Beckhoff ELX3351 EtherCAT Terminal 1-Channel Intrinsically Safe Analog Input Module

Description

Executing high-precision force and weight measurements within hazardous areas is directly enabled by the Beckhoff ELX3351 EtherCAT Terminal. This intrinsically safe (Ex i) input module is designed for the direct connection of strain gauges and resistor measuring bridges in full-bridge configurations. Featuring high-resolution 24-bit analog-to-digital conversion, it guarantees precise signal acquisition even under demanding industrial conditions. The module integrates self-calibration mechanisms and dynamic filters to compensate for thermal drift and high-frequency mechanical vibration, making it a reliable choice for hazardous-area weighing, load cell monitoring, and process vessels.

Features

• Intrinsically Safe (Ex i) Interface: Direct connection to sensors located in Zone 0/20 and Zone 1/21 environments without requiring external barriers.
• High-Resolution Measurement: 24-bit analog conversion with 32-bit internal presentation for micro-volt level accuracy.
• Resistor Bridge Compatibility: Optimally interfaces with full-bridge strain gauges and resistor bridges ranging from 300 Ohm to 1.5 kOhm.
• Advanced Signal Filtering: Configurable 50 Hz filters and dynamic low-pass options with a typical limit frequency of 3.6 kHz.
• Hardware Self-Calibration: Internal reference pathways run automatic calibration cycles to eliminate measurement errors over time and temperature.

Applications

• Hazardous Weighing Systems: Direct connection to platform scales, vessel weighing systems, and silo level monitors in explosive dust or gas atmospheres.
• Process Industry Automation: Tension, torque, and force measurements in chemical, oil, and gas processing lines.
• Test Bench Engineering: Dynamic load monitoring and strain gauge testing in laboratory environments requiring explosive safety.

Technical Specifications Table

Empirical Engineering Insights

Alternative Models & Compatibility

Unlike the standard EL3351 terminal designed for non-hazardous zones, the ELX3351 is built strictly for Ex i intrinsically safe loops. Standard EL series terminals and ELX series terminals cannot be mixed on the same power segment without proper physical isolation. You must use an ELX9560 or ELX9410 power feed terminal to isolate the intrinsically safe power contacts from the standard EtherCAT terminal block segment to maintain Ex certification validity.

Application Pitfalls & Engineering Notes

When deploying the ELX3351 in high-vibration applications such as mixing vessels or chemical reactors, utilize the built-in dynamic low-pass filters instead of basic averaging. If the self-calibration feature is active, minor fluctuations in loop cycle times may occur during calibration intervals (typically every few minutes). Ensure your TwinCAT control loops allow for these brief, microsecond-level calculation variances, or schedule calibrations during known process idle states.

Commissioning & Wiring Tips

To minimize measurement noise over long cable runs to the strain gauge, utilize shielded twisted-pair cables with the shield connected to the terminal housing's functional ground. Ensure safe separation distances of at least 50 mm between the intrinsically safe wiring connected to the ELX3351 and any non-intrinsically safe cabling in the control panel to comply with IEC 60079-14 standards.

Installation Guidelines