Measuring light curtains vs safety curtains

When you stand in front of a new machine and do the risk assessment, one question comes up again and again:

“Do we need a safety light curtain here, or a measuring light curtain… or both?”

If you work in packaging, logistics, press shops, robot cells, woodworking, battery, 3C or plastics, this choice shows up in almost every project. Let’s break it down in simple words and real shop-floor stories, using NEW STAR’s product families from thelightcurtains.com as a reference.

What is a safety light curtain for machine guarding?

A safety light curtain creates an invisible wall between people and a hazard.
One side sends infrared beams, the other side receives. When a hand, arm or body breaks the beams, the curtain sends a safety stop signal to the relay or safety PLC and the motion stops.

Key points in normal engineer language:

• It’s a Type 2 or Type 4 safety device. Type 4 is the high level for presses, robots and most high-risk machines.
• It has dual OSSD outputs, self-diagnosis and redundant circuits. If something inside fails, it goes to safe state.
• It’s designed to help you reach PL d/e or SIL2/3 together with the rest of the safety chain.

At NEW STAR we ship many form factors: compact machine safety light curtains, front ultra-thin safety curtains, heavy-duty models, and waterproof safety light curtains for wet enviroments.

Typical safety light curtain use cases

You use a safety light curtain whenever a person can reach a danger zone:

• Presses and press brakes – finger or hand protection in front of the tool.
• Injection molding / die casting – guarding the mold area and eject zone.
• Robotic cells and gantries – entrance protection, multi-sided access around the working envelope.
• Woodworking and panel saws – body protection near saw infeed, large panel handling.
• Packaging lines – conveyor entry / exit guarding, palletizer and depalletizer access.

Here the goal is simple: don’t let a person get hurt. Data is secondary, safety is first.

What is a measuring light curtain for dimensioning and detection?

A measuring light curtain looks almost the same from outside: emitter bar, receiver bar, plenty of beams. But the job is different.

Instead of just saying “blocked / not blocked”, it tells you which beams are blocked. The controller can then calculate object:

• height
• width
• position
• profile or shape
• sometimes even basic counting and gap detection

So in normal words: safety curtain = stop the machine, measuring curtain = measure the stuff.

On the NEW STAR side, the NST series in our Measurement Light Curtains category gives you:

• NPN / PNP switching outputs
• analog 0–10 V or 4–20 mA for height or distance
• RS-485 / RS-232 with simple protocol (for example Modbus) so PLC or IPC can read full beam pattern

Real-world uses of measuring curtains

You see measuring curtains a lot in:

• DWS and logistics – automatic carton and parcel dimensioning before sorting or billing.
• Conveyor systems – pallet height check before AS/RS, crash avoidance at low tunnels.
• Woodworking and metal – board width and thickness detection, log shape tracking before cutting.
• Battery and 3C electronics – pack or module size check before assembly and welding.
• Plastics and rubber – part presence and height check before trimming, punching or inspection.

In these jobs you still care about safety, of course, but the main pain is wrong size, wrong product, jam, or rework. Measuring curtain gives you live data so operators dont need to “eyeball” everything.

Measuring light curtains vs safety curtains: quick comparison

Key difference table

So even if the hardware looks similar, the design target is completely different.

How to choose: risk, data and enviroment

Step 1 – Look at human risk first

If a person can reach:

• a moving tool
• a nip point
• a hot surface
• a crushing zone

…you start with a safety light curtain or other guarding device.
You check:

• required safety category (often Type 4),
• needed resolution (finger / hand / body),
• and safety distance according to your country standard.

Only after that you ask: Do we also need measurement here?

Step 2 – Decide what data you really need

Ask your team some simple but hard questions:

• Do we just need to stop when someone enters?
• Or do we want to know exact height of each carton?
• Do we need to track position for a robot or shuttle?
• Is there any quality rule like “reject if height out of range”?

If you say “yes” to the second part, you probably need a measuring light curtain in addition to the safety model. Sometimes they share same housing, sometimes they are two separate curtains on same frame.

For example:

• Press line: safety curtain in front of tool, measuring curtain upstream to check part size before loading.
• DWS cell: measuring curtain above belt, safety curtain or safety scanner around operator access.

Step 3 – Check enviroment and mechanical details

This is where ultra-thin and special housings help:

• Tight machine frame → use front ultra-thin or side ultra-thin safety curtains so they don’t collide with sliding doors.
• Coolant, oil mist, food washdown → use Waterproof Safety Light Curtain models.
• Tall robot cell → choose Multi-Sided Access Protection with stacking and muting.

NEW STAR’s catalog covers compact safety light curtains, ultra-thin profiles, heavy-machine and multi-side safety curtains, plus custom Non Standard variants for OEM frames. So you don’t have to redesign the whole machine just because the sensor is fat.

How NEW STAR puts both worlds together for OEM, integrators and end users

NEW STAR is set up as a one-stop machine safety sensors manufacturer:

• Safety Light Curtains Categories – Compact, Front Ultra-Thin, Side Ultra-Thin, General Use, Heavy Machine, High-Precision, Multi-Sided Access Protection, Waterproof.
• Measurement Light Curtains – for DWS, conveyors, stack height, profile.
• Other safety devices – laser scanners, safety mats, interlock switches.
• Flow and photoelectric sensors – for water treatment, HVAC, chemical flow and material detection.

We mainly serve:

• equipment builders and automation integrators,
• EHS and safety managers,
• process / production managers and maintenance,
• purchasing and compliance people who need stable, certifed supply.

Because we design and build both safety and measuring curtains under one ISO9001 factory, you can:

• standardize on one brand across packaging/logistics, press and machine tools, injection/Die-casting, robotic systems, wood and panel lines, auto parts, battery and 3C, metal, plastics and rubber, home appliance, pharma, food and beverage.
• do OEM / ODM: your color, label, connector, cable length, even special mounting holes.
• mix safety guarding plus measurement in one delivery, instead of chasing multiple suppliers.

And honestly, this reduce small headaches for your team: fewer datasheets, fewer spare types, easier training. Maybe my English still a bit broken, but the idea is clear.

Quick checklist before you lock the spec

You can keep this simple list next to your P&ID or layout drawing:

• Is someone exposed to a hazard here?
  • Yes → must use a safety light curtain or other guarding device.
• Do we need actual size or position data?
  • Yes → add a measuring light curtain in that zone.
• Is there enough space and good mounting?
  • If not, look at compact or ultra-thin families.
• Is enviroment wet, dusty, hot?
  • Consider waterproof or heavy-machine versions.
• Who is the owner?
  • EHS checks safety level.
  • Automation checks I/O, protocol, PLC side.
  • Purchasing checks certificates, lead time and volume price (no need to calculate cost here, just make sure its acceptable).

When you walk through a new line with this in mind, the “measuring light curtains vs safety curtains” question becomes much easier. One protects people, one feeds data, and sometimes both come from the same place – in this case, from NEW STAR at thelightcurtains.com.