Emerson Fisher FIELDVUE DVC6000, Instruction Manual

Page: 154 / 162

DVC6000 Digital Valve Controllers
September 2013 Glossary-6
Travel Cutoff
Defines the cutoff point for the travel, in percent
of ranged travel. There are two travel cutoffs:
high and low. Once travel exceeds the cutoff, the
drive signal is set to either maximum or minimum,
depending on the Zero Control Signal and if the
cutoff is high or low. Minimum opening time or
minimum closing time are not in effect while the
travel is beyond the cutoff. Use the travel cutoff to
obtain the desired seat load or to be sure the
valve is fully open.
Travel Deviation
The difference between the analog input signal (in
percent of ranged input), the “target” travel, and
the actual “ranged” travel.
Travel Deviation Alert
Checks the difference between the target and the
ranged travel. If the difference exceeds the Travel
Deviation Alert Point for more than the Travel
Deviation Time, the Travel Deviation Alert is
active. It remains active until the difference is less
than the Travel Deviation Alert Point.
Travel Deviation Alert Point
An adjustable value for the target travel and the
ranged travel difference, expressed in percent,
When this value is exceeded by the travel
deviation for more than the Travel Deviation
Time, the Travel Deviation Alert is active. Valid
entries are 0% to 100%. Typically this is set to
5%.
Travel Deviation Time
The time, in seconds. that the travel deviation
must exceed the Travel Deviation Alert Point
before the alert is active. Valid entries are 1 to 60
seconds.
Travel Limit
A setup parameter that defines the maximum
allowable travel (in percent of ranged travel) for
the valve. During operation, the travel target will
not exceed this limit. There are two travel limits:
high and low. Typically the travel limit low will be
used to keep the valve from going completely
closed.
Travel Range
Travel, in percent of calibrated travel, that
corresponds to the input range.
Travel Sensor
A device within the FIELDVUE instrument that
senses valve stem or shaft movement. The travel
sensor is mechanically connected to the valve
stem or shaft.
Travel Sensor Motion
Establishes motion of the travel sensor. While
viewing the end of the travel sensor shaft, if
increasing air pressure to the actuator causes the
shaft to rotate clockwise, travel sensor motion is
CW. If increasing air pressure causes the shaft to
rotate counterclockwise, travel sensor motion is
CCW.
Tuning
The adjustment of control terms or parameter
values to produce a desired control effect.
Tuning Set
Preset values that identify gain settings for a
FIELDVUE instrument. The tuning set and supply
pressure together determine an instrument’s
response to input signal changes.
Watch Dog Timer
A timer that the microprocessor must rearm
periodically. If the microprocessor is unable to
rearm the timer, the instrument goes through
reset.
Zero Power Condition
The position of the valve (open or closed) when
the electrical power to the instrument is removed.
Zero Power Condition (ZPC) is determined by
relay and actuator action as follows:
Single Acting Direct (Relay C) Upon loss of
power instrument goes to zero air output at port
A. On loss of pneumatic supply failure direction is
per the actuator fail mode.
Double Acting (Relay A) Upon loss of power
instrument goes to full supply air output at port B.
A goes to zero air output. The failure direction
upon loss of pneumatic supply cannot be
determined.
Single Acting Reverse (Relay B) Upon loss of
power instrument goes to full supply air output at
Port B. On loss of pneumatic supply failure
direction is per the actuator fail mode.
B
Glossary