M-3120 Beckhoff
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The Beckhoff M-3120 is a parallel IO module from the M Parallel IO Modules series with a compact aluminum housing and a weight of 600 grams. It features four encoder channels with 24-bit counter width and supports a data interface through II/O-Lightbus. The module has a supply voltage of 24 V DC and a transmission rate of 2.5 MBaud.
Internal Product Review
The M-3120 is a Beckhoff parallel I/O module built in a compact aluminum housing. Support for 4 encoder channels and a 24-bit counter width gives the module strong position-feedback capability for motion and counting tasks. The II/O-Lightbus interface with 25 µs/32 bit transfer time makes the M-3120 a fast, well-engineered choice for responsive control systems.
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Product Description:
The M-3120 incremental encoder interface module belongs to the M Parallel IO Modules series from Beckhoff. Designed for distributed industrial automation, the unit links quadrature encoders to a field controller over Beckhoff’s II/O-Lightbus backplane. By translating position counts into bus data, it enables high-resolution motion tracking within machines that require synchronized axis reporting. It serves as a dedicated parallel input node with latch functions and counter logic located close to the sensor, allowing host processors to retrieve prepared position words with minimal latency. This arrangement reduces the amount of encoder processing that must occur in the central controller while preserving timely position updates for coordinated machine functions.
The module operates from 24 V DC logic power and draws only 0.1 A, so several units can share the same auxiliary supply. Its Lightbus port transfers a double-word image at a rate of 25 µs per 32 bits, while the serial layer sustains a throughput of 2.5 Mbaud. Internally, the counter logic stores incremental values in a 24-bit register and uses a matching 24-bit zero latch, allowing continuous counting while a synchronous snapshot is captured for reference. The zero-latch function preserves the sampled position without interrupting the ongoing count, which supports repeatable reference detection during machine movement. The printed circuit assembly is secured inside a compact aluminum housing that measures 68 mm deep, 76 mm high, and 170 mm wide, providing electromagnetic shielding without consuming excessive panel space.
Up to four incremental encoders can be attached through a single 15-pin D-sub female connector, and each channel supports 1x, 2x, or 4x evaluation to suit the required resolution. Higher evaluation modes count additional signal edges from the quadrature inputs, increasing the number of measurable position increments for each encoder cycle. The front connector also routes sensor power, and the module supplies a maximum of 1 A at 24 V to the connected encoders, eliminating the need for separate power wiring. The enclosure weighs 600 g, keeping the load on the DIN rail modest. Encoder activity LEDs are controlled by the II/O-Lightbus microcontroller, allowing channel activity to be checked directly at the module. The connector arrangement consolidates encoder signals and sensor power at the front of the housing, helping keep cabinet wiring organized and accessible.
