Original ABB 3BDH000741R1 CTI 21-P EX Spare

The Original ABB 3BDH000741R1 CTI 21-P EX Spare 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

1. ABB CTI 21 series signal transducer / interface module, hazardous-area (EX) version
2. Converts process current (CT secondary) signal into standard 4–20 mA output
3. 2-wire passive loop-powered output configuration
4. Designed for use in potentially explosive atmospheres with certified CTs and intrinsic-safety wiring
5. 24 V DC supply class
6. ABB legacy industrial control product line

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

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.

1. 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.
2. What does "EX" mean here? It designates the version intended for potentially explosive atmospheres.
3. 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).

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