Introduction
Temperature measurement in industrial automation has evolved from bulky, single-point transmitters to compact, high-density I/O modules that fit directly on a DIN rail. The Allen-Bradley 1794-IRT8 represents that evolution. As part of the Flex I/O 1794 series from Rockwell Automation, this module combines eight channels of RTD and thermocouple input in one space-saving unit. It eliminates the need for separate signal conditioners and reduces wiring complexity in temperature-critical processes.
What Is the 1794-IRT8?
The 1794-IRT8 is a Flex I/O combination module that supports both RTD and thermocouple sensors. It provides Eight (8) channels arranged in Two (2) groups of Four (4). The module accepts nominal input ranges of -40…100 mV DC for thermocouples and 0…325 mV for RTDs. A resolution of 14 bits ensures precise temperature readings. The module ships with two cold junction compensators to improve thermocouple accuracy. Its front panel includes a green power status indicator and eight red open input indicators for quick diagnostics.
Technical Specifications
| Specification | Value |
|---|---|
| Manufacturer | Rockwell Automation |
| Series | Flex I/O 1794 |
| Part Number | 1794-IRT8 |
| Inputs | 8 channels (2 groups of 4) |
| Resolution | 14 bits |
| Accuracy | 0.05% of full range in mV mode with filtering selected; 0.10% hardware only |
| Nominal Input Voltage | -40…100 mV DC (thermocouple); 0…325 mV (RTD) |
| Mounting | DIN Rail |
| Indicators | 1 green power status; 8 red open input |
| Operating Temperature | 0 to 55 °C (32 to 131 °F) |
| Storage Temperature | –40…85 °C (–40…185 °F) |
| Vibration | 5g @ 10 to 500 Hz |
| Operating Shock | 30 g |
| Terminal Base | 1794-TB3G, 1794-TB3GS, 1794-TB3GK |
| Nominal Voltage | 24 Volts DC |
Industry Applications
1. Heat Treatment Furnaces
Heat treatment requires precise temperature control across a wide range. The 1794-IRT8 supports thermocouple types B, E, J, K, TXK/XK(L), N, R, S, and T, covering temperatures from -270 to 1800 °C. This makes it ideal for monitoring multiple zones in a furnace. The open-input detection feature alerts operators if a thermocouple fails, preventing scrap parts.
2. Food and Beverage Processing
RTD sensors are preferred for their stability and repeatability. The 1794-IRT8 accepts 2-wire, 3-wire, and 4-wire RTDs, including 100 ? Pt ? = 0.00385 Euro and 100 ? Pt ? = 0.003916 U.S. With 14-bit resolution, it captures small temperature changes critical for pasteurization and fermentation. The module’s DIN-rail mounting saves panel space in crowded control cabinets.
3. Pharmaceutical Manufacturing
Regulatory compliance demands accurate, traceable temperature data. The 1794-IRT8 provides selectable data formats in °C, °F, and °K, simplifying integration with existing control systems. Its 0.05% accuracy (with filtering) ensures reliable readings for validation reports. The module’s diagnostics help maintain data integrity by flagging open circuits immediately.
Installation and Setup
Mount the 1794-IRT8 on a standard DIN rail within a Flex I/O system. Connect it to a compatible terminal base such as the 1794-TB3G, 1794-TB3GS, or 1794-TB3GK. Use thermocouple wire as specified by the sensor manufacturer for thermocouple inputs, and Belden 8761 for millivolt signals. The module requires a 24 V DC power adapter. Ensure the operating temperature remains between 0 and 55 °C. Verify that the keyswitch position matches your configuration before powering up.
Maintenance and Reliability
Regular inspection of terminal connections prevents signal drift. Check the red open input indicators; if lit, inspect the corresponding sensor and wiring. The module withstands 5g vibration at 10 to 500 Hz and 30 g shock, making it suitable for harsh environments. Store spare modules between –40 and 85 °C. Periodically verify accuracy using a calibrated signal source. The 1794-IRT8’s solid-state design minimizes wear, but environmental factors like humidity and contaminants can affect performance. Keep the enclosure clean and ensure adequate ventilation.
Compatibility and Integration
The 1794-IRT8 integrates seamlessly with Allen-Bradley Flex I/O systems. It communicates with controllers via the Flex I/O adapter, supporting various networks. The module’s data formats include °C, °F, °K, and raw counts, allowing flexible programming. It works with a wide range of RTD and thermocouple types, reducing the need for multiple module variants. For system throughput, refer to the module’s specifications: 7.4 ms for mV, 8.0 ms for 2-wire RTD, and 10.0 ms for 3-wire RTD.
Selection Guide
Before purchasing, confirm your sensor type and wiring configuration. The 1794-IRT8 supports 2-wire, 3-wire, and 4-wire RTDs, as well as thermocouple types B, E, J, K, TXK/XK(L), N, R, S, and T. Ensure you have the correct terminal base (1794-TB3G, 1794-TB3GS, or 1794-TB3GK) and a 24 V DC power adapter. For reliable supply, consider SpareTechPLC as your source for genuine Allen-Bradley components. They offer expert support to match the module with your existing Flex I/O system.
FAQs
1. What types of sensors can I connect to the 1794-IRT8?
The module supports RTDs (2-wire, 3-wire, 4-wire) including 100 ? Pt, 200 ? Pt, 500 ? Pt, 100 ? Nickel, 120 ? Nickel, 200 ? Nickel, 500 ? Nickel, and 10 ? Copper. It also supports thermocouple types B, E, J, K, TXK/XK(L), N, R, S, and T.
2. How many channels does the 1794-IRT8 have?
It has eight (8) channels in two (2) groups of four (4).
3. What is the resolution of the 1794-IRT8?
The module offers 14-bit resolution.
4. What indicators are on the 1794-IRT8?
There is one green power status indicator and eight red open input indicators.
5. What is the operating temperature range?
The 1794-IRT8 operates from 0 to 55 °C (32 to 131 °F).
