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Available in versions that supply four,eight, 16 and 32 control loops, the controllers can accept thermocouple, RTD, process, linear and pulse inputs. A selected eight loop version also accepts carbon potential. Auto-tuning automatically sets PID parameters for Time/Temperature Profiling(Ramping) Four to 32-Loop Programmable auto-tuning controllers(see auto-tuning above) are able toexecute ramp and soak profiles suchas temperature changes over time,along with hold, or soak/cycle duration. Selected controllers are available in CE compliant versions. Applications include heat treating, complex process furnaces and environmental chambers. Limits/Alarms These controllers are specificallydesigned to provide safety limitcontrol over process temperature. They are capable of acceptingthermocouple, RTD or process inputs with limits set for the high or lowtemperature. Limit control is latchingand part of a redundant control circuitto positively shut a thermal systemdown in case of an over-limitcondition. Multi-LoopTwo-Loop These units can receive two inputsand produce two or more outputs for direct and reverse acting control. They accept thermocouple, RTD, process and event inputs. Auto-tuning (see auto-tuning above) automatically sets PID parameters for optimum performance. Outputs include alarms, events, process, serial communications and data logging. Selected controllers are available in CE compliant versions. Applications include foodservice equipment, complex process furnaces and environmental chambers. Single-LoopAuto-Tuning Used to automatically set PIDparameters for optimum thermalsystem performance. Capable ofaccepting a variety of sensor inputs,including thermocouple, RTD and process. The controller senses therate of temperature increase (reverseacting) or decrease (direct acting) and adjusts the output action to minimize set point over- and under- shoot. PID output action requires asolid state power controller towithstand rapid switching cycles. Auto-tuning controllers can have morethan one output channel for alarms,retransmit and serial communications. Selected controllers are available inCE compliant versions. Some controllers feature a percentpower default operation or will de- energize the system upon sensor break. Controllers with NEMA 4X frontpanels are well suited for wet or corrosive environments. Applications include batchprocessing ovens and furnaces, environmental chambers and analytical equipment. Used for non-critical orunsophisticated thermal systems to provide on-off temperature control fordirect or reverse acting applications. The basic controller acceptsthermocouple or RTD inputs andoffers an optional percent powercontrol mode for systems without temperature sensors. This categoryalso includes cartridge thermostats.These units operate on their sheath'sthermal expansion and are available in reverse and directing acting modes. They can be wired interconnected or for pilot duty with a relay. The cartridgethermostat can alsoserve as a non- latching limit controller. Applicationsinclude foodservice and generalprocess control. Basic

W A T L O W

Application Guide catalog - 7347 Application Guide

TemperatureControllers

Controller Overview

Watlow offers controllers of twodifferent types, temperature controllers and power controllers. Control panels are pre-assembled temperature and power controller packages mounted in a suitable electrical enclosure.A temperature controller produces anoutput action based on the input signal received from a sensor. Controllers used in cooling applications are called direct acting. Controllers used in heating applications are called reverse acting. Depending on the controller, output actions can control a heating or cooling device, or some other aspect of a process (ratio mixing, conveyor speed, etc.).Temperature controllers are eithersingle-loop or multi-loop. Single-loop temperature controllers are good for basic temperature control. Various levels of sophistication can reducetemperature under-and over-shoot,produce alarm actions and perform data logging functions as well as serial communications.Multi-loop temperature controllers(also called process controllers) aregood for applications where temperature and other processvariables need to be controlled in a coordinated fashion.Temperature controllers are eithersingle-loop or multi-loop. Single-loop controllers have one input, and one or more outputs to control a thermal system. Multi-loop controllers have multiple inputs and outputs, and are capable of controlling several aspects of a process. More control loops permit controlling and coordinating more process system functions.
Temperature Controllers 99