BECKHOFF KS4021 Bus Terminal 1-Channel Analog Output 4-20 mA

Product Overview

The KS4021 (KS4021) Bus Terminal processes analog control signals in the range between 4 and 20 mA with a 12-bit resolution. Designed for harsh industrial environments such as chemical processing, water treatment plants, and power generation facilities, this single-ended analog output module transmits signals with galvanic isolation to the actuator level. Its compact, high-efficiency design directly addresses industrial downtime risks by utilizing pluggable wiring levels, which allow for rapid field replacement without disconnecting individual terminal wires. Operating on the proven Beckhoff K-bus system, the module ensures reliable, real-time data communication back to the central PLC or IPC controller.

Technical Configuration

The KS4021 features a single-ended circuit topology, optimizing it for space-constrained control cabinets where individual channel routing is required. It receives power directly from the 24 VDC power contacts, though it supports an alternative 15 VDC supply via a KL9515 power supply terminal to accommodate specialized system architectures.

The process image utilizes 1 x 16-bit data, with an optional 1 x 8-bit control and status byte for advanced diagnostics. It requires zero hardware configuration or address settings, enabling pure plug-and-play integration into the TwinCAT engineering environment. The terminal housing features a double slot and key connection system for robust side-by-side DIN rail mounting.

Technical Specifications

Product FAQs

What is the practical difference between the KS4021 and the KL4021?

The primary difference lies in the housing design. The KS4021 features a pluggable wiring level, allowing the entire terminal block electronics to be swapped out while leaving the field wiring intact. The KL4021 uses fixed wiring terminals where cables must be individually disconnected during service.

How does the module handle output errors if the load resistance exceeds 500 Ohm?

If the total loop resistance exceeds 500 Ohm, the internal digital-to-analog converter will saturate. This prevents the module from driving the full 20 mA current, resulting in an inaccurate output signal and triggering an error status bit in the PLC process image.

Does this terminal require manual configuration in TwinCAT?

No manual address or parameter configuration is required on the hardware itself. The K-bus automatically detects the module type and position upon system startup, mapping the 16-bit output data directly into the controller configuration.

Field Installation and Wiring Instructions

• Pluggable Terminal Block Operation: To release or insert individual wires, use a standard slot screwdriver to actuate the integrated tension clamp mechanism. Strip all signal wires to exactly 9 to 10 mm. Ensure the connection cross-section matches the specification (AWG 28 to 16 for solid or stranded wires).

• Shielding and Noise Mitigation: For industrial environments with high electromagnetic interference (EMI), always use shielded twisted-pair cables for the 4 to 20 mA loop. Ground the cable shield at only one end—ideally at the entry point of the control cabinet—to prevent ground loops.

• ATEX Zone 2 Safety Mandates: When installing the module in hazardous areas marked II 3 G Ex nA IIC T4 Gc, the terminal must be mounted inside an IP54 rated enclosure conforming to EN 60079-15. Do not disconnect or insert the pluggable wiring levers while the system is energized.