What it is and what it handles
The Siemens 6ES7138-4DK00-0AB0 is an ET 200SP technology module that interfaces an SSI absolute encoder and outputs a speed setpoint as an analog voltage. It packs three digital inputs, one digital output, and one analog output into a 30 mm wide slice, with a depth of 52 mm so it sits flush in the standard ET 200SP carrier.
Input signals and timing
The module accepts 0 to 10 V and –10 to +10 V analog inputs, plus RS-422 for the encoder. Input threshold for signal '1' is L+ (–1 V) with a typical 9 mA draw, so it works with standard 24 V sensor supplies. Latch time is 400 µs plus the age of the encoder value, giving a predictable capture delay for position detection. Transition times from 0 to 1 are max 1.3 ms (typical 150 µs), and 1 to 0 is max 200 µs. Shielded cable max 1 000 m; unshielded max 600 m. At higher frequencies: 320 m at 125 kHz, 8 m at 2 MHz.