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Product Overview
The Allen-Bradley 1756-IRT8I is an eight-channel isolated temperature-sensing analog input module for the ControlLogix platform, engineered to accept RTD, thermocouple, and millivolt signals on a per-channel basis. As a member of the 1756 ControlLogix I/O family, the 1756-IRT8I provides individually isolated channels, meaning each input is electrically separated from the others and from the backplane, a design that eliminates ground loops and prevents noise from one sensor circuit from corrupting readings on adjacent channels . This channel-to-channel isolation is particularly valuable in applications where sensors are distributed across different equipment zones or where mixed sensor types must coexist in a single module without electrical interference.
The 1756-IRT8I supports a comprehensive range of temperature sensors. For RTD inputs, it accepts 100, 200, 500, and 1000 Ohm platinum sensors with alpha 385 or 3916 curves, 10 Ohm copper sensors, and 100, 120, 200, or 500 Ohm nickel sensors with alpha 618 or 672 curves . For thermocouple inputs, the module handles Types B, C, D, E, J, K, N, R, S, T, and TXK/XK (L), with linearization performed according to ITS-90 standards . A direct millivolt range of ±100 mV is also available for low-level signal acquisition. This breadth of sensor compatibility allows the 1756-IRT8I to serve as a universal temperature input module across diverse process heating, cooling, and monitoring applications.
Within the ControlLogix architecture, the 1756-IRT8I occupies a single slot and communicates with the controller through the backplane, drawing 200 mA at 5.1V DC and 150 mA at 24V DC in its original A-series revision . The module requires a separately ordered 36-pin removable terminal block (1756-TBCH or 1756-TBS6H) and, for thermocouple applications, two 1756-CJC cold-junction compensation jumpers that are not included with the module . Rockwell Automation lists the 1756-IRT8I with Active lifecycle status, ensuring continued availability for both new installations and maintenance replacements .
Technical Specifications
| Parameter Name | Parameter Value |
|---|---|
| Product Model | 1756-IRT8I |
| Manufacturer | Allen-Bradley (Rockwell Automation) |
| Product Type | Isolated Temperature-Sensing Analog Input Module |
| Input Channels | 8, individually isolated and configurable |
| Input Signal Types | RTD (3-wire or 4-wire), Thermocouple, mV |
| RTD Sensor Types | 100/200/500/1000 Ω Pt (α=385, 3916); 10 Ω Cu; 100/120/200/500 Ω Ni (α=618, 672) |
| Thermocouple Types | B, C, D, E, J, K, N, R, S, T, TXK/XK (L) |
| Millivolt Range | ±100 mV |
| Resolution | 24 bits (23.98 bits across actual range) |
| RTD Resolution | 0.06 mΩ/count (1–500 Ω range) |
| TC Resolution | 0.01 μV/count |
| Backplane Current (5.1V DC) | 200 mA (A-series); 20 mA (B-series) |
| Backplane Current (24V DC) | 150 mA |
| Power Dissipation | 4.6 W (A-series); 4.67 W (B-series) |
| Isolation Voltage | 250V continuous (channel-to-channel and channel-to-backplane) |
| CJC Sensors | Two required for thermocouple use; 1756-CJC ordered separately |
| Terminal Block | 1756-TBCH or 1756-TBS6H (36-pin, ordered separately) |
| Operating Temperature | 0°C to 60°C (32°F to 140°F) |
| Lifecycle Status | Active |
