EL1002 by Beckhoff

The EL1002 is an EtherCAT digital input terminal manufactured by Beckhoff as part of the EL EtherCAT Terminals series. It is used in industrial automation to bring discrete sensor or switch information onto the fieldbus, allowing a controller to monitor on/off states through the process image. The unit accepts 24 V DC signals commonly used by proximity sensors and pushbuttons and presents them to the EtherCAT master without additional gateway hardware. Its compact housing snaps onto a DIN rail alongside other terminals, forming a modular I/O assembly that shares the EtherCAT coupler and supply rails.

The module provides 2 galvanically isolated input channels, each wired through a three-wire connection method so that supply, signal, and reference conductors reach the sensor through the same connector. The permissible field voltage is 24 V DC (-15%/+20%), and each channel draws only 3 mA, minimizing the load placed on connected sensors. Internal comparators recognize 11 to 30 V as a logic-high signal, ensuring reliable detection even when a moderate voltage drop occurs along the cable. Both channels are sampled simultaneously, which maintains deterministic edge capture during periods of high network traffic. This arrangement allows the terminal to monitor two independent field devices while occupying minimal space in the I/O assembly.

Before an event reaches the bus, the circuitry applies a 3 ms input filter that suppresses contact bounce and brief electrical disturbances. The backplane must provide 24 V DC power to the terminal electronics, after which the EtherCAT master receives a process-image entry that is 2 input bits wide and updates during every communication cycle. A falling edge is recognized after the signal drops below the -3 to +5 V low-state threshold, preventing an inactive signal from being interpreted as a high state. The filter timing is suitable for the typical debounce requirements of mechanical limit switches while remaining responsive enough for routine sensor scanning. The process-image format also allows the controller to evaluate each channel independently without additional data conversion.