Allen-Bradley 1794-IT8 Flex I/O Thermocouple Input Module

Allen-Bradley 1794-IT8 Flex I/O Thermocouple Input Module

Product Introduction 1794-IT8

The 1794-IT8 module from Allen-Bradley offers a versatile and precise analog input solution. This module belongs to the Flex I/O family, which delivers a flexible and cost-effective I/O system for modern control architectures. It features eight isolated input channels that support multiple thermocouple types or millivolt signals. With 16-bit resolution, the 1794-IT8 ensures accurate data conversion for demanding process control and temperature monitoring tasks.

Core Technical Specifications 1794-IT8

The 1794-IT8 excels in both accuracy and reliability. It supports a wide range of thermocouple sensors, including types J, K, E, R, N, S, B, C, T, and L. Additionally, it accepts a nominal millivolt input range of ±76.5 mV. The module achieves a typical resolution of 16 bits, or 2.384 microvolts per count, which guarantees precise signal detection.

Furthermore, the module provides a normal-mode rejection ratio of -60 dB at 60 Hz, effectively filtering out electrical noise. Its channel bandwidth spans 0 to 2.62 Hz, and the normal-mode system throughput reaches 325 milliseconds. For power considerations, the 1794-IT8 draws 20 mA from the FlexBus and dissipates a maximum of 3W at 31.2V DC, which translates to a thermal dissipation of 10.2 BTU/hour. The module's data format supports both 16-bit 2’s complement and offset binary, ensuring broad compatibility with most PLC data tables.

Functional Features and Configuration 1794-IT8

The 1794-IT8 simplifies system integration through its block-transfer operation for data exchange and configuration. This method allows the PLC to send configuration words to the module and read input data words from it. Moreover, the module requires a specific keyswitch position—Position 3 on its terminal base—for safe mounting. It also includes two cold junction compensators (CJC) that must reside on the terminal base unit to ensure accurate thermocouple readings.

Installation Best Practices

Installing the 1794-IT8 correctly involves a few straightforward steps. First, rotate the keyswitch on the terminal base unit—such as the 1794-TB2, -TB3, or -TB3T—to Position 3. Next, insert the module firmly into the base and secure it. The module accepts both grounded and ungrounded thermocouples, so connect your sensors to the appropriate terminals on the base unit. Finally, supply the module with the required 24V DC power. A red/green status indicator on the front panel provides immediate visual feedback on the module's operational health.

Packaging and Shipping Information

Your order will include the following items:

• 1 x 1794-IT8 Thermocouple/mV Input Module

• 1 x Insertable Label for channel identification

• Note: The terminal base unit and Cold Junction Compensator (CJC) are not included and must be ordered separately.

• Shipping: We ship all orders via FedEx, UPS, or DHL for fast and reliable delivery.

Frequently Asked Questions (FAQ)

1. What types of thermocouple sensors does the 1794-IT8 support?
The 1794-IT8 supports a comprehensive list of thermocouple types, including J, K, E, R, N, S, B, C, T, and L sensors.

2. What is the resolution of the 1794-IT8 module?
This Flex I/O module offers a 16-bit resolution, which provides high-precision data conversion for your input signals.

3. What is the required keyswitch position for the 1794-IT8?
You must set the keyswitch on the terminal base unit to Position 3 before inserting the 1794-IT8 module.

4. How does the 1794-IT8 communicate with the PLC?
The module uses a block-transfer programming method to move data and configuration information between its memory and the PLC's data table.

5. Does the 1794-IT8 include the terminal base unit?
No, the terminal base unit (e.g., 1794-TB2, -TB3) and the Cold Junction Compensator are not included and must be purchased separately.