Karrie FD200 Series DC Spring-Return LVDT

Overview

The Karrie FD200 Series DC Spring-Return Linear Variable Differential Transformer (LVDT) is an industrial-grade displacement transducer engineered for high-reliability position sensing in demanding environmental conditions. Unlike traditional AC-operated LVDTs requiring external signal conditioning, the FD200 integrates a built-in DC-to-DC converter and solid-state electronics to deliver directly usable analog output—eliminating the need for external demodulation circuitry. Its spring-return armature design ensures consistent mechanical centering without external biasing, enabling repeatable zero-position recovery after full-stroke deflection. The sensor operates on a robust electromagnetic principle: core displacement modulates mutual inductance between primary and secondary windings, with internal electronics converting this differential voltage into a stable, low-impedance DC output. This architecture supports long-term stability and minimal hysteresis—critical for closed-loop control systems in automated machinery and structural monitoring applications.

Key Features

• IP68-rated hermetic sealing achieved via fully welded stainless steel housing and molded waterproof circular connectors—validated for continuous submersion in water, oil, and particulate-laden environments.
• Spring-return armature mechanism provides passive, self-centering behavior without reliance on external springs or magnetic latching—reducing mechanical wear and extending service life beyond 50 million cycles.
• Low-noise analog output (≤5 mV rms) with 250 Hz bandwidth enables real-time feedback in dynamic motion control systems, including servo-valve positioning and hydraulic actuator monitoring.
• Multi-output compatibility: factory-configurable 0–5 V, 0–10 V, or 4–20 mA outputs—ensuring seamless integration with PLCs, DAQ systems, and SCADA platforms compliant with IEC 61000-6-2/6-4 EMC standards.
• Thermal stability optimized through matched expansion coefficients of coil former, core, and housing—delivering <0.01 %/°C temperature coefficient across the full operating range (–25 °C to +85 °C).
• High-resolution measurement capability (0.1 µm) combined with ±0.25 % full-scale linearity error—meeting performance thresholds required for precision metrology in CNC machine tool calibration and aerospace component testing.

Sample Compatibility & Compliance

The FD200 is designed for direct integration into metallic, composite, and hydraulically actuated mechanical assemblies where space-constrained, non-contact position feedback is required. Its compact 20 mm outer diameter and axial mounting configuration support installation in tight envelopes typical of servo cylinders, brake calipers, and turbine blade clearance sensors. The device complies with RoHS Directive 2011/65/EU and meets IEC 60529 for IP68 ingress protection. While not intrinsically safe, it is suitable for use in Zone 2 hazardous locations when installed with appropriate barrier systems per IEC 60079-11. For regulated industries—including medical device manufacturing and automotive Tier-1 supply chains—the FD200’s traceable calibration documentation and material certifications (e.g., EN 10204 3.1) support GLP/GMP audit readiness.

Software & Data Management

As a self-contained analog transducer, the FD200 does not require embedded firmware or host software for basic operation. However, its standardized output signals are natively compatible with industry-standard data acquisition frameworks—including National Instruments DAQmx, Keysight PathWave, and MATLAB Data Acquisition Toolbox—enabling time-synchronized multi-channel acquisition and post-processing. When deployed in networked IIoT architectures, the 4–20 mA variant interfaces directly with HART-enabled field devices for diagnostic parameter readout (e.g., internal temperature, supply voltage status). All factory calibration reports include NIST-traceable uncertainty budgets per ISO/IEC 17025 requirements, supporting long-term data integrity in FDA 21 CFR Part 11-compliant validation protocols.

Applications

• Aerospace: Landing gear extension monitoring, flap actuator feedback, and engine vane position sensing under vibration and thermal cycling.
• Industrial Automation: Real-time stroke verification in hydraulic presses, injection molding machines, and robotic end-effector positioning.
• Civil Infrastructure: Long-term settlement and expansion joint displacement monitoring in bridges, tunnels, and high-speed rail viaducts.
• Energy & Process: Valve stem position feedback in coal-fired boiler controls, slurry flow regulation in cement kiln feed systems, and paper machine nip load optimization.
• Transportation: Brake pad wear measurement in heavy-duty commercial vehicles and suspension travel sensing in intelligent rail bogies.

FAQ

What is the maximum cable length supported for 4–20 mA output without signal degradation?
For standard twisted-pair shielded cable (AWG 22), the FD200 maintains signal integrity up to 1,000 meters—subject to loop resistance ≤ 600 Ω and proper grounding per IEC 61000-6-2.

Can the FD200 be calibrated for custom stroke ranges outside 0–200 mm?
Yes—Karrie offers OEM calibration services for stroke lengths from 0.5 mm to 500 mm, with corresponding linearity and temperature coefficient recharacterization documented in the final certificate.

Is the stainless steel housing compatible with seawater immersion?
The AISI 316L stainless steel construction resists chloride-induced pitting; however, prolonged static immersion in undiluted seawater requires optional electropolished finish and crevice-free weld inspection per ASTM A967.

Does the FD200 meet MIL-STD-810G for shock and vibration?
While not formally certified, the FD200 has demonstrated operational resilience to 50 g shock (half-sine, 11 ms) and 20 g RMS random vibration (10–2000 Hz) in third-party laboratory testing—data available upon request.