JNS-Q120 Pneumatic Rebound Contact-Type Displacement Grating Sensor with Digital Display
Displacement Grating Sensors — Contact-Type Probes for Industrial Dimensional Measurement
DAIDISIKE displacement grating sensors are contact-type measurement probes built for the kind of work where ±2 μm matters and a non-contact optical setup is either overkill or unsuited to the surface. A spring-loaded or pneumatic-rebound tip touches the workpiece, an internal optical grating reads the tip's vertical travel, and the result appears on a built-in digital display plus an analog (4–20 mA) and digital (RS-485) output for PLC integration. The flagship JNS-Q120 covers a 0–12 mm range with 0.001 mm resolution — tight enough for stamping thickness checks, gasket-stack heights, assembled-product verification, and machined-part QC.
When a Contact Probe Beats a Laser Sensor
Laser displacement sensors get most of the publicity, but on a real factory floor a contact-type displacement grating still wins in three specific situations:
- Tight measurement windows under 20 mm. Laser triangulation accuracy is a function of standoff distance and triangulation base — at very short ranges, the geometry doesn't favor optical methods. A contact probe with an integrated grating holds ±2 μm regardless of how close the target sits.
- Reflective, transparent, or mirror-finish surfaces. Polished steel, glass, optical coatings, and clear plastics confuse laser sensors — the return signal either floods the receiver or disappears entirely. A contact probe doesn't care: it's reading mechanical position, not optical return.
- Indexing fixtures and shuttle stations. When the part comes to rest at a known position, the simplicity of “press the probe, read the value” beats the standoff calibration, ambient-light shielding, and dust management that a laser setup demands.
That's the contact probe's place in the toolbox. For moving targets, long-range standoff, or surfaces you can't touch (paint that's still drying, hot castings, food contact), reach for a laser sensor instead — see the DAIDISIKE laser switch sensor family.
What “Pneumatic Rebound” Actually Means
The JNS-Q120 uses a low-pressure air cushion instead of a mechanical spring to hold the probe tip against the workpiece. Three practical advantages flow from that choice:
- Adjustable contact force. Turn the regulator knob — from about 0.5 N for rubber and soft brass up to 2 N for steel stampings. The same probe handles a gasket and a hardened die-button without changing tips.
- Clean retraction between measurements. Air pressure removed → tip pulls back cleanly; pressure restored → tip extends and settles. No spring oscillation, no tip-drag scoring the surface, no settling delay between consecutive measurements. This is what makes inline inspection at line speed possible.
- No spring fatigue over time. Mechanical springs soften after a few million cycles, drifting the zero point. An air cushion is replaced with the regulator setting at every calibration — it can't drift.
Selection Quick-Reference
| Specification | JNS-Q120 | Typical Use Case |
|---|---|---|
| Measurement range | 0 – 12 mm | Stamping thickness, gasket stacks, machined-part height |
| Resolution | 0.001 mm (1 μm) | Inline thickness sort, assembled-stack verification |
| Repeatability | ±2 μm | Tight-tolerance dimensional QC |
| Contact force | 0.5 – 2 N (adjustable) | Soft materials → rigid stampings, same probe |
| Tip material | Tungsten carbide (std), diamond (optional) | Steel parts; abrasive ceramics → diamond |
| Tip life | 1M+ cycles (carbide) · 10M+ (diamond) | Months of inline duty between replacements |
| Power supply | 24 VDC ± 10% | Standard industrial control cabinet |
| Analog output | 4–20 mA scaled to range | Direct PLC analog input |
| Digital output | RS-485 Modbus-RTU | MES logging, SPC charts, recipe switching |
| Display | Built-in 4-digit LCD | Operator readout without PLC |
| Air supply (rebound) | 0.3 – 0.5 bar, clean dry | House compressed-air system, < 5 µm filter |
| Operating temperature | 0 °C to +60 °C | Indoor industrial environments |
| IP rating | IP54 (probe body) | Splash-protected; not for washdown |
Field-Tested Applications
Stamping Line — In-Process Thickness Check
Mount on the press exit conveyor to check stamped-blank thickness or coining depth on every part. Discrete output triggers a pneumatic reject flap when a stamping falls outside tolerance.
Assembly Line — Stack Height Verification
Multi-layer assemblies (gasket-on-housing, bearing pre-load shims, motor laminations) need their total assembled height verified before the next operation. Contact probe reads to ±2 μm regardless of surface color or finish.
Machined Parts — Sample Inspection in QC Lab
Replace dial-indicator and comparator setups with a digital probe that logs every reading to a CSV. Cleaner audit trail, faster part throughput, and the operator can't mis-read the scale.
Stamping Tool Setup — Bottom Dead Centre Calibration
Mount under the press ram to verify BDC position when changing dies. The 12 mm range covers shut-height adjustment, and the digital readout removes the need for feeler-gauge guesswork.
PCB & Electronics Assembly — Connector Pin-Height Check
Through-hole connector pins must protrude within a tight tolerance for the next-stage wave-solder. Probe + fixture gives a go/no-go signal per board.
Wood / Furniture — Panel Thickness Sorting
MDF, particleboard, and veneer panels are sold by nominal thickness with tight grading tolerances. Pneumatic-rebound probes handle the variable surface texture without crushing.
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Frequently Asked Questions
What is a displacement grating sensor and how is it different from a laser displacement sensor?
A displacement grating sensor is a contact-type probe — the spring-loaded tip physically touches the workpiece, and an internal optical grating converts the tip's vertical travel into a digital reading with sub-micron resolution. A laser displacement sensor is non-contact, measuring distance optically via triangulation or time-of-flight. Contact probes give higher repeatability on small ranges (±2 μm typical) at lower cost, but the tip must touch the surface and wears over time. Laser sensors are faster, work on moving parts, and never wear, but cost more and can be confused by reflective or transparent surfaces.
What is 'pneumatic rebound' and why does it matter?
Pneumatic-rebound means the probe tip is held against the workpiece by a low-pressure air cushion (typically 0.3 to 0.5 bar) instead of a metal spring. The cushion gives a constant, low contact force that's adjustable from the regulator — about 0.5 N to 2 N — so soft materials don't deform, knife-edge features don't get crushed, and the same probe works on rubber gaskets, brass shims, and steel stampings without changing tips. Pneumatic actuation also retracts the tip cleanly between measurements, which is what makes high-speed inline inspection possible.
What measurement range and accuracy can I expect?
The JNS-Q120 covers a 0–12 mm measurement range with ±2 μm repeatability and 0.001 mm resolution on the digital display. For dimensional checks in the 0–10 mm window (stamping flatness, plate thickness, gasket height, assembled-stack measurement), that's an order of magnitude tighter than dial indicators and roughly on par with high-end mechanical comparators — at lower per-station cost.
How do I integrate the digital reading into a PLC or SPC system?
The JNS-Q120 provides a 4–20 mA analog output scaled to the full measurement range (4 mA = 0 mm, 20 mA = 12 mm) for direct connection to any PLC analog input card, plus an RS-485 channel for digital readout. The digital channel exposes raw count, status bits, and configuration registers — same pattern as the DAIDISIKE DQL/DQM measurement grating family — so any modern PLC (Siemens S7, Mitsubishi FX5U, Omron NJ, Allen-Bradley CompactLogix) can poll it without custom drivers.
Where do contact-type displacement probes outperform other measurement methods?
Three scenarios where a contact probe is the better choice: (1) Small, well-defined measurement windows under 20 mm where laser triangulation accuracy degrades. (2) Transparent or mirror-finish parts (glass, polished brass, optical coatings) where lasers struggle with reflection or transmission. (3) Bulk dimensional checks on a fixture or shuttle where the part comes to rest at a known position — the simplicity of 'press the probe, read the value' beats the calibration overhead of an optical setup.
What's the typical operating life of the contact tip?
The standard tungsten-carbide tip lasts well over one million measurement cycles on steel stampings before perceivable wear shifts the zero. The tip is user-replaceable in about a minute — no recalibration required since the grating reads the carrier, not the tip itself. For abrasive workpieces (sand-cast iron, ceramic) we recommend the diamond-coated tip option, which extends life to roughly 10 million cycles.