Safety laser scanner selection starts with the hazard, not the longest range in a catalog. Identify who can approach a dangerous movement, from where, in which operating mode, and how long the entire machine takes to become safe after detection. A scanner can shape a two-dimensional field around a pallet opening, the front of a robot cell, or an area where a person could remain. It cannot see behind a pallet or column, protect every height above and below its scan plane, or contain ejected material. This guide gives factory engineering, EHS, and purchasing teams in Thailand a practical path from requirements to RFP, FAT, and SAT.
Define the safety function before choosing a scanner
Describe the hazard and the action it demands
“Detect a worker” is too vague for procurement. Identify the hazardous movement and the task: automatic running, setup, cleaning, jam removal, maintenance, or recovery. Specify whether intrusion must stop the motion, prevent startup, or merely trigger an operational warning. Map people, carts, pallets, and material at each machine state. If the field changes when a pallet arrives, document the signal that selects the field and the safe behavior if that signal disappears or conflicts with another signal.
Risk assessment determines the required safety function and performance. A device specification such as Type 3 or PL d does not prove the complete function: OSSD outputs, external device monitoring, safety controller, contactors, and drive must work together. Our safety PLC validation guide addresses the controller and validation work. Here the focus is whether the sensing geometry and selected product can meet the requirement.
Decide when an area scanner fits
A horizontal field can suit an open side of a guarded robot cell or a conveyor transfer where people must be detected before reaching a hazard. The route to the hazard must cross the active detection plane, stopping must finish before contact, and restart behavior must account for a person remaining inside. A scanner measures a plane at a defined height. A person may step over or under it, or hide behind a fixture. Fences, another scanner, or another protective device may therefore be necessary.
A light curtain often guards a plane across an opening, while a scanner can monitor an irregular floor-level area. Neither is automatically cheaper or safer. Compare actual opening geometry, material flow, object resolution, stopping time, blind spots, and cleaning conditions. The safety light curtain selection guide helps compare the two layouts on the same hazard.
Keep protective and warning fields distinct
Intrusion into a protective field causes the safety outputs to move to the safe state and the hazardous movement to stop. A warning field can provide an operational signal, early indication, or a request for controlled slowing. SICK explicitly warns that a warning field must not be used to protect people. A longer warning range therefore cannot make up for a protective field that is too short. Put both ranges in separate columns of the bid comparison.
The global OMRON OS32C specification illustrates why the exact variant and resolution matter. For the standard OS32C, the stated safety range is 1.75 m at 30 mm resolution, 2.5 m at 40 mm, and 3.0 m at 50 or 70 mm; its warning range is 10.0 m. The OS32C-[][][]-4M variant reaches a 4.0 m safety range at 70 mm and has a 15.0 m warning range. These figures belong to that published specification, not to every regional package or every safety scanner. First decide what must be detected, then compare protective range at that setting.
Pilz describes a stationary PSENscan example in which entering a warning zone initiates controlled braking and entering the protected field stops dangerous movement. That is a useful sequence, but it does not grant permission to delay the safety stop. If slowing is part of the distance assumption, assess its failure and monitoring. Keep the protective function valid under the documented worst case.
Calculate distance using measured stopping time
Include the whole response chain
The field must begin far enough from the danger point that the movement ends before a person can reach it. ISO 13855:2024 covers positioning and dimensioning safeguards relative to human approach. KEYENCE presents a horizontal approach example as S = K × T + C + A, with T covering scanner response and machine stopping time. The constants and conditions depend on approach direction, detection plane height, resolution, and the applicable edition of the standard. A worked example on a vendor page is not a ready-made distance for a Thai machine.
Measure the actual longest stopping time from the relevant safety input to the end of dangerous motion. Do not substitute an operator’s impression of an emergency stop. Test relevant speeds, loads, temperature or pressure conditions, and wear states. Record the method and results so that a future drive or brake replacement triggers a new measurement. OMRON’s safety guidance also calls for measurement on the actual system and periodic checks for a changed stopping time.
Range in a brochure is not usable field size
Compare the farthest required point with the protective range available at the selected resolution, including measurement and installation allowances. Overlay the configured field on a scaled plan. Look for a narrow unprotected strip beside a wall, a route near the scanner body, or a corner outside the active field. KEYENCE explains that an unprotected gap large enough for the minimum detectable object needs additional measures. Mark the tested field boundary on the factory floor and check the physical installation against the file in the configuration tool.
The scan-plane height cannot be chosen solely to avoid nuisance stops. A low plane may encounter debris, pallet corners, and floor irregularities. A high one can allow entry below it. A coarser resolution may extend the available range on some models while becoming unsuitable for the body part the design must detect. Check height, resolution, and the actual access path together. A colored area on a floor plan does not prove that a person cannot pass beneath a conveyor frame.
Design for blind spots and restart
Laser scanning does not see through a pallet, column, box, or machine frame. SICK’s operating instructions explicitly state that the area behind an object in the monitored field cannot be monitored. Draw the area for an empty opening, a pallet in transit, and a pallet stopped in the opening. A person could remain behind the active field after it clears; in that situation automatic restart may be unacceptable. Define the restart interlock, the reset location, visibility of the whole danger zone, and whether a person inside can reach the reset.
Two scanners are not a guarantee of zero blind spots. Their planes may be at different heights, a column may obstruct both, or the selected fields may differ during startup. In a multi-scanner design, verify overlap, wiring faults, reset behavior, and maintenance states. Walk the routes a person can actually use and compare them with the active fields.
Do not ask intrusion detection to contain ejected material
A scanner detects intrusion. It does not stop flying chips, hot liquid, falling items, or fragments. ISO 13855’s scope excludes hazards from emissions and mechanical part failure. Keep physical guards and covers where those hazards exist. Likewise, if entrapment can occur during the stopping interval, change the machine or guard design rather than drawing a smaller field around the problem.
Prove every field-switching state
Multiple field sets can help when pallets pass or operating modes change, but the transition is part of the safety function. State which signal selects each field, what happens during power-up, a broken input, lost communication, conflicting inputs, emergency stop, and mode change. SICK describes monitoring cases tied to machine state or speed and addresses switching timing. Create a sequence table that shows the active field at every transition.
“Turn off the field when the load arrives” is an incomplete requirement. Specify how the load is recognized, which portions remain monitored, and how a person beside or behind it is prevented from entering. FAT should test invalid signal order and intrusion during switching, not just the expected cycle. SAT should repeat the checks with the real pallet shape, placement tolerance, and reflective surfaces.
Separate stationary and AGV/AMR applications
Some scanners serve stationary machines and mobile vehicles. Pilz lists both applications for PSENscan, and SICK’s vehicle instructions size mobile protective fields using stopping distance and additional allowances. A stationary machine RFP should not be copied directly to an AGV. A vehicle needs fields for each speed and travel direction, braking under load and floor conditions, side exposure in turns, near-body undercutting, and crossing-point blind spots. Verify the field-switch timing at each speed.
Conversely, a mobile vehicle’s long warning field or staged slowing is not automatically a stationary machine safeguard. The fixed machine design starts with time to reach its hazard. Keep separate safety-function lists, drawings, and test records even if both applications use the same product family.
Compare products against the factory requirement
Complete the comparison in a useful order
List the hazard and required function first; then worst-case stopping time and required distance; then resolution and plane height; then installation angle and blind spots; then field switching and safe outputs; finally the environment and maintenance. At a Thai site, inspect dust, condensation, heat, washdown, forklift impact, and power quality. An IP65 rating alone does not establish suitability for every washdown or condensation condition.
OMRON’s OS32C page publishes resolution, protective and warning ranges, response and switching times, OSSD details, temperature, humidity, and ingress rating together. Use numbers from the same exact model and document. Do not take a minimum response time such as “from 80 ms” as the worst case for a different scan configuration. Confirm the selected configuration, safety controller interface, diagnostic access, configuration software support, spare parts, and replacement procedure.
Compare installed cost and recovery time
Request the cost of the scanner, bracket, protection, cabling, controller changes, drive or contactor work, engineering, configuration, stopping-time measurement, FAT, SAT, training, and spares. A lower scanner price can be outweighed by a second unit or additional guarding. Include downtime for installation. Ask who retains the configuration backup and how quickly a replacement can be supplied locally.
| Item | Ask the supplier to provide | Acceptance focus |
|---|---|---|
| Safety function | Hazard, stop and restart scope, required performance | Assess the whole circuit |
| Detection | Resolution, protective range at that setting, scan angle | Check the farthest point and margins |
| Time | Configured response, switching, measured machine stop | Use worst-case measured conditions |
| Fields | Drawings for protection, warning, and each mode | Test transitions and blind spots |
| Interface | OSSD, EDM, reset, controller compatibility | Verify fault response |
| Environment | Temperature, humidity, cleaning, reflections, vibration | Match the actual Thai site |
| Handover | Configuration backup, test records, training, spares | Make recovery reproducible |
What to include in the RFP
Send the same revised plan and section drawings to all bidders. Include hazards, operating modes, people and material routes, maximum speed and load, measured stopping time, existing fences and openings, obstacles, cleaning and ambient conditions, safety circuit information, and the desired acceptance schedule. Highlight areas a person can enter but the scanner cannot see. Ask each bidder for field drawings by mode, distance-calculation inputs, signal table, fault state, restart method, separate countermeasures for uncovered areas, and FAT/SAT procedure.
Compare bids on the same safety function, not on unit price alone. One bid may contain one scanner; another may require two scanners plus a fence. Their coverage, restart behavior, maintenance burden, and exclusions can differ materially. Request a marked-up plan, assumption table, and exclusions as common deliverables. State whether Thai-language operator instructions and English or Japanese engineering records are needed. Name the factory, machine builder, EHS, and maintenance staff who must witness each test.
Apply the method to three typical layouts
At a robot-cell service entrance, decide whether guarding the threshold is enough or whether presence inside the cell must also be detected. If the latter, inspect behind robot pedestals, under transfer fixtures, and behind an open door. Keep reset outside the hazard and in view of the area. At a forklift pallet opening, record pallet dimensions, placement variation, and the space beside the load. Demand a safe state after a failed load-detection signal and no unmonitored interval during switching. At a packaging line with frequent manual access, warning can improve awareness, but the protective boundary still must stop the hazard; observe where cartons and temporary stock obstruct the scan.
Control changes after installation
Keep field files, drawings, distance calculations, and stopping-time records under the same revision. A layout, speed, pallet, drive, or guard change may require a new assessment and test. Record which mode and field were active when a stop occurred; investigate contamination, reflection, and genuine intrusion before changing a field. After scanner replacement, check bracket angle, field boundary, stop, and restart on the machine rather than relying only on a restored file. Define who approves settings and where backups are kept across headquarters and the Thai site.
FAT and SAT: prove the drawing on real equipment
At FAT, test that intrusion into each protective field puts OSSDs in the safe state and stops dangerous motion. Check each operating mode, wrong field-selection order, input conflict, lost communication, power cycling, emergency stop, reset, and external device monitoring. Confirm the delivered configuration revision. Where practical, measure stopping time under maximum relevant load and feed it back into the distance calculation.
At SAT, use the as-built dimensions and actual routes. Test corners of the field, near the scanner, behind columns, both sides of a pallet, above and below the plane, and with material stopped in the opening. Verify that a person remaining inside cannot cause an unsafe restart and that the reset position affords visibility. If nuisance trips appear, investigate the cause before shrinking a protective field. Repeat under cleaning, dust, water, and reflection conditions that occur in operation.
Retain installation photos, exported field files, configuration software and firmware versions, stopping-time results, test objects, pass/fail evidence, and owners for open items. Define daily functional checks and periodic inspection. The record should allow a new team to reproduce the acceptance test after a modification.
Safety laser scanner selection FAQ
Is a longer protective range always better?
Sufficient range is essential, but resolution, height, response time, error allowance, and obstacles determine whether it is usable. Check the active protective field at the chosen settings and never count warning range as protective range.
Can a warning field stop a machine safely?
A warning signal can support display or controlled slowing, but it is not the personnel-protection function described for the protective field and safety outputs. If slowing affects the distance calculation, validate the failure and monitoring assumptions.
Should we choose a light curtain or a scanner?
Compare a guarded opening with an area near the floor, then evaluate stopping time, access paths, material movement, blind spots, and physical guarding. Neither device contains ejected material.
Can one scanner type serve an AMR and a fixed machine?
Some products support both, but settings and validation are application-specific. Mobile systems add speed, braking, turning, travel direction, and near-vehicle access. Maintain separate safety-function and test documents.
What must a Thai factory prepare before requesting quotations?
Prepare plans and sections showing the hazard, modes and traffic, measured stopping time, existing safety circuit, environmental conditions, and acceptance expectations. A site survey may fill gaps, but resolve distance and uncovered areas before final order.
Conclusion
Select a safety laser scanner by mapping the hazard and access route, measuring stopping time, sizing the protective field, eliminating or guarding blind spots, designing switching and restart, and checking the factory environment. Require calculations and exclusions in the RFP, then verify configuration and physical coverage at FAT and SAT. This produces a decision based on a working safety function rather than a catalog headline.
If you are planning a Thai factory installation or retrofit and need to organize field drawings, stopping-time measurements, or the interface with an existing safety circuit, contact TOMAS TECH. We can help define the information needed for a comparable proposal even while some site conditions are still being measured.
