24 Vdc Digital Input Module - 40 Channel (T8403) Technical Overview

1. Module Architecture & Channel Redundancy

The 24 Vdc Digital Input Module - 40 Channel (T8403) features a triplicated design for each of its 40 field 

inputs (as visualized in Figure 6-9: 24Vdc Digital Input Module). This triplication enhances reliability by 

providing redundant measurements for each input. The input voltage is measured and compared against 

user-configurable threshold voltages to determine and report the field input state, ensuring accuracy and 

adaptability to different operational requirements.

2. Cable Fault Detection & Line Monitoring

The module supports advanced fault detection for field cables:

Open & Short-Circuit Detection: When a line-monitoring device is installed at the field switch, the module 

can detect open and short-circuit conditions in field cables.

Independent Channel Monitoring: Line monitoring functions are configured independently for each input 

channel, allowing granular control and diagnostics for every input path.

3. Sequence of Events (SOE) Reporting

The module includes on-board Sequence of Events (SOE) reporting with a resolution of 1ms. Any change 

of state in an input channel triggers an SOE entry, enabling precise tracking of event timing. States are 

determined by voltage thresholds that can be configured on a per-channel basis, making the module suitable 

for applications requiring high temporal accuracy (e.g., process control, event logging).

4. Status LEDs & Customizable Indications

The module’s front panel features input channel status LEDs (one per field input) that provide real-time 

visibility into channel health and state:

LED Behavior: The state of each LED depends on the voltage level of the input I/O signal. The input 

voltage is measured and compared against six threshold levels (four configurable, two fixed), which define 

seven threshold bands (detailed in Section 8). Each band can be assigned a specific indicator mode: off, 

green, red, flashing green, or flashing red.

Default LED Indications (summarized in Table 6-3: Default Digital Input Module LED Indications):

Off: Open field switch (contact).

Green: Closed field switch (contact).

Green – flashing: Associated channel input voltage out of range (below the lowest or above the highest 

trip threshold).

Red – flashing: Associated channel fault.

Customization: Users can configure voltage thresholds and LED modes to suit individual application 

needs. Without customization, the default indicators are optimized for digital inputs without line monitoring.

5. Application Suitability

The T8403 module is ideal for industrial environments requiring:

High-density digital input (40 channels in a single module).

Redundant measurement for critical inputs.

Detailed fault diagnostics (cable faults, voltage range issues).

Precise event timing (1ms SOE resolution) for sequence-dependent processes.

How we deliver

Supply Ability:In stock,within 3 days send the products.

Price:The more you order,the lower price you will get.

Our products is ship with original factory new package.

We will cover our our professional foam protective packaging to keep worldwide shipping no damaged.

We have many couirer partner,like DHL,TNT,FeDex and UPS

The factory will strictly test all the goods before shipment,and the warehouse staff will also check the 

integrity of the product packaging when it is shipped.