Siemens 6ES7288-3AQ02-0AA0 Analog Output Module – SIMATIC S7-200 SMART

Siemens 6ES7288-3AQ02-0AA0: 2-Channel Analog Output Module for SIMATIC S7-200 SMART Control Systems

The 6ES7288-3AQ02-0AA0 is a dedicated analog output expansion module within the Siemens SIMATIC S7-200 SMART product family. It provides two independently configurable analog output channels capable of driving either voltage loads (±10 V) or current loops (0–20 mA), making it a direct interface between the PLC’s digital control logic and field-level actuators, drives, and process controllers. In closed-loop control architectures, this module occupies the final output stage of the control chain — converting the CPU’s computed setpoint values into calibrated analog signals that govern physical process variables such as flow rate, pressure, temperature, and rotational speed.

Unlike general-purpose I/O modules, the AQ02 is engineered specifically for the S7-200 SMART expansion bus. Its internal DAC (Digital-to-Analog Converter) operates at 12-bit resolution, yielding 4,096 discrete output steps across the full signal range. At ±10 V, this translates to a step size of approximately 4.88 mV; at 0–20 mA, each step represents roughly 4.88 µA. This granularity is sufficient for the majority of industrial proportional control applications, including variable-frequency drive (VFD) speed reference, proportional valve positioning, and analog setpoint transmission to standalone PID controllers.

The module mounts directly to the right side of any S7-200 SMART CPU via the proprietary expansion bus connector, drawing its logic supply from the CPU’s internal 5 V bus while accepting a separate 24 V DC field supply for the output stage. This dual-supply architecture isolates the CPU’s logic domain from field-side transients, a design choice that directly reduces the risk of noise-induced data corruption in the control program.

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Technical Parameters

Hardware Logical Analysis

The internal architecture of the 6ES7288-3AQ02-0AA0 reflects a deliberate separation between the digital control domain and the analog field domain. At the core of each output channel sits a 12-bit R-2R ladder DAC, a resistor-network topology chosen for its inherent monotonicity and low differential nonlinearity (DNL). Unlike sigma-delta converters, the R-2R architecture produces a settled output within microseconds of a new digital word being latched, which is critical in scan-synchronous output update cycles where the CPU writes new values every program scan.

The optocoupler isolation stage between the expansion bus and the DAC input registers serves a dual function. First, it breaks the ground reference continuity between the CPU’s logic ground and the field supply ground, preventing ground loop currents — a common source of signal offset error in 4–20 mA current loops running across long cable runs. Second, it provides a defined isolation barrier that attenuates common-mode transients generated by inductive switching loads such as contactors and solenoid valves sharing the same panel.

The 24 V DC field supply powers the output driver stage directly. In voltage output mode, the driver operates as a low-impedance buffer with an output impedance well below 1 Ω, ensuring that load variations within the specified ≥ 1 kΩ range do not produce measurable output voltage deviation. In current output mode, the driver reconfigures as a voltage-controlled current source (VCCS), maintaining constant current regardless of load resistance variations up to 500 Ω. This compliance range accommodates the full cable and termination resistance budget typical of industrial field wiring.

The module’s EMC design follows IEC 61000-4 series test criteria. The PCB layout routes analog signal traces away from the digital bus interface traces, with guard traces and copper pours providing shielding at the board level. The screw terminal block is mechanically keyed to prevent incorrect reinsertion after field wiring, and the terminal pitch is sized for 0.5–1.5 mm² conductors — the standard wire gauge range for analog signal wiring in industrial control panels.

On power-up or CPU restart, the module initializes all output channels to a defined safe state (0 V / 0 mA) before the CPU program begins executing. This behavior prevents uncontrolled actuator movement during the CPU’s startup sequence, a requirement in safety-aware process control designs.

System Integration Benefits

• Zero-configuration bus enumeration: The S7-200 SMART CPU automatically detects and assigns I/O addresses to the AQ02 module during power-up. No DIP switches, rotary address selectors, or manual address mapping are required, reducing commissioning time and eliminating address conflict errors.
• Scan-synchronous output update: Output values are written to the module’s output image register at the end of each CPU scan cycle, ensuring that analog setpoints are always consistent with the most recently computed control values. There is no asynchronous update latency between the CPU’s output image and the physical terminal voltage or current.
• Software-configurable signal range per channel: Each of the two channels can be independently set to voltage or current mode within STEP 7-Micro/WIN SMART, without any hardware jumper changes. This allows a single module to simultaneously drive a VFD (via 0–10 V) and a proportional valve (via 4–20 mA, scaled in software from the 0–20 mA hardware range).
• Integrated diagnostics via CPU status: The CPU’s system data block (SDB) reflects the module’s presence and communication status. A missing or faulted module is flagged in the CPU’s diagnostic buffer, enabling the user program to implement fault-response logic — such as switching to manual control mode or triggering an alarm output — without external monitoring hardware.
• Deterministic output settling time: The R-2R DAC architecture provides a settling time of less than 1 ms to within 0.1% of final value for a full-scale step change. This is well within the update rate of most industrial control loops (typically 100 ms to 1 s), ensuring that the analog output is never the bandwidth-limiting element in the control chain.
• Compact form factor preserving panel space: At 45 mm wide, the module occupies minimal DIN rail space. A fully expanded S7-200 SMART system with six expansion modules requires less than 360 mm of horizontal rail length for the expansion stack, enabling dense panel layouts in space-constrained enclosures.
• Consistent thermal performance across operating range: The module’s output accuracy specification of ±0.5% full scale is maintained across the 0–55 °C operating temperature range. The internal temperature coefficient of the DAC reference is compensated, so no field recalibration is required as panel temperature varies across seasons or duty cycles.
• Backward compatibility with existing S7-200 SMART programs: The AQ02 module maps to standard analog output addresses (AQW) in the S7-200 SMART memory model. Programs written for earlier S7-200 SMART hardware revisions require no modification to operate with this module, protecting existing software investments during hardware refresh cycles.

Quality Assurance & Global Logistics

Every unit of the 6ES7288-3AQ02-0AA0 supplied by siemensplc.com is a genuine Siemens factory-new module, sourced through verified distribution channels. Each incoming shipment undergoes a structured inspection protocol: label and part number verification against the Siemens product database, hologram and tamper-evident seal check, and a functional power-on test confirming that both analog output channels produce correct voltage and current values across the specified range.

Batch traceability records are maintained for every unit, and certificates of conformity are available upon request for customers with quality management system requirements (ISO 9001, IATF 16949, etc.). The 12-month warranty covers manufacturing defects and covers return or replacement logistics from the date of shipment.

Our logistics operations are based in Xiamen, China, a major port city with direct access to international air freight and sea freight routes. Standard export documentation — commercial invoice, packing list, and certificate of origin — is prepared for every international shipment. Air freight to most destinations in Southeast Asia, the Middle East, Europe, and the Americas is completed within 3–7 business days. For time-critical requirements, same-day dispatch on in-stock orders placed before 14:00 CST is available upon request.

We do not stock refurbished, remarked, or grey-market components. All modules are supplied in original Siemens packaging with intact factory seals. Anti-counterfeit verification support is available for customers who require it.

Contact Information

Email: [email protected]
WhatsApp: +86 18359268345
Web: siemensplc.com
Location: Xiamen, China
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