Siemens 6ES7221-3BD30-0XB0 SIMATIC S7-1200 SB 1221 4DI 24VDC 200kHz Digital Input Signal Board

The Siemens 6ES7221-3BD30-0XB0 SIMATIC S7-1200 SB 1221 signal board adds 4 current-sourcing digital inputs at 24 V DC to a compact CPU, with a 200 kHz high-speed counting input option. It draws 40 mA from the backplane bus, dissipates 1 W, and mounts directly onto the CPU front without extra rack space.

Technical Specifications

Certifications & Standards

• CE
• CSA
• UL
• cULus
• FM
• RCM
• KC
• Marine

Selection Notes

This SB 1221 variant provides 4 current-sourcing inputs at up to 200 kHz; a higher-channel-count sibling in the same signal board family instead offers 8 inputs at 100 kHz. Choose this 4-channel 200 kHz version when the application needs faster edge detection on fewer points, such as a quadrature encoder input, and the 8-channel version when more digital sensing points matter more than raw counting speed. The 50 m shielded cable length limit is notably shorter than the 500 m rating on standard S7-1200 digital input modules, reflecting the higher 200 kHz bandwidth this board is built for.

Applications

Fits high-speed counting tasks directly on an S7-1200 CPU without a rack slot: quadrature encoder feedback, fast proximity sensor pulses, and flow-meter counting up to 200 kHz per channel.