| ***Spare part*** SIMATIC S7-1200, Digital input SM 1221, 8 DI, 24 V DC, Sink/Source |
| Supply voltage |
| Rated value (DC) | 24 V |
| permissible range, lower limit (DC) | 20.4 V |
| permissible range, upper limit (DC) | 28.8 V |
| Input current |
| from backplane bus 5 V DC, max. | 105 mA |
| Digital inputs |
| from load voltage L+ (without load), max. | 4 mA; per channel |
| Output voltage |
| Power supply to the transmitters |
| present | Yes |
| Power loss |
| Power loss, typ. | 1.5 W |
| Digital inputs |
| Number of digital inputs | 8 |
| in groups of | 2 |
| Input characteristic curve in accordance with IEC 61131, type 1 | Yes |
| Number of simultaneously controllable inputs |
| all mounting positions |
| — up to 40 °C, max. | 8 |
| horizontal installation |
| — up to 40 °C, max. | 8 |
| — up to 50 °C, max. | 8 |
| vertical installation |
| — up to 40 °C, max. | 8 |
| Input voltage |
| Rated value (DC) | 24 V |
| for signal "0" | 5 V DC at 1 mA |
| for signal "1" | 15 V DC at 2.5 mA |
| Input current |
| for signal "0", max. (permissible quiescent current) | 1 mA |
| for signal "1", min. | 2.5 mA |
| for signal "1", typ. | 4 mA |
| Input delay (for rated value of input voltage) |
| for standard inputs |
| — parameterizable | Yes; 0.2 ms, 0.4 ms, 0.8 ms, 1.6 ms, 3.2 ms, 6.4 ms and 12.8 ms, selectable in groups of four |
| for interrupt inputs |
| — parameterizable | Yes |
| Cable length |
| shielded, max. | 500 m |
| unshielded, max. | 300 m |
| Interrupts/diagnostics/status information |
| Diagnostics function | Yes |
| Alarms |
| Diagnostic alarm | Yes |
| Diagnostics indication LED |
| for status of the inputs | Yes |
| for maintenance | Yes |
| Potential separation |
| Potential separation digital inputs |
| between the channels, in groups of | 2 |
| Degree and class of protection |
| IP degree of protection | IP20 |
| Standards, approvals, certificates |
| CE mark | Yes |
| FM approval | Yes |
| RCM (formerly C-TICK) | Yes |
| Ambient conditions |
| Free fall |
| Fall height, max. | 0.3 m; five times, in product package |
| Ambient temperature during operation |
| min. | 0 °C |
| max. | 55 °C |
| horizontal installation, min. | 0 °C |
| horizontal installation, max. | 55 °C |
| vertical installation, min. | 0 °C |
| vertical installation, max. | 45 °C |
| permissible temperature change | 5°C to 55°C, 3°C / minute |
| Ambient temperature during storage/transportation |
| min. | -40 °C |
| max. | 70 °C |
| Air pressure acc. to IEC 60068-2-13 |
| Storage/transport, min. | 660 hPa |
| Storage/transport, max. | 1 080 hPa |
| Relative humidity |
| Operation at 25 ℃ without condensation, max. | 95 % |
| Connection method |
| required front connector | Yes |
| Mechanics/material |
| Enclosure material (front) | |
| Plastic | Yes |
| Dimensions |
| Width | 45 mm |
| Height | 100 mm |
| Depth | 75 mm |
| Weights |
| Weight, approx. | 170 g |
| last modified: | 03/13/2019 |
