Muting vs Blanking in Safety Light Curtains: Which Function Do You Need?

What is the difference between muting and blanking?

The useful distinction is a controlled operating condition versus an allowed interruption pattern. Muting changes when the relevant protective function is active. Blanking changes which interruptions the light curtain accepts while it continues monitoring according to its configured rules.

Muting and blanking are not interchangeable ways to stop nuisance trips. A dirty lens, loose bracket or incorrect alignment calls for fault diagnosis. An operator needing routine access may call for a different safeguarding arrangement—not a larger ignored area.

This guide supports function selection and document review. A competent machine-safety professional must assess and validate any change before hazardous operation. Neither feature makes an ordinary process sensor suitable for personnel protection.

When should you use muting for material transfer?

Consider muting when material must cross the light curtain and the machine can establish a controlled, temporary condition in which the suspended protection is not needed to prevent hazardous access. Conveyor entry and exit are common examples. Muting can also apply to a non-hazardous phase of a machine cycle; material transfer is not its only use. SICK explains this distinction.

In a transfer application, the logic evaluates a permitted combination or sequence of inputs. That is not the same as the light curtain inherently recognizing “person” or “pallet.” The sensor arrangement, load geometry and physical guarding must make the distinction reliable.

1. Establish a valid condition. The specified inputs and machine state satisfy the approved muting logic.
2. Control the passage. The load crosses while the required sequence, timing and access restrictions remain valid.
3. Restore protection. The defined completion condition ends muting; an invalid sequence or timeout is handled as specified by the safety system.

This describes the operating concept, not a sensor-positioning recipe. Two-sensor, four-sensor, entry-only and bidirectional arrangements have different constraints. Some systems support partial muting; others suspend protection over the entire field. Use the documented function and scope of the selected device/controller combination.

ReeR's material-handling guidance makes this combined responsibility explicit: input placement and additional side protection must prevent personnel access throughout the muted passage. Its application drawings are useful references, not universal dimensions to copy. See the muting application guidance.

How should a stalled load be handled?

A stopped load or broken sequence is a recovery condition, not a reason to extend muting indefinitely. Where the exact system provides an override function, its permitted initiation, duration, operator controls and exit conditions need a separate recovery procedure. If access for jam clearing is required, follow the machine's safe isolation procedure; do not bridge outputs or use a standard PLC bit as a substitute for the safety function.

Should the obstruction use fixed or floating blanking?

Start with the object's behavior in the protective field. A fixed obstruction suggests fixed blanking. An expected object that changes position suggests floating blanking, if its movement and size fit a documented function. In both cases, the remaining field must provide the required detection, and the opening around the object must not allow undetected access.

What happens if a fixed object is removed?

That is one of the most important questions to ask before selecting fixed blanking. Some configurations monitor the expected object's presence and position; others have different permitted tolerances or operating rules. Do not assume that “blanked” means beams are simply switched off and left unmonitored.

Illustrative example: a fixture crosses the protective field during production but is removed for changeover. The original choice of fixed blanking may suit production. It does not automatically cover the empty-fixture condition. Confirm the response to removal, which operating mode is allowed during changeover, and whether a new gap could permit access.

The fixture's physical width also matters. Blocking the relevant beams does not necessarily close every possible reach-around path. Mechanical measures may be needed beside the fixture. Pilz's blanking guidance discusses this residual opening.

Is floating blanking the same as reduced resolution?

Not reliably across manufacturers. Floating blanking may monitor an expected moving object within a defined area, including its presence. Reduced resolution generally permits specified small interruptions without requiring one particular object to remain there. Terminology and combinations vary.

Compare the actual behavior: must the object be present; how far can it move; how small can it become; what additional interruption is detected; and what happens outside those limits? A setting called “one beam” is not enough information to answer these questions.

Will blanking change detection capability or safety distance?

It can. The relevant value is the effective detection capability for the configured mode, not just the physical resolution printed on the device. A larger resolution value in millimeters means a larger object may be needed for reliable detection—not finer protection.

Changing detection capability can change the distance needed between the field and the hazard. The assessment also depends on approach geometry, the configured protective-device response, the rest of the safety chain and the machine's measured stopping performance. A nominal beam count cannot determine that distance on its own.

Keep three separate questions in the review: what the field detects, how quickly the complete system responds, and whether a person can reach the hazard by another route. ISO 13855:2024 addresses safeguard positioning; the applicable machinery standard and device instructions also need to be considered.

What must be checked before enabling either function?

A successful normal cycle is only one part of the evidence. The review must also establish what happens when the process departs from the expected load, object position or sequence.

Plan these checks with qualified personnel using the manufacturer's prescribed test pieces and a controlled validation procedure. Prevent hazardous motion or exposure as required by that procedure. Never test personnel exclusion by putting a person through a live opening, riding a load or deliberately creating a live wiring fault.

IEC 62046 covers the selection, positioning, configuration and commissioning of protective equipment used to detect persons. A light curtain's Type, certificate or supported feature list is product evidence; it does not establish that the complete machine safety function reaches its required performance level or safety integrity level.

What should the supplier confirm for your exact system?

Ask for the function description and configuration evidence, not just a “muting/blanking available” checkbox. The light curtain, safety controller or expansion module, and their software versions can determine what is actually supported.

• Exact hardware and revision: sender/receiver model numbers, suffixes, controller or module, firmware and applicable manual revision.
• Permitted behavior: muting scope and sequence, blanking presence monitoring, size/position tolerances, allowed function combinations and recovery conditions.
• Safety-related values: effective detection capability and response time for the intended settings, plus the relevant product conformity and reliability data.
• Configuration control: an identifiable approved parameter record, access restrictions and the changes that require reassessment or revalidation.

For an xsz sensor quotation, have each requested function confirmed for the quoted system; this comparison is not a declaration that every model includes it. If the documentation cannot establish a required behavior, keep that configuration unapproved while the gap is resolved.

The practical choice: investigate muting for a controlled passage, fixed blanking for an expected fixed obstruction, and floating blanking for a supported moving obstruction. Then check the access routes, configured detection capability and fault behavior that the feature name does not tell you.