Allen‑Bradley 1790D-TN0C2 Current Output Module

Allen‑Bradley 1790D-TN0C2 2 Channel Analog Current Output Module

Product Introduction

The 1790D-TN0C2 from Allen‑Bradley provides two single‑ended analog current outputs in a compact DeviceNet base module. Each channel outputs 0‑20 mA with 12‑bit resolution. The resolution step size is 4.88 µA per bit, which gives you fine control over field devices.

Furthermore, this module delivers a conversion time of only 2 ms per channel. Overall accuracy is specified at 0.2% of full scale across the entire operating temperature range of 0‑55°C. One of the key advantages is that no field calibration is required, which reduces maintenance time and eliminates the need for precision test equipment.

Therefore, the 1790D-TN0C2 suits precision analog control applications. For example, you can control proportional valves, analog actuators, chart recorders, or variable frequency drives (VFDs). Additionally, dual red/green I/O status indicators help you monitor each channel's condition at a glance.

Technical Specifications (Analog Outputs)

• Outputs per module: 2 channels, single‑ended, non‑isolated between channels

• Output current range: 0…20 mA (key parameter)

• Resolution: 12 bits, 1/4096 max, 4.88 µA/bit (key parameter)

• Converted data format: Binary data, 0000 to 0FFF (max scale)

• Conversion time: 2 ms per channel

• Overall accuracy: 0.2% of full scale @ 0…55°C

• Calibration: None required (key advantage)

• Allowable external output load resistance: 600 Ω maximum

• Insulation resistance: 20 MΩ minimum at 250V dc (between insulated circuits)

• Indicators: 2 red/green I/O status LEDs

The binary data format uses a 12‑bit straight binary value. A count of 0000 corresponds to 0 mA, while 0FFF (4095 decimal) corresponds to 20 mA. This straightforward mapping simplifies programming in most PLC systems.

General & Power Specifications

• DeviceNet power supply: 24V dc nominal (range 11‑28.8V dc)

• DeviceNet power dissipation: 1.2W max at 28.8V dc

• Field power supply: 24V dc nominal (range 21.6…26.4V dc, +10%)

• Field power dissipation: 1.5W max at 26.4V dc

• Isolation:

  • I/O to logic: photocoupler isolation, 1250V ac rms type test for 60 seconds

  • DeviceNet to logic: non‑isolated

  • Field power: non‑isolated

• Wiring terminal block: M3.0 screw type, torque 7 lb‑in max (use copper or copper‑clad aluminum conductors)

Important limitation: This analog base module can accommodate a maximum of two discrete expansion modules. Do not attempt to add more than two expansion modules to the 1790D-TN0C2.

Mechanical & Environmental Information

The 1790D-TN0C2 mounts on a standard DIN rail or panel. It operates reliably from 0°C to 55°C ambient temperature. Storage temperature ranges from -40°C to 85°C. Humidity tolerance is 5‑95% non‑condensing.

Additionally, the module's field power dissipation is 1.5W maximum, while DeviceNet dissipation is 1.2W maximum. Total heat output remains low, so forced cooling is typically unnecessary. The high insulation resistance (20 MΩ minimum) ensures reliable separation between insulated circuits.

Installation Guidelines

First, disconnect DeviceNet power and the external 24V dc field power supply. Next, mount the 1790D-TN0C2 on a DIN rail or using panel mounting screws.

For wiring, use copper conductors sized 0.5‑1.5 mm² (20‑16 AWG). Tighten each M3 screw to 7 lb‑in maximum. Connect the external 24V dc field power supply to the designated field power terminals. Ensure the voltage stays within 21.6‑26.4V dc.

Then connect each analog output channel to its load. The external load resistance must not exceed 600 Ω. For example, a 250 Ω resistor gives a 0‑5V signal, while 500 Ω gives 0‑10V. Connect the DeviceNet cable to the module's pass‑through connectors.

If you need additional I/O points, you can attach up to two discrete expansion modules. Finally, apply field power first, then apply DeviceNet power. Monitor the red/green status LEDs to confirm normal operation.

Packaging List (Per Unit)

• 1790D-TN0C2 2 Channel Analog Current Output Module – 1 pc

• Terminal block (pre‑attached) – 1 pc

• Quick start guide (printed) – 1 pc

• Dust cover – 1 pc

Note: No certificates or warranty documents are included in the package.

Shipping & Delivery

We ship worldwide via FedEx, UPS, or DHL. All modules are packed in anti‑static and anti‑shock materials. Tracking number will be provided within 24 hours after dispatch.

Frequently Asked Questions (FAQ)

1. Can I output 4‑20 mA instead of 0‑20 mA with the 1790D-TN0C2?
Yes. Simply scale your binary output values accordingly. 4 mA corresponds to 819 counts (20% of 4095), while 20 mA is 4095 counts. The module natively outputs 0‑20 mA, so you must handle the 4‑20 mA scaling in your PLC program.

2. What happens if I exceed the 600 Ω load resistance?
The output current will drop below the commanded value, and accuracy will degrade. For reliable operation, always keep the load resistance at or below 600 Ω per channel.

3. Why does the module not require calibration?
The 1790D-TN0C2 uses factory‑trimmed precision components. The 0.2% full‑scale accuracy is maintained over temperature without user adjustments. This feature saves you both time and equipment costs.

4. How many expansion modules can I add to this analog base?
A maximum of two discrete expansion modules can be connected. This limitation applies specifically to the 1790D-TN0C2 analog base. Exceeding this may cause power supply or communication issues.

5. What do the red/green status LEDs indicate?
Green means the channel is operating normally with a valid output. Red indicates an error condition, such as missing field power, an open circuit, or a shorted load. Check your wiring and load resistance if you see a red LED.