1771-IFMS | Allen-Bradley | PLC Intrinsically Safe Fast Millivolt Input Module

Product Description

The 1771-IFMS is a high-performance, 8-channel differential analog input module designed for the Allen-Bradley PLC 5 platform, specifically engineered to capture low-level 0–50 mV signals in hazardous environments. Featuring an intrinsically safe architecture and 12-bit resolution, this conformal-coated module provides a rapid 14.5 ms update rate and high-precision data conversion (0.1% accuracy) without the need for external power, making it an essential component for critical millivolt measurements in volatile industrial settings.

Technical Specifications

• Module Architecture: Fast Millivolt Analog Input

• Input Configuration: 8 Differential Channels (Intrinsically Safe)

• Measurement Range: 0 to 50 mV DC

• A/D Resolution: 12-bit binary

• Data Representation: ±32,767 Binary or ±9,999 BCD (selectable)

• Sampling Rate: 14.5 ms update for all 8 channels

• System Accuracy: 0.1% of range at 25 °C

• Non-Linearity: ±1 LSB

• Backplane Current Draw: 750 mA

• Isolation: Differential through intrinsically safe circuitry

• Required Wiring Arm: 1771-WG

• Environmental Protection: Conformal Coated PCB

• Mounting Compatibility: 1771 Universal I/O Chassis

• Unit Mass: 1.22 kg (2.69 lbs)

Application and Installation

This module is primarily utilized in process industries such as chemical refining, oil and gas, and pharmaceutical manufacturing where millivolt-level signals originate from Class I, II, or III hazardous locations. The 1771-IFMS ensures that the energy levels sent into the hazardous area are limited to prevent ignition.

Engineering FAQ

What is the benefit of the conformal coating on this module?The coating provides a thin polymeric film over the components of the 1771-IFMS. This is essential for PLC 5 systems located near sea air or chemical processing lines where airborne contaminants could otherwise cause short-circuiting or traces to corrode over time.

How does the "Fast" designation affect signal processing?With an update time of 14.5 ms for the entire channel block, the 1771-IFMS is significantly quicker than standard analog modules. This makes it suitable for high-speed PID loops or protective monitoring where millivolt fluctuations must be detected and processed by the PLC 5 processor in near real-time.