Allen-Bradley 1790D-TN4V0 CompactBlock LDX Analog Input Block

The Allen-Bradley 1790D-TN4V0 is a CompactBlock LDX base block with 4 analog input channels. It is part of the DeviceNet distributed I/O family, allowing remote analog signal acquisition without a local PLC rack. The block accepts 4-20 mA current signals from sensors such as pressure transmitters, flow meters, and level sensors. Each channel has 12-bit resolution and is isolated from the backplane. The 1790D-TN4V0 communicates over DeviceNet using standard ODVA profiles, making it compatible with Allen-Bradley PLCs (ControlLogix, CompactLogix) and other DeviceNet masters. The unit is IP20 rated and designed for DIN rail mounting.

Technical Specifications

Number of analog inputs: 4, differential. Input signal: 4-20 mA (sinking). Input impedance: 250 Ω. Resolution: 12 bits (0-4095 counts). Accuracy: ±0.5% of full scale at 25°C, ±1.5% over temperature. Update time: 10 ms per channel (typical). DeviceNet communication: baud rates 125, 250, 500 kbps (automatic). Power supply: 24 V DC (11-25 V), consumption 80 mA. Dimensions: 120 mm × 80 mm × 60 mm. Weight: 0.3 kg. Operating temperature: 0°C to 55°C. Storage: -40°C to 85°C. Humidity: 5-95% non-condensing. Protection: IP20. Certifications: CE, UL, RoHS.

Key Features

• 4 analog inputs, 4-20 mA range, 12-bit resolution

• DeviceNet slave interface for remote I/O

• Compact block design includes built-in DeviceNet connector

• Removable terminal blocks for easy wiring

• LED status indicators for power and network

• DIN rail mounting

• Compatible with Allen-Bradley RSLogix 5000 via EDS file

DeviceNet Integration

The 1790D-TN4V0 appears as a DeviceNet slave node. It supports polled I/O and explicit messaging. The I/O data consists of 8 bytes of input data (4 channels × 2 bytes) plus status bytes. Configuration parameters include input range, filter time, and scaling. The device’s EDS file can be imported into RSNetWorx for DeviceNet to set the node address and baud rate. The block can be connected to a DeviceNet trunk line via the 5-pin open-style connector.

Applications

The 1790D-TN4V0 is used to bring analog signals into a DeviceNet network without a local PLC. Typical applications include remote monitoring of tank levels, pump pressures, and flow rates in water treatment, chemical processing, and packaging lines.

Installation and Wiring

Mount the block on a 35 mm DIN rail. Connect 24V DC power to the V+ and V- terminals. Connect the DeviceNet cable to the 5-pin connector (V+, CAN_H, shield, CAN_L, V-). For each analog channel, connect the sensor (+) to the input terminal and sensor (-) to the common terminal (ANLG COM). Use shielded twisted-pair cable for analog signals. Set the DeviceNet node address using the DIP switches on the block. Baud rate is auto-detected or set via DIP switches. After wiring, power up and verify the Module Status LED (green).

Maintenance and Diagnostics

LED indicators: MOD (green/red) for module status, NET (green/red) for network status. If the MOD LED is red, check power supply and internal fault. The block has no user-serviceable parts. Clean with compressed air periodically.

Conclusion

The Allen-Bradley 1790D-TN4V0 CompactBlock LDX provides a cost-effective, space-saving solution for adding 4 analog inputs to a DeviceNet network. Its compact design and straightforward integration make it suitable for distributed I/O applications.