Purchase now: Allen Bradley 1746-NI16I Analog Current Module
Purchase now: Atlantechdrives provides you the 1746-NI16I, a high-density analog input module meticulously designed by Allen Bradley for the SLC 500 programmable logic controller series. This specific module is engineered exclusively to process analog current signals, making it an essential component for continuous process control applications. It provides 16 single-ended input channels capable of reading standard industrial 4-20 mA, 0-20 mA, or +/- 20 mA signals. By converting these continuous analog currents into precise 16-bit digital values, the 1746-NI16I allows the SLC 500 processor to accurately monitor fluid levels, pipeline pressures, temperature transmitters, and variable speed drive feedbacks across complex manufacturing environments.
Technical Specifications of the 1746-NI16I
The 1746-NI16I utilizes advanced sigma-delta analog-to-digital (A/D) conversion technology to provide exceptionally high resolution and noise immunity. The high-density design saves valuable chassis space, replacing four standard 4-channel modules.
- Part Number: 1746-NI16I
- Module Type: High-Density Analog Input
- Signal Type: Current (mA) Only
- Number of Channels: 16 Single-ended inputs
- Input Range: -20 to +20 mA, 0 to 20 mA, 4 to 20 mA
- Resolution: 16-bit (Highly precise)
- Input Impedance: 250 Ohms
- Backplane Current Draw: 125 mA at 5V DC, 75 mA at 24V DC
- Update Time: Programmable (depending on filter settings)
Expert Tips: Troubleshooting 4-20mA Loops
Working with current loops requires specific diagnostic techniques. Expert Tip: If the PLC is reading a zero or erroneous value from a sensor connected to the 1746-NI16I, do not immediately break the wire to insert your multimeter in series. Instead, leverage the module’s known input impedance. The 1746-NI16I has a fixed 250-ohm internal resistor across each input channel. You can use your digital multimeter set to DC Voltage to measure across the input terminals (e.g., IN+ and IN-). According to Ohm’s Law (V = I * R), a healthy 4 mA signal will show exactly 1.0V DC across the terminals, and a 20 mA signal will show 5.0V DC. This allows you to verify the analog signal safely without interrupting the active loop or risking a process shutdown.
Installation and Maintenance Advice
Because the 1746-NI16I has 16 single-ended channels, all inputs share a common return path. It is absolutely critical to prevent ground loops. Ensure that the 24V DC power supply driving your analog sensors is grounded at one single point in the control cabinet. Always use high-quality, individually shielded twisted-pair cables (like Belden 8761) for your analog runs, and ground the drain wire (shield) only at the PLC chassis end, never at the sensor end. Leaving the shield floating at the sensor prevents current from traveling along the shield and inducing electrical noise into the delicate mA signal.
Frequently Asked Questions (FAQs)
Q: Can the 1746-NI16I read 0-10V DC signals?
A: No. The «I» in the part number stands for Current. Applying a direct 10V or 24V voltage source across these terminals can burn out the internal 250-ohm shunt resistor. For voltage applications, you must use the 1746-NI16V.
Q: Does this module supply loop power to 2-wire transmitters?
A: No, the 1746-NI16I is a passive receiver. You must provide an external 24V DC power supply wired in series with your 2-wire transmitters to power the loop.
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This 16-channel current module is technically designed for high-density racks such as the 1746-A10 chassis.
