Glossary
June 2017
Instruction Manual
D103176X012
69
Pressure Sensor
A FIELDVUE instrument internal device that
senses pneumatic pressure. DVC2000 digital
valve controllers have one actuator pressure
sensor.
Primary Master
Masters are communicating devices. A primary
master is a communicating device permanently
wired to a field instrument. Typically, a
HART‐compatible control system or a computer
running ValveLink Software is the primary master.
In contrast, a secondary master is not often
permanently wired to a field instrument. The 375
Field Communicator or a computer running
ValveLink Software communicating through a
HART modem could be considered a secondary
master.
Note: If one type of master takes an instrument
Out Of Service, the same type must put it In
Service. For example, if a device set up as a
primary master takes an instrument Out Of
Service, a device set up as a primary master must
be used to place the instrument In Service.
Quick Opening
A valve flow characteristic where most of the
change in flow rate takes place for small amounts
of stem travel from the closed position. The flow
characteristic curve is basically linear through the
first 40 percent of stem travel. One of the input
characteristics available for a FIELDVUE
Instrument. See also, Equal Percentage and
Linear.
Random Access Memory (RAM)
A type of semiconductor memory that is normally
used by the microprocessor during normal
operation that permits rapid retrieval and storage
of programs and data. See also Read Only
Memory (ROM) and Non‐Volatile Memory (NVM).
Rate
Amount of change in output proportional to the
rate of change in input.
Read‐Only Memory (ROM)
A memory in which information is stored at the
time of instrument manufacture. You can
examine but not change ROM contents.
Seat Load
Force exerted on the valve seat, typically
expressed in pounds force per lineal inch of port
circumference. Seat load is determined by shutoff
requirements.
Set Point Filter Time
The time constant, in seconds, for the first‐order
input filter.
Software
Microprocessor or computer programs and
routines that reside in alterable memory (usually
RAM), as opposed to firmware, which consists of
programs and routines that are programmed into
memory (usually ROM) when the instrument is
manufactured. Software can be manipulated
during normal operation, firmware cannot.
Stroking Time
The time, in seconds, required to move the valve
from its fully open position to fully closed, or vice
versa.
Temperature Sensor
A device within the FIELDVUE instrument that
measures the instrument's internal temperature.
Travel
Movement of the valve stem or shaft which
changes the amount the valve is open or closed.
Travel Accumulator
The capability of a FIELDVUE instrument to record
total change in travel. The value of the Travel
Accumulator increments when the magnitude of
the change exceeds the Travel Accumulator
Deadband. To reset the Travel Accumulator, set it
to zero.
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