Keyence flow sensor FD-P100 FDP100 FD-P100

Keyence FD-P100 | Flow Pressure Sensor Head — Liquid Flow Detection, PLC-Compatible, Inline Mounting

Overview

The Keyence FD-P100 is the sensor head component of Keyence's separate-amplifier digital flow sensor system, covering a flow range of 10 to 100 litres per minute in liquid monitoring applications.

It works as part of an integrated system: the FD-P100 sensor head is installed directly in the flow line, while a separate amplifier unit (FD-V70A for DIN rail or FD-V75A for panel mounting) is mounted at a convenient control panel location — keeping the electronics away from the fluid, heat, and vibration at the detection point.

This split architecture is the practical advantage of the separate-amplifier design.

The sensor head itself carries no electronics at risk from coolant spray, process temperature, or mechanical vibration. Its job is purely fluid mechanical: to generate the signal that the amplifier processes.

The amplifier, mounted in a controlled panel environment, contains the display, threshold comparators, analogue output, and PLC interface.

Engineers familiar with Keyence's FD series will recognise this as the same philosophy used across the FD-V product family — sensor heads matched to amplifiers, each optimised for their respective operating environments.

In PLC-based manufacturing systems, the FD-P100 provides the flow data that PLC programs use for cooling circuit monitoring, coolant flow confirmation before machining operations begin, process fluid control, and alarm generation when flow drops below minimum safe thresholds.

The amplifier's NPN or PNP open-collector outputs (depending on amplifier variant) connect directly to the PLC's digital input module without intermediate signal conditioning.

Key Specifications

Separate-Amplifier Architecture — Two Components, One System

The FD-P100 sensor head and its paired amplifier form a system where physical separation between the sensing point and the control electronics is the defining engineering advantage.

In manufacturing environments where the sensor must be positioned close to pumps, inside machine enclosures, adjacent to heat sources, or anywhere that subjects electronics to stress, the split architecture allows optimal sensor placement without compromising amplifier reliability.

The amplifier's dual-level LED display provides simultaneous visibility of both the current flow value and the programmed threshold — a practical feature during commissioning (setting the threshold accurately) and during routine maintenance checks (confirming the process is operating within specification without stopping the machine).

The display updates five times per second in normal operation, fast enough to see transient flow variations in real time.

Two control outputs from the amplifier provide independent threshold monitoring — one output can signal "normal flow confirmed" while the second signals "flow too low, halt operation."

This dual-output capability serves safety interlock applications where confirmation of both minimum and maximum flow bounds is required in a single installation.

Response Time and Analogue Output

The selectable response time (0.5 to 60 seconds) is not a limitation — it is a deliberate averaging function that determines how quickly the displayed and output values respond to flow changes.

Short response times (0.5–1 second) are appropriate when detecting rapid flow shutdowns or surges.

Longer response times (5–60 seconds) average out turbulence-induced fluctuations in steady-flow applications, producing a stable display and output that does not trigger false alarms from momentary pulsing.

The analogue output (via amplifier), with 0.5% full-scale accuracy at 20°C/25°C, translates the full 10–100 L/min flow range into a proportional electrical signal suitable for PLC analogue input modules.

This continuous signal allows supervisory systems to trend flow data over time, calculate cumulative consumption, and detect gradual degradation in pump or filter performance as a progressive trend rather than only responding to threshold crossings.

PLC Integration — Direct Connection to Control Systems

The amplifier paired with the FD-P100 is designed from the ground up as a PLC field device.

Power is drawn from the PLC's 24V DC field power supply; the NPN or PNP output logic directly matches the PLC input card polarity without adapters; the analogue output connects to standard 4–20 mA or voltage analogue input channels.

No signal converters, relay interfaces, or intermediate amplifier stages are required between the FD system and the PLC.

For process confirmation interlocks — where a machining cycle cannot begin until cooling flow is verified — the PLC reads the flow status output from the FD amplifier as a standard digital input.

The machine program waits for "flow confirmed" before authorising the next operation, exactly as it would with any other field sensor.

FAQ

Q1: The FD-P100 is described as a "sensor head" — what does the complete system consist of?

The FD-P100 is the in-line sensing element only. A complete operational system requires pairing the FD-P100 with a compatible Keyence FD-V series amplifier: FD-V70A (DIN rail, NPN output), FD-V70AP (DIN rail, PNP output), FD-V75A (panel mount, NPN), or FD-V75AP (panel mount, PNP).

The amplifier provides the 12–24V DC supply, processes the sensor head signal, drives the LED display, generates the switching outputs, and provides the analogue output.

The sensor head alone produces no usable output.

Q2: What liquids are compatible with the FD-P100?

The FD series is designed for industrial liquid flow monitoring including cooling water, cutting coolants, hydraulic oils, and general process liquids. Compatibility with specific chemicals, solvents, or high-temperature liquids should be confirmed against Keyence's compatibility data for the FD-P series wetted materials before installation.

For aggressive chemicals or ultra-pure liquids where material contamination is a concern, confirm wetted part materials against the process fluid specification.

Q3: How are the flow thresholds set on the amplifier?

The FD-V70A/V75A amplifiers provide threshold setting through front-panel buttons while monitoring the current flow value on the LED display.

Two independent threshold levels (upper and lower limit) can be configured independently. 

The amplifier also supports bank switching via external input — a PLC can select between up to four pre-programmed threshold sets by switching bank inputs, allowing the same sensor to serve multiple products or process conditions without manual threshold adjustment.

Q4: What is the analogue output accuracy figure of 0.5% F.S. referenced to?

The 0.5% full-scale accuracy applies at a fluid temperature of 20°C and an ambient temperature of 25°C — the standard reference conditions for Keyence's FD series accuracy specification.

At other fluid or ambient temperatures, thermal effects on both the sensor head and the amplifier electronics may produce slightly larger deviations.

For flow monitoring applications requiring accuracy across a wide temperature range, evaluate the amplifier's temperature coefficient specification and the expected operating temperature range.

Q5: Can the FD-P100 detect both flow rate and pressure simultaneously?

The FD-P100 is a flow sensor head. Pressure measurement requires a separate pressure sensor.

The "P100" designation in the flow range indicates the maximum flow rate (100 L/min) rather than a pressure measurement function.

For simultaneous flow and pressure monitoring, a separate pressure transmitter or switch connected to the same PLC is the standard approach.