INDUCTIVE DISPLACEMENT / OEM CONFIGURATION[email protected]
LVDTPRECISION METROLOGY

LVDT ENGINEERING GUIDE / REVIEWED 5 NOVEMBER 2026

How an LVDT works.
What its wires actually mean.

A transformer measures the core position. The complete measurement depends on excitation, phase-sensitive demodulation, calibration and the mechanical installation.

One primary. Two opposed secondaries.

An AC-excited primary couples magnetic flux through a movable core into two secondary coils. Around electrical null, their differential output changes with displacement. The AC phase encodes direction; a compatible demodulator produces a signed position signal.

Vout ∝ VS1 − VS2

This is an idealized relationship within the specified linear measuring range. Actual scaling depends on excitation, coil sensitivity, phase, load and electronics. Reversing connections can reverse the sign.

A DC-LVDT includes excitation and demodulation electronics. It still uses a transformer internally; its external supply and conditioned output are DC or digital.

INDUCTIVE POSITION / LIVE PRINCIPLEAC EXCITED
S₁PS₂−+Signed demodulated output (idealized)

Vout ∝ VS1 − VS2 Phase-sensitive demodulation gives direction.

SIGNAL INTEGRATION

3, 4, 5 or 6 wires: identify the circuit first.

Wire count and cable colour do not identify a universal pinout. Use the released sensor and conditioner drawings.

Conditioned DC · 3-wire

+V → sensor

Common ↔ PLC reference

Signal → voltage / current input

Separate supply and output; check output load. Colours such as red, black and green are examples only.

Conditioned DC · 4-wire

Supply + / supply return

Signal + / signal return

Confirm isolation and reference

A fourth wire may have another purpose. A two-wire 4–20 mA loop needs its own wiring diagram.

AC-LVDT · 4 / 5 / 6-wire

2 primary excitation leads

4-wire: opposed secondaries internally joined

5-wire: centre tap; 6-wire: separate coils

Match phase, amplitude, frequency and topology to the conditioner. Pair with LVP-AMP after review.

Half-bridge / digital

3-wire may be an inductive half-bridge

RS485: power, A/B and reference per model

Orbit requires its network interface

Half-bridge, analogue AC and digital networks are distinct interfaces.

Read the LVDT excitation & connection guide ↗

Before power: check this signal chain.

  1. Identify the exact sensor model and drawing: AC-LVDT, conditioned DC, half-bridge or a proprietary digital probe.
  2. For AC, match excitation amplitude/frequency, primary impedance, phase shift, input topology, sensitivity and cable loading. Check secondary polarity and conditioner null/span settings.
  3. For voltage output, check input impedance and common reference. For 4–20 mA, identify two-wire loop or separately powered wiring and verify compliance voltage/load. Confirm the actual current at null and the sign of travel; never assume 4 mA means electrical null.
  4. For RS485, confirm power, reference, shielding, termination, addressing and protocol registers. A/B labels alone do not establish interoperability.
  5. Move through the approved range against a displacement reference; record zero, span, residual error, direction and temperature.

MECHANICAL SELECTION

Free core, guided rod or spring contact?

Free unguided core

Separate the moving core from the coil body. External guidance must maintain clearance; the electromagnetic sensing element has no sliding electrical contact.

Captive guided rod

A guided assembly simplifies linkage. Review side load, rod alignment, bearings and usable travel before integrating.

Spring-return probe

A contact tip follows the measured surface. Review tip force, pre-travel, overtravel and contact wear.

Concept schematics. Non-contact induction does not make bearings, springs or contact tips wear-free.

Stroke and calibration: avoid the two common mix-ups.

Does ±25 mm mean a 25 mm total stroke?

No. ±25 mm describes a bipolar range spanning 50 mm. State the range convention and electrical null when requesting a configuration.

Does 0.001 mm micrometer resolution prove 1 μm calibration accuracy?

No. Calibration requires reference uncertainty, alignment, fixture stiffness, thermal control, repeatability and traceability as applicable. A 25 mm stand cannot verify a 600 mm full-range sensor without a suitable method and equipment.

Can an LVDT simulator calibrate the mechanical sensor?

A simulator can check a compatible conditioner or acquisition channel. It does not test the sensor core, coil geometry, probe mechanics or full measurement chain.

Can multiple AC probes operate next to each other?

Review carrier frequency, cable routing, shielding and synchronization. Master/slave synchronization is an equipment-specific option, not a universal remedy for cross-talk.

Manufacturer references used for interface review

Beckhoff: LVDT and half-bridge connection types ↗TE Connectivity: HSTA / HSTAR AC-LVDT family ↗Solartron Metrology: non-repeat and measurement noise ↗

Published by LVDT Precision Metrology. Manufacturer data applies to its identified products, not to LVP performance qualification.

REQUEST A CONFIGURATION REVIEW

Tell us what
moves. And how
you need to read it.

LVDT sensor, probe or complete signal chain.

Send the working range, mechanical arrangement and electrical interface. Add the original model when reviewing a replacement.

[email protected] ↗
Drawings, CAD and calibration documentation are configuration-specific. Engineering will confirm the proposed scope, price and schedule.
LVDT engineering RFQ

Complete the installation.

Optional accessories · reference budgets in USD · final price by quotation.

Selected accessory budget: $38Sensor, tax and freight excluded. No payment at this stage.