DDK-G Laser Displacement Sensor 30-250 mm

Name: DDK-G Laser Displacement Sensor 30-250 mm
Brand: DAIDISIKE
SKU: gdk-series-laser-displacement-sensor
Availability: InStock

Micron-class CMOS triangulation in a 65-gram body: five range grades, resolution from 2 um, and your choice of 4-20 mA, 0-10 V or RS485 - now fully documented from the 2026 factory datasheet.

DDK-G laser displacement sensor product photo, compact aluminum body with OLED panel

🔍 Click to enlarge · 1/10

Technical Specifications

Model code	DDK-G (current factory code; formerly catalogued as GDK - identical hardware). Order as DDK-G{30\|50\|85\|120\|250}{N\|P}{M\|-485}.
Measurement principle	Laser triangulation onto a CMOS array: spot centroid located with sub-pixel interpolation, factory-calibrated to displacement; one raw reading per sampling cycle, averaged 1/16/64 times by response mode
Light source / laser class	655 nm red semiconductor laser, max 1 mW - Class 2 (IEC/JIS), Class II (FDA)
Reference distances / windows	30 mm (26-34), 50 mm (40-60), 85 mm (65-105), 120 mm (60-180), 250 mm (100-400) - all in mm
Resolution	High-resolution mode: 2 / 5 / 10 / 30 / 75 um by grade. Fast mode: 4 / 8 / 15 / 45 / 150 um.
Linearity	+/-0.1% F.S. (30/50/85/120 mm grades); +/-0.3% F.S. (250 mm grade)
Response time	Fast max 2 ms (1 sample) / standard max 11.5 ms (16) / high-res max 36.5 ms (64); 250 mm grade: 2.5 / 15.5 / 48.5 ms. Sampling cycle 500 us (750 us on the 250 grade).
Temperature drift	+/-0.08% F.S. per degC
Output versions	Analog current: 4-20 mA, load <=300 ohm, supply DC 12-24 V, max 60 mA. Analog voltage: 0-10 V, impedance 100 ohm, supply DC 18-24 V, max 40 mA. RS485: supply DC 12-24 V, max 40 mA.
Switching outputs	NPN or PNP per model, max 100 mA / DC 30 V, residual 1.8 V - two on analog versions; one on RS485 versions per the circuit diagram (factory confirmation advised)
MF multifunction input	Pink wire; menu-assignable to zero-set / teach / laser-off; trigger = pulse >20 ms to 0 V (NPN models) or +24 V (PNP models), then release
Wire colours	Brown +V, blue 0 V, black switching output 1, white switching output 2 (analog types), pink MF, grey analog output or RS485 A+, shield analog ground or RS485 B-. Blue and the shield join inside the housing - route the supply negative through blue and reserve the shield for the analog return.
Display / keys	OLED showing threshold Q1 and live measured value; SET + up/down keys; OUT1/OUT2 orange indicators
Protection	IP64; reverse-connection protection; overcurrent protection
Environment	Operating -10 to +45 degC (no freezing), 35-85% RH; storage -20 to +60 degC, 35-95% RH; sunlight <=10,000 lx, incandescent <=3,000 lx; vibration 10-55 Hz 1.5 mm 2 h/axis; shock approx. 50 G x3/axis
Warm-up	Internal circuit stable in approx. 1.5 s; rated accuracy after max 15 min warm-up
Construction	Aluminium alloy housing, PMMA lens; 50 (W) x 60 (H) x 20.4 (D) mm; two phi-4.5 mounting holes; 65 g cable type (excl. cable), 90 g connector type
Cable	phi-5, 2 m PVC, AWG24 - 6-core on analog versions, 8-core on RS485 versions; connector termination available
Rated test conditions	23 degC, DC 24 V, high-resolution mode, sampling at factory setting, target at range centre, 50 x 50 mm white ceramic

Overview

DDK-G is the code the factory now prints on its nameplates and paperwork; this page previously listed the identical instrument as GDK. Same sensor, same five range grades - and as of the 2026 datasheet release, a far more complete public specification. Every open item the earlier catalogue could not answer - supply voltage, laser class, IP rating, temperature limits, dimensions, weight - is now published and tabulated below, together with an English datasheet PDF compiled from the factory original.

What you are buying is a CMOS triangulation instrument: a 655 nm Class 2 laser paints a spot on the target, the receiving optics throw that spot onto a CMOS line, and where the spot lands converts geometrically into a distance value refreshed every 500 microseconds. The commercial consequence of that physics is a selection rule: the nearer grades measure finer. The 30 mm grade resolves 2 um with a 0.1 x 0.1 mm spot; the 250 mm grade trades resolution (75 um) and spot size (1.75 x 3.5 mm) for standoff and a 300 mm span. Buy the shortest reference distance your fixture allows, not the longest one that seems safe.

Ordering is a three-letter sentence: grade, polarity, interface. DDK-G50N-485 reads as 50 mm reference distance, NPN switching output, RS485 communication. The M suffix buys an analog version instead - state 4-20 mA or 0-10 V when ordering, because the two differ in supply range (12-24 V versus 18-24 V). Twenty standard models cover the matrix, all IP64, all 50 x 60 x 20.4 mm, all with the pink-wire multifunction input that gives one-touch zero-setting after a product changeover.

Two honesty notes from the source document. The factory datasheet carries a handful of printing errors - a linearity figure typeset as 'f.5.', a wire-colour line that contradicts its own circuit diagrams - and this page publishes the corrected readings, with the corrections themselves documented in the FAQ so your incoming-inspection team is never surprised. And two items remain genuinely unpublished: the RS485 register map and formal repeatability data. Both are available through a factory inquiry; neither has been guessed at here.

Key Facts — DDK-G at a glance

DDK-G is the current factory model code; GDK was the former catalogue listing of the same series - order codes on new paperwork read DDK-G30NM through DDK-G250P-485.
Twenty standard models: five reference distances (30/50/85/120/250 mm) x two polarities (N = NPN, P = PNP) x two interfaces (M = analog current or voltage, -485 = RS485).
Resolution follows the grade: 2 / 5 / 10 / 30 / 75 um in high-resolution mode, coarsening to 4-150 um in fast mode - the nearer the reference distance, the finer the reading.
Full-scale linearity holds +/-0.1% through the four nearer grades and relaxes to +/-0.3% on the 250 mm grade - for the G30 that bounds deviation within roughly 8 um over its 8 mm span.
Three response modes trade speed against averaging: fast max 2 ms (1 sample), standard max 11.5 ms (16 samples), high-resolution max 36.5 ms (64 samples); the 250 mm grade runs about 30% slower in each mode.
The measuring windows in real numbers: 26-34 mm, 40-60 mm, 65-105 mm, 60-180 mm and 100-400 mm - place the target's nominal position near the window centre, where triangulation is most linear.
Now published in the 2026 datasheet: 655 nm 1 mW Class 2 (IEC/JIS) laser, IP64 housing, -10 to +45 degC operating, temperature drift +/-0.08% F.S. per degC, aluminium body 50 x 60 x 20.4 mm at 65 g, reverse-connection and overcurrent protection.
The pink wire is a menu-assignable multifunction (MF) input - zero-set, teach or laser-off - triggered by a >20 ms pulse; configured as zero-set it re-references the sensor after a changeover without touching the panel.
Wire colour corrections from the factory's own circuit diagrams: pink = MF input and grey = analog output (the datasheet's text says otherwise once; the diagrams and nameplate agree it does not), with the shield doubling as RS485 B- on -485 models.
On -485 models the factory's own circuit drawing carries a single switch channel, not the pair fitted to analog versions - design as though the second output is absent until the factory states otherwise.
All rated figures assume the printed test conditions: 23 degC, DC 24 V, high-resolution mode, white ceramic target at range centre - budget margin for dark, glossy or hot targets.

Features & Benefits

From spec-sheet gaps to a complete engineering file

The earlier GDK listing had to answer 'not yet published' for supply voltage, IP rating, laser class and dimensions. The 2026 DDK-G datasheet closes every one of those items, and this page tabulates them all - plus a compiled English PDF - so a design review can finish in one sitting.

2 um where it counts, standoff where it helps

The grade ladder is the product's real feature: 2 um resolution and a 0.1 mm spot at 30 mm reference for coating and float-height work, up to 400 mm of reach on the 250 grade for lines where the sensor must sit clear of heat, splash or travel. One series covers the ladder; you pick the rung.

The 85 and 120 mm grades most catalogues skip

Competing series often jump from 50 mm straight to 200 mm, forcing the target to the edge of some grade's window. The DDK-G's five-step ladder keeps the target near window centre - which is where linearity, spot size and signal margin are all at their best.

Interface chosen at order, not adapted in the panel

4-20 mA for long, noisy runs; 0-10 V for short in-cabinet wiring into a standard PLC analog card; RS485 when the value should travel as digits with no A/D stage. Each in NPN or PNP - twenty part numbers so the sensor matches the system instead of the system adapting to the sensor.

One-touch zero after every changeover

Assign the pink MF wire to zero-set and a >20 ms pulse re-references the sensor to the new product - from the PLC, without opening the panel or touching the keys. Teach and laser-off are the other two menu options on the same wire.

Commissioning-proof electricals

Reverse-connection protection on the supply, overcurrent protection on the output, and both documented in the datasheet rather than assumed. The OLED panel shows threshold and live value side by side, so setup is a reading, not a guess.

65 grams, 20.4 mm thin, IP64

The aluminium body disappears into fixtures: 50 x 60 x 20.4 mm on two phi-4.5 holes. IP64 handles workshop dust and splash; where coolant sprays persistently, a window guard or air purge extends its territory (and the datasheet is candid that washdown is not its rating).

Errata handled before they reach your incoming inspection

The factory PDF's typos - 'f.5.' for f.s., a wire-colour line contradicting the diagrams - are corrected here against the circuit diagrams and nameplate, with each verdict documented. What we could not verify (RS485 register map, repeatability) is flagged, not fabricated.

Applications

Battery electrode coating and calendering lines — A C-frame pair of G30 heads reads the web from both faces for differential thickness at 2 um, surfacing areal-density drift long before the winder sees it. Run high-resolution mode for a steady value, carry it across the gantry on 4-20 mA, and let the two switch channels raise out-of-band product on their own.

Float-height and coplanarity checks in 3C assembly — Mid-frame bonding gaps, display lamination, connector pin height: the 30 mm grade's 0.1 mm-square spot fits a bezel edge or a single pin, and a lift of a few hundredths of a millimetre reads clearly at production takt in standard mode. The -485 version streams values straight into SPC software.

Rotating-part runout and thickness on machining lines — Brake discs, gear end faces, stamped rings: fast mode's 2 ms ceiling keeps up with spindle speed while the PLC computes peak-to-peak. Choose the G50 or G85 by part diameter so the surface stays inside the window across the full rotation.

Strip, plate and profile gauging at standoff — The G120 and G250 grades put 60-400 mm between the optics and hot, oily or vibrating stock. Note the G250's larger spot (1.75 x 3.5 mm centre) suits broad flat surfaces, and red-hot material radiating into the 655 nm band needs a separate evaluation before commitment.

Board and panel inspection in dusty workshops — Engineered boards, gypsum panels and flooring measure well - good diffuse surfaces - but the environment argues for the G85/G120 standoff, an air purge where dust concentrates, and 4-20 mA for the long runs typical of board plants.

Level, stack and roll-diameter feedback for automation — Hopper level, pallet stack height, winder roll diameter: large position scatter favours the G120 (+/-60 mm) or G250 (+/-150 mm) windows. RS485 skips the analog stage, the switching output serves as the in-position flag, and MF-as-zero-set resets the reference at each changeover.

Models & Ordering Information

Analog output models (M suffix - specify 4-20 mA or 0-10 V at order)

DDK-G30NMDDK-G30PMDDK-G50NMDDK-G50PMDDK-G85NMDDK-G85PMDDK-G120NMDDK-G120PMDDK-G250NMDDK-G250PM

Grade + N (NPN) or P (PNP) + M. Current type supplies from DC 12-24 V, voltage type from DC 18-24 V - state which analog signal you need when ordering. Two switching outputs fitted alongside the analog channel. Formerly catalogued with the GDK prefix - same hardware.

RS485 communication models (-485 suffix)

DDK-G30N-485DDK-G30P-485DDK-G50N-485DDK-G50P-485DDK-G85N-485DDK-G85P-485DDK-G120N-485DDK-G120P-485DDK-G250N-485DDK-G250P-485

Measurement travels digitally on RS485 (grey = A+, shield = B-); no analog channel. Per the circuit diagram these carry one switching output, not two - confirm with the factory if your design needs both. 8-core cable instead of 6-core.

Downloads

DDK-G Laser Displacement Sensor - English DatasheetEvery order code, the grade-by-grade tables, hookup for all three electrical versions including the pink multifunction wire, the full environmental block, surface-handling advice and the rated test conditions - translated from the 2026 factory original with its printing errata fixed.0.18 MB

How to Select

Step 1 - Fix the grade from the fixture, not from caution: measure the real standoff available, pick the grade whose window brackets it, and prefer the nearest grade that fits - resolution improves from 75 um to 2 um as the reference distance drops from 250 mm to 30 mm.
Step 2 - Position for the window centre: mount so the target's nominal position sits near the reference distance. Triangulation linearity, spot size and signal margin all degrade toward the window edges - centre placement is free performance.
Step 3 - Pick the interface by where the value must travel: 4-20 mA for long or electrically noisy runs (load <=300 ohm), 0-10 V for short in-cabinet wiring (note the higher 18-24 V supply floor), -485 for digital transfer into SPC or multi-drop wiring. Then N or P to match the PLC's input polarity.
Step 4 - Pick the response mode per duty: fast (2 ms) for rotating or moving targets, standard (11.5 ms) for takt-time inline checks, high-resolution (36.5 ms) for static precision reads - and remember the 250 grade runs ~30% slower in every mode.
Step 5 - Audit the target surface before ordering: polished metal needs the head angled away from the mirror direction; transparent film echoes from both faces and demands a sample trial; very dark matte finishes call for a nearer grade; glowing-hot stock clashes with the sensor's red measurement band altogether.
Step 6 - Wire it clean: negative rail through blue, analog return via the shield (the two join internally), the analog line kept away from power conductors, and MF on pink if you want one-touch zero-set. Allow 15 minutes of warm-up before trusting micron-level readings.
Step 7 - Close the two open items if they matter: RS485 register map and formal repeatability data are unpublished - request both through us before committing a tolerance-critical or protocol-dependent design.

When NOT to specify the DDK-G — and what to use instead

Metre-range distance jobs: crane positioning, silo level, long-travel tracking

Why not: The longest DDK-G window ends at 400 mm from the sensor face; this is a short-range precision instrument, not a ranging device.

Use instead: a metre-range laser distance sensor such as DDA-Y/DDB-Y, DDK-F or DSK-CG

A tolerance study that must cite documented repeatability or accuracy, not resolution

Why not: The 2026 datasheet publishes resolution and linearity but no repeatability figure; acceptance criteria built on an assumed repeatability fail audits.

Use instead: requesting factory repeatability data for your target material first, or the DK-G series, which publishes repeatability figures

Washdown cells, coolant-jet zones, or condensing environments

Why not: IP64 covers dust and splash only, and the environmental table excludes freezing and condensation.

Use instead: the LK-F series with its IP67 housing, or a windowed guard / air purge in front of a DDK-G

An RS485 integration that must be designed before protocol documentation is in hand

Why not: Only the physical layer is published; the register map and protocol are factory-confirmation items.

Use instead: the 4-20 mA version into a PLC analog card, or obtaining the protocol document through us before freezing the comms design

Red-hot or self-luminous targets

Why not: Hot stock glows in the same red wavelengths the instrument measures with, corrupting the reading.

Use instead: a separate evaluation with your actual process temperatures before specifying any triangulation sensor

The five grades side by side (2026 factory datasheet)

Rated at 23 degC, DC 24 V, high-resolution mode, white ceramic target at range centre. Spot sizes defined at 1/e-squared intensity; stray light outside the spot means nearby shinier objects can disturb the reading.

Item	DDK-G30	DDK-G50	DDK-G85	DDK-G120	DDK-G250
Reference distance	30 mm	50 mm	85 mm	120 mm	250 mm
Measuring range	+/-4 mm	+/-10 mm	+/-20 mm	+/-60 mm	+/-150 mm
Measuring window	26-34 mm	40-60 mm	65-105 mm	60-180 mm	100-400 mm
Resolution (high-res)	2 um	5 um	10 um	30 um	75 um
Resolution (fast)	4 um	8 um	15 um	45 um	150 um
Linearity	+/-0.1% F.S. (8 mm)	+/-0.1% F.S. (20 mm)	+/-0.1% F.S. (40 mm)	+/-0.1% F.S. (120 mm)	+/-0.3% F.S. (300 mm)
Spot at centre	0.1 x 0.1 mm	0.5 x 1.0 mm	0.75 x 1.25 mm	1.0 x 1.5 mm	1.75 x 3.5 mm
Spot near / far end	0.15 x 0.15 both	0.6 x 1.2 / 0.4 x 0.9	0.9 x 1.5 / 0.6 x 1.0	1.2 x 1.8 / 0.5 x 0.8	1.5 x 2.5 / 2.0 x 4.5
Response fast / std / high-res	2 / 11.5 / 36.5 ms	2 / 11.5 / 36.5 ms	2 / 11.5 / 36.5 ms	2 / 11.5 / 36.5 ms	2.5 / 15.5 / 48.5 ms
Sampling cycle	500 us	500 us	500 us	500 us	750 us

2026 DDK-G factory datasheet (printing errata corrected)

Specifications we do not publish yet

We only publish a figure once we are confident it is true. The items below are still being validated through further testing and real-world customer feedback, so for now we would rather leave them open than guess. If one of them matters to your design, ask us for the latest validated status.

Repeatability is not published for this series - request factory test data for tolerance-critical duties.
The RS485 protocol / register map is not published; only the physical layer (RS485, A+/B-) is documented.
Whether the two switching outputs on analog versions support independent thresholds is not stated in the datasheet.
The -485 variant's switch-channel count reads as one on the circuit drawing yet merges ambiguously in the spec table - treated as single here pending factory clarification.
Footnote markers *2 and *3 in the factory datasheet have no corresponding note text; no content has been invented for them.

Frequently Asked Questions

Why did the model name change from GDK to DDK-G?

DDK-G is the code the factory prints on the 2026 datasheet and the product nameplate; GDK was how earlier catalogue pages - including an earlier version of this one - listed the same series. Nothing about the hardware changed. Quotations and new orders should carry DDK-G codes; if your records say GDK, we will cross-reference them without fuss.

Which grade should I order if my mounting distance is, say, 70 mm?

The one whose window brackets your real standoff with the target near window centre - at 70 mm that is the DDK-G85 (window 65-105 mm), not the G120, even though the G120's window technically also covers 70 mm at its edge. Edge-of-window operation costs linearity and spot quality; centre placement is the whole reason the five-step grade ladder exists.

What resolution do I actually get, and under what conditions?

In high-resolution mode: 2 um on the G30, then 5/10/30/75 um up the ladder; fast mode roughly doubles those figures. All ratings assume the printed test conditions - 23 degC, DC 24 V, white ceramic target at range centre - so budget margin for dark, glossy or moving surfaces, and let the sensor warm up (max 15 min) before trusting micron-level numbers.

Is resolution the same thing as accuracy for tolerance studies?

No, and mixing them up is the most common displacement-sensor purchasing error. Resolution is the smallest visible change; linearity (+/-0.1% F.S., or +/-0.3% on the 250 grade) bounds deviation across the span; repeatability - the figure most tolerance studies actually need - is not published for this series and should be requested from the factory for your target material before a tolerance-critical commitment.

What is the difference between the M and -485 versions in daily use?

M versions push an analog value - 4-20 mA (best over long, noisy runs) or 0-10 V (fine for short in-cabinet wiring, needs the DC 18-24 V supply) - plus two switching outputs for alarm flags. The -485 versions replace the analog channel with RS485 digital transfer (grey = A+, shield = B-) on an 8-core cable, draw less current, and per the circuit diagram carry one switching output instead of two.

What does the pink wire do?

It is the MF multifunction input. Assign it in the menu to zero-set, teach, or laser-off; trigger it with a pulse longer than 20 ms - to 0 V on NPN models, to +24 V on PNP models - then release. Wired to a PLC output and set to zero-set, it re-references the sensor after every product changeover with no human at the panel.

We heard the factory datasheet has printing errors - what was corrected?

Four items, each resolved against the factory's own circuit diagrams and nameplate: linearity figures typeset as 'f.5.' and 'f.8.' (both are f.s.); a text line calling the MF wire grey (it is pink - grey is the analog output); a 550 us sampling figure in the test-conditions footnote (the specification rows' 500/750 us prevail); and the G120's far-end spot size, which we reproduce exactly as printed (0.5 x 0.8 mm) without reinterpretation. The English PDF on this page carries the corrected values.

Can it measure shiny, transparent or black targets?

With precautions. Polished metal throws the beam away like a mirror - angle the head a few degrees off that mirror direction and prove the setup on a sample part. Transparent film answers with two faint echoes, one from each face, so the reading wanders - run a sample trial before committing. Very dark matte surfaces starve the receiver of signal - drop to a nearer grade for margin. And glowing-hot stock emits light in the very red band the sensor reads; that case needs its own evaluation. In every doubtful case we would rather test your sample than have you discover the physics at commissioning.

Is IP64 enough for my environment?

IP64 means dust-tight and splash-protected: normal workshop dust, chips and incidental spray are fine. It is not a washdown or coolant-jet rating - persistent spray or oil mist calls for a windowed guard or air purge in front of the optics. The operating window is -10 to +45 degC, non-freezing, non-condensing.

Does the RS485 version speak Modbus RTU?

The datasheet specifies the physical layer (RS485, grey A+ / shield B-) but publishes no protocol or register map. Request the protocol documentation through us before designing the comms integration - do not assume Modbus RTU from the connector.

Can the DDK-G act as a safety sensor for personnel protection?

No. It is a measurement instrument with no IEC 61496 certification and must never be the device that stops a machine to protect a person. For guarding duty, specify a certified safety light curtain wired through a safety relay; the DDK-G's job is dimensions, not people.

What should be on the purchase order so nothing bounces?

Grade (30/50/85/120/250), polarity letter (N or P), interface (M with '4-20 mA' or '0-10 V' written out, or -485), and termination (2 m cable - 6-core analog / 8-core RS485 - or the 90 g connector version). Add your target material if it is glossy, transparent or hot, and ask for repeatability data if the duty is tolerance-critical. Certification documents are available on request.

Works Well Together

On the same machine or line, DDK-G is typically ordered together with: Laser Distance Sensors · Contact Displacement Sensors · Relay & Timer Modules

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