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Measuring a machine's real stopping performance to calculate the safety distance a guard or light curtain needs, per ISO 13855.
Stop time measurement determines the overall stopping performance of a machine — the real-world time between a safeguard being triggered (e.g. a light curtain, interlocked guard, or E-stop) and all hazardous motion actually ceasing. This measured value is the critical input to the ISO 13855 safety-distance formula, S = (K × T) + C, which calculates the minimum distance a safeguard must be positioned from the hazard zone.
A safety distance calculated from an assumed or theoretical stop time is not a safety distance — it's a guess. If the real stopping time is longer than assumed, a light curtain or interlocked guard can be positioned too close, meaning a person's hand or body can reach the hazard before the machine has actually stopped moving. Getting this measurement right is what turns a safeguard from a checkbox into an actual, physical guarantee of safety.
Stop Time Measurement applies wherever a safeguard's position depends on how fast a machine actually stops.
ISO 13855 sets the safety-distance formula that a machine's measured stopping performance feeds into.
Stop time measurement determines the overall stopping performance of a machine — the real-world time between a safeguard being triggered (e.g. a light curtain, interlocked guard, or E-stop) and all hazardous motion actually ceasing. This measured value is the critical input to the ISO 13855 safety-distance formula, S = (K × T) + C, which calculates the minimum distance a safeguard must be positioned from the hazard zone.
Prazamana measures actual stopping performance to calculate the required safety distance per ISO 13855. In simple terms, the longer the total stopping time, the further the safeguard must be from the hazard, because a person can cover more distance while the machine is still moving. ISO 13855 combines the stopping time with an approach speed and other factors to give the minimum distance.
Prazamana offers stop time measurement testing to calculate the required safety distance per ISO 13855. It can be booked on its own or with EMI/EMC, LVD and noise testing. As part of its wider machine safety offering, it also provides machine risk assessment, machine guarding, safety devices and CE marking consultancy. Tell the team about your machine and they will scope the right tests.
It is relevant wherever safeguards are placed at a distance from a hazard and the machine takes time to stop, for example machines protected by light curtains, laser scanners, radar sensors or interlocked gates, and robotic cells and presses. Please describe your machine to the team to confirm what is needed.
Tell us about the machinery and its safeguards and we'll scope the measurement.
