BECKHOFF EL31xx Series 16 Bit EtherCAT Analog Input Terminal Manual

BECKHOFF EL31xx High speed Analog Input Terminal: On site Diagnosis, Troubleshooting, and Maintenance Guide

The Beckhoff EL31xx series EtherCAT analog input terminal is a high-speed 16 bit acquisition module designed for high-performance measurement applications. Compared to the EL30xx series, its conversion time is significantly reduced (up to about 35 µ s), it supports distributed clock (DC) synchronization, and offers differential or single ended input options. The product covers multiple signal types such as ± 10   V, 0... 20   mA, 4... 20   mA, including EL310x, EL311x, EL312x, EL314x, EL315x, EL316x, and configurable EL3174 sub models.

When on-site engineers use these terminals, they may encounter issues such as measurement value jumps, over range alarms, disconnection indications, terminals unable to enter the OP state, or synchronization errors. This document aims to provide a comprehensive hardware diagnostic and parameter configuration guide for the EL31xx series, based entirely on official technical documentation, focusing on practical operational scenarios, covering the entire process from installation and wiring, LED status interpretation, process data analysis to filter settings and factory reset.

1. Overview of Product Series and Key Selection Points

EL31xx terminals are classified into the following main categories based on signal type and input structure:

Model Series Signal Range Input Type Typical Model

EL310x -10...+10   V differential EL3101/2/4

EL311x 0... 20 mA differential EL3111/2/4; EL3112-0011 is ± 20 mA

EL312x 4... 20mA differential EL3121/2/4; EL3124-0090 with TwinSAFE SC

EL314x 0... 20   mA single ended EL3141/2/4; EL3142-0010 is ± 10 mA

EL315x 4... 20   mA single ended EL3151/2/4

EL316x 0... 10   V single ended EL3161/2/4

EL3174-10/0...+10   V/-20/0/+4...+20   mA configurable (U/I) EL3174-0002 (differential isolation), EL3174‑0090（TwinSAFE SC）

Key differences in selection:

Differential input (EL310x/311x/312x): Each channel has independent signal pairs (+/-), strong resistance to common mode interference, and supports long-distance transmission. Common mode voltage (Ucm) limit: EL310x is ± 35   V (for internal GND), EL311x/EL312x is ± 10   V.

Single ended input (EL314x/315x/316x): The signal reference ground is either the 0   V power contact or the internal GND. The wiring is simple and suitable for situations where the sensor and terminal ground potential are consistent. Some models (such as EL3154) provide 24V output to power two-wire sensors.

EL3174 series: Each channel can be independently configured with voltage or current mode. EL3174-0002/0032 adopts differential input and electrical isolation between channels (test voltage 2500   VDC), while EL3174-0090 supports safe single channel (TwinSAFE SC).

2. Key points for installation and wiring

2.1 Mechanical Installation and ESD Protection

The terminal is installed vertically on a 35 mm DIN rail, with at least 30 mm ventilation gap reserved above and below.

EL9011/EL9012 end caps must be used to seal the ends to ensure protection level and ESD protection.

ESD sensitivity: Avoid direct contact with spring contacts; Workbenches, packaging, and personnel should be grounded.

2.2 Power contacts and E-bus power supply

The E-bus (5   V) is provided by the left coupler, and the total current should not exceed 2   A. When exceeding the limit, the EL9410 and other power supply input terminals need to be inserted.

The power contacts transmit 24V on-site power supply, but some terminals' input reference ground is not connected to the power contacts (such as EL3101/3102, EL3111/3112, etc.), which requires special attention.

The PE contact (protective grounding) is the first to connect and can carry a short-circuit current of 125 amperes. During insulation testing, the PE connection should be disconnected.

2.3 Common mode voltage processing for differential current input (0/4... 20 mA)

For differential current inputs such as EL311x/EL312x, internal measurement is carried out through a 33 Ω shunt resistor, and the potential difference (Ucm) between the midpoint of the resistor (CMP) and the internal GND (GND_int) must not exceed the specification (usually ± 10   V). The 1/2 channel terminal leads GND_int to the terminal point and can be externally wired to stabilize the common mode potential.

Correct wiring example: Both sensors use low side measurement (negative terminal connected to GND) - CMP potential is about 0.33   V, Ucm<0.5   V, which meets the requirements.

Example of incorrect wiring: A low side measurement (5   V) and a high side measurement (12   V) - the potential difference between the two CMP channels is greater than 10   V, resulting in measurement errors. At this point, GND_int should be connected to an auxiliary potential (such as 6V) to center CMP.

4-channel terminals (EL3114/EL3124): GND_int is internally connected to the 0   V power supply contact, and it must be ensured that the common mode potential of all channels meets Ucm, Max.

2.4 Shielded Connection

Analog sensors and encoders must use shielded twisted pair cables. The shielding layer should be single ended grounded through terminal point 4 or 8 (Shield) to avoid mixing with GND_int.