In Olympic swimming events, the winner is the first person to touch a pressure-sensitive wall pad at the end of the pool. How does this pad know that a person has touched it rather than just registering the pressure of splashing water? If a swimmer just brushed it, would it fail to register their finish?
鈥� At the end of each lane there is a touch pad 90 centimetres high, 240 cm wide and 1 cm thick. Touching the pad stops the clock. Omega, the manufacturer of the touch pads used during the 2008 Olympics in Beijing, claimed that the pads react to the slightest touch from a swimmer鈥檚 hand, but not to the splashing of water.
鈥淭he manufacturer claims the pads react to the slightest touch but not to the splashing of water鈥�
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However, after the argument around 鈥榮 victory over in the 100 metres butterfly final at the games, later verified by digital images, it was revealed that a pressure of approximately 3 kilograms per square centimetre must be applied to the pad to activate it and stop the clock. Therefore, it can be said that the victor is the person who touches the pad with enough pressure and not necessarily the one who touches the pad first.
Joanna Jastrzebska, North Shields, Tyne and Wear, UK
鈥� The pressure pad鈥檚 tolerances are supposed to require a swimmer鈥檚 touch before it will trigger a response. A pulse of water would have to come from a high-power nozzle to apply enough pressure to trigger the pad.
A swimmer approaching the end of a race cannot push a narrow enough or strong enough stream of water to trigger the pad. However, brushing the pad lightly may also not trigger it and so these days timing officials check overhead, high-speed cameras 鈥� like those used in track races 鈥� if the pad is just brushed or they are uncertain of the winner for any reason.
Adrian Skinner, Bournemouth, Dorset, UK
鈥� The pads are screw-fixed to the poolside along their top edge and in close contact with the poolside behind. The swimmer鈥檚 positive and forcible pressure on the pad must close any gap between the pad and the poolside, or it may not register.
You have to hit the pad quite firmly to register, either at the turn or at the finish. Just occasionally the pad does indeed fail to register, either through poor swimmer contact or pad malfunction. This is why there are back-up timekeepers on each lane 鈥� both human and electronic 鈥� in order to verify a result. If a world or championship record is at stake, there must be at least three timekeepers present, and one of them has to be electronic.
The final published time may have to be scrutinised by the referee if there has been a mechanical problem, sometimes a compromise or average time may be recorded at the referee鈥檚 discretion. Sometimes the record has to be disallowed if the electronic timing device is in any way compromised.
If a pad should malfunction during the course of a race, it is removed and exchanged between events which takes about 5 minutes. The new pad is tested by punching it manually while timekeepers in a control room monitor the effect.
In major events, reaction times off the starting blocks are also electronically measured by sensors and displayed instantly on the scoreboard (this identifies false starts) and the changeover time is also registered in relays, to show if the outgoing swimmer left the blocks before the incoming swimmer hit the pad. Relay swimmers still in the water while the race continues must take care not to touch any of the pads by mistake when they exit the pool, to avoid confusing the timing systems.
鈥淚n major events reaction times off the starting blocks are also electronically measured鈥�
Phil Sears, Amateur Swimming Association club coach, Dorking Swimming Club, Westcott, Surrey, UK