Siemens 6ES7321-1BH02-0AA0 SIMATIC S7-300 SM 321 16DI 24V DC Input Module

Overview

SIEMENS SIMATIC S7-300

6ES7321-1BH02-0AA0 SIMATIC S7-300 SM 321 16DI 24V DC Input Module

An isolated SM 321 module with sixteen 24 V DC inputs, a 20-pin front connector, IEC 61131 Type 1 input characteristics and green channel status indicators.

At a Glance

Brand	Siemens
Model	6ES7321-1BH02-0AA0
Product Type	Digital input signal module
Core Function	Reading field sensor and switch states
Application	Compatible S7-300 signal-module assemblies

One field-input group

The sixteen inputs form one group and are isolated from the backplane.

Fixed input delay

Both signal transitions have a 1.2–4.8 ms delay range.

Local status display

Green LEDs show channel states without module diagnostic or interrupt functions.

Product Overview

6ES7321-1BH02-0AA0 provides sixteen 24 V DC input channels for a compatible S7-300 assembly, with optocoupler separation between the input group and the backplane bus.

The module uses a 20-pin front connector and IEC 61131 Type 1 input characteristics, with fixed input delays and green input status indication.

Ordering focus: Match the 24 V DC signal levels, 20-pin wiring connector and single-group isolation arrangement, and keep two-wire sensor quiescent current within its limit.

Key Functions

Read the sixteen field signals

The inputs recognize the specified DC signal-0 and signal-1 voltage ranges, with a typical signal-1 current of 7 mA.

Separate the field group from the backplane

The sixteen-channel field group is optically isolated from the backplane, while its channels are not isolated from one another.

Display input state directly

Green channel indicators show the input state, while this variant does not generate diagnostic alarms or hardware interrupts.

Official Specifications

Input Channel Count	16
Rated Supply and Range	24 V DC; permissible L+ range 20.4–28.8 V DC
Input Characteristic	IEC 61131 Type 1
Signal-0 Input Voltage	−30 to +5 V
Signal-1 Input Voltage	13–30 V
Typical Signal-1 Input Current	7 mA
Input Delay in Both Directions	1.2–4.8 ms; not parameterizable
Two-Wire Sensor Quiescent Current	Maximum 1.5 mA
Backplane Current Consumption	Maximum 10 mA from 5 V DC
Typical Power Loss	3.5 W
Field Isolation Arrangement	One group of 16 inputs; no channel-to-channel separation
Backplane Isolation and Test	Optocoupler separation; insulation tested at 500 V DC
Front-Connector Requirement	20-pin
Channel Status Indication	Green input-status LEDs
Maximum Cable Length	1000 m shielded; 600 m unshielded
Dimensions (Width × Height × Depth)	40 × 125 × 120 mm
Approximate Weight	200 g

Official source:Siemens SM 321 Data Sheet

Frequently Asked Questions

Can I use a two-wire sensor with 6ES7321-1BH02-0AA0?

Two-wire sensors are supported when their quiescent current does not exceed 1.5 mA.

Which front connector is required for 6ES7321-1BH02-0AA0?

The module requires a compatible 20-pin front connector.

Can I configure a shorter input delay on 6ES7321-1BH02-0AA0?

The 1.2–4.8 ms input delay is fixed and cannot be parameterized.

Will 6ES7321-1BH02-0AA0 generate a hardware interrupt when an input changes?

This module does not provide hardware interrupts or diagnostic alarms.

Can I put electrically independent field potentials on separate channels of 6ES7321-1BH02-0AA0?

The sixteen inputs form one group without channel-to-channel isolation.

What voltage should I provide for a clear signal 1 on 6ES7321-1BH02-0AA0?

The specified signal-1 input range is 13–30 V DC.

Can I keep all sixteen channels active on 6ES7321-1BH02-0AA0 at the mounting-temperature limit?

All sixteen inputs may be active up to 60 °C horizontally or 40 °C vertically.

Compatibility & Ordering Notes

Before ordering 6ES7321-1BH02-0AA0: Select the SM 321 24 V DC input variant with the correct 20-pin front connector and match the sensor leakage, signal voltage and isolation requirements to the field circuit.

Compatibility Checklist for 6ES7321-1BH02-0AA0

• Use a compatible S7-300 signal-module assembly and 20-pin front connector.
• Keep the input supply and signal levels within the specified DC ranges.
• Limit any two-wire sensor quiescent current to 1.5 mA.
• Treat all sixteen field inputs as one common group rather than separately isolated channels.
• Account for the fixed 1.2–4.8 ms delay in the required signal timing.
• Use the mounting-temperature limits for simultaneous input operation and keep cables within the specified length.

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