Yokogawa YVP20S - Manual (Page 170)

App-1
IM 21B04C50-01E
APPENDICES
Appendix A Glossary and Acronyms
TA01-1.EPS
FAS Fieldbus Access Sublayer
FMS Fieldbus Messaging Service
MIB Management Information Base
SMIB System Management Information Base
MAN Manual mode
RCAS Remote Cascade mode
LO Local Override mode
IMan Initialization manual mode
ROUT Remote output mode
Cas Cascade mode
AUTO Automatic mode
OOS Out of Service mode
Algorithm A set of rules that control the operation of an object through software.
Closed The valve position in which the flow is minimum or zero. See tight shutoff.
AO Analog Output block
Basic Device A Basic Device is any device not having the capability to control communications on an H1 fieldbus
segment.
0xf7 See hexadecimal. This is the number 247 represented in hexadecimal notation. The 0x preamble
indicates hexadecimal notation.
1.#INF This is the representation of infinity as expressed in IEEE 754 floating point arithmetic. It is used in
fieldbus devices to set a parameter to a value that does not interfere with operation, such as for a
limit, for example.
ATC Air to close The combination of a single acting actuator and the control valve where the valve is closed when air
pressure is applied to the actuator. A spring opens the valve when air pressure is removed.
Capabilities File A Capabilities File describes the communication objects in a fieldbus device. A configuration device
can use Device Description (DD) Files and Capabilities Files to configure a fieldbus system without
having the fieldbus devices online.
Characteristic The positioner input setpoint command may be selectively modified to provide a desired relationship
between setpoint and valve position. In the valve, the relationship between stroke and Cv is also
called valve inherent characteristic. It is often adjusted by design, to equal percentage, for example.
The positioner characteristic is applied to modify the setpoint to travel relationship of the actuator.
The characteristic of the positioner should be chosen to compliment the valve. If the valve is equal
percentage, the positioner should be set to linear. If a linear valve is installed the positioner may be
set to an equal percentage characteristic to improve flow control. Local display can be used to select
the custom characteristic, but cannot adjust the points.
ATO Air to open The combination of a single acting actuator and the control valve where the valve is open when air
pressure is applied to the actuator. A spring closes the valve when air pressure is removed.
Communications Stack A Communications Stack is device communications software which provides encoding and decoding
of User Layer messages, deterministic control of message transmission, and message transfer.
Compliance voltage The voltage that must be available at the control system output in order to drive the control current
through all the resistive devices in series with it.