ABB 3BDH000741R1 Replacement CTI 21-P EX Transducer

The ABB 3BDH000741R1 Replacement CTI 21-P EX Transducer is the hazardous-area (EX) version of the ABB CTI 21 signal-conditioning / transducer module family, used to convert process current signals into a standardized 4–20 mA interface signal in industrial measurement and control applications.

Key Features

• ABB CTI 21 series signal transducer / interface module, hazardous-area (EX) version
• Converts process current (CT secondary) signal into standard 4–20 mA output
• 2-wire passive loop-powered output configuration
• Designed for use in potentially explosive atmospheres with certified CTs and intrinsic-safety wiring
• 24 V DC supply class
• ABB legacy industrial control product line

Technical Specifications

• Type Designation: CTI 21-P EX
• Order Code: 3BDH000741R1
• Product Type: Current transducer / signal interface module, EX version
• Input Signal: AC current from a CT — 0–1 A or 0–5 A AC RMS
• Output Signal: 4–20 mA DC, linear with input
• Accuracy: ±0.5% of reading (typical)
• Supply Voltage: 24 V DC (20–30 V DC per source)
• Hazardous Area: EX / intrinsically-safe interface design
• Origin: Switzerland

Installation Notes

1. Verify the module’s actual input type (current vs. temperature) and wiring against the system documentation before installation.
2. Use a certified current transformer (CT) suitable for the hazardous area; match CT ratio and burden to the module input.
3. Install the hazardous-area wiring per intrinsic-safety standards, respecting cable parameters (Ci, Li) and proper CT secondary grounding.
4. Commission with a loop check — verify 4–20 mA output tracks the input signal — before returning the loop to service.

Common Questions

What is the CTI 21-P EX? It is the hazardous-area (EX) version of the ABB CTI 21 transducer/interface module family, described by suppliers as converting CT current signals to a 4–20 mA output for hazardous-location applications. Note that the CTI 21 family also includes temperature-input variants — confirm the exact function against the unit label.

What does “EX” mean here? It designates the version intended for potentially explosive atmospheres.

Which CT should be used? A certified CT suitable for the hazardous area, with ratio and burden compatible with the module’s input (0–1 A or 0–5 A class per market data).