Allen-Bradley 1790D-T4T0 4-Channel Thermocouple Base Module for DeviceNet

Product Overview

When temperature measurement accuracy is critical in industrial processes, the Allen-Bradley 1790D-T4T0 4-channel thermocouple base module for DeviceNet provides a reliable solution. This I/O module from the CompactBlock LDX series reads small millivolt signals from thermocouples, digitizes them, and transmits temperature data to a central processor over a DeviceNet network. It supports up to four independent temperature sensors, making it suitable for multi-point monitoring applications.

Technical Specifications

The 1790D-T4T0 accepts thermocouple inputs within a range of -76.50 mV to 76.50 mV and supports sensor types B, E, J, K, R, S, T, N, and 10 µV thermocouples. Resolution is 16 bits with 0.1 °C/bit or 0.1 °F/bit for thermocouple sensors. The module uses a 20-bit Sigma-Delta modulation converter and outputs data in 16-bit integer (2's complement) format. Scan time is 140 ms per channel with a notch filter set at 60 Hz. Overall accuracy is 0.2% full scale over the 0 to 55 °C temperature range. The module operates on a DeviceNet power supply of 24 V DC nominal, with a voltage range of 11 to 28.8 V DC. Field power requires 24 V DC nominal, range 21.6 to 26.4 V DC (+10%). Power dissipation is 1.2 W max at 28.8 V DC for DeviceNet and 1.5 W max at 26.4 V DC for field power. Isolation between I/O and logic uses photocoupler isolation with a type test of 1250 V AC RMS for 60 seconds. DeviceNet to logic and field power are nonisolated. Indicators include four red/green I/O status LEDs. Wiring uses a terminal block (M3.0) with a screw torque of 7 lb-in max, using copper or copper-clad aluminum conductors.

Industry Applications

This module excels in temperature monitoring for industrial ovens, chemical reactors, and HVAC systems. For example, in a plastic extrusion line, four thermocouples can monitor barrel zone temperatures, ensuring consistent melt quality. The 1790D-T4T0's open wire detection alerts operators to sensor faults, reducing unplanned downtime. Its compact design fits easily into existing DeviceNet networks, simplifying integration.

Installation and Setup

Mount the 1790D-T4T0 on a DIN rail in a clean, dry environment within the 0 to 55 °C operating range. Connect DeviceNet power (24 V DC) and field power (24 V DC) as per specifications. Wire thermocouples to the terminal block, ensuring correct polarity and using copper or copper-clad aluminum conductors. Tighten screws to 7 lb-in max. Configure the notch filter (10 Hz, 25 Hz, 50 Hz, 60 Hz, 100 Hz, 250 Hz, or 500 Hz) via software to match line frequency and reduce noise. Verify open wire detection by simulating a disconnected sensor.

Maintenance and Reliability

From a maintenance engineer's perspective, the 1790D-T4T0 offers straightforward serviceability. Periodically inspect terminal connections for tightness and check for corrosion. The module's photocoupler isolation protects against ground loops, enhancing reliability in harsh industrial environments. With no moving parts, the primary wear point is the terminal block; ensure screws are not overtightened. The 0.2% accuracy over 0 to 55 °C ensures consistent performance, reducing recalibration frequency.

Compatibility and Integration

The 1790D-T4T0 integrates seamlessly with DeviceNet networks, communicating with Allen-Bradley controllers such as CompactLogix or ControlLogix via a DeviceNet scanner. It supports multiple thermocouple types, allowing flexible sensor selection. The module's 16-bit resolution and 140 ms scan time per channel provide reliable data for process control loops.

Selection Guide and Purchasing Advice

Before purchasing, verify that your system uses DeviceNet and that the power supply meets the 24 V DC nominal requirement. The module weighs 0.50 lbs (0.23 kg) and is compact, so ensure adequate DIN rail space. For complete technical specifications for the 1790D-T4T0, please contact BluePLC Industrial. As a trusted supplier, BluePLC Industrial can confirm current lifecycle status and availability, ensuring you receive genuine Allen-Bradley components for your automation needs.