Siemens 6ES7421-1FH20-0AA0

Technical specifications

Manufacturer

Siemens

Manufacturer part no.

6ES7421-1FH20-0AA0

Type

Digital input module

Application

Digital input module

Used with

SIMATIC S7-400 rack

Input current / from backplane bus 5 V DC, max.

80 mA

Power loss, typ.

12 W

Number of digital inputs

16

Digital inputs / Input characteristic according to IEC 61131

Type 2

Number of simultaneously controllable inputs / Number of simultaneously controllable inputs

16

Input voltage / Type of input voltage

AC/DC

Input voltage / Rated value (UC)

230 V; 120/230 V UC (47 ... 63 Hz)

Input voltage / for signal "0"

0 to 40 V AC/ -40 to +40 V DC

Input voltage / for signal "1"

74 to 264 V AC; 80 to 264 V DC, -80 to -264 V

Input current / for signal "0", min.

0 mA; AC: 0 mA; DC: 0 mA

Input current / for signal "0", max. (permissible quiescent current)

6 mA; AC: 6 mA; DC: 2 mA

Input current / for signal "1", typ.

10 mA; at 120 V: 10 mA AC, 1.8 mA DC; at 230 V: 14 mA AC, 2 mA DC

Input delay (for rated value of input voltage) / for standard inputs / at "0" to "1", max.

20 ms; AC: 20 ms; DC: 15 ms

Input delay (for rated value of input voltage) / for standard inputs / at "1" to "0", max.

30 ms; AC: 30 ms; DC: 25 ms

Cable length / shielded, max.

1 000 m

Cable length / unshielded, max.

600 m

Connectable encoders / 2-wire sensor

Yes

Connectable encoders / 2-wire sensor / permissible quiescent current (2-wire sensor), max.

5 mA; AC: 5 mA

Interrupts/diagnostics/status information / Diagnostics function

No

Diagnostics indication LED / Status indicator digital input (green)

Yes

Potential separation digital inputs / between the channels

Yes

Potential separation digital inputs / between the channels, in groups of

4

Potential separation digital inputs / between the channels and backplane bus

Yes

Isolation tested with

1 500 V AC

Width

25 mm

Technical documents (1)

• Siemens data sheet 6ES7421-1FH20-0AA0

Key features

• 16 digital inputs, 120/230 V AC (47 to 63 Hz) or DC
• Signal "1" at 74 to 264 V AC or 80 to 264 V DC
• Isolated in groups of 4
• IEC 61131 type 2 inputs
• Discontinued by Siemens on 1 October 2026

About the Siemens 6ES7421-1FH20-0AA0

The Siemens 6ES7421-1FH20-0AA0 is the 120/230 V SM 421 with 16 inputs in groups of 4; the 6ES7421-1EL00-0AA0 has 32 inputs for 120 V only. Siemens's data sheet gives signal "1" at 74 to 264 V AC or 80 to 264 V DC, IEC 61131 type 2 inputs, an input delay from 0 to 1 of up to 20 ms on AC and 15 ms on DC, and 12 W typical power loss. SiePortal shows its phase-out announced on 1 October 2025 and its product cancellation on 1 October 2026.

What is the 6ES7421-1FH20-0AA0 used for?

It reads mains-voltage signals at 120 or 230 V into an S7-400 CPU.

Lifecycle and successor

Discontinued.

Before you order

What to photograph or confirm so the right unit is quoted.

Check the order number and the input voltage on the module: 1FH20 takes 120/230 V, 1EL00 takes 120 V.