Allen-Bradley 1771-ILK Analog Input | 8 Isolated Channels PLC5

Product Introduction

The Allen-Bradley 1771-ILK analog input module delivers reliable analog signal acquisition for your PLC5 control system. This module offers eight fully isolated differential input channels, each rated at 1000V isolation, which effectively eliminates ground loop problems and improves measurement accuracy. The 1771-ILK supports a wide variety of field instruments by accepting both unipolar voltage signals (0–5V, 1–5V, 0–10V DC) and unipolar current signals (4–20mA, 0–20mA). Additionally, this module features a conformal coating that protects the circuitry against moisture, dust, and chemical contaminants. Therefore, the Allen‑Bradley 1771‑ILK is particularly suitable for harsh industrial environments where standard modules might fail prematurely.

Technical Specifications

Input Channels and Signal Ranges
The 1771-ILK provides eight isolated differential inputs with 1000V of isolation between channels and the backplane. For voltage inputs, you can configure each channel for 0–5V, 1–5V, or 0–10V DC. For current inputs, the module accepts 4–20mA and 0–20mA. This selection of unipolar input options makes the Allen‑Bradley 1771‑ILK compatible with most standard transmitters and sensors used in process control applications.

Resolution and Data Format
This module offers a resolution of 15 bits plus a sign bit, translating to 16-bit total resolution. Consequently, it delivers precise measurement across the entire input range. The 1771-ILK supports two data formats: natural binary and BCD scaling to ±9999. For all unipolar ranges (0–5V, 1–5V, 0–10V, 0–20mA, and 4–20mA), the digital count spans from 0000 to +4095. This flexibility allows you to choose the format that best matches your PLC programming and HMI requirements.

Update Rate and Accuracy
The channel update time is 500 ms for all eight channels, while the internal scan rate is 50 milliseconds. Meanwhile, the module maintains high accuracy across different signal types, though specific accuracy figures are consistent with the standard 1771-IL model. The Allen‑Bradley 1771‑ILK ensures stable and repeatable readings for monitoring and closed-loop control.

Built‑In Protection and Diagnostics
To enhance system reliability, the 1771-ILK includes open‑circuit detection, which immediately alerts you to broken sensor wiring. Input overvoltage protection safeguards the internal circuitry from accidental high‑voltage spikes. Furthermore, the auto‑calibration feature compensates for temperature drift, maintaining long‑term accuracy without manual recalibration. The conformal coating adds an extra layer of defense against environmental stress, making the 1771-ILK a robust choice for demanding installations.

Mechanical and Environmental Parameters

Power Requirements
The 1771-ILK draws 1.3 Amperes from the backplane and does not require any external power supply. Therefore, installation is straightforward, as you only need to insert the module into a compatible 1771 chassis slot.

Mounting and Wiring
This module is rack‑mountable and occupies a single slot in any 1771 I/O chassis. The recommended wiring arm for this module is the 1771‑WF (sold separately). This wiring arm simplifies field terminations and maintenance. Additionally, the module includes a status indicator that provides visual confirmation of operational status, aiding in troubleshooting.

Conformal Coating Advantage
The conformal coating on the 1771-ILK is a thin protective layer applied to the circuit board. This coating resists moisture, dust, and corrosive fumes. For this reason, the Allen‑Bradley 1771‑ILK is ideal for use in chemical plants, food processing facilities, and outdoor installations where environmental exposure is a concern.

Signal Delay Characteristics
For AC signals, the typical off‑delay is 24 ms (±10 ms). For DC signals, the typical off‑delay is 20 ms (±9 ms). These values are important when designing time‑sensitive control logic, as they affect how quickly the module responds to input changes.

Installation Guidelines

Chassis Installation
First, power down your 1771 chassis before inserting the 1771-ILK. Choose an available slot, preferably away from high‑voltage or high‑noise modules. Push the module firmly into the backplane connector until it seats properly. The single‑slot design allows you to maximize I/O density within your rack.

Wiring Connections
Next, attach the 1771‑WF wiring arm to the front of the module. Use shielded twisted‑pair cables for all analog signal connections to minimize electromagnetic interference. For differential inputs, connect the positive and negative leads to the corresponding terminals on the wiring arm. If you are using current loops, ensure the internal resistor is correctly configured. Always verify polarity and signal levels before reapplying power to the system.

Configuration and Setup
After physical installation, configure the input ranges using the module’s hardware jumpers or through your PLC5 programming software. Select either natural binary or BCD data format to match your application needs. Then, write a block transfer read instruction in your PLC logic to retrieve the analog data from the Allen‑Bradley 1771‑ILK. Finally, monitor the status indicator to confirm normal operation.

Packaging List

• Allen-Bradley 1771-ILK isolated analog input module (1 unit)

• Product documentation (installation instructions and user manual)

• No certificates or warranty cards are included in the package

Shipping Method: FedEx, UPS, or DHL

Frequently Asked Questions

1. What is the main difference between the 1771-IL and the 1771-ILK?
The primary difference is the conformal coating on the 1771-ILK. This protective layer makes the Allen‑Bradley 1771‑ILK more resistant to moisture, dust, and chemicals, making it suitable for harsh environments.

2. Which wiring arm does the 1771-ILK require?
The 1771-ILK uses the 1771‑WF wiring arm. Please ensure you order this accessory separately, as it is not included with the module.

3. Does the 1771-ILK support only unipolar input signals?
Yes, the 1771-ILK as configured for unipolar operation supports 0–5V, 1–5V, 0–10V, 0–20mA, and 4–20mA ranges. The digital output for all these ranges is 0000 to +4095.

4. How does the conformal coating affect installation?
The conformal coating does not change the installation procedure. However, the Allen‑Bradley 1771‑ILK provides better long‑term reliability in humid or dusty environments compared to uncoated modules.

5. What data formats does the 1771-ILK support?
This module supports natural binary and BCD scaling to ±9999. You can select the preferred format during configuration to match your PLC5 programming requirements.