Product Overview

The 1771-CFM is a high-performance, four-channel flow measurement interface designed for the Allen-Bradley PLC-5 platform. This module serves as a bridge between industrial flowmeters and the control system, offering precise totalization and frequency measurement. Engineered for versatility, it supports independent configuration of each channel to accommodate various meter types and operational requirements. The hardware is compatible with several 1771 universal I/O chassis, ensuring seamless integration into existing legacy systems while providing the high-speed processing necessary for accurate flow monitoring.

Technical Specifications

• Number of Inputs: 4 independent flowmeter channels

• Input Signal Support: 2 flowmeter inputs and 1 gate input per channel

• Maximum Input Frequency: 100 kHz (120 kHz gate input overrange capability)

• Accumulation Capacity: Programmable totalizer from 0 to 9,999,999

• Logic Compatibility: 5V to 30V DC (TTL compatible)

• Input Impedance: 5 kΩ ±30% resistive

• Gate Input Specs: Dual ranges (5V to 12V and 12V to 30V DC); 22mA max current

• Output Configuration: 4 source outputs (1A per channel); 5V to 30V DC range

• Switching Performance: Totalizer-triggered ON/OFF in <100 µs; other modes <1 ms

• Signal Conditioning: Jumper-selectable high-speed or low-pass (<70 Hz) filtering

• Gate Debouncing: Software-selectable ~1s delay for transition stability

• Chassis Compatibility: 1771-A1B, A2B, A3B, A3B1, A4B (Series A/B); 1771-AM1, AM2

• Processing Latency: 1.3 ms to 5.0 ms module scan time; 5.5 ms BTW processing

• Integrated Power Supply: 24V DC output at 12mA for sensor excitation

• Backplane Power Consumption: 0.8A max @ 5V DC

Operational Applications and Modes

The 1771-CFM is specifically designed for liquid and gas measurement applications where precise volume tracking is critical. It supports multiple operational modes:

• Totalizer Mode: Ideal for batching operations where the gate input starts and stops the accumulation.

• Non-resettable Totalizer: Used for lifetime tracking of fluid throughput.

• Frequency/Rate Measurement: For real-time monitoring of flow velocity. The four onboard outputs can be mapped to any channel, allowing for hardware-level triggers when specific flow volumes are reached, effectively bypassing software scan latencies for critical shut-off valves.