GDK Series Laser Displacement Sensor — 2 µm at 30 mm
A compact CMOS triangulation sensor with five reference distances from 30 to 250 mm — including the 85 and 120 mm grades most series skip — so the target sits near range centre, where a triangulation sensor is at its best.
- Resolution 2–75 µm; linearity ±0.1% F.S.
- 655 nm Class 2 (IEC/JIS) laser, 1 mW max
- Response max 2 ms (fast) to 36.5 ms (high-res)
- 4-20 mA / 0-10 V / RS485 + two NPN/PNP outputs
- IP64 aluminum body, MF multifunction input
How Laser Triangulation Reads Microns
The GDK projects its 655 nm spot onto the target; the receiving lens images that spot onto a CMOS array at an angle. When the target moves toward or away from the sensor, the imaged spot slides along the CMOS — and that lateral shift converts geometrically into distance. Because a micron-scale target move produces a measurable pixel shift, the 30 mm grade resolves 2 µm without touching the part.
Specifications by Range Grade (Catalog Data)
| Item | GDK-30 | GDK-50 | GDK-85 | GDK-120 | GDK-250 |
|---|---|---|---|---|---|
| Models | GDK-30N(P)M / -485 | GDK-50N(P)M / -485 | GDK-85N(P)M / -485 | GDK-120N(P)M / -485 | GDK-250N(P)M / -485 |
| Reference distance | 30 mm | 50 mm | 85 mm | 120 mm | 250 mm |
| Measuring range | ±4 mm | ±10 mm | ±20 mm | ±60 mm | ±150 mm |
| Resolution | 2 µm (4 µm fast) | 5 µm (8 µm fast) | 10 µm (15 µm fast) | 30 µm (45 µm fast) | 75 µm (150 µm fast) |
| Linearity | ±0.1% F.S. (F.S. = 8 mm) | ±0.1% F.S. (F.S. = 20 mm) | ±0.1% F.S. (F.S. = 40 mm) | ±0.1% F.S. (F.S. = 120 mm) | ±0.3% F.S. (F.S. = 300 mm) |
| Spot size (centre) | 0.1 × 0.1 mm | 0.5 × 1.0 mm | 0.75 × 1.25 mm | 1.0 × 1.5 mm | 1.75 × 3.5 mm |
| Spot size (near / far end) | 0.15 × 0.15 mm both | 0.6 × 1.2 / 0.4 × 0.9 mm | 0.9 × 1.5 / 0.6 × 1.0 mm | 1.2 × 1.8 / 0.5 × 0.8 mm | 1.5 × 2.5 / 2.0 × 4.5 mm |
| Response time — fast | max 2 ms (1 sample avg. + sensitivity switch max 1 ms) | max 2.5 ms | |||
| Response time — standard | max 11.5 ms (16 samples, 8.5 ms + max 3 ms) | max 15.5 ms | |||
| Response time — high-res | max 36.5 ms (64 samples, 32.5 ms + max 4 ms) | max 48.5 ms | |||
| Sampling period | 500 µs (factory setting) | 750 µs | |||
Spot size defined at 1/e² (13.5%) of centre intensity — objects of higher reflectance adjacent to the spot can cause false readings outside the defined spot area. Test conditions: 23 °C, DC24 V, high-resolution mode, 550 µs sampling, centre position, 50 × 50 mm white ceramic target.
Electrical & Environmental (All Grades)
| Light source | Red semiconductor laser, 655 nm, max output 1 mW |
|---|---|
| Laser class | Class 2 (IEC/JIS) · Class II (FDA) |
| Supply voltage | Analog-current & RS485 types: DC12–24 V (+10%/−5%) · analog-voltage type: DC18–24 V (+10%/−5%) |
| Current consumption | max 60 mA (incl. analog output) · RS485 type max 40 mA |
| Switching outputs 1/2 | NPN or PNP, max 100 mA / DC30 V, residual voltage 1.8 V |
| Analog output | 4–20 mA (load ≤300 Ω) or 0–10 V (output impedance 100 Ω) |
| Communication | RS485 on -485 models (protocol details: contact factory) |
| MF multifunction input | Zero-shift, teach, laser-off via menu; NPN: MF wire to 0 V >20 ms · PNP: MF wire to +24 V >20 ms |
| Protection circuits | Reverse-connection protection, overcurrent protection |
| Temperature drift | ±0.08% F.S./°C |
| Protection rating | IP64 |
| Ambient temperature / humidity | Operating −10 to +45 °C (no freezing), 35–85% RH · storage −20 to +60 °C |
| Ambient illuminance | Sunlight ≤10,000 lx · incandescent ≤3,000 lx |
| Vibration / shock | 10–55 Hz, 1.5 mm double amplitude, 2 h per axis · approx. 50 G (500 m/s²), 3 times per axis |
| Warm-up | Internal circuit stable ≈1.5 s; full warm-up max 15 min |
| Housing / lens | Aluminum alloy / PMMA |
| Cable | φ5, 2 m PVC, AWG24 — 6-core (analog types) / 8-core (RS485 types) |
| Weight | 65 g cable type (excl. cable) · 90 g connector type |
Dimensions & Feature Summary
GDK vs Our Other Displacement & Distance Series
| Series | Positioning | Pick it when… |
|---|---|---|
| GDK (this page) | Fine-resolution triangulation, 30–250 mm, 2–75 µm, IP64 | You need micron-class reading at short range, or the 85/120/250 mm intermediate grades other series skip. |
| DK-G Series485 | Triangulation, 30–400 mm centres, 10–200 µm repeatability, IP60 | You need the 400 mm centre distance or the DK-G's documented repeatability figures. |
| LK-F CMOS Series | CMOS triangulation, 30–400 mm, IP67 housing | Washdown or dusty conditions demand the IP67 body. |
| DSK-CG | Long-range distance measurement, 1–80 m, mm-class | The job is metre-range ranging (cranes, AGV, racks), not micron displacement. |
| DDA-Y / DDB-Y · DDK | Industrial laser distance sensor families | Alternative long-range ranging platforms — compare interfaces and range on their pages. |
GDK is a measurement component, not an IEC 61496 certified safety device — never use it as the sole protection for personnel. Repeatability data for GDK has not been published; for tolerance-critical acceptance criteria request test data from the factory first.
Frequently Asked Questions
What resolution and linearity does the GDK series achieve?
Resolution runs from 2 µm at the 30 mm reference distance to 75 µm at 250 mm (4–150 µm in fast mode). Linearity is ±0.1% of full scale on the 30/50/85/120 mm grades and ±0.3% F.S. on the 250 mm grade — full scale being the grade's total measuring span (e.g. 8 mm for the 30 mm grade). Resolution, linearity and repeatability are different quantities; ask us for the correct one for your tolerance study.
What laser does the GDK use, and is it safe to work around?
A 655 nm red semiconductor laser with 1 mW maximum output — Class 2 under IEC/JIS and Class II under FDA classification. Class 2 visible lasers are considered safe for momentary exposure because of the blink reflex, but the beam should never be viewed intentionally; follow your plant's laser handling rules.
How fast does the GDK respond?
Three selectable modes: fast (1 averaging sample) responds within max. 2 ms, standard (16 samples) within max. 11.5 ms, and high-resolution (64 samples) within max. 36.5 ms — the 250 mm grade adds roughly 30% (2.5/15.5/48.5 ms). The factory sampling period is 500 µs (750 µs for the 250 mm grade). Pick fast mode for moving targets and high-resolution mode for the finest reading on static targets.
How big is the laser spot?
At the measuring-range centre the spot ranges from 0.1 × 0.1 mm on the 30 mm grade to 1.75 × 3.5 mm on the 250 mm grade (defined at 1/e² = 13.5% of centre intensity). The small spot on short-range grades is what lets the GDK resolve narrow steps, small parts and fine gaps.
Which output types are available?
Per model: a 4-20 mA current output (load ≤300 Ω), a 0-10 V voltage output (output impedance 100 Ω), or an RS485 communication version — each with two additional NPN or PNP switching outputs rated max. 100 mA / 30 V DC (residual voltage 1.8 V) for threshold alarms. Supply is DC12–24 V for the current and RS485 types, DC18–24 V for the voltage type.
How does GDK differ from the DK-G and LK-F displacement series?
GDK is the fine-resolution short/mid-range option: 2 µm at 30 mm, five grades up to 250 mm, IP64. DK-G covers 30–400 mm centres with 10–200 µm repeatability and IP60; LK-F is the CMOS series with IP67 housing and grades to 400 mm. If you need metre-range distance rather than micron displacement, move to the DSK-CG laser distance sensor instead.
What should export buyers confirm before ordering?
Confirm the grade (30/50/85/120/250), output letter (M analog / -485), NPN or PNP, and cable termination (φ5 6-core 2 m PVC cable for analog types, 8-core for RS485; a connector version is also listed at 90 g). Modbus protocol details for the RS485 version and repeatability data should be confirmed with the factory. MOQ and lead time are quoted per model; certification documents are available on request.
Specs reviewed by Engineer Cai, Senior Application Engineer. See certificates.