Datalogic Safety Light Curtains: Choosing Type, Resolution & Safety Distance
SG4 and SG2 safety light curtains for presses, packaging machines and robot cells — with a worked safety-distance example.
A Datalogic safety light curtain puts an invisible guard across a dangerous opening. The moment a finger, hand or body breaks the beams, the machine stops. Choosing one comes down to three decisions: the safety Type your risk assessment needs, the resolution that matches what you are protecting, and the safety distance between the curtain and the hazard. This guide walks through each decision using the Datalogic SG4 and SG2 ranges we supply in India.
Type 4 or Type 2?
| Datalogic SG4 | Datalogic SG2 | |
|---|---|---|
| Safety type (IEC 61496) | Type 4 | Type 2 |
| Maximum safety level | PL e / SIL 3 | PL c / SIL 1 |
| Typical machines | Presses, robot cells, high-risk packaging | Lower-risk handling and assembly |
| Versions | BASE, BASE AutoRestart, muting, EXTENDED | Standard |
The required level always comes from the machine risk assessment (ISO 12100 / ISO 13849-1).
Pick the Resolution for What You Protect
14 mm — finger
Detects a finger. Lets you mount the curtain closer to the hazard, keeping the machine compact.
30 mm — hand
Detects a hand. The most common choice for presses, packaging machines and loading stations.
Larger — body
Detects a person walking through an access opening, such as the entry to a palletiser or robot cell.
Datalogic SG4 curtains are offered with 14 mm or 30 mm resolution and protected heights from 150 mm up to 1800 mm. Choose the height so the whole opening is covered — no gaps above, below or at the sides.
Worked Example: Safety Distance
EN ISO 13855 formula for curtains up to 40 mm resolution: S = K × T + C, with K = 2000 mm/s and C = 8 × (d − 14).
| Input | Value | Note |
|---|---|---|
| Resolution d | 30 mm | SG4 hand-protection curtain |
| Total stopping time T | 0.10 s | Curtain response + machine stopping time (measured) |
| K × T | 2000 × 0.10 = 200 mm | Approach speed × time |
| C | 8 × (30 − 14) = 128 mm | Intrusion allowance |
| Safety distance S | 328 mm | Minimum distance from curtain to hazard |
Example only. The final distance must be calculated and verified by a qualified person using the measured stopping time of your machine.
Datalogic Safety Products in Stock
Datalogic SG4-30-075-OO-E
Type 4, 30 mm resolution
Rs. 45,000
Datalogic SG4-30-030-00-X
Type 4, 30 mm resolution
Rs. 24,500
Datalogic SG4-RB2-050-OO-E
SG4 series safety device
Rs. 51,773
Datalogic SG4-S2-050-PP-E
SG4 series safety device
Rs. 57,418
Datalogic SG2-30-075-OO-X
Type 2, 30 mm resolution
Rs. 93,218
Datalogic SE-SR2
Safety relay module
Rs. 15,500
Installation and Daily-Check Checklist
- Cover the whole opening. Add fixed guards so nobody can reach over, under or around the curtain.
- Keep the calculated distance. Mount at or beyond the safety distance — never closer.
- Wire through a safety relay. Connect the OSSD outputs to a safety module such as the SE-SR2 that monitors the machine contactors.
- Align and test. Align transmitter and receiver, then pass the test rod of the correct diameter through the whole field — the machine must stop every time.
- Check every shift. Repeat the test-rod check daily and after any maintenance.
Muting, Blanking and Auto-Restart Explained
Auto-restart vs manual restart
Manual restart needs an operator reset after each interruption; auto-restart suits positions where nobody can stand inside the protected area.
Muting
Temporarily ignores the curtain while material passes on a conveyor, using muting sensors — available on the SG4 muting version with L, T or X muting kits.
EXTENDED functions
Remote configuration, monitoring and cloning of settings across identical machines.
Safety Light Curtain FAQs
What is the difference between a Type 2 and a Type 4 safety light curtain?
Both are defined by IEC 61496. A Type 4 curtain such as the Datalogic SG4 is designed for high-risk machines and can be used up to PL e / SIL 3. A Type 2 curtain such as the SG2 is intended for lower-risk applications, up to PL c / SIL 1. Your machine risk assessment decides which one is required.
Which resolution do I need — 14 mm or 30 mm?
A 14 mm resolution detects a finger and is used when the curtain must be mounted close to the hazard. A 30 mm resolution detects a hand and is common on presses, packaging machines and robot cells. Larger resolutions are used for body detection at access openings.
How do I calculate the safety distance?
EN ISO 13855 gives S = K × T + C. For a 30 mm curtain use K = 2000 mm/s and C = 8 × (d − 14). T is the total stopping time of the curtain plus the machine. The result must be at least 100 mm; if it is above 500 mm you may recalculate with K = 1600 mm/s, but S cannot then be less than 500 mm.
Why do I need a safety relay with a light curtain?
The curtain’s OSSD safety outputs must switch the machine through a safety-rated circuit. A safety relay module such as the Datalogic SE-SR2 monitors the outputs and the contactors so a single fault cannot leave the machine running.
What is the SG4 EXTENDED version?
The EXTENDED version adds programmable functions and allows remote configuration, monitoring and cloning of settings, which is useful when you install several identical machines.
Plan Your Machine Guarding With Us
Send the opening size, machine type and stopping time. Our team will suggest the Datalogic curtain, height and safety relay — and quote from stock.
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