Secondary Coils: Frequency Range 400 Hz to 20 kHz

Component Specifications

Definition

Secondary coils are wound wire components in Linear Variable Differential Transformer (LVDT) feedback devices that, when excited by a primary coil's alternating current, produce voltage signals corresponding to the position of a movable ferromagnetic core. These coils are precisely wound and positioned to create differential output for accurate displacement measurement in industrial machinery.

Working Principle

When an AC voltage excites the primary coil, it induces voltages in two secondary coils wound in opposite directions. The movable core's position changes the magnetic coupling between primary and secondary coils, creating differential voltage output proportional to displacement.

Materials

Copper magnet wire (typically 38-44 AWG), polyurethane or polyamide-imide insulation, epoxy encapsulation, bobbin material (PBT, nylon, or ceramic), ferromagnetic core (nickel-iron alloy or permalloy).

Technical Parameters

Parameter	Typical range	Notes & selection driver
Linearity	±0.25% to ±0.5% of full range
Inductance	10-500 mH
Resistance	100-5000 ohms
Sensitivity	2-5 mV/V/mm
Frequency Range	400 Hz to 20 kHz
Operating Temperature	-40°C to +125°C

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Standards

ISO 9001, DIN EN 60529, IEC 60068

Parent Products

This component is used in the following industrial products

Feedback Device (e.g., LVDT)

A sensor component in servo valves that provides real-time position feedback of the valve spool to the control system.

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Engineering Analysis

Risks & Mitigation

Electromagnetic interference
Insulation breakdown
Mechanical damage to windings
Temperature sensitivity
Signal drift over time

FMEA Triads

Trigger: Vibration-induced wire fatigue
Failure: Open circuit in coil winding
Mitigation: Use epoxy encapsulation, implement strain relief, and conduct vibration testing per MIL-STD-810

Trigger: Moisture ingress
Failure: Insulation breakdown and short circuit
Mitigation: Apply conformal coating, use IP67-rated housing, and specify proper storage conditions

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

±0.1% of full scale output for precision applications

Test Method

IEEE 1193 standard for LVDT testing, including null voltage, phase shift, and linearity verification

Procurement Evaluation Criteria

A practical evidence checklist for RFQ preparation and supplier evaluation.

Technical documentation

Request current drawings, revision history, and a signed specification sheet.

Manufacturing capability

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Inspection readiness

Confirm test methods, calibrated equipment, sampling plans, and traceable reports.

Supplier transparency

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Manufacturers of Secondary Coils

Manufacturer profiles associated with Secondary Coils.

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Compiled and source-reviewed by the CNFX editorial team. Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review

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Frequently Asked Questions

What is the difference between primary and secondary coils in LVDT?

Primary coils receive excitation voltage to create magnetic field, while secondary coils generate output signals proportional to displacement through electromagnetic induction.

How do secondary coils achieve linear output?

Through precise winding geometry, symmetrical positioning, and differential connection that cancels common-mode errors while amplifying displacement-related signals.

Data Basis

Editorial classification, named public sources where available, and source-reviewed manufacturer records. See the editorial policy.

Preliminary Technical Classification

This page supports structured research, RFQ preparation, and supplier evaluation. It does not replace buyer-led supplier qualification, standards review, or technical approval.

Secondary Coils