Description
Key Technical Specifications
| Parameter | Value |
|---|---|
| Manufacturer | ABB |
| Product ID | 3BDH000741R1 |
| Type Designation | CTI 21-P Ex |
| Product Type | Temperature Input Module |
| System | ABB Symphony Plus |
| I/O Series | MR Series |
| Number of Channels | Up to 32 |
| Channel Configuration | Independently configured |
| Supported Temperature Sensors | Thermocouples, Pt100, Ni100 |
| Other Input Signals | mV, V, resistance |
| Input Range 1 | -10 to +20 mV |
| Input Range 2 | -10 to +80 mV |
| Input Range 3 | -10 to +460 mV |
| Input Range 4 | 0 to +1.0 V |
| Input Range 5 | 0 to +5.0 V |
| Supply Voltage | 20–33 VDC |
| Current Consumption | 250 mA at 24 VDC |
| Power Dissipation | 6 W |
| Sensor/Transmitter Supply | 1.0 mA ±1.7%, constant-current supply |
| Line-Break Threshold | 2.5 kΩ ±10% |
| Isolation | Central galvanic; channel-wise functional isolation |
| Ex Protection | II (2) G [Ex ib IIC Gb] |
| ATEX Certificate | PTB 03 ATEX 2143 X |
| Applicable Standards | EN 60079-0, EN 60079-11 |
| Operating Temperature | 0 to 50°C at rack ventilation temperature |
| Dimensions | 40.64 × 311.15 × 160 mm |
| Width | 1.6 in |
| Depth | 6.3 in |
| Height | 12.25 in |
ABB’s catalog provides the above electrical, isolation, Ex, environmental, and dimensional specifications.
Important detail: ABB documentation describes the module as supporting up to 32 independently configured temperature input channels. Older descriptions sometimes reduce this to “16-channel” operation. The actual channel arrangement depends on the selected input configuration and associated wiring/accessories.
Product Introduction
ABB 3BDH000741R1 CTI 21-P Ex
The ABB 3BDH000741R1 CTI 21-P Ex is a temperature-input module for the ABB Symphony Plus MR Series I/O system. It accepts thermocouples, Pt/Ni 100 resistance thermometers, millivolt, voltage, and resistance signals, making it suitable for process-temperature acquisition across a range of industrial applications.
The important distinction is the Ex-rated input architecture. The CTI 21-P Ex provides intrinsically safe sensor interfaces with onboard sensor supply and channel-wise functional isolation. It is intended for applications where field instrumentation may be associated with hazardous areas, subject to the complete installation and certification requirements.
3BDH000741R1
Application Scenarios & Field Pitfalls
Engineering Pain Point
A temperature channel that suddenly reads high, low, or open circuit is not automatically a bad transmitter. With the CTI 21-P Ex, the fault path can include the thermocouple or RTD, extension cable, cold-junction arrangement, sensor supply, terminal assembly, channel configuration, and Ex interface. Start by proving the field signal at the module terminals.
Typical Applications
- Oil & Gas — Reactor, separator, compressor, furnace, and process-pipeline temperature measurement.
- Petrochemical — Distillation-column temperature monitoring, heater control, and process-temperature protection.
- Power Generation — Bearing, winding, steam, feedwater, and auxiliary-system temperature monitoring.
- Chemical Processing — Temperature acquisition from thermocouples and RTDs associated with hazardous-area process equipment.
Technical Pitfalls to Avoid
- Do not treat CTI 21-P Ex as an ordinary analog-input card.
It is specifically designed for temperature and low-level analog measurement with an intrinsic-safety architecture. The Ex interface is part of the module’s intended application. - Verify the sensor type in the engineering configuration.
Thermocouple, Pt100, Ni100, mV, voltage, and resistance inputs require different configuration and signal handling. A physically correct replacement can still produce incorrect readings if the channel configuration is wrong. - Check the 20–33 VDC supply.
ABB specifies this supply range and approximately 250 mA at 24 VDC. Do not diagnose individual sensor channels before confirming stable rack power. - Do not bypass the Ex requirements.
The module carries II (2) G [Ex ib IIC Gb] certification. Associated field wiring, barriers/interfaces, installation location, and sensor circuits must comply with the applicable hazardous-area design. - Check line resistance when diagnosing RTDs.
CTI 21-P Ex supports compensation of line resistance. Long RTD wiring can otherwise create measurement errors that look like calibration problems. - Do not use ordinary voltage measurements as the only thermocouple test.
Thermocouple signals are low-level millivolt signals. Electrical noise, incorrect extension cable, polarity reversal, and poor termination can produce believable but incorrect temperatures. - Check cold-junction compensation.
Thermocouple accuracy depends on proper reference-junction compensation. If several thermocouple channels shift together, investigate the common reference and module configuration before replacing individual sensors. - Respect the 1 mA sensor supply.
ABB specifies an onboard constant-current supply of 1.0 mA ±1.7%. Do not connect a field device that expects a different excitation arrangement without confirming compatibility. - Check the line-break threshold.
ABB specifies 2.5 kΩ ±10%. An open or high-resistance sensor circuit can therefore generate a diagnostic condition that differs from a normal process-value failure. - Do not assume every 3BDH000741R1 has identical software behavior.
ABB product records identify the module with software-version information in the product description. Confirm the installed Symphony Plus configuration and module revision before commissioning a replacement.
Related Products
- ABB CTI 21-P 3BDH000740R1 — Non-Ex version of the CTI 21-P temperature-input family. It is the relevant comparison when the field installation does not require the Ex-rated input architecture.
- ABB CTI 21-P Ex 3BDH000741R1 — The exact product covered here. It is intended for temperature and low-level analog acquisition where the intrinsic-safety architecture is required.
- ABB CFI 10-P 3BDH000735R1 — Four-channel frequency-input module in the same MR Series family. It is useful for speed, pulse, and frequency measurement but does not replace CTI 21-P Ex for temperature acquisition.
- ABB CBO 22-P 3BDH000736R1 — Binary-output module in the MR Series. It provides discrete outputs rather than temperature inputs and is complementary to CTI 21-P Ex in mixed I/O systems.
- ABB CI 120 Ex — Associated cable-clamp/accessory hardware identified in ABB’s product description as necessary for CTI 21-P Ex installations. Verify the exact terminal/accessory arrangement before replacement.
- ABB CI 121 Ex — Alternative associated cable-clamp hardware referenced by ABB for the CTI 21-P Ex installation. The correct accessory depends on the cabinet and wiring arrangement.
- ABB Symphony Plus MR Series I/O — The system-level I/O family containing CTI 21-P Ex. It provides the rack/backplane environment in which the module operates.
- ABB Symphony Plus — DCS platform into which the CTI 21-P Ex integrates. The module is an I/O component, not a standalone temperature controller.
- ABB Temperature Transmitters — Field devices that can feed compatible analog signals to CTI 21-P Ex. Verify the actual transmitter output and whether the module’s input range and intrinsic-safety arrangement are appropriate.
