Product Description:

The KL1904 is an input module manufactured by Beckhoff. It provides four potential-free input channels for acquiring discrete sensor states and forwarding them to a PLC over the system’s K-bus. This arrangement supports condition monitoring and safety interlocking in automated equipment. The signals are handled as on or off states, which makes the terminal suitable for switch-based field devices rather than measured process values.

This module operates from a supply of 24 V DC, allowing direct connection to common control cabinet power rails. Field devices are wired through a 2-wire scheme that simplifies installation and avoids extra supply conductors. The unit has a typical reaction time of 4 ms, so changing input states are passed to the controller quickly. During bus operation, the terminal draws 48 mA of K-bus current, which should be included when sizing a larger terminal assembly. Power contacts embedded in the terminal can carry up to 10 A, allowing auxiliary load current to continue to downstream terminals. Each input also withstands a 500 V DC insulation test voltage, providing separation between field circuits and the internal electronics.

Beckhoff maps the terminal onto TwinSAFE/Safety over EtherCAT, permitting mixed standard and safe signals on the same bus structure. The enclosure measures 12 x 100 x 68 mm, so multiple terminals can be lined up densely on a 35 mm DIN rail inside shallow control enclosures. A polycarbonate housing and an IP20 rating protect internal circuitry from accidental finger contact and typical cabinet dust levels. Sensor leads may extend up to 100 m without violating the stated signal integrity, which helps when switches are mounted away from the control cabinet. Mounting requires only a snap onto the rail, and once the unit is locked in place, the power contact system continues low-voltage distribution through adjacent terminals.