Siemens SM 321 (6ES7 321-1BH02-0AA0) – SIMATIC S7-300 Digital Input Module (16 DI)

Siemens SM 321 (6ES7 321-1BH02-0AA0) – SIMATIC S7-300 Digital Input Module (16 DI)

The Siemens SM 321 (Part No. 6ES7 321-1BH02-0AA0) is a fundamental Digital Input Module for the modular SIMATIC S7-300 and ET 200M PLC systems. This module provides 16 separate 24 V DC inputs, enabling the PLC to process signals from field devices like switches and proximity sensors. Its robust, electrically isolated design ensures reliable and safe connection of industrial sensors in various control applications.

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Quick Navigation

• About This Digital Input Module
• Applications
• Why ROMA Industrial Company
• Technical Specifications
• Key Features & Benefits

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About This Digital Input Module

This product is a Digital Input Module, often referred to as a **PLC Input Card** or **SM 321**, which serves as the interface between field sensors and the central processing unit of the PLC. The module connects up to 16 field devices operating on a 24 V DC signal, meeting the Type 1 input characteristics according to IEC 61131. Key features include **electrical isolation** between the inputs and the PLC backplane, which protects the sensitive electronics of the PLC from electrical noise or voltage spikes from the field. It is a vital component for monitoring binary states in industrial automation.

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Applications

This digital input module is suitable for reading the ON/OFF status of devices in various industrial control systems, including:

• Machine Tool Position Sensing (using Proximity Sensors)
• Safety Interlocks and Limit Switches
• Control Panel Pushbuttons and Selector Switches
• General Binary Signal Monitoring in Manufacturing

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Why ROMA Industrial Company

ROMA Industrial is your trusted partner for a full range of industrial supplies across categories like Motion Control & Mechatronics, Electrical & Automation, and Fluid Power & Control. We are committed to providing top-tier products and service to keep your operations running smoothly. We partner with world-class shipping providers like FedEx, DHL, and UPS to ensure fast and reliable delivery worldwide. We accept returns to fulfill your satisfaction and accept variable payments methods including PayPal, credit cards, and more. We are a supplier in Europe, USA, and Saudi Arabia.

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Technical Specifications

• Manufacturer: Siemens
• Part Number: 6ES7 321-1BH02-0AA0
• Model Number: SM 321
• Product Type: Digital Input Module
• Number of Inputs: 16 Digital Inputs
• Input Voltage: 24 V DC
• Input Characteristics: Type 1 (according to IEC 61131)
• Input Delay: 1.2 ms to 4.8 ms
• Isolation: Electrically Isolated (in a single group of 16)
• Series: SIMATIC S7-300 / ET 200M
• Power Loss (Typ.): 3.5 W
• Hazardous Location: Approved for Class I, Div 2 and Zone 2
• Weight: N/A

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Key Features & Benefits

• Channel Density: Provides 16 digital inputs in a compact module, optimizing PLC rack space.
• Electrical Isolation: Isolation ensures the protection of the PLC’s backplane from field disturbances.
• Standard Compliance: Meets Type 1 input characteristics (IEC 61131) for reliable sensor interfacing.
• Industrial Ready: Approved for Class I, Div 2 hazardous locations, ensuring safe use in demanding environments.