Technical Specifications
| Parameter Name | Parameter Value |
|---|---|
| Product Model | 1756-IRT8I |
| Manufacturer | Allen-Bradley / Rockwell Automation |
| Product Type | Isolated RTD/Thermocouple/mV Analog Input Module |
| Product Series | ControlLogix 1756 I/O |
| Input Channels | 8 isolated channels (independently configurable) |
| Input Types | RTD, Thermocouple, mV, Resistance (Ohms) |
| Resolution | 24-bit |
| Conversion Method | Sigma-Delta continuous |
| Channel Isolation | 250V AC (continuous), reinforced insulation |
| Module Scan Time | 1 ms |
| RTD Types | Pt100/200/500/1000 (α=385/3916), Ni100/120/200/500, Cu10 |
| Thermocouple Types | B, C, D, E, J, K, N, R, S, T, TXK/XK(L) |
| mV Range | -100 to +100 mV |
| Resistance Ranges | 1–500Ω, 2–1000Ω, 4–2000Ω, 8–4000Ω |
| Backplane Current (5.1V) | 200 mA |
| Backplane Current (24V) | 150 mA |
| Maximum Power Dissipation | 4.6 W |
| Thermal Dissipation | 15.7 BTU/hr |
| Terminal Block | 36-pin removable terminal block (RTB) |
| Compatible RTBs | 1756-TBNH, 1756-TBCH, 1756-TBS6H |
| CJC Sensors | 2 built-in (requires external 1756-CJC for TC measurement) |
| Operating Temperature | 0°C to 60°C |
| Storage Temperature | -40°C to 85°C |
| Dimensions (W×H×D) | 34.6 × 145.2 × 139.6 mm |
| Weight | 0.45 kg (1.0 lb) |
| Certifications | CE, UL, CSA, FM, ATEX, IECEx, RCM, CCC |
| Hot-Swappable | Yes (RIUP supported) |
Main Features and Advantages
The Allen-Bradley 1756-IRT8I delivers a unique combination of high-precision measurement, exceptional flexibility, and robust noise immunity that makes it a standout choice for industrial temperature monitoring applications. Its 24-bit Sigma-Delta ADC provides measurement resolution of 1 part in 16,777,216, enabling the module to detect even the smallest signal variations from thermocouples and RTDs. In practical terms, this translates to a resolution of 0.01°C for Type K thermocouples and 0.06 milliohms per count for resistance measurements — performance that meets the exacting demands of precision thermal control.Channel-level configuration flexibility is a defining characteristic of the Allen-Bradley 1756-IRT8I. Each of the eight input channels can be independently programmed for a different sensor type, measurement range, filter setting, and engineering unit. This means a single module can simultaneously acquire data from a Pt100 RTD in a water tank, a Type J thermocouple in an oven, and a millivolt-level pressure transmitter — all with individual calibration and alarming parameters. This eliminates the need to purchase separate modules for each sensor type, reducing hardware count, cabinet space, and engineering complexity.Superior noise immunity is achieved through the module’s comprehensive isolation architecture. With 250V continuous isolation between channels and between channels and the backplane, the Allen-Bradley 1756-IRT8I effectively blocks ground loops and common-mode interference. This is particularly valuable in environments with variable frequency drives, large motors, and other sources of electromagnetic noise where non-isolated modules often produce unstable or inaccurate readings.Comprehensive diagnostics further enhance the reliability of the Allen-Bradley 1756-IRT8I. The module provides over-range and under-range detection, open-wire (broken sensor) detection, CJC sensor fault detection, and process alarms. These built-in diagnostic capabilities enable rapid identification and resolution of field wiring issues, minimizing unplanned downtime. Additionally, the module’s hot-swappable design allows for replacement without powering down the entire system — a critical advantage in continuous-process industries where downtime translates directly to lost production.
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