Beckhoff Automation I/O Terminals have digital multimeter function

Cost-effective and flexible Beckhoff Automation EL3681 and KL3681 terminals replace stand-alone digital multimeters and are compatible with most fieldbuses.


Beckhoff Automation I/O Terminals have a digital multimeter inside.Adding more measurement functions I/O terminals, Beckhoff Automation released the new EL3681 and KL3681 I/O terminals. By integrating digital multimeters into I/O nodes, users can expect a streamlined and low cost alternative to stand-alone digital multimeters, the company says. The modules provide high precision and simple, high-resistance measurement from 300 mV to 300 V and cost $305 (U.S. list) each, the company said in a June 15, 2010 announcement.

Using the digital multimeter terminals with fieldbus interface for measuring current and voltage, measured values can be processed in the I/O system or by the master controller. These dynamic measuring terminals are available for the Beckhoff Bus Terminal system, which offers support for most major fieldbuses as well as for the high performance EtherCAT Terminal system, the company said.

Equipping industrial systems with the Beckhoff KL3681 (Bus Terminal) and EL3681 (EtherCAT Terminal) significantly increases flexibility thanks to the wide input range and automated measuring range selection.

In measuring applications, the expected voltage is often not known during the planning phase. Automatic adjustment of the measurement range simplifies use and reduces stock levels. Beckhoff’s digital multimeter terminals measure dc and ac voltages; in the case of ac voltage, the effective (RMS) value is determined.

Very high immunity to interference is achieved via the complete galvanic isolation of the electronic measuring system and a measurement interval of typically 200 ms. The measured result is equivalent to that of a good hand-held multimeter, but the I/O terminals also have an interface to most major fieldbuses via which it can be read out and parameterized, the company said.

Measurement ranges are:

  • Voltage: 300 mV to 300 V dc, 100 mV to 300 V ac; and
  • Current: 100 mA, 1 A, 10 A ac/dc.

In applications that utilize a powerful CPU, ultra fast communication (such as via EtherCAT), real-time software and an I/O interface to the outside world, Beckhoff PC-based control technology represents the ideal system for high-precision, high-speed measuring equipment, the company says.

EtherCAT is a registered trademark of Beckhoff Automation GmbH. Beckhoff Automation provides advanced, open automation products based upon proven technologies so that customers can implement high performance control systems faster and at a lower overall cost than traditional PLC and motion control systems. Beckhoff’s “New Automation Technology” product range includes PC based control, industrial PCs, automation controllers, operator interface, I/O, servo drives and motors. With representation in more than 60 countries, Beckhoff is well positioned to provide global sales and service to its customers. Sales and service are handled by the company, without intermediaries, to provide faster response and improved communications.

Beckhoff Automation LLC is located in Burnsville, MN, near Minneapolis.

See research and more I/O products in the February 2010 feature article, “I/O Modules: Product research and advice from Control Engineering subscribers.”

Also see the System Integration channel at

- Edited by Mark T. Hoske, Control Engineering content strategist,

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