Contact Displacement Sensors (Probes)

Choosing Contact Displacement Sensors (Probes) components

Contact probe selection comes down to measuring range, accuracy class, contact tip style, and the readout/conditioner the probe pairs with. Contact probes wear over time as the tip rubs against the target; cycle-rated probes and replaceable tips extend useful life.

Specs to confirm before ordering:

Measuring range — typically ±0.5, ±1, ±2.5, ±5, or ±10 mm
Resolution and linearity — sub-micrometer to 0.1 µm class for high-end probes
Contact force — affects measurement on soft or flexible parts
Tip style and material: ruby ball (standard), carbide ball (long life), flat foot (averages over an area), knife edge (line contact)
Tip mounting: M2.5 threaded (most common), M3 threaded, or fixed
Probe technology: LVDT (analog mV signal), inductive-bridge, digital (with built-in conditioner), pneumatic
Output: analog millivolt LVDT (needs conditioner), 0–5 V / 0–10 V conditioned analog, digital RS-232/RS-485, USB, or proprietary controller bus
Conditioner/readout pairing — LVDT probes are typically calibrated to a specific conditioner
Mounting body diameter — typically 8 mm or 10 mm for fixture mounting
Spring return or pneumatic retraction for cycle applications

Common gotchas: LVDT probes are AC-excited and produce a small mV signal that must be amplified and conditioned — connecting an LVDT to a generic PLC analog input gives no useful signal. The probe and the conditioner are usually a matched pair with stored calibration; switching either alone changes the readout. Probe tips wear and lose accuracy over time; ruby tips last longest but are more expensive than steel. Probe contact force pushes on soft targets and gives compressed readings; high-cycle applications on soft materials need low-force probes or non-contact alternatives.

Typical applications: dimensional inspection in measuring fixtures, in-process gauging on machine tools, flatness and parallelism checks on machined parts, thickness verification through stack inspection, and assembly verification on precision parts. On legacy installations, exact-OEM probe replacement preserves the matched conditioner calibration.

For obsolete contact probes, send the OEM part number for a sourcing quote.

Do you stock obsolete contact probes?

Yes. Discontinued Mahr Millimar first generations, retired Solartron Metrology DP/DS codes, end-of-life Tesa, and earlier Heidenhain MT-series are sourced through our supplier network.

Do probe and conditioner need to be matched?

For LVDT probes, generally yes — calibration is stored in the conditioner and tied to the probe. Switching one alone changes the readout. Digital probes with built-in electronics avoid this dependency.

Ruby vs. carbide vs. steel tip — which should I use?

Ruby for highest accuracy and longest life — minimal wear on the tip itself. Carbide for high-cycle applications with cost-conscious budgets. Steel for low-cycle or general inspection.

How often do probe tips need replacement?

Depends on cycle count, target hardness, and contact force. For typical inspection fixtures: ruby tips can last years; carbide tips last months to a year; steel tips show wear within weeks of high-cycle use. Replace when accuracy verification (with a known artifact) shows drift.

Can the probe be used in coolant or oil?

Some probes are sealed for coolant exposure — confirm the IP rating on the probe body. Probes for dry inspection fixtures are not necessarily sealed against coolant intrusion.

What is the warranty?

12-month functional warranty. Tip wear from normal use is not covered as a warranty event. Damage from over-travel, impact, or contamination is not covered.

Contact Displacement Sensors (Probes)

Keyence GT-71A Amplifier Unit, DIN Rail Type, NPN

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Keyence GT-72A Amplifier Unit, DIN Rail Type, NPN

Keyence GT-72AP Amplifier Unit, DIN Rail Type, PNP

Keyence GT-75A Amplifier Unit, Panel Mount Type, NPN

Keyence GT-75AP Amplifier Unit, Panel Mount Type, PNP

Keyence GT-76A Amplifier Unit, Panel Mount Type, NPN

Keyence GT-76AP Amplifier Unit, Panel Mount Type, PNP

Keyence GT-A10 Sensor Head, Air Cylinder Model

Keyence GT-A22L Sensor Head, Low Measuring Force Type, Air Cylinder Model

Keyence GT-H10 Sensor Head

Keyence GT-H10L Sensor Head, Low Measuring Force Type

Keyence GT-H22L Sensor Head, Low Measuring Force Type

Keyence GT2-100N Amplifier Unit, Large Display Amplifier

Keyence GT2-100P Amplifier Unit, Large Display Amplifier

Keyence GT2-550 Amplifier expansion unit supporting multi-head connection

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