Model 621: Watlow Series F4 controller and Series 97 limit

The Model 621 Profiling Temperature Controller is a full-featured, industrial quality rackmount temperature controller capable of executing complex temperature profiles (temperature setpoint sequences as a function of time). Up to 30 amps of AC power can be controlled ranging from 100 to 250 VAC.

The Model 621 is an exceptionally user-friendly stand-alone programmable temperature profiler. For more versatility, the Model 621 can be controlled via standard digital communications, and process values or setpoint values can be can be made available through the optional analog output.

Real-time Clock and Profile Storage

Up to 256 steps may be programmed and stored in up to 40 user-named profiles. The ability to ramp, soak, autostart, jump and repeat segments offers tremendous flexibility in setting up a wide a variety of complex profiles. A real-time clock allows any profile to be started at any time, which can be specified as a specific date and time, a day of week, or the profile can be repeated daily. The 4x20 alphanumeric display and one-button context-sensitive help greatly simplifies programming and configuration.

Powerful features for demanding process requirements

Advanced features like guaranteed soak band and wait for deviation can be configured so that the controller will wait until the process value has reached and/or has remained within a certain deviation band before clocking soak time or moving on to the next profile step. Up to five sets of PID parameters can be stored allowing a different set to be used for each step of an executing profile.

Dual alarm relays, four event inputs and eight event outputs are available via internal screw terminals that allow additional control of profile execution and the control of other process equipment by the Model 621.

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 Model 621 comes standard with either RS-232 or RS-485 digital communications for the main controller. Note, both RS-232 and RS-485 communications are accessible on the Model 621, but only one is wired to the back panel at the factory. Changing from one interface to the other can easily be done in the field. Additionally, analog output can be ordered for the main controller of the 621 -- while still having the digital communications fully functional. Analog input for remote setpoint adjustment is not available on the Model 621. The limit 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.