Product basic information

Product model: 6ES7421-7DH00-0AB0

Belonging to the Siemens SIMATIC S7-400 series, which is a digital input module (SM 421)

Core positioning: A 16 channel digital input module with isolation function, supporting alarm and diagnostic functions, suitable for digital signal acquisition in industrial automation systems. The document version was last modified on June 7, 2025, and there may be further adjustments to the content.

Core electrical and input specifications

（1） Power supply and power consumption

Parameter category details

The backplane bus current is obtained from the backplane bus with a 5V DC power supply and a maximum current of 150mA

Typical power loss value of 8W; voltage division scenario: 3.5W at 24V DC, 6.5W at 48V DC, 8.0W at 60V DC

（2） Digital input characteristics

Specific specifications of input parameters

Number of channels: 16 digital input channels, supporting simultaneous control of 16 channels

Input voltage type AC/DC universal (AC/DC), rated voltage UC is 24V-60V (frequency 47-63Hz)

Signal Level – Signal “0”: -6 to+6V DC, 0 to 5V AC

-Signal “1”: 15 to 72V DC, -15 to -72V DC, 15 to 60V AC

Typical value of 4mA when input current signal “1”, range 4-10mA

Input delay supports parameterized settings, with rated values available in 0.5ms, 3ms, 10ms, and 20ms

Fixed current limit for wire breakage monitoring, minimum: 18k Ω at 24V (15-35V), 39k Ω at 48V (30-60V); maximum: 56k Ω at 60V (50-72V), monitoring condition: current I>0.7mA

Cable length – shielded cable: maximum 1000m

-Unshielded cable: 100m at 0.5ms delay, 600m at 3/10/20ms delay

Sensor compatibility supports 2-wire sensors, with a maximum allowable static current of 0.5mA (range 0.5-2mA)

Mechanical and isolation specifications

（1） Size and weight

Dimensions: Width 25mm, Height 290mm, Depth 210mm

Weight: Approximately 600g

（2） Isolation performance

Isolation test voltage: 1500V AC

Isolation method:

-Between channels: not isolated

-Channel grouping: isolation

-Isolation between channel and backplane bus

Functional characteristics

（1） Interruption and Diagnosis

Functional Category Capability Details

The diagnostic function supports parameterized diagnosis, can read diagnostic information, and can monitor disconnection faults

Alarm function supports parameterized diagnostic alarms

Hardware interrupts support parameterized hardware interrupts

Status indicator – digital input status indicator light (green): displays input status

-Channel fault indicator light (red, marked F): displays channel fault

（2） Classification code

Corresponding code for classification standard version

eClass 14/12/9.1/9/8/7.1/6 27-24-22-04

ETIM 10/9/8/7 EC001419

IDEA 4 3566

UNSPSC 15 32-15-17-05

Certification and Compliance

（1） Basic certification

General product certification, China RoHS, KC certification, EMV certification, RCM certification, CCC certification

（2） Dangerous Areas and Maritime Certification

Hazardous areas: IECEx certification, FM certification (supporting use in hazardous areas)

Maritime applications: ABS (American Bureau of Shipping), NK (Japan Classification Society), CCS (China Classification Society) certifications, supporting deployment in maritime scenarios