Local Override (LO) A possible mode of a function block where the block can only be
monitored, and no changes can occur to its set points.
Manual (MAN) A possible mode of a function block where the final element is
manually input by a user, as opposed to being controlled by its
algorithms.
Out Of Service (OOS) A possible mode of a function block which means the block does not
run its internal algorithms and cannot be used.
Process Variable (PV) A process variable is a condition of the process fluid (a liquid or gas)
that can change the manufacturing process in some way. Common
process variables include pressure, temperature, flow rate, etc.
Readback This is the parameter in an output function block which indicates the
actual feedback of a process, as opposed to the desired value.
Remote Cascade (RCAS) A possible mode of a function block which refers to an input derived
from non-function block outputs.
Resource Block (RB) A block that describes the characteristics of the fieldbus device such
as; the device name, manufacturer and serial number.
Schedules Communication events that occur at the same time during each
control cycle. The schedule defines when Function Blocks (FBs)
execute and when data / status information is published on the bus.
Segment A Foundation Fieldbus network is made up of devices connected by a
serial bus. This serial bus is called a segment (also known as a link).
A section of an H1 fieldbus that is terminated in its characteristic
impedance. Segments can be linked by Repeaters to form a longer
H1 fieldbus. Each Segment can include up to 32 H1 devices.
Transducer Block (TB) A block that is an interface to the physical, sensing hardware in the
device. It also performs the digitising, filtering, and scaling
conversions needed to present input data to function blocks, and
converts output data from function blocks. The block decouples the
Function Blocks from the local input/output (I/O) functions required to
read the limit switches and command the actuator to move.
Virtual Communication Preconfigured or negotiated connections between virtual field devices
Relationship (VCR). on a network. The quantity of VCRs able to be handled by an H1
gateway, or Link Master usually determines the number of devices on
an FF highway.
Virtual Field Device (VFD) The virtual field device is a model for remotely viewing data described
in the object dictionary. The services provided by the Fieldbus
Messaging Specification allow you to read and write information about
the object dictionary, read and write the data variables described in
the object dictionary, and perform other activities such as uploading or
downloading data and invoking programs inside a device.
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