Cameron Scanner 2000 microEFM, Руководство пользователя по оборудованию

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C-15
Scanner
®
2000 microEFM Appendix C
Fieldbus Operations
The Foundation™ Fieldbus Protocol Manual for Scanner 2000 provides a list of the parameters supported
by the Scanner 2000 fieldbus module. Neither resource blocks nor transducer blocks can be linked to other
function blocks to build a control strategy. However, process variable parameters from the transducer block
can be mapped to an AI block and used as an input for the AI block. None of the other transducer block
parameters are available for use as AI block inputs.
Engineering Units
The Engineering units used for process variables are written to Modbus
®
registers during the configuration of
the Scanner 2000 using the ModWorX Pro configuration software provided with the Scanner 2000. The units
are then converted to fieldbus code by the fieldbus module.
Since the preconfigured units are being transferred to the fieldbus module, rather than the module having to
convert raw inputs to a desired unit before publishing the values to the network, there is little need for scaling
process values with a fieldbus configuration tool.
NOTE F
oundation
™ fieldbus supports combined units for many rate measurements. However Scanner 2000
does not support these combined unit displays. Instead, flow rate is represented as two separate
measurements (volume and time) that are displayed as two parameters in the host interface software.
Status
Every measured or processed parameter in the transducer block and AI blocks is represented by two elements
in the configuration tool: a value and a status. Process variable status descriptions and values are continually
displayed within the analog input block section of the configuration tool.
Status can indicate a hardware, communication, or other fault. Each status is made up of three forms of
intelligence: quality, sub-quality, and limit condition.
• Quality indicates status in general terms: good, uncertain, or bad.
• Sub-Quality provides additional information to help explain the problem. For example, if the quality sta
-
tus is “bad,” the sub-quality status may indicate “device failure” or configuration error.”
• Limit Condition identifies if there is a limit placed on the value or not. For example, “limited high” in -
dicates that value has reached its upper limit, and “constant” means the value cannot go higher or lower.
Typically, the limit condition is set to “none.”
Fieldbus Troubleshooting
There are many parameters in the resource, transducer and analog input blocks that can assist users in
troubleshooting operations problems. Some of the most commonly used parameters are described below.
A change in the status of a measured or processed parameter may be the earliest indication of a problem. See
Status, page C-15 , for details.
General Errors
Block Error
The block mode (MODE_BLK) parameter exists in all blocks and can indicate a potential problem. Check
the Target mode and the Actual mode. If they do not match, there is likely a problem. Check the block error