Model 521: Watlow Series 96 controller and Series 97 limit

Utilizing the Watlow Series 96 controller, the Model 521 Rackmount Temperature Controller is a fully autotuning PID temperature control system with a robust, simple user interface allowing for front panel control of setpoint. Up to 30 amps of AC power can be controlled ranging from 100 to 250 VAC.

A ramp-to-setpoint feature can be enabled so that the controller gradually ramps the setpoint to the final target value over a user-settable time or rate. The Model 521 can be controlled via computer through its optional digital communications interface or remote setpoint programming can be acheived through optional analog I/O.

Features

• Autotuning, solid-state, PID control using variable time-base proportioned switching for precise, reliable control and extended heater life
• Universal power input and heater output: operates from any voltage ranging from 100 to 250VAC, 50 to 60 Hz; provides and controls heater power of the same voltage characteristic as the input, up to 30A
• Well-heatsinked solid-state relay for long-life
• Maximum over-temperature protection utilizing an independent limit module
• Power line protection via internal double-pole magnetic circuit breaker
• Open loop protection shuts down output if open loop operation is detected
• Simultaneous display of process temperature, control setpoint, over-temperature limit, and limit sensor temperature; Percent duty cycle can also be displayed
• Industrial rackmount enclosure with twist-lock AC receptacles and universal thermocouple connectors
• Several communications options available, including MODBUS message protocol over RS-232 or RS-485, analog input and/or analog output

Profiling Option allows ramp-soak programming

As an option, the Model 521 can be fitted with a profiling (ramping) option that allows temperature versus time profiles to be programmed into the controller. Up to 16 ramp and soak steps can be programmed and executed without the need for a computer. Looping and jumping allow for continuous and repetitive temperature cycling. Advanced features like wait for deviation and wait for event input (only enabled if analog input is present) assist in guaranteeing that process values are reached before clocking soak time or moving to the next event.

Communications options

Analog and digital communications options can and must be independently specified for the main controller and the limit controller. If RS-485 digital communications is specified for both the main and limit controllers, the two controllers are wired to a common 9-pin D-sub connector. The main and limit controllers are then accessed via address values of 1 and 2 (default values), respectively. If RS-232 is specified for both the main and limit controllers, each controller is wired to its own 9-pin D-sub connector. In this case, a single computer would need to use two serial ports to communicate with both the main and limit controller at the same time.

The default configuration of the Model 521 is without any remote analog or digital communications. RS-232 digital communications, RS-485 digital communications, or analog output can be added as an option for the main controller (choose one only). Analog input (analog remote setpoint adjustment) is also available as an option for the main controller of the 521. The limit controller can be ordered with RS-232, RS-485, or analog output.

Communications Protocol

Both the Model 521 and the Model 621 temperature controllers use the industry standard MODBUS RTU messaging protocol over either RS-232 or RS-485 interfaces. MODBUS provides a robust communications protocol by incorporating verified message reception and CRC (checksum) error detection. MODBUS is used by several of the most popular industrial PLC's.

Analog Input and Analog Output Ranges

Analog input and analog output support all the common industrial DC ranges: 0-5V, 0-10V, 1-5V, 4-20mA, and 0-20mA. The main and limit controllers can independently be configured to map the full resolution of the analog range to the desired range of temperatures.