Specs & Selection — Safety Light Curtains
Match the documented detection capability, not beam spacing, to the access hazard. Check the complete protected field, operating range and worst-case response against the required safety function. Then calculate separation using the complete stopping chain and assess reaching over, under and around the field.
1) Selection principles & constraints
Control variables
- Detection capability d: the manufacturer's specified detectable object size; separate from pitch.
- Protected height: actual sensing field and end zones, not housing length.
- Range: exact near/far limits, mirrors and ambient-light conditions.
- Total response: sensor + safety logic + final elements + measured machine stopping time and allowances.
- Synchronization: exact supported method and EMC/optical installation instructions.
Non-negotiables
- Determine the required Type and PLr/SIL from the risk assessment and applicable machine standard.
- Use the applicable ISO 13855:2024 method and assess all approach paths, including reach-over.
- Use approved safety inputs for each OSSD channel; reset and EDM functions must be documented where required.
- Follow actual cable routing, shield termination and separation instructions; no universal 200 mm rule is assumed.
2) Selection matrix — spec trade-offs
| Use case | Resolution | Typical protective height | Usable range | Typical response | Why it’s chosen | Watch-outs |
|---|---|---|---|---|---|---|
| Finger access at tooling | Documented finger detection, e.g. 14 mm | Cover the evaluated opening and end zones | Exact model limits | Maximum for selected configuration | Detect the required test object at the specified separation | A 10 mm pitch may correspond to 18 mm detection; check machine suitability |
| Hand access at conveyors / loading | Documented detection, not a 30/40 mm pitch label | Prevent reaching over, under and around | Exact limits including mirrors | Complete stop-chain budget | Application-specific detection and access geometry | Coarser detection can require different positioning rules |
| Tight retrofit inside a frame | Same required detection as the original safety function | Actual field and dead zones, not overall length | Variant-specific | Do not infer from profile size | Fit only after safety and interface checks | No universal 30×17.5 mm DQC/JER interchangeability |
This is a selection checklist, not a family-level performance table. Use the exact variant's current manual and safety evidence.
3) 10 mm specifications — verify finger detection before selecting height and range
First check Is 10 mm the documented detection capability or merely beam pitch? The DQA/DQC factory table pairs 10 mm pitch with 18 mm detection, which does not establish a 14 mm finger-detection function. Use the manufacturer-specified test piece, not an arbitrary 14 or 20 mm rod.
Mounting: Follow the exact field-edge, reflective-surface, bracket and optical-interference requirements; no universal 5–10 mm frame margin or 300 mm reflection clearance is specified here.
| Spec | Recommended | Notes |
|---|---|---|
| Protected height | Cover the evaluated opening; 500/600 mm only if the exact field fits | Check end zones and reach-around; no unvalidated stacking |
| Range | Use exact model's permitted near/far range | Mirrors, contamination and reflective objects change installation constraints |
| Response | Use confirmed maximum, not a generic 10–15 ms | Include logic, final elements, measured stopping and allowances |
Acceptance: With hazardous motion disabled, use the specified test piece over the complete field and its boundaries according to the manual. Qualified personnel then verify the complete stop and restart functions under a controlled plan. Check EDM only where designed and documented; use the prescribed inspection intervals, not an invented quarterly schedule.
4) 30/40 mm specifications — hand-access limits and 3–6 m range checks
When to consider Select a documented detection capability appropriate to hand access and the applicable positioning method. If fingers can reach through to danger, a coarse-pitch device is not made suitable by its hand-guard label.
| Spec | Recommended | Notes |
|---|---|---|
| Detection | Confirm actual detectable object size | 30/40 mm pitch is not automatically hand-detection capability |
| Protected height | Match all relevant access paths | Add appropriate fixed/interlocked guards for uncovered access |
| Range | Verify the exact 3–6 m requirement against the chosen variant | Longer range does not establish protective classification or alignment margin |
5) Slim 30×17.5 mm retrofits — for tight spaces
A narrow slot is a mechanical constraint, not an approved product cross-reference. The current MK and JER pages describe 25×23 mm and 29.3×29.3 mm bodies respectively; do not assume DQC, DQZ or JER fits a 30×17.5 mm envelope. Obtain the actual drawing and cable-bend space.
- Use the specified brackets and support spacing, including vibration and impact conditions.
- Check actual protected field, end zones, range and connector clearance before reusing mounting holes.
- Verify synchronization and EMC by the exact manual; do not rank wired versus optical as universally safer.
6) 6-step selection workflow + worked example
- Define the protective function: machine eligibility, access hazard, required Type and PLr/SIL.
- Measure access geometry: opening, approach paths, field end zones and space behind the device.
- Verify detection and range: use exact documented capability, not pitch or family shorthand.
- Calculate separation: total sensor, logic, final-element and machine stopping time, plus required allowances.
- Confirm interfaces: compatible safety channels, synchronization, reset, feedback and environmental limits.
- Validate and record: complete-field test, controlled stop/restart verification and periodic inspection plan.
7) FAQ
Is 14 mm “finger protection” better than 10 mm?
If 10 mm and 14 mm are both documented detection capabilities, 10 mm detects a smaller specified object. Neither number is automatically better for every application. Confirm that the catalog number is detection capability rather than beam pitch: DQA/DQC factory data pair 10 mm pitch with 18 mm detection. Select documented safety performance, geometry, range and response time together; do not infer finger protection from a suffix.
When should I pick optical sync (JER) instead of wired sync (DQC)?
Choose the synchronization method that the exact transmitter/receiver pair supports and the installation permits. Optical synchronization can avoid a dedicated sync conductor, but optical interference and cabling still need assessment. Wired synchronization is not a universal guarantee of greater EMC immunity. Verify current JER and DQC wiring drawings, pulse-compatible safety interfaces and immunity evidence rather than selecting from the family name.
How much protective height is “enough”?
Use the manufacturer's declared protected field and end-zone dimensions to cover all access paths throughout machine movement. Housing length and the span between first and last beams do not alone prove safe coverage. If multiple pairs are required, validate gaps, overlap, optical interference and restart prevention. Only use a documented safety cascade where supported; never join raw OSSD outputs to create one channel.
Use the light curtain range and model evidence after defining these requirements. For detailed geometry, continue to effective protected-height checks or the installation and wiring references.
Sources: ISO 13855:2024, SICK deTec4 Core installation and test instructions as an exact-model example, and the DAIDISIKE DQA/DQC factory detection table. Apply the selected device's own manual; one manufacturer's instructions are not a universal pinout.