FOXBORO 743CB-DF 743CB Series

743CB Series FIELD STATION MICRO Controller
The 743CB is a self-contained, field-mounted, microprocessor-based controller with the ability to perform control functions for up to two independent loops. In addition to the standard proportional, integral, and derivative (PID) functions, the controller provides many enhanced functions including Foxboro’s patented EXACT tuning algorithm, user- configurable control functions, auto selector control, split range outputs, auto/manual transfer stations, assignable 3-variable indicator functions, totalization, a comprehensive calculation capability, and signal conditioning. Standard controller signals include: four analog inputs, two frequency inputs, two contact inputs, an optional platinum RTD direct input, two analog outputs, and two contact outputs. A fluorescent display is used to show the control variables in bargraph format, and to provide precision digital readout. It also displays an electronic loop tag, controller status, and alarm indication. A keypad, located on the front of the controller, is used for operator interface and configuration. The controller is housed in a field-mounted enclosure that meets IEC IP66 and that also provides the environmental and corrosion resistant protection of NEMA Type 4X. The enclosure can be mounted to a surface or panel, or mounted to a nominal DN50 or 2 in pipe. FEATURES • Two Independent PID Controllers • Single Station Cascade Control • Single Station Auto Selector Control • Split Range Outputs • Ratio Control • Batch (Discontinuous) Control • Totalization • 3-Variable Indicators • Auto/Manual Transfer Stations • Assignable Alarms • Algebraic Computation • Dynamic Compensation with Lead/Lag, Impulse, and Dead Time Functions
• Boolean Logic Capability • EXACT Control (Foxboro U.S. Patent RE 33267) • Flexible Configuration Blocks with Internal Signal Routing • Fully Interactive Display • Configuration and Display of an Independent Variable • Pulse Driven Input • RS-485 Serial Communications for Operation and Configuration • Nonvolatile Memory • Transportable Configuration • Power Failure Recovery Logic • Front Panel Keypad for Both Configuration and Operator Interface • Internal Signal Sources for Calibration • Integral Field Power Supply • Passcode Security
TWO INDEPENDENT CONTROLLERS Two completely independent control strategies can be used. All control support functions are available for both loops, thereby allowing high-performance, enhanced control of each loop. CASCADE CONTROL With this controller configuration, the output of one of the controllers (primary controller) drives the set point of the other (secondary) controller. This configuration can improve the performance of certain control loops where load disturbances are a factor. AUTO SELECTOR CONTROL Two controllers with a single selected output are combined in this configuration to provide constraint control or dual mode control. The choice of lower, higher, or logic-selected output is configurable. The inherent design prevents controller windup and offers independent or interlocked auto/manual functions. SPLIT RANGE OUTPUTS The two 4-20 mA outputs can be driven from a single controller. This allows one measured variable to be controlled by two manipulated variables. A typical application is a temperature control system in which both the heating medium and the cooling medium are manipulated. ACTUAL OUTPUT INDICATION The output bargraph and digital indicator can be configured to display the actual 4-20 mA output value, or any analog signal, such as valve position feedback. TOTALIZERS Up to two 7-digit totalizers are available. The totalizers can be set to integrate up to a preset value or down from a preset value, and produce a logic event output. Any internal or external signal can be totalized. Totalization and EXACT tuning are mutually exclusive. For example, if one controller is configured for EXACT tuning, only one totalizer is available. EXACT CONTROL EXACT control uses microprocessor technology to make ongoing controller adjustments based on the actual, real time process dynamics. This is in direct contrast to other “self-tuning” controllers that establish the values of tuning parameters based on an arbitrary process model. While continuously scanning the process variables, EXACT control initiates corrective action upon sensing a process upset. The user selects the desired response by specifying the desired damping and overshoot-to-load change, such as quarter amplitude damping. Values of EXACT can be read by the user. EXACT control functions as if your best operator is on the job 24 hours a day. It can be turned on or off at the keypad or by configuring logic functions, allowing these controllers to function as advanced PID controllers. EXACT control is available on both control loops. 3-VARIABLE INDICATOR Up to two 3-variable indicator faceplates are available. Each variable has its own bargraph, digital engineering units, and loop tag. The 3-variable faceplates are mutually exclusive with controllers and auto/manual stations. If only one controller or manual station is configured, one 3-variable faceplate will be available. AUTO/MANUAL TRANSFER STATION Up to two auto/manual stations are available. Auto/manual stations are mutually exclusive with controllers and indicators. For example, if only one indicator or manual station is configured, one auto/manual station will be available. PULSE DRIVEN INPUT There is provision for two pulse inputs, forming a pulse up/pulse down pair that can be assigned to any scaled signal such as remote set point. This function is compatible with the signals used for older stepping motor type devices.