Beckhoff EL1819 vs KL1819: Which Digital Input Terminal Fits Your System?

The Beckhoff EL1819 and KL1819 look similar on a parts list. Both are compact, high-density terminals with 16 digital inputs for 24 V DC control signals, LED channel indication and one-wire connection technology. Their model numbers differ by only one letter. That similarity can make purchasing a replacement seem straightforward.

The important difference is the I/O platform. The EL1819 is an EtherCAT Terminal that communicates through the E-bus, while the KL1819 is a Bus Terminal that communicates through the K-bus. Their input filters also operate at different speeds. These distinctions affect which coupler or controller can use the terminal and whether the input response fits the application.

This guide compares the published specifications for the Beckhoff EL1819 and KL1819 and provides a practical verification checklist for maintenance, engineering and purchasing teams. It is not a substitute for reviewing the machine documentation and the current Beckhoff manuals before installation.

EL1819 vs KL1819 at a glance

Specifications above are summarized from the current Beckhoff product pages for the EL1819 EtherCAT Terminal and KL1819 Bus Terminal. Always use the exact manual revision and approvals applicable to the terminal being installed.

The main difference: EtherCAT E-bus or K-bus

The first purchasing question should not be “Which model is newer?” It should be “Which terminal system is already installed?” The EL prefix identifies the EtherCAT Terminal family. The KL prefix identifies the Bus Terminal family. Each terminal depends on the compatible bus coupler, controller and terminal assembly that surrounds it.

Because the EL1819 and KL1819 share a compact housing and similar field-side input characteristics, a technician can reasonably mistake one for the other when reading a faded label or copying a handwritten bill of materials. Physical similarity does not establish system compatibility. A replacement order should preserve the full manufacturer part number, including the EL or KL prefix.

Before ordering, inspect the adjacent coupler or controller and record its full model number. Then confirm whether the rack is an EtherCAT Terminal assembly or a Bus Terminal assembly. A photograph of the complete terminal station is often more useful than a close-up of only the suspect module. Enicstra’s Beckhoff product catalog can help buyers browse related parts, but the installed system documentation remains the authority for compatibility.

Input-filter speed: 10 µs versus 0.2 ms

Beckhoff specifies a typical 10 µs input filter for the EL1819 and a typical 0.2 ms input filter for the KL1819. Converting both values to the same unit makes the comparison clearer: 0.2 ms equals 200 µs. The EL1819’s published input filter is therefore 20 times shorter than the KL1819’s.

That comparison describes the terminal’s input filter, not the total response time of the machine. End-to-end behavior also depends on the sensor, network cycle, controller task, program logic and output hardware. A faster input filter can be useful when capturing short transitions, but it can also make the system more responsive to brief electrical events. Engineers should select the filter behavior required by the application rather than treating the smallest number as automatically better.

For ordinary maintained-state signals such as limit switches, basic proximity sensors or interlocks, both filters may be fast relative to the mechanical process. For short pulses or high-speed edge detection, the 10 µs EL1819 specification may become an important design constraint. Confirm the minimum pulse duration and complete signal chain before making a substitution.

What the two terminals have in common

Sixteen 24 V DC inputs in a narrow housing

Both models provide 16 digital inputs in a 12 mm-wide terminal housing. This high channel density is useful where control-cabinet space is limited. Beckhoff lists EN 61131-2 type 1/3 input behavior, a nominal voltage of 24 V DC with a -15%/+20% range, and a typical input current of 3 mA for each model.

One-wire field connection

The EL1819 and KL1819 use one-wire connection technology. The common reference for the inputs is the 0 V power contact. This arrangement supports a dense terminal layout, but it also means the surrounding power-contact arrangement and sensor wiring must be checked carefully. Do not assume that an existing multi-wire sensor circuit can be transferred without reviewing its schematic.

Direct plug-in wiring and status indication

Beckhoff describes direct plug-in connection for solid conductors and spring actuation for fine-stranded conductors and ferrules. Each channel has a signal-status LED. Those similarities can simplify cabinet service because technicians encounter a familiar connection approach, but they do not remove the need to verify conductor size, strip length and terminal assignment against the applicable manual.

Can an EL1819 replace a KL1819?

Not as a simple one-for-one terminal swap. The EL1819 and KL1819 belong to different bus families. Even when the field signals and cabinet dimensions appear compatible, the host bus, coupler and configuration environment must match the selected terminal family.

A migration from a K-bus station to an EtherCAT station can be a legitimate engineering project, but it is broader than replacing one failed input terminal. It may require changes to the coupler or controller, network design, I/O mapping, software configuration, validation and documentation. Treat that work as a controlled system modification.

If the goal is to restore an existing machine with minimal change, match the complete installed part number first. Buyers looking specifically for the K-bus version can review the Beckhoff KL1819 product page. For a broader view of modular industrial I/O, browse Enicstra’s controllers and I/O systems category.

Replacement checklist for maintenance and purchasing teams

1. Record the complete part number. Confirm EL1819 or KL1819 from the side label, front marking, machine bill of materials or electrical drawing.
2. Identify the terminal system. Record the adjacent coupler or controller and determine whether the station uses EtherCAT E-bus or K-bus.
3. Document the field circuit. Confirm 24 V DC signals, common reference, sensor type and the one-wire connection arrangement.
4. Check response requirements. Determine whether the application depends on short pulses or fast edges that make the 10 µs versus 0.2 ms filter difference relevant.
5. Review power and current budgets. Use the terminal-station design tools and current Beckhoff documentation to check internal-bus and power-contact loading.
6. Verify environmental requirements. Confirm operating temperature, enclosure protection, approvals and any hazardous-location requirements for the actual installation.
7. Capture configuration evidence. Save I/O mapping, controller project backups and photographs before removing hardware.
8. Validate after installation. Test every input channel, diagnostic indication, machine interlock and relevant safety or process function under the site’s approved commissioning procedure.

How to request the correct Beckhoff terminal

Provide the manufacturer, exact part number, quantity and required condition. Include the coupler or controller model when there is any uncertainty between EL and KL terminal families. For obsolete or difficult-to-source assemblies, photographs of the label and complete terminal station can help prevent a near-match from being quoted as an equivalent.

Enicstra supports industrial teams sourcing current, surplus and hard-to-find automation components. If the exact terminal is not listed, request a quote with the full Beckhoff part number and installation details. For additional system context, see our guide to integrating Beckhoff automation components.

Frequently asked questions

What is the difference between Beckhoff EL1819 and KL1819?

The EL1819 is an EtherCAT Terminal using the E-bus, while the KL1819 is a Bus Terminal using the K-bus. The EL1819 has a typical 10 µs input filter; the KL1819 has a typical 0.2 ms input filter. Both provide 16 digital inputs for 24 V DC signals.

Are the EL1819 and KL1819 physically the same size?

Beckhoff publishes dimensions of 12 x 100 x 68 mm for both models. Matching dimensions do not make the terminals electrically or system-compatible, because they belong to different bus families.

Does the EL1819 require configuration?

Beckhoff lists no address or configuration setting for the terminal itself. The EtherCAT station and controller project still need the correct hardware configuration and I/O mapping.

Which information should I send when requesting a replacement?

Send the complete model number, quantity, condition requirement, coupler or controller model, and clear photographs of the label and terminal station. Include any application requirement related to short pulses, approvals or environmental conditions.