Siemens 6ES5420-4UA14 SIMATIC S5-420 Digital Input Module – 32-Channel 24 V DC, Non-Isolated Compact Design

Product Overview

The 6ES5420-4UA14 is a SIMATIC S5-420 series digital input module from Siemens, built in the non-isolated compact form factor for S5-90U, S5-95U, S5-100U central racks and their distributed counterparts ET 100U and ET 200U. Where the standard S5 rack line (S5-115U/135U/155U) uses deeper, per-module-isolated DI cards on the 120 mm rail, the compact 6ES5420-4UA14 is shallower, lighter, and trades per-channel galvanic isolation for doubled channel density—32 digital inputs at 24 V DC in a single module, versus 16 on the isolated siblings. This makes it the default high-density DI choice for compact S5 machines where panel width is tight and isolation is handled once at the rack or power-supply level rather than per module.Each of the 32 inputs on the 6ES5420-4UA14 accepts standard 24 V DC industrial sensor signals (PNP sourcing into the module, or NPN with external wiring considerations), with a nominal 7 mA per-channel input current and a selectable input delay of 1.2 ms / 4.8 ms / 19.2 ms configurable via STEP 5 parameters—useful for debouncing mechanical contacts versus accepting fast prox transitions. The module is non-isolated (“compact, non-floating”), meaning all 32 inputs reference a common 0 V/M return that is tied to the compact rack’s internal M bus; this simplifies field wiring (one common return instead of per-group isolation barriers) but mandates that the installer respects the shared-M architecture—mixing grounded and floating field devices on the same 6ES5420-4UA14 without planning can create ground-loop surprises. Power for the module’s front-end logic is drawn from the +5 V / +24 V backplane supplied by the S5-90U/95U/100U CPU or IM interface; no separate 24 V feed is needed for the DI electronics themselves, though the field sensors naturally require their own 24 V supply.In the S5 compact ecosystem the 6ES5420-4UA14 typically neighbours the 6ES5430-4UA14 (32 DO compact), 6ES5450-4UA14 (analog I/O) and 6ES5380-8MA11 (timer) in the same shallow-profile rack. For MRO teams still supporting S5-90U/95U/100U lines in water treatment, packaging, material handling and legacy process cells, the module is a frequent storeroom line-item: compact racks age well mechanically, but DI modules take the brunt of sensor shorts and transient spikes, and having a verified 6ES5420-4UA14 on the shelf turns a “three-shift line down” into a 20-minute swap.

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Description

Technical Specifications

Parameter	Value
Product Model	6ES5420-4UA14
Manufacturer	Siemens
Product Type	Digital Input Module (Compact, Non-Isolated)
Series	SIMATIC S5-420
Number of Inputs	32, single-ended
Input Voltage	24 V DC (rated 20.4 – 28.8 V DC)
Input Current (typ.)	~7 mA per channel @ 24 V
Input Delay	1.2 ms / 4.8 ms / 19.2 ms (selectable, STEP 5 parameter)
Isolation	Non-isolated (shared M, compact rack bus)
Compatible Racks	S5-90U, S5-95U, S5-100U, ET 100U, ET 200U
Sensor Compatibility	PNP (source) standard; NPN with wiring adaptation
Status Display	LED per input channel
Operating Temperature	–25 °C to +60 °C
Storage Temperature	–40 °C to +70 °C
Dimensions (L × W × H)	210 × 263 × 35 mm
Weight (approx.)	0.48 kg
Protection Class	IP20 (control-cabinet)

Main Features and Advantages

32-channel density in a single compact slot. The standout trait of the 6ES5420-4UA14 is channel count per footprint. Standard S5-115U/135U isolated DI modules (6ES5421 family) typically give you 16 or 32 inputs in the deeper full-size rail profile; the compact 6ES5420-4UA14 delivers 32 inputs in the shallow S5-90U/95U/100U envelope, meaning a four-module compact rack can land 128 DIs where a standard rack would need eight slots for the same count. For OEM machine builders who standardised on S5-100U panels in the 1990s—packaging formers, cartoners, palletisers—the 6ES5420-4UA14 is what lets them keep IO counts high without widening the enclosure.Selectable input delay for contact vs. solid-state. Unlike “dumb” DI blocks that either react instantly (and therefore count every contact bounce) or lag fixed, the 6ES5420-4UA14 offers three delay steps: 1.2 ms for clean prox / encoder-z / high-speed tally; 4.8 ms for general machine signalling; 19.2 ms for noisy mechanical limit switches and relay aux-contacts that need bounce suppression. Set via STEP 5 module parameters (not jumper—pure software), this lets one spare 6ES5420-4UA14 serve multiple machine roles across a plant just by downloading a different parameter set. No hardware change, no jumper hunting on a live rack.LED per channel for front-panel triage. Thirty-two green LEDs on the module face give instant visual on which inputs are seeing 24 V. During a 3 a.m. call-out on a 25-year-old S5-95U, an operator can see at a glance whether the guard-door limit (Input 12) is stuck high or the photo-eye (Input 27) has lost its 24 V feed—without STEP 5, without a PG, without decoding PI bytes. In legacy plants where the original .STP file lives on a dead hard drive and nobody remembers which I-address maps to which device, those LEDs are the fastest triage tool on the rack.Non-isolated compact trade-off, deliberately chosen. The 6ES5420-4UA14 is “non-isolated compact” by design, not by omission. In S5-90U/95U/100U machines, isolation is normally provided once at the 24 V sensor supply or at the rack’s power entry; per-module isolation would double the footprint and add cost for no gain in a machine-built panel where all sensors share one switched 24 V PSU. The shared-M architecture of the 6ES5420-4UA14 simplifies terminal-block layout—one common return rail instead of four isolated groups—and keeps the module price point below the isolated 6ES5421 siblings. The caveat is real and worth stating: mixing sources (e.g., one channel wired to a grounded NPN device while the rest are PNP) on the same 6ES5420-4UA14 can create sneak paths through the shared M. Installers who respect the shared-M rule get decades of trouble-free service; those who don’t, learn fast.Backplane-powered, no extra feeds. The 6ES5420-4UA14 draws its logic power from the compact rack backplane (+5 V / +24 V supplied by CPU or IM), so the module itself needs no terminal wiring for power—only the 32 field wires + the shared M return. In a panel with four 6ES5420-4UA14 modules (that’s 128 DIs), power planning is just “rack PSU sized for CPU + modules”; no individual fusing per DI card, no 24 V terminal duplication. This is part of why compact S5 panels stay narrow.