Allen-Bradley 1794-IRT8 Flex I/O RTD/TC Module

1794-IRT8 Flex I/O 8-Channel RTD/Thermocouple Input Module

Product Introduction 1794-IRT8

The Allen-Bradley 1794-IRT8 is a versatile combination module for the Flex I/O system. Specifically, it accepts both RTD and thermocouple inputs across its 8 channels. These channels are arranged in two groups of four for flexible configuration. Moreover, this module provides 14-bit resolution with selectable data formats including °C, °F, and °K. It ships with two cold junction compensators to enhance thermocouple accuracy. Additionally, the 1794-IRT8 includes open circuit detection for reliable fault diagnosis. Therefore, this module is an ideal solution for mixed temperature sensing applications.

Resolution and Accuracy 1794-IRT8

The 1794-IRT8 delivers reliable measurement performance with its 14-bit resolution. In millivolt mode with filtering selected, the accuracy reaches 0.05% of full range. Without filtering, the accuracy is 0.10% of full range in hardware-only mode. Meanwhile, the module offers multiple data format options. These include °C, °F, and °K with implied decimal point (XXX.X), as well as -32767 to +32767 and 0 to 65535 formats. Additionally, it supports 0 to 5000 (ohm mode) and -4000 to +10000 (mV mode) formats. This flexibility allows seamless integration with various control systems.

System Throughput 1794-IRT8

The 1794-IRT8 provides fast and predictable system throughput for each channel. For mV mode, the throughput is 7.4 ms. For RTD mode, it varies by configuration: 8.0 ms for 2-wire, 10.0 ms for 3-wire, and 10.4 ms for 4-wire. For thermocouple mode, it achieves 8.0 ms in °F and 8.8 ms in °C or °K. Meanwhile, the module features 850V DC isolation for robust protection. The FlexBus current draw is 20 mA, with maximum power dissipation of 3.0 W at 31.2V DC and thermal dissipation of 10.2 BTU/hr.

Diagnostic Features

The 1794-IRT8 includes essential diagnostic functions for reliable operation. Specifically, it features open circuit detection that upscales the reading to maximum value when a sensor fault occurs. The open input detection time is 2 scans for timely fault notification. Additionally, the module provides overvoltage capability of 15V DC continuous at 25°C. Eight red LED indicators show open input conditions, while one green LED indicates power status. These diagnostics help maintenance teams quickly identify and resolve sensor issues.

Mechanical and Environmental Parameters

The Allen-Bradley 1794-IRT8 operates reliably in diverse industrial environments. Its operating temperature range is 0 to 55°C, with storage from -40 to 85°C. The module withstands vibration of 5g at 10 to 500 Hz and operating shocks of 30g. It also handles non-operating shocks of 50g. The relative humidity tolerance is 5 to 95% non-condensing. This module mounts on DIN rail and requires terminal bases such as 1794-TB3G, 1794-TB3GS, or 1794-TB3GK. The nominal voltage is 24V DC, and it comes in series variations A and B. For wiring, use thermocouple wires as specified by the manufacturer, or Belden 8761 for millivolt signals.

Packaging List

• Allen-Bradley 1794-IRT8 RTD/Thermocouple Input Module (1 unit)

• Cold Junction Compensators (2 units)

• Installation Instructions Manual

Shipping Information

We ship all orders using reputable global carriers. Specifically, your 1794-IRT8 will be dispatched via FedEx, UPS, or DHL. This ensures fast and reliable delivery to your facility.

Frequently Asked Questions (FAQ)

Q1: Can the 1794-IRT8 mix RTD and thermocouple inputs on the same module?
Yes, the 1794-IRT8 supports mixing RTD and thermocouple inputs across its 8 channels. However, channels are organized in two groups of four, so configuration flexibility applies within each group.

Q2: What terminal base units work with the 1794-IRT8?
The 1794-IRT8 requires terminal bases 1794-TB3G, 1794-TB3GS, or 1794-TB3GK. These bases provide the necessary connections for RTD and thermocouple wiring.

Q3: What diagnostic features does the 1794-IRT8 offer?
The 1794-IRT8 includes open circuit detection that upscales readings to maximum value upon sensor fault. It also features eight red LED indicators for open input status and one green LED for power.

Q4: Does the 1794-IRT8 support 3-wire RTD connections?
Yes, the 1794-IRT8 supports 2-wire, 3-wire, and 4-wire RTD connections. The system throughput varies by configuration, with 3-wire mode at 10.0 ms.

Q5: What is the purpose of the cold junction compensators?
The 1794-IRT8 ships with two cold junction compensators. These devices increase measurement accuracy when operating in thermocouple mode by compensating for temperature variations at the connection points.