Allen-Bradley 1746-NI4 Overview
The Allen-Bradley 1746-NI4 is a versatile analog I/O module from the SLC 500 series. It provides four non-isolated differential input channels that you can configure for either voltage or current signals. This flexibility makes it suitable for a wide range of monitoring and control applications in industrial environments.
With a 16-bit resolution, the module ensures precise data conversion. It uses Delta-Sigma modulation to convert analog signals into digital values. For current inputs, the coding range is -16,384 to +16,384, while voltage inputs use -32,768 to +32,767. This allows for accurate representation of process variables.
Key Technical Specifications
The 1746-NI4 operates with a backplane current of 25 mA at 5 Volts and 85 mA at 24 Volts DC. It supports input signal ranges of -20 to +20 mA or -10 to +10V DC. The module has a bandwidth of 10 Hertz and an update time of 512 microseconds, making it responsive for real-time applications.
Resolution is a critical factor in analog modules. The 1746-NI4 offers 16-bit resolution, with a repeatability of ±1 LSB and non-linearity of 0.01%. These specifications ensure high accuracy and consistency in measurements.
Input Configurations and Accuracy
For current inputs, the module provides an input impedance of 250 Ohms and a resolution of 1.22070 µA per LSB. The overall accuracy at 25°C is ±0.365% of full scale, improving to ±0.642% at 60°C. For voltage inputs, the impedance is 1 mega Ohm, with a resolution of 305.176 µV per LSB. Accuracy at 25°C is ±0.284% of full scale, and at 60°C it is ±0.504%.
The step response time is 60 milliseconds, which is adequate for most process control loops. Cable lengths can be 0.5, 1, 2.5, or 5.0 meters, giving you flexibility in installation.
Installation and Compatibility
This module fits into any I/O slot except slot 0 of the SLC 500 chassis. It works with both fixed and modular SLC 500 controllers. The fixed hardware version has embedded I/O with limited expansion, while the modular version offers a fully customizable system. This compatibility makes the 1746-NI4 a practical choice for upgrades or new installations.
The module includes a removable terminal block for easy wiring. A DIP switch on the circuit board lets you select between voltage or current input for each channel. You must set this correctly to avoid damaging the module. For instance, do not connect a voltage source to a channel configured for current input.
Diagnostics and Status Indication
Built-in LED indicators show the status of each channel and the overall module operation. This provides quick diagnostics, which you can also access through the controller's diagnostic interrupt. Such features reduce troubleshooting time and increase system availability.
In summary, the Allen-Bradley 1746-NI4 offers reliable performance with its high resolution and flexible input options. Its compatibility with SLC 500 systems and robust design make it a solid choice for your analog input needs.