SEGMENsensor LVDT gauging probe sensors are precision displacement transducers designed for automated dimensional measurement, 100% in-process inspection, and coordinate gauging fixtures. The hardened probe tip (ruby ball, carbide, or flat) rides directly on the workpiece surface. Stroke 5–50 mm. Linearity ±0.05% FS. AC LVDT output or integrated 4-20mA/0-10V signal conditioner. Stainless steel housing. CE certified. OEM from Shenzhen since 2019, OEM volume supply.
A SEGMENsensor LVDT gauging probe is a precision displacement transducer whose ruby, carbide or flat tip touches the workpiece directly, for automated dimensional inspection and gauging fixtures. The tip moves the LVDT core, and the probe outputs an AC differential signal or a conditioned 4-20 mA / 0-10 V signal over strokes of 5–50 mm.
Stroke options are 5, 10, 25 and 50 mm.
Reference-grade probes reach ±0.02% FS linearity, and hysteresis is below 0.01% FS.
Probe tips are hardened ruby balls of 1 or 2 mm, tungsten carbide, flat disc or needle.
Gauge bodies are 316L stainless steel with 8 mm or 12 mm diameter; the DC version runs on 15–30 V DC.
Qualification samples are 1–5 pcs, and the probes are CE and RoHS compliant.
Last updated · SEGMENsensor Engineering Team
Watch: how to choose, mount and wire an LVDT
LVDT Sensor: How to Choose, Mount and Wire It (AC vs DC)Gauging probe, separate core or pen type; AC or DC output; mounting without side load, setting the null point, and wiring to a PLC or a signal conditioner.
LVDT displacement sensors: how to choose one, mount it, and wire it. An LVDT has one primary coil and two secondary coils. A movable core changes how strongly they couple, so the output follows the core position, with no contact and no wear. With the core in the centre, the null point, the two secondary signals cancel. Move the core either way and the output rises, and its sign tells you the direction. There are three main types. Gauging probes have a spring-loaded tip for dimension checks, with ranges from ±0.5 mm to ±5 mm. Separate-core LVDTs, where the core rides on the moving part, cover ±2 to ±100 mm. Pen-type sensors with a built-in conditioner reach ±500 mm. Next, choose the output. An AC LVDT needs an external excitation of 1–10 kHz and a signal conditioner. A DC LVDT has the electronics built in. Supply 10–30 V DC, and read 4–20 mA, 0–10 V, or RS485 Modbus directly. Mounting. Centre the core in the bore so it never rubs the tube, and keep side loads off the probe. Clamp the body on its housing without over-tightening, so the housing is not deformed. For a ± range, set the reference position at the centre: the output reads zero, or 12 mA on a 4–20 mA output. Wiring a DC LVDT: supply + and 0 V, and the signal to the PLC analog input. Use shielded cable and ground the shield at one end only. An AC LVDT connects to a signal conditioner: its excitation output drives the primary, and the two secondaries return to its input. Keep the cable away from motor and drive cables. Before you order, specify the stroke, linearity, output, supply, temperature and connection. Linearity is ±0.25% FS as standard, or ±0.1% FS for high accuracy. SEGMENsensor makes gauging probes, separate-core and pen-type LVDTs, in 303 or 316L stainless steel, rated IP67. SEGMENsensor LVDT sensors. OEM volume supply. Datasheets and quotes at segmensensor.com.
How an LVDT WorksOne-minute animation of the linear variable differential transformer: primary and two secondary coils, the moving core, the null position, and how the size and phase of the difference signal give distance and direction.
What is an LVDT, and how does it measure position? An LVDT has three coils: a primary coil in the middle, and a secondary coil on each side. A movable core slides inside, on a push rod. An AC voltage excites the primary. With the core centred, both secondaries pick up equal voltages, and the difference is zero. When the core moves, one secondary couples more strongly than the other. The size of the difference shows how far the core moved, and its phase shows the direction. Electronics turn this into a DC signal, such as 4–20 mA. The core never touches the coils, so there is no wear. SEGMENsensor LVDT sensors: strokes from ±0.5 mm to ±500 mm. Learn more at segmensensor.com.
What is an LVDT Gauging Probe Sensor?
An LVDT gauging probe sensor is a Linear Variable Differential Transformer packaged as a precision measurement probe for contact dimensional gauging applications. Unlike position measurement LVDTs that couple the core to a moving machine part, a gauging probe LVDT has an exposed probe tip (ruby, carbide, or flat steel) on the extending rod that directly contacts the part surface being measured. The probe tip displacement drives the LVDT core, producing a voltage (AC) or conditioned current (4-20mA) signal proportional to the dimension. Gauging LVDTs are the reference-grade sensors in automated gauging fixtures, post-process inspection cells, and inline quality control systems for precision machined components.
Specifications
LVDT Gauging Probe Sensor — Full Specification Table
Standard and reference-grade configurations. AC LVDT and DC conditioned (4-20mA / 0-10V) output options. All models CE and RoHS certified.
±3V AC differential (5V primary excitation, 2–10 kHz)
Output (DC)
4-20mA (2-wire) / 0-5V / 0-10V / ±5V (3-wire)
Supply Voltage (DC)
15–30V DC (conditioned)
Probe Tip Options
Hardened ruby ball (1 mm or 2 mm dia.) / Tungsten carbide ball / Flat disc / Needle
Probe Rod
Stainless steel hardened, ∅5 mm or ∅8 mm
Housing Material
Stainless steel 316L
Housing Diameter
8 mm / 12 mm (gauge body standard)
Thread
M8 / M12 (for fixture mounting)
Operating Temperature
0°C to +60°C (calibrated range)
Thermal Coefficient
<50 ppm/°C (full output span)
Connector
M12 4-pin (DC) / Flying lead (AC)
Samples
Samples 1–5 pcs for qualification; volume per project
Lead Time
Confirmed with the quotation
Certifications
CE, RoHS
Download the LVDT displacement sensor datasheet (PDF)
Measuring ranges, linearity, output options, core and spring-loaded versions, housing dimensions, connectors, temperature limits and the ordering code. No registration required.
The values below are the same as the specification table above, with inch and °F conversions added for US and UK fixture drawings. Conversions are calculated values (1 in = 25.4 mm).
Stroke: 5 mm (0.197 in) / 10 mm (0.394 in) / 25 mm (0.984 in) / 50 mm (1.969 in).
Linearity: ±0.05% FS standard, ±0.02% FS reference grade. On a 10 mm stroke, ±0.05% FS is ±5 µm (±0.0002 in), calculated.
Hysteresis: <0.01% FS.
Output: ±3 V AC differential (5 V primary excitation, 2–10 kHz), or DC 4-20 mA (2-wire) / 0-5 V / 0-10 V / ±5 V (3-wire).
Supply (DC version): 15–30 V DC.
Probe tip: hardened ruby ball 1 mm (0.039 in) or 2 mm (0.079 in), tungsten carbide ball, flat disc or needle.
Probe rod: hardened stainless steel, ∅5 mm (0.197 in) or ∅8 mm (0.315 in).
Gauge body: 316L stainless steel, ∅8 mm (0.315 in) or ∅12 mm (0.472 in), M8 or M12 mounting thread.
Calibrated temperature range: 0 to +60 °C (32 to 140 °F); thermal coefficient <50 ppm/°C.
Connection: M12 4-pin connector (DC) or flying lead (AC).
Compliance: CE, RoHS 3.
Spring-Loaded vs Free
What is a spring-loaded LVDT gauging probe?
A spring-loaded LVDT gauging probe has an internal return spring that pushes the probe rod out, so the ruby or carbide tip stays in contact with the part and follows its surface; the part pushes the rod back and the LVDT core reports how far. A free (unconstrained) probe has no return spring: the fixture, an actuator or the moving part sets the rod position. SEGMENsensor gauging probes are supplied as free probes with a spring-loaded option, on the same strokes, tips and outputs listed above.
Point
Spring-loaded gauging probe
Free (unconstrained) probe
How the tip meets the part
Return spring extends the rod; tip rests on the surface
Fixture, actuator or the moving part positions the rod
Typical use
Diameter, height, thickness and runout checks in gauging fixtures; surface following
Positions where the rod is coupled to a moving part, or contact is set by the fixture
Mounting
Clamp the ∅8 / ∅12 mm body or use the M8 / M12 thread; keep the rod axis normal to the surface
Same body and thread; align the coupling so there is no side load on the rod
Contact force
Set by the spring; the value for your part and tip is confirmed per project
Set by your fixture
What to specify
Stroke (5 / 10 / 25 / 50 mm), linearity grade, tip type, AC or DC output, connector, body diameter and annual volume
Illustration: a free probe is positioned by the fixture; a spring-loaded probe keeps its tip on the part with an internal return spring.
Request qualification samples for your gauging fixture
Qualification samples are 1–5 pcs and ship in 5–7 working days; production lead time and MOQ are confirmed with the quotation. Send your stroke, tip and output and we reply within 24 hours.
Three output and grade options to match your measurement system, PLC architecture, and tolerance requirements.
⚡AC LVDT Version
Connects to a dedicated LVDT signal conditioning card or measurement amplifier
Highest possible resolution — limited only by the signal processing chain, not the sensor
Ideal for high-precision coordinate measurement benches and metrology instruments
Pure analog signal path with no embedded electronics — lowest sensor thermal error
→ Best for metrology instruments & CMM fixtures
🔌DC 4-20mA Version
Direct connection to PLC / DCS analog input — plug-and-play integration
No external signal conditioner required — embedded demodulator inside the housing
Ideal for in-line production inspection stations and automated gauging fixtures
24V DC loop powered, 2-wire wiring, standard industrial connection
→ Best for PLC-based production line gauging
🏆Reference Grade ±0.02% FS
±0.02% FS linearity with active temperature compensation
Supplied with NIST-traceable calibration certificate and calibration data file
Suitable for metrology laboratory, sampling inspection stations, and certified test measurement
Mass production lead time confirmed with the quotation; available in AC and DC output versions
→ Best for metrology labs & certified inspection
Applications
LVDT Gauging Probe Applications in Precision Manufacturing
From automotive engine components to aerospace turbine blades — LVDT gauging probes deliver reference-grade dimensional measurement across industries.
⚙️
Engine Component Gauging
Bore diameter, step height, and runout on crankshafts, camshafts, and pistons in engine assembly quality control lines.
✈️
Turbine Blade Inspection
Airfoil thickness and profile measurement in aerospace inspection fixtures for high-pressure turbine and compressor blades.
🔩
Bearing Inner/Outer Race
Wall thickness and raceway profile measurement in bearing production lines — critical for noise and fatigue life control.
⚡
Gear Tooth Profile
Tooth spacing and involute profile gauging in gear hobbing quality control — detects pitch error and profile deviation.
🖥️
PCB Flatness Testing
Board warpage and component height measurement in SMT assembly — identifies boards outside bow/twist specification.
🦴
Orthopedic Implant
Hip stem taper, acetabular cup diameter — precision gauging in medical device manufacturing to ISO 13485 requirements.
🏎️
Automotive Cylinder
Liner bore diameter, piston ring gap measurement in engine assembly — 100% in-process gauging at production line rate.
🏭
Die Casting Flash
Part thickness at parting line for flash detection and reject sorting — replaces manual inspection with automated gauging fixture.
How to Use
How to Use an LVDT Gauging Probe in a Production Fixture
Three steps from fixture installation to automated accept/reject output in a production gauging cell.
01
Mount & Align
Install the gauging probe sensor in the fixture or measurement stand using M8/M12 thread. The probe axis must be perpendicular to the surface being measured. Contact force is controlled by the spring-loaded version (0.3–1 N) or by fixture depth stop. Ensure probe stroke mid-point aligns with the nominal part dimension (null zone).
02
Zero Calibration
Place a gauge block or reference master part at nominal dimension under the probe. Zero the signal conditioner output (for AC: null voltage; for 4-20mA: 12mA = mid-stroke). Record this physical position as the measurement datum. Repeat zero calibration at the start of each production shift and after thermal stabilisation.
03
Measure & Reject
Load the workpiece into the fixture. The probe tip contacts the measured surface and reads the dimensional deviation from nominal. The PLC reads the analog signal and compares against the ±tolerance band. OK/NG digital outputs trigger part sorting — pass or reject — without operator intervention. Cycle time typically 0.5–2 seconds per part.
Why SEGMENsensor
OEM LVDT Gauging Probe Factory — Verified Quality
Every LVDT gauging probe ships with factory calibration data, CE declaration, and RoHS compliance certificate.
Technical and sourcing questions from OEM buyers and quality engineers about LVDT gauging probe sensors.
What is the difference between an LVDT gauging probe and a standard LVDT position sensor?
A standard LVDT position sensor has the core mechanically coupled (attached) to the moving part of the machine — it measures machine displacement. An LVDT gauging probe has a free, exposed probe tip that contacts a part surface to measure its geometry — the core follows the probe tip by spring contact or free sliding. Gauging probes are built to tighter linearity specifications (±0.02–0.05% FS vs ±0.1% FS) and use precision hardened probe tips to ensure repeatable contact. The housing is machined to close dimensional tolerances for press-fit or threaded installation in gauge bodies and CMM-style fixtures.
What probe tip material should I choose for my gauging application?
Ruby ball (aluminium oxide): hardest natural material after diamond, excellent wear resistance, ideal for ferrous and non-ferrous workpieces, widely used in automated gauging — recommended as the default. Tungsten carbide ball: harder than steel, resists abrasion from cast iron, sintered parts, or abrasive workpieces. Flat disc tip: for measuring into grooves, chamfers, or against shoulders where a ball tip would fall into the geometry. Needle point: for surface tracing, fine groove measurement, and deep bore probing. SEGMENsensor supplies all four options in 1 mm and 2 mm contact diameters.
What linearity specification do I need for production gauging?
For production inspection with tolerances ≥±0.05 mm: standard ±0.05% FS (on a 10 mm stroke = ±5 µm linearity) is more than sufficient. For tolerances of ±0.02–0.05 mm: use ±0.05% FS with careful zero calibration and temperature control. For tolerances <±0.02 mm: use the ±0.02% FS reference-grade version with NIST-traceable calibration. As a rule: the gauging sensor's linearity error should be less than 10% of your part tolerance. Calibrate the zero reference at the beginning of each production shift.
How do I connect an LVDT gauging probe to a PLC analog input?
If using the DC conditioned version (4-20mA output): wire as a standard 2-wire loop-powered transmitter — Brown (+) to PLC analog input positive, Blue (–) to PLC analog input negative, with 24V DC loop supply. Set PLC scaling: 4mA = minimum stroke (fully retracted), 20mA = maximum stroke (fully extended). If using raw AC LVDT output: you need an LVDT signal conditioner (demodulator) between the sensor and the PLC. The conditioner provides the AC excitation and converts the AC differential output to a DC voltage or 4-20mA. SEGMENsensor recommends the DC conditioned version for direct PLC integration.
What is the contact force of an LVDT gauging probe and does it affect measurement accuracy?
The free-probe (unconstrained) version has no spring — probe contact force is determined entirely by the fixture design (typically 0.1–0.5 N from a light fixture clamp or gravity). The spring-loaded version applies 0.3–1.0 N (adjustable) to maintain positive contact. Contact force affects measurement only if it deflects the workpiece (thin-wall parts, PCBs). For rigid machined parts, the force is irrelevant. For soft or thin parts (<0.5 mm sheet), use the free-probe version with gravity or fixture contact. In automated gauging cells, the part is loaded and clamped before probing — the probe contact force is usually less than 0.5 N, causing negligible part deflection.
What is LVDT gauging probe null position and how do I set it?
The null position is the electrical zero point — the probe location where the LVDT differential output is zero volts (for AC output) or 12mA (for 4-20mA output, corresponding to mid-stroke). For gauging, the null is not usually at zero but at the nominal dimension: place a calibration standard (gauge block at nominal size) under the probe, then zero the signal conditioner's offset to read 0V or 12mA. Now all deviations from nominal register as + (oversize) or – (undersize). The LVDT's linearity and drift are minimized near null, so design your gauge fixture to operate within ±20% of stroke around the null point for best accuracy.
Can LVDT gauging probes be used in wet or coolant environments?
Standard LVDT gauging probes are rated IP54 (splash-resistant) — suitable for coolant mist environments in CNC cells. For direct coolant spray or parts washing environments, specify the IP67 sealed version with stainless steel housing and sealed probe rod bearing. The probe tip (ruby or carbide) is unaffected by coolant or water. For food-grade or pharmaceutical applications requiring washdown with cleaning agents, use the all-stainless 316L housing with PTFE-sealed probe exit. The probe rod bearing material should be confirmed compatible with the cleaning agent.
What is the MOQ and lead time for LVDT gauging probe sensors from a China factory?
OEM volume supply for standard LVDT gauging probe sensors (stroke 5, 10, 25 mm; 4-20mA DC output; M12 connector; ruby ball tip). Samples of 1–5 pcs ship in 5–7 days. Production lead time: confirmed with the quotation. Custom configurations (reference grade ±0.02% FS, AC output, non-standard stroke, carbide/flat/needle tip, IP67, NIST calibration certificate, OEM label): lead time confirmed at order. CE declaration of conformity and factory calibration report included. Factory: SEGMEN (Shenzhen) Industrial Development Co., Ltd., Registration No. 91440300MAEUXXQU04, Shenzhen, Guangdong, China.
What is the difference between a spring-loaded and a free LVDT gauging probe?
A spring-loaded LVDT gauging probe has an internal return spring that keeps the tip on the part, so it suits diameter, height and thickness checks in gauging fixtures. A free probe has no return spring, and the fixture, an actuator or the moving part positions the rod. SEGMENsensor offers both on 5, 10, 25 and 50 mm strokes with the same tips and outputs.
How do I convert the stroke and linearity of an LVDT gauging probe to inches?
Divide millimetres by 25.4. The 5, 10, 25 and 50 mm strokes are 0.197, 0.394, 0.984 and 1.969 in. Linearity is a percentage of full scale, so on a 10 mm stroke ±0.05% FS equals ±5 µm, about ±0.0002 in, and the ±0.02% FS reference grade equals ±2 µm (calculated values).
What information do you need to quote an LVDT gauging probe?
Send the stroke, linearity grade (±0.05% or ±0.02% FS), tip type, AC or DC output (4-20 mA, 0-5 V, 0-10 V or ±5 V), connector, body diameter (8 or 12 mm) and annual volume. Price depends on these options and the quantity. We quote within 24 hours on working days, FOB China with 100% T/T in advance, and qualification samples of 1–5 pcs ship in 5–7 working days.
Ready to Source LVDT Gauging Probe Sensors from a China OEM Factory?
Tell us your stroke, required linearity, probe tip type, and output signal — we'll send a quote, datasheet, and fixture integration note within 24 hours.
