Watlow F4T User Manual

Watlow F4T • 94 • Chapter 5 Function Reference
The graph shown below illustrates a thermal system with a long lag time. Curve A represents
a typical single loop control system with PID parameters that
allow a maximum heat up rate. Too much energy is intro-
duced and the set point is overshot. In most systems with
long lag time, the process value may never settle out to an
acceptable error. Curve C represents a single loop control
system tuned to minimize overshoot. This results in unac-
ceptable heat up rates, taking hours to reach the set point.
Curve B shows a cascade system that limits the energy intro-
duced into the system, allowing an optimal heat up rate with
minimal overshoot.
Signals
Direction Label Type Function
Receivers
PVO Analog Process value feedback for the outer loop.
PVI Analog Process value feedback for the inner loop.
RSP Analog
Set point for the loop when REN is on.
See: Remote Set Point Type
PSP Analog Set point from the profile engine when profiling is used.
REN Digital
Active state causes loop to control to the Remote Set
Point.
See: Remote Set Point, Remote Set Point Type and Use
Remote Set Point Active Level
IDLE Digital
Active state causes loop to control to the Idle Set Point.
See: Use Idle Set Point Active Level
OFF Digital
Forces Control Mode to Off while active.
See: Off Active Level
MAN Digital
Forces Control Mode to Manual while active.
See: Manual Active Level
TUN Digital
Active state initiates autotuning.
See: Initiate Autotune Active Level
SSP Digital
Active state switches the block from cascade to simple
set point control.
See: Simple Set Point (SSP) Enable and Disable Active
Level
Transmitters
HT Analog % Heating needed: 0% is no heat and 100% is full heat.
CL Analog % Cooling needed: 0% is no cooling and 100% is full cooling.
PWR Analog %
Heating or cooling needed: -100% is full cooling, 0% is no
heating or cooling and 100% is full heating.
SP Analog
Set Point for use with Alarms or other blocks. Firmware
release 3.0 and above renames CSP to SP.
MP Analog %
Manual Power for use with other blocks. Firmware re-
lease 3.0 and above renames OSP to MP.
*Off Digital
Reflects the current state of "Control Mode Active":
Off = On, Auto = Off, Manual = Off
*Available in firmware release 3.0 and above.
Time
Temperature
Cascade
Curve A (PID)
Set
Point
Curve B (Cascade)
Curve C (Single-control)

Watlow F4T Specifications

General

Inputs	Thermocouple, RTD, mA, V
Outputs	Relay, SSR, mA, V
Communication	Ethernet, Modbus RTU
Data Logging	Yes
Certifications	CE, UL, cUL, RoHS
Control Modes	PID, On/Off
Power Supply	100 to 240 VAC
Operating Temperature	0 to 50°C
Enclosure Rating	IP65
Display	4.3 in. (109 mm) color touch panel LCD
Control Loops	Up to 4