from the AI block is in engineering units and contains a status indicating the quality of the measurement. The measuring device may have several measurements or derived values available in different channels. Use the channel number to define the variable that the AI block processes.

The AI block supports alarming, signal scaling, signal filtering, signal status calculation, mode control, and simulation. In Automatic mode, the block’s output parameter (OUT) reflects the process variable (PV) value and status. In Manual mode, OUT may be set manually. The Manual mode is reflected on the output status. A discrete output (OUT_D) is provided to indicate whether a selected alarm condition is active. Alarm detection is based on the OUT value and user specified alarm limits. The block execution time is 30 ms.

Table D-1. Analog Input Function Block Parameters

Number

Parameter

Units

Description

01

ST_REV

None

The revision level of the static data associated with the function block. The

 

 

 

revision value will be incremented each time a static parameter value in the block is

 

 

 

changed.

02

TAG_DESC

None

The user description of the intended application of the block.

03

STRATEGY

None

The strategy field can be used to identify a grouping of blocks. This data is not

 

 

 

checked or processed by the block.

04

ALERT_KEY

None

The identification number of the plant unit. This information may be used in the host

 

 

 

for sorting alarms, etc.

05

MODE_BLK

None

The actual, target, permitted, and normal modes of the block.

 

 

 

Actual: The mode the “block is currently in”

 

 

 

Target: The mode to “go to”

 

 

 

Permitted: Allowed modes that target may take on

 

 

 

Normal: Most common mode for target

06

BLOCK_ERR

None

This parameter reflects the error status associated with the hardware or software

 

 

 

components associated with a block. It is a bit string, so that multiple errors may be

 

 

 

shown.

07

PV

EU of XD_SCALE

The process variable used in block execution.

08

OUT

EU of OUT_SCALE

The block output value and status.

 

 

or XD_SCALE if in

 

 

 

direct L_TYPE

 

09

SIMULATE

None

A group of data that contains the current transducer value and status, the simulated

 

 

 

transducer value and status, and the enable/disable bit.

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Emerson 848T Appendix D Function Blocks, Analog Input AI Function Block, Number Parameter Units Description, Out, Simulate

848T specifications

The Emerson 848T is a state-of-the-art temperature transmitter designed for accurate and reliable temperature measurement in various industrial applications. This device has gained recognition for its advanced features and robust performance, making it a popular choice among engineers and technicians in the field.

One of the key highlights of the Emerson 848T is its unique dual-channel capability, which allows it to seamlessly monitor two temperature sources simultaneously. This functionality is particularly beneficial in processes where multiple temperature points need to be assessed, optimizing efficiency and reducing the need for additional equipment. It supports various sensor types, including thermocouples, RTDs, and resistance temperature detectors, making it versatile for different applications.

The 848T is equipped with sophisticated digital processing technology, which enhances its accuracy and stability. It features a 24-bit analog-to-digital converter, ensuring precise measurement and minimizing drift over time. Moreover, the device boasts a wide operating temperature range, accommodating ambient conditions from -40°C to 85°C. This durability makes it suitable for harsh environments commonly encountered in industries such as oil and gas, pharmaceuticals, and power generation.

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