Flowserve MX FOUNDATION Fieldbus Field Unit - Manual (Page 81)

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MX/QX FOUNdaTION Fieldbus Field Unit FCd LMENIM2330-01 – 08/11
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Proportional Integral Derivative Control Methodology Control loop feedback algorithm that
calculates an “error” value as the difference between a measured “process variable” and a desired
“setpoint”. The weighted sum of the three P-I-D actions is used to adjust the process via a control
element such as the position of a valve.
PLC Programmable Logic Controller, an intelligent microprocessor-based replacement for relay
logic systems, used for process and machinery control applications.
RS-232C An EIA standard for serial data transmission found in almost all personal computers
and other serial communication systems not exceeding 30 feet. Recently the EIA has renamed the
standard EIA-232.
RS-485 An EIA standard for half duplex, serial data transmission used in multipoint, or parallel,
communication systems. This is an excellent choice for long distance serial data read only 16-bit
unsigned value. Contains field unit status and digital input status transfer because it includes data
rates up to 10 megabytes/second, excellent noise rejection, and the ability to withstand up to +/•7
volts of instantaneous common mode voltage without loss of signal.
RTU Remote Terminal Device, a generic name for an intelligent device remotely located, used for
control or data collection purposes.
Serial Data Transmission The transmission of digital data bits sequentially over a transmission
medium. Compare to parallel data transmission
Twisted Pair A serial digital data communications medium incorporating two wires twisted together
to minimize interference from near-by noise sources. Limitorque recommends Belden’s 3076F, or
equivalent cable.