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The SFD-3002 and SFD-3003 interlock operators are auxiliary units in the DDZ-S series of instruments, and they represent a type of D-type operator. It is used in conjunction with electric actuators featuring forward/reverse orientation control, enabling a seamless switch between manual and automatic modes of the control system; in manual mode, it allows remote operation of the valve position. It can receive system event signals to enable safety interlock protection, thereby improving the reliability of the system. Key features of the SFD-3002 and SFD-3003 type interlock operators: ① They provide dual displays for both 4-20mA control signals and valve position signals, with the display format being 41-segment LED bars ； ②Features seamless manual/automatic switching as well as forward and reverse remote control of valve positions ； ③The manual/automatic switch and the forward/reverse manual control switches use membrane buttons, which are waterproof and dustproof ； ④It has 3 event signal channels that can receive event signals from regulators, servo amplifiers, and system contacts, display and process them, and provide protection functions with 3 operating states: \"fully open,\" \"fully closed,\" or \"remain in place.\" ； ⑤It features 2 M/A status signals and 1 tracking voltage signal (1-5V). This product boasts a novel design, attractive appearance, comprehensive functions, and high versatility, making it suitable for use in the automatic control systems of various industrial sectors such as power plants, light industry, chemicals, and metallurgy. Servo operator yunrun.com.cn/product/1249.html Main technical specifications: Input signal: The regulator signal is 4-20mA ； The position feedback current is 4-20mA; the display error is ±2.5%. The event signal accepted is a contact signal: an open state indicates normal operation, while a closed state indicates an event. The rated output power is 220VAC/5A. The tracking voltage ranges from 1-5V. Operating conditions: supply voltage of 220VAC/50Hz. Dimensions: The SFD-3002 model has dimensions of 80×160×250mm (width×height×depth) ； The dimensions of the SFD-3003 are 72×144×250 mm (width×height×depth). The working principle of the SFD-3002 and SFD-3003 interlock operators is based on electronic circuits. The functions of the SFD-3002 and SFD-3003 interlock operators are primarily implemented through such electronic circuits. It consists of a power supply circuit, an operation switch, a control circuit, a relay conversion circuit, an event handling circuit, and a display circuit, among other components. The principle block diagram is shown in Figure 1. http://yunrun.com.cn/upload/201911/10/201911102320031847.png Figure 1: Block diagram of the interlock operator’s principle. 1. Operation switch: The operation switch uses membrane keys that were widely used in the 1990s (also known as membrane switches or touch switches). These switches have a long service life (over 1 million operations), excellent waterproof and dustproof properties, and are integrated with the instrument’s panel. 2. Control Circuit: The control circuit receives manual/auto switch signals, controls the relay conversion circuit, and outputs a 1-5V tracking voltage signal as well as A/M status contact signals to enable seamless switching between manual and auto modes. It also controls the power output circuit to facilitate switching between the manual and auto power circuits ； In the circuit, the manual mode is set to take precedence over the automatic mode, ensuring that the instrument remains in manual mode once it is powered on. In automatic mode, it has a function to lock via manual operation ； Upon receiving the output signal from the event processing circuit, the control circuit is able to automatically switch from its original automatic mode to manual mode, that is, to a backup operation mode for handling events. 3. Relay conversion circuit: The relay conversion circuit primarily receives signals from the control circuit and operation switch, enabling seamless switching between A/M modes, output from the power circuit during manual operation, as well as interlocking between forward and reverse manual operations. 4. Event handling circuit: The event handling function is what distinguishes the S-type operator from the DDZ-Ⅱ and DDZ-Ⅲ types of operators; it can receive 3 type of event signals (system, regulator, and amplifier event signals). As long as any event signal is received, the operator can be switched from automatic mode to manual mode. Moreover, a four-position toggle switch allows the valve to be pre-selected to stay in one of three safe positions: fully open, fully closed, or in its original position, thereby enhancing the safety and reliability of the process control system. When an event signal is detected, a flashing alarm signal is emitted. To determine the position of the valve when operators handle the event status in detail, the design takes into account the possibility of operating the forward and reverse manual control signals during the event status, thereby allowing manual control of the valve’s opening degree. 4. Display circuit: The display circuit of the interlock operator uses an LED bar display circuit, consisting of 41 wires, with a display error of ±2.5%. It adopts a dual-display format, showing the regulator output signal (MV) on one display and the valve position signal (VP) on the other. In the automatic mode, it can be seen that the valve position signal tracks the changes in the regulator’s output signal ； In manual mode, it is possible to observe the changes in the regulator’s output signal and the position signal of the throttle valve. It features an LED light bar for display, with shock resistance, and offers clear and intuitive visualization. Structure and Commissioning of SFD-3002 and SFD-3003 Interlock Operators 1. Instrument Structure The interlock operator features a panel-mounted instrument structure. The interior consists of 4 printed circuit boards, among which the display circuit board, the power supply circuit board, and the wiring circuit board are mounted with screws to the front frame, the bottom plate, and the rear part of the enclosure, respectively. The control circuit board is installed on the left side of the instrument; the various printed circuit boards are connected to each other through ribbon cable connectors. The instrument’s external wiring terminals use a modular connector consisting of 30 cores (1 22-core core and 1 8-core core). The instruments are mounted on the dashboard or console using specialized brackets. 2. Instrument tuning: Wiring diagram of the system composed of the SFD-3002 and SFD-3003 type interlock operators, servo amplifiers, and electric actuators. This article focuses on the debugging methods for the interlock operator itself; see Figures 2 and 3. http://yunrun.com.cn/upload/201911/10/201911102330266495.png http://yunrun.com.cn/upload/201911/10/201911102331407919.png Figure 2: Wiring terminal diagram of the SFD-3002 interlock operator. Figure 3: Panel layout of the SFD-3002 interlock operator. ① Manual operation: a. Connect an AC 220VAC power supply to the external wiring terminals 28, 29, and 30; at this point, the “M” indicator light will turn on, indicating that the electric operator is in manual mode. "On the MV” and “VP” column displays, the first-row columns should be lit. b. Use the ohm meter function of a multimeter to check that the terminals 14 and 15, as well as 16 and 17, are in a short-circuited state. c. Press the on (▲) membrane switch, and use the AC voltage function of a multimeter to measure points 25 and 29; if the voltage at these two terminals is 220VAC, it indicates that the actuator is operating in the forward direction. d. Press the off (▲) membrane switch, and use the AC voltage function of a multimeter to measure terminals 26 and 29; if the voltage at these terminals is 220VAC, it indicates that the actuator is operating in reverse. ②Automatic operation a: Press the “A” membrane switch, and the automatic indicator light “A” will turn on, indicating that the operator is in automatic mode. b. Use a multimeter to check that terminals 14 and 15, as well as 16 and 17, are in an open circuit state. c. Use a multimeter to check that terminals 23 and 25, as well as 24 and 26, are in a short-circuited state. ③Calibration of MV and VP light bar displays: a. When 4-20mA signals are input to terminals 1 and 2, the MV display should gradually brighten from 0% to 100%. Conversely, it darkens. b. When 4-20mA signals are input to terminals 3 and 4, the VP display should gradually brighten from 0% to 100%. Conversely, it darkens. ④Event handling verification: a. When switching to automatic mode, shorting terminals 5 and 6 should cause the system to automatically switch to manual mode; at the same time, the event indicator light ALM1 should flash ； b. When automatic operation is initiated, shorting terminals 7 and 8 should automatically switch it to manual mode; at the same time, the event indicator light 2 will flash ； c. When automatic operation is initiated, shorting terminals 9 and 10 should cause it to switch automatically to manual mode; at the same time, the event indicator light ALM3 will flash ； ⑤Selection of the actuator’s safe position when the event is in a certain state – this is a function that can be implemented only when a system composed of operators, servo amplifiers, and electric actuators is operating. There is a four-digit toggle switch on the operator control circuit board, preset to the position shown in Figure 3. a indicates that the actuator is in the fully open position when the event is active; in other words, when the event occurs, the actuator automatically moves to the fully open position. b indicates that the actuator is in a closed position when the system is in event mode; that is, when an event occurs, the actuator automatically moves to its fully closed position. c means that the actuator remains in its original position when in the event state; in other words, when the event occurs, the actuator stays where it was. Figure 4: Selection of the actuator’s safe position during event status – This event handling function of the interlock operator enhances the reliability of the system’s safe operation. Can the SFD-3002 and SFD-3003 servo operators be replaced with each other? The SFD-3002 and SFD-3003 type interlock operators were introduced by Shangzhiyi at the beginning of the 2000s. These intelligent servo operators offer performance in terms of intelligence, precision, reliability, and service life that is comparable to that of imported instruments. Their dimensions conform to internationally standard sizes; for example, the interlock operator with model number YR-GFYS835-014-12/12-MMNN-1-N-T can fully replace the SFD-3002, but it cannot replace the SFD-3003 type operator due to differences in their dimensions.