Siemens 6ES5420-4UA12 Input Module | 32-Point 24V DC 0.46kg

Technical Specifications and Input Design

This digital input module interfaces with 24V DC field devices for SIMATIC S5 systems. The Siemens 6ES5420-4UA12 reads signals from pushbuttons, limit switches, and proximity sensors. You can install this unit into any standard S5-115U or S5-135U rack slot. Its high-density design saves valuable rack space for other modules. The module weighs approximately 0.46 kilograms. Its dimensions measure 25 cm in height, 5 cm in width, and 21 cm in depth.

Parameter	Specification
Brand	Siemens
Model	6ES5420-4UA12
Category	Digital Input Module / 24V DC Input Unit
Weight	0.46 kg
Height	25 cm
Width	5 cm (single slot)
Depth	21 cm
Number of Inputs	32 points
Input Voltage Range	20-30V DC (nominal 24V DC)
Input Type	Sink (negative common)
Input Current per Point	7 mA typical at 24V DC
Minimum ON Voltage	15V DC
Maximum OFF Voltage	5V DC
Response Time	4 milliseconds typical
Isolation Voltage	500V AC between field and logic
Energy Storage	None (no battery or capacitors)
Component Count	Single PCB with 32 optocoupler circuits

Wiring and Group Configuration

The module divides its thirty-two inputs into four isolated groups of eight. Each group shares a common return terminal for wiring convenience. You can connect different voltage sources to each group safely. The Siemens 6ES5420-4UA12 uses a front-panel 50-pin female connector. This connector accepts a ribbon cable or pre-wired terminal block. Each input point includes a green LED status indicator. This LED lights when the input detects a valid ON signal level.

Signal Processing and Noise Immunity

The input circuits filter electrical noise for reliable industrial operation. Each channel requires at least 15V DC to register an ON condition. The module uses optocoupler technology for complete electrical isolation. Consequently, the backplane logic remains safe from field wiring faults. The inputs respond within 4 milliseconds to any voltage change. This response captures short-duration events from high-speed sensors effectively. The module operates perfectly with two-wire or three-wire DC sensors.

Installation and Operational Guidelines

You must insert this module into any standard S5 I/O rack slot. The backplane supplies 5V DC power to the optocoupler circuits. The module draws approximately 180 mA from this backplane supply. It stores no input states when you remove system power. Therefore, the CPU receives fresh input data after each power-up cycle. You should verify the applied voltage stays below 30V DC. Exceeding this limit will permanently damage the input circuits. The module requires no external power supply for normal operation.