Siemens 6ES7 521-1BH0-0AA0 Digital Input Module

Siemens 6ES7 521-1BH0-0AA0 Digital Input Module is a 16‑channel digital input interface designed for SIMATIC S7-1500 systems, delivering 16 channels of 24 V DC digital inputs. It is described as a DI 16x24V DC BA module, with 16 inputs in groups of 16 and an IEC 61131 input type 3, making it suitable for standard 24 V DC sensor and switch wiring. The module's timing spec lists a typical input delay of 3.2 ms, useful for timing‑critical control tasks. In Siemens documentation for DI modules, the 6ES7 521 family is presented alongside other DI products as part of SIMATIC S7-1500 digital input modules. This module is commonly used to read the on/off state of 24 V DC sensors, switches, and other digital signals into the PLC, enabling reliable, scalable digital I/O in automation applications.