535-PROF User's Manual
Appendix 6
A-21
Glossary
three mode control:
(See control action
PID)
time proportioning control:
A control
algorithm that expresses output power
(0–100%) as a function of percent ON
versus percent OFF within a preset cycle
time.
time proportioning output:
A controller
output assigned by software to facilitate
time proportional control (typically a
relay, SSR, or SSR Drive output).
tracking:
A function that defines
whether the local setpoint will track the
remote setpoint. When the controller is
transferred to a local setpoint, that local
setpoint value will match the remote
process value when the transfer occurs.
transmitter (2-wire):
A device used to
transmit data via a two wire current loop.
A two-wire transmitter is loop powered.
transmitter (4-wire):
A device used to
transmit data via a current loop or a DC
voltage. A 4-wire transmitter uses 2
wires for data and 2 wires for power.
triac:
Solid state switching device used
to switch alternating current signals on
and off. Triac circuits are sometimes
referred to as solid state relays (SSR).
trip point:
Value which determines
when that set of PID values becomes
active.
velocity position proportioning:
This is
a control technique where valve position
is determined by calculating the amount
of time it takes to open/close a valve by
moving the valve for a portion of that
time.
windup:
Saturation of the integral mode
of a controller developing during times
when control cannot be achieved, which
causes the controlled variable to
overshoot its setpoint when the obstacle
to control is removed.
wild stream:
In mixing applications that
require materials to be mixed to a
desired ratio, this is the one part of the
material that is uncontrolled.
