Product Overview
Industrial temperature measurement often requires flexibility to handle both RTD and thermocouple sensors within the same system. The Allen-Bradley 1794-IRT8 from the Flex I/O 1794 series addresses this need directly. Manufactured by Rockwell Automation, this module is a combination input module that supports eight channels arranged in two groups of four. It accepts nominal input ranges of -40…100 mV dc for thermocouples and 0…325 mV for RTDs. With a resolution of 14 bits, it provides reliable signal conversion for diverse temperature sensing applications.
Technical Specifications Breakdown
Key parameters for the 1794-IRT8 are listed below for quick reference:
| Feature | Specification |
|---|---|
| Brand | Allen-Bradley |
| Series | Flex I/O 1794 |
| Part Number | 1794-IRT8 |
| Manufacturer | Rockwell Automation |
| Product Description | Flex IO 8-Channel RTD / Thermocouple Input Module |
| Number of Channels | 8 |
| Resolution | 14 bits |
| Nominal Input Voltage Ranges | -40…100 mV dc for thermocouples; 0…325 mV for RTDs |
| Accuracy | 0.05% of full range in mV mode with filtering selected; Hardware only = 0.10% of full range in mV mode |
| Operating Temperature | 0 to 55 C (32 to 131 F) |
| Storage Temperature | –40…85 °C (–40…185 °F) |
| Mounting | DIN Rail |
| Indicators | 1 green power status indicator; 8 red open input indicators |
| Nominal Voltage | 24 Volts DC |
| System Throughput | 7.4 ms - mV; 8.0 ms - ? - 2-wire; 10.0 ms - ? - 3-wire; 10.4 ms - ? - 4-wire; 8.0 ms - 2-wire RTD ( °F); 10.4 ms - 4-wire RTD ( °F); 8.8 ms - 2-wire RTD ( °C), ( °K); 10.8 ms - 4-wire RTD ( °C), ( °K); 9.8 ms - 3-wire RTD ( °F); 10.0 ms - 3-wire RTD ( °C), ( °K); 8.0 ms - Thermocouples ( °F); 8.8 ms - Thermocouples ( °C), ( °K) |
| Vibration | 5g @ 10 to 500 Hz |
| Operating Shock | 30 g |
| Series Variations | A and B |
Industry Applications
In process industries such as chemical refining and food processing, accurate temperature monitoring is critical for quality control. The module supports a wide range of RTD sensors including 100 ? Pt ? = 0.00385 Euro (-200…+870 °C) and 10 ? Copper ? = 0.00427 (-200…+260 °C), as well as thermocouple types like B, E, J, K, TXK/XK (L), N, R, S, and T. This versatility allows engineers to standardize on one module for multiple temperature sensing points, reducing spare parts inventory and simplifying training.
Installation & Setup Guidance
Mount the module on a DIN rail within the FLEX I/O system. Connect it to a compatible terminal base such as the 1794-TB3G, 1794-TB3GS, or 1794-TB3GK. The module ships with two cold junction compensators that improve accuracy in thermocouple mode. For signal wiring, use thermocouple wires as specified by the TC manufacturer and Belden 8761 for millivolt signals. Ensure the nominal voltage of 24 Volts DC is supplied to the power adapter.
Maintenance & Reliability
Periodically inspect the green power status indicator and the eight red open input indicators to verify normal operation. The module includes diagnostic functions such as open circuit detection, where the reading upscales or defaults to max value in RTD and thermocouple mode. Open input detection time is 2 scans. The module also offers overvoltage capability of 15V DC continuous at 25 °C. Keep the operating environment within 0 to 55 C (32 to 131 F) and avoid exceeding storage temperature limits of –40…85 °C (–40…185 °F).
Compatibility & Integration
The module is designed for the FLEX I/O system and works with the listed terminal bases. It supports 2-wire, 3-wire, and 4-wire RTD configurations. Data formats include °C, °F, °K (implied decimal point XXX.X), -32767…+32767, 0…65535, 0…5000 (? mode) (implied decimal point XXX.X), and -4000…+10000 (mV mode) (implied decimal point XXX.XX).
Selection Guide & Purchasing Advice
When selecting a temperature input module for your FLEX I/O system, verify that the sensor types and wiring configurations match your application. The 1794-IRT8 supports both RTD and thermocouple inputs, making it a versatile choice. For current lifecycle status and availability, please contact SpareTechPLC before ordering. SpareTechPLC offers this module along with compatible terminal bases and accessories.
Troubleshooting & Common Issues
If an open input is detected, the module reading will upscale or default to the maximum value. Check the red open input indicators on the front panel. Ensure that thermocouple wires are properly connected and that cold junction compensators are installed. For mV mode, verify that the input signal is within the -40…100 mV dc range. If accuracy issues arise, confirm that filtering is selected to achieve 0.05% of full range accuracy.
Frequently Asked Questions (FAQs)
What types of RTD sensors does the 1794-IRT8 support?
The module supports 100 ? Pt ? = 0.00385 Euro (-200…+870 °C), 100 ? Pt ? = 0.003916 U.S. (-200…+630 °C), 200 ? Pt ? = 0.00385 Euro (-200…+630 °C), 500 ? Pt ? = 0.00385 U.S. (-200…+630 °C), 100 ? Nickel ? = 0.00618 (-60…+250 °C), 120 ? Nickel ? = 0.00672 (-60…+250 °C), 200 ? Nickel ? = 0.00618 (-60…+250 °C), 500 ? Nickel ? = 0.00618 (-60…+250 °C), and 10 ? Copper ? = 0.00427 (-200…+260 °C).
What thermocouple types are compatible?
Compatible types include B (300…1800 °C), E (-270…1000 °C), J (-210…1200 °C), K (-270…1372 °C), TXK/XK (L) (-200…800 °C), N (-270…1300 °C), R (-50…1768 °C), S (-50…1768 °C), and T (-270…400 °C).
What is the resolution of the module?
The module has a resolution of 14 bits.
What terminal bases are compatible?
Compatible terminal bases include 1794-TB3G, 1794-TB3GS, and 1794-TB3GK.
What is the nominal voltage requirement?
The nominal voltage is 24 Volts DC.
