Emerson 848T manual Network Communication, Link Active Scheduler LAS, Fieldbus Link

Page 86

Rosemount 848T

Reference Manual

00809-0100-4697, Rev EA October 2011

NETWORK COMMUNICATION

Figure C-2. Simple, Single-Link Fieldbus Network

Link Active Scheduler (LAS)

Two types of alerts are defined for the block: events and alarms. Events are used to report a status change when a block leaves a particular state, such as when a parameter crosses a threshold. Alarms not only report a status change when a block leaves a particular state, but also report when it returns back to that state.

Figure C-2illustrates a simple fieldbus network consisting of a single segment (link).

 

LAS

 

 

 

 

Fieldbus Link

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Link Master

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Basic Devices and/or link master devices

All links have one Link Active Scheduler (LAS). The LAS operates as the bus arbiter for the link. The LAS does the following:

•recognizes and adds new devices to the link.

•removes non-responsive devices from the link.

•distributes Data Link Time (DL) and Link Scheduling Time (LS) on the link. DL is a network-wide time periodically distributed by the LAS to synchronize all device clocks on the bus. LS time is a link-specific time represented as an offset from DL. It is used to indicate when the LAS on each link begins and repeats its schedule. It is used by system management to synchronize function block execution with the data transfers scheduled by the LAS.

•polls devices for process loop data at scheduled transmission times.

•distributes a priority-driven token to devices between scheduled transmissions.

Any device on the link may become the LAS. The devices that are capable of becoming the LAS are called Link Master devices (LM). All other devices are referred to as basic devices. When a segment first starts up, or upon failure of the existing LAS, the link master devices on the segment bid to become the LAS. The link master that wins the bid begins operating as the LAS immediately upon completion of the bidding process. Link masters that do not become the LAS act as basic devices. However, the link masters can act as LAS backups by monitoring the link for failure of the LAS and then bidding to become the LAS when a LAS failure is detected.

Only one device can communicate at a time. Permission to communicate on the bus is controlled by a centralized token passed between devices by the LAS. Only the device with the token can communicate. The LAS maintains a list of all devices that need access to the bus. This list is called the “Live List.”

Two types of tokens are used by the LAS. A time-critical token, Compel Data (CD), is sent by the LAS according to a schedule. A non-time critical token, pass token (PT), is sent by the LAS to each device in ascending numerical order according to address.

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Contents Reference Manual 00809-0100-4697, Rev EA OctoberPage Rosemount 848T High Density Temperature Transmitter with Customer Central National Response Center InternationalPage Table of Contents Appendix a Operation MaintenanceSection TOC-2Process leaks could result in death or serious injury Safety MessagesSection Introduction Electrical shock could cause death or serious injuryOverview Fieldbus host or configuration toolMaintenance of the Rosemount 848T Temperature Transmitter TransmitterService Support Rosemount 848T Section Installation Safety Messages MountingMounting to a DIN Rail Without an Enclosure Mounting to a Panel with a Junction BoxMounting to a 2-in. Pipe Stand Aluminum/Plastic Junction Box Stainless Steel Junction BoxConnections WiringSpur Signal Wiring Devices 1 through Leads and terminalsAnalog Inputs RTD or Ohm InputsThermocouple or Millivolt Inputs Ohm resistor in the loop when switched to the left ConnectorsPower Supply Analog InputConnections Power SupplySurges/Transients Shielded Wire GroundingMA loop 848T Power Supply Sensor Wires Shield ground pointsTransmitter Enclosure optional Fieldbus busSwitch is not functional SwitchesSimulate Enable SecurityTransmitter Tag TaggingCommissioning Tag Sensor TagUsing Conduit Entries InstallationUsing Cable Glands Section Configuration Standard ConfigurationTransmitter Configuration Custom Configuration Methods Rosemount 848T Function Common Configurations for High Density ApplicationsTypical Profiling Application BlockMeasuring Temperature Points Individually Monitoring Application with a Single SelectionMultiple Analog Input or Analog Input Block Configuration Number Parameter Description Block ConfigurationResource Block 00809-0100-4697, Rev EA October Resource Block Parameters Startwithdefaults SaveconfignowSaveconfigblocks FailedenableAutomatic Auto Block ErrorsModes Block is processing its normal background memory checksPlantWeb Alerts Out of Service OOSAlarm Detection Status Handling00809-0100-4697, Rev EA October Failure Alarms FailedmaskAlarm Maintenance Alarms/Priority AlarmAdvisory Alarms Alarm Type Active Event Recommended Action Recommended Actions for PlantWeb AlertsRESOURCE.RBSFTWRREVALL Transducer BlocksRESOURCE.HARDWAREREV, Channel Definitions for the 848T Transducer Block ErrorsTransducer Block Channel Definitions Channel DescriptionTransducer Block Modes 00809-0100-4697, Rev EA October Block/Transducer ErrorTransducer Block Alarm Detection Block outputs reflect the analog input measurementSENSOR3CONFIG SENSOR1CONFIGSENSOR2CONFIG SENSOR4CONFIGChanging the Sensor Configuration in the Transducer Block Transducer Block Sub-Parameter Tables 11. Xderror Sub-Parameter Structure12. Sensorconfig Sub-Parameter Structure 15. Calstatus Structure 13. Sensorstatus Sub-Parameter Structure14. Sensorcal Sub-Parameter Structure 16. Transducer Status Sub-Parameter StructureStructure StructureDual Sensor Status Table Structure Parameter Description 20. Validation Config Sub-Parameter StructureSensor Calibration in the Sensor Transducer Block Rosemount 848T Foundation Operation and MaintenanceFoundation Fieldbus Information Commissioning Addressing Sensor Check Hardware MaintenanceRestart with Defaults Restart Processor cyclingSymptom Possible Cause Corrective Action TroubleshootingTransducer Block Troubleshooting Symptom Possible Causes Corrective ActionFunctional Specifications Appendix a Reference DataBackup Link Active Scheduler LAS Update TimeAlarms Transient ProtectionPhysical Specifications Performance Specifications Function BlocksAccuracy Sensor Option Sensor Reference 3-Wire RTDsAccuracy for Differential Configurations Input RangesSensor Option Alarm Levels Accuracy Analog Sensors 4-20mAAmbient Temperature Effect Rosemount 848T Dimensional DrawingsAmbient Temperature Notes Examples Top ViewFront View Side View Stainless Steel Junction Box-Cable Gland option code JS2Side View Front View Stainless Steel Junction Box-Conduit Entry option code JS3 Side ViewStainless Steel Junction Box Style JS Mounting OptionsAluminum/Plastic Junction Box Styles JA and JP Front View Side ViewOrdering Information OptionsConduit Electrical Connector Standard Software Configuration StandardSpecial Temperature Test Expanded Enclosure Options StandardRosemount 848T Hazardous Locations Certificates Table B-2. Entity Parameters for Non Incendive Field WiringAppendix B Product Certificates North American ApprovalsPower/Bus Canadian Standards Association CSA Certifications Atex Certifications Power/Bus SensorEuropean Approvals Special Conditions for Safe UseCi = Li = Rosemount 848T Special Conditions of Safe Use IECEx CertificationsRosemount 848T Parameters Terminals of power/loop China NEPSICertificationsJapanese Certifications Intrinsically Safe and NON-INCENDIVE Installations Installation Drawings Figure B-1. FM Intrinsic Safety/ Fisco 00809-0100-4697, Rev EA Rosemount 848T Figure B-2. CSA Intrinsic Safety/ Fisco Rosemount 848T Rosemount 848T Appendix C Foundation fieldbus Technology Overview Function BlocksSnap InputOutput Linkages StatusResource Blocks Device Descriptions Block OperationInstrument- Specific Function Blocks Alerts Transducer BlocksFieldbus Link Network CommunicationLink Active Scheduler LAS LAS Parameters MID x ST DataPublisher/Subscriber Backup LASAddressing Scheduled Transfers Report DistributionDevice Device Y Device Z Unscheduled TransfersSchedule Function Block Scheduling Number Parameter Units Description Appendix D Function BlocksAnalog Input AI Function Block OUTOutscale AlarmhysXdscale IooptsFunctionalitySimulation OUT mode in manOUT mode in auto 63% of ChangeDirect Signal ConversionFiltering IndirectIndirect Square Root ConditionsValue of the block output OUT may be set manually Table D-3. Alarm Priority LevelsManual Man BAD if Limited Uncertain if in Manual modeAdvanced Features Uncertain if LimitedXdblock AI Block TroubleshootingApplication Information HIHILIMIT, LolimitMultiple Analog Input MAI Function Block Table D-4. Multiple Analog Input Function Block ParametersCAPSTDDEV1 Figure D-4. Multiple Analog Input Function Block Schematic SimulateTable D-5. Blockerr Conditions Option in Manual or Out of Service mode onlyDevices such as flowmeters Block output OUT may be set manually MAI Block Troubleshooting IN1 IN2 IN3 IN4 IN5 IN6 IN7 Input Selector Function BlockTable D-6. Input Selector Function Block Parameters OUT OutrangeSelected SelecttypeMingood OpselectAlarm OUT INn DISABLEnMode Logic Selection FunctionalityTable D-8. Alarm Priority Levels OUT reflects the selected valueBlock Execution Use Uncertain as GoodIsel Block Troubleshooting Index NumericsAlarm Detection Configuration Errors Modes AutomaticMaintalarms Troubleshooting Errors Modes AutomaticPage Rosemount Inc Pacific Private Limited

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.

Another significant characteristic of the Emerson 848T is its configurable output options. Users can choose from a range of output signals, including 4-20 mA, which provides a standard interface for integration into existing control systems. Additionally, it offers a HART communication protocol, allowing for easy configuration, calibration, and diagnostics through a digital interface. This feature enhances the transmitter's usability, enabling operators to perform adjustments without direct access to the device.

The device is designed with user-friendliness in mind. Its intuitive setup procedure and robust graphical user interface simplify the commissioning process, ensuring that even those new to the technology can easily navigate the system. An integrated LCD display provides real-time readings and status information, facilitating monitoring at a glance.

In summary, the Emerson 848T temperature transmitter combines reliable performance, user-friendly design, and advanced digital technologies. Its dual-channel capability, wide sensor compatibility, and adjustable output options make it an essential tool for achieving precise temperature measurements in various industrial settings. With these compelling features, the Emerson 848T stands out as a leading choice for professionals seeking accuracy and efficiency in their temperature monitoring applications.
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