Allen-Bradley 1771-CFMK PLC-5 Configurable Flowmeter Module

Product Overview

The 1771-CFMK is an Allen-Bradley configurable flowmeter module engineered for high-accuracy rate calculation and pulse totalizing within PLC-5 and related 1771 I/O chassis systems. Occupying a single I/O slot with a unit weight of approximately 0.9 kg (2.0 lbs), this intelligent block-transfer module bridges field flow sensing devices directly with Allen-Bradley PLC-2, PLC-3, PLC-5, and PLC-5/250 processing architectures. Flexible in operation, the 1771-CFMK can function natively as a CFM module or serve as a functional replacement for legacy QRC and QRD modules. Operating on a 1 Amp backplane current draw with peak heat dissipation of 13 Watts, it delivers precise measurement capabilities for demanding process control tasks across power, chemical, and oil and gas industries.

Core Technical Advantages

• Flexible Multi-Signal Input Handling: Features 4 input channels that support magnetic pickup flowmeters (50 mV to 200 VAC), 4–40 VDC TTL-compatible pulse signals, and Bently Nevada 3300 proximity probe inputs.
• Versatile Dual-Function Modes: Each channel can be individually configured for flowmeter pulse input or high-speed gate control input to handle rate calculations or totalizing tasks.
• Broad Legacy Processor Compatibility: Seamlessly integrates with classic Allen-Bradley PLC-2, PLC-3, PLC-5, and PLC-5/250 series processors with block-transfer capabilities.

Technical Specifications

Industrial Applications

• Oil & Gas Pipeline Metering: Calculates continuous flow rates and volume totals from magnetic pickup turbine meters on fluid transport lines.
• Food & Beverage Batch Processing: Manages high-speed ingredient dispensing and liquid recipe metering using DC pulse flow sensors.
• Turbine & Rotating Equipment Monitoring: Processes proximity probe inputs from Bently Nevada systems for rotational speed and flow tracking.
• Power Generation Plant Management: Monitors high-pressure steam and boiler feed-water totals inside utility control systems.

Wiring & Installation

• 1771 Chassis Slot Insertion: Align the lightweight 0.9 kg module with keying bands and slide it firmly into the target slot on the 1771 I/O rack until securely latched to the backplane.
• Field Signal Wiring: Connect pulse, magnetic pickup, or proximity sensor wires to the corresponding terminal arm, utilizing shielded twisted pairs to protect low-level signal paths.
• Block Transfer Programming: Configure the PLC program using block-transfer read (BTR) and block-transfer write (BTW) instructions to transfer operational setup data and read flow values.
• Power Isolation & Safety: Disconnect main chassis power before installing or removing the 1771-CFMK card to prevent backplane bus transients.

Engineering Advantages

• Legacy Replacement Flexibility: Directly replaces legacy QRC and QRD modules, reducing redesign downtime during system revamps.
• Low Output On-State Drop: Delivers minimal voltage drop (0.6 Ohms × current) across output circuits for reliable control interfacing.
• Single-Slot Efficiency: Packs 4 flexible input channels and 4 solid-state outputs into a single-slot 1771 footprint to optimize rack space and panel weight distribution.

Technical FAQs

Q1: Which sensor types work with the 1771-CFMK inputs?
A1: Magnetic pickups (50mV–200VAC), 4–40VDC pulses, and Bently Nevada 3300 proximity probes.

Q2: Can the 1771-CFMK replace older QRC/QRD modules?
A2: Yes. It can operate as a CFM module or as a direct replacement for QRC/QRD cards.

Q3: How does the CPU read flow data from this module?
A3: The host PLC uses block-transfer read (BTR) and write (BTW) instructions over the backplane.