Backup/Manual Loading Stations — Models MXAB / MXCB

‘Backup Station’ series is used to hold and manually load the control signals in case these automatic signals from the DCS, PLC or PID controller are lost. Basically, the Backup Station has (A) an analog/discrete input, (B) an analog output and (C) a contact input. In normal operating mode, it isolates (A) the control signal from the host device and outputs (B) analog MV signal to the final control element such as control valve, damper or actuator, in monitoring (C) the host’s RUN signal status. When the RUN signal is lost or an external signal to switch to a manual control is received, it stops responding to the input signal and holds the MV signal. Then external UP-DOWN commands can increase or decrease the MV signal to manually control the final control element. Two ‘field-configurable’ types are newly available: Model MXAB and MXCB. BASIC BACKUP FUNCTION • MXAB Used Independently The MXAB, Analog Backup Station, accepts analog process signals such like 4 to 20 mAdc. In normal operating mode, it responds proportionally to its input (= computer output) in the response time of less than 0.5 seconds. If the computer fails, this will be detected as a ‘STOP’ command and its output will be held at the value prior to the breakdown. • MXCB Used Independently The MXCB, Computer Backup Station, responds to ‘UP’ or ‘DOWN’ contact closure signals from the computer to in crease/decrease its output in the preset ramp rate. If the computer fails, this will be detected as a ‘STOP’ command and its output will be held at the value prior to the break down. • MXAB/MXCB Used in Combination with the ST/STL Manual Loader The ST and STL are panel mounted Manual Loaders with a meter on the front. By introducing these devices into the backup control loop, the ‘STOP’ command will override computer output and then put the MXAB/MXCB in the manual operation mode if the computer fails. Typical backup loop is configured as shown in the figure below. BACKUP MODES As backup action, you can select two operating modes as listed below: Trace Back Mode: Outputs the input value just before the failure. Trace-back time is programmable within the range of 0 to 20 seconds in order to use more reliable signals than those already erratic at the moment of failure. Fixed Value Mode: Outputs the pre-programmed value. ADDITIONAL FEATURES EEPROM Memory Even when the power is lost, data is stored into the EEPROM memory without time limitation. Restart Modes Two Restart Modes after the power loss and recovery are selectable: (1) Tracks the input signal or (2) Outputs the pre-programmed value. Transition Speed The transition speed to track the new input when the Backup Station is switched back from MANUAL to AUTO mode, is programmable in order to avoid abrupt change in the MV output. UP-DOWN Response Time The ramp rate with the UP-DOWN commands is programmable within the range of 1 second to 999 seconds for travelling the full-scale range. Also the response time can be increased gradually at the starting up to the UP-DOWN Response Time setting. Loop Test Output A simulated 0% and 100% MV output signal can be provided from the MXAB/MXCB in order to check the receiving instrument without commissioning the whole system at the system startup test. The MX-UNIT series is now equipped with this function as standard. Filter Functions The moving average filter is programmable to filter unwanted noise out of the output signals. Display Range Scaling Process signals can be monitored in actual engineering unit on the front 4-digit digital meter. Status LED In case of the computer/DCS failure, the front LED flashes and displays an error code. Instant Reset All parameters can be reset to the factory default setting by the front key operations. Control Signal Logic Positive or negative logic for the ‘STOP’ ‘UP’ ‘DOWN’ signals is selectable at site. Field-configurable Input/Output Ranges The MXAB/MXCB is suitable for last-minute specification changes. BACKUP STATION LINE-UP Models AB2 and CB2 are analog, fixed-range version of the MXAB and MXCB. Backup/Manual Loading Stations with the built-in meter are also available (models ABF, ABF1 and ABF2). (Click model No. to view specifications in PDF)   ANALOG BACKUP COMPUTER BACKUP   Model No. JB2 MXAB AB2 MXCB CB2 Programming Hand-held console Front-keypad N/A Front-keypad N/A CAS input 4 - 20 mA DC Max. ±30 V DC (field-selectable) Specific range within ±300 V DC Dry contact (Saturation voltage Max.1 V, Sink current 0.5 mA) MV output 4 - 20 mA DC Max. 0-20 mA DC Max. ±10 V DC (field-selectable) Specific range within 0-20 mA DC or -10 to +12 V DC Max. 0-20 mA DC Max. ±10 V DC (field-selectable) Specific range within 0-20 mA DC or -10 to +12 V DC Discrete input (UP/DOWN) Dry contact 5 V DC / 3 mA Dry contact (Saturation voltage Max.1 V, Sink current 0.5 mA) Power input 15 - 35 V DC 100-240 V AC 12-24 V DC 110 V DC 100, 110, 115, 120 V 200, 220, 240 V AC 12, 24 V DC 100-240 V AC 12-24 V DC 110 V DC 100, 110, 115, 120 V 200, 220, 240 V AC 12, 24 V DC   PANEL-MOUNT ANALOG BACKUP   Model No. ABF3 Display Bargraph + Digital PV input 4 - 20 mA DC, 0 - 20 mA DC, 0 - 10 V DC, 0 - 5 V DC, 1 - 5 V DC, -10 - +10 V DC, -5 - +5 V DC CAS input 4 - 20 mA DC, 0 - 20 mA DC, 0 - 10 V DC, 0 - 5 V DC, 1 - 5 V DC, -10 - +10 V DC, -5 - +5 V DC MV output 4 - 20 mA DC, 0 - 20 mA DC, 0 - 10 V DC, 0 - 5 V DC, 1 - 5 V DC, -10 - +10 V DC, -5 - +5 V DC Power input 24 V DC, 100 - 240 V AC