The best mechanical diving automatic watches under $500 in 2017
Some manufacturers say their watches with a water rating of 300 meters or more are suitable for recreational scuba diving. Others saymechanical diving watches require a score of only 200 meters; others say it can be 200 meters as long as it is specifically marked as a diving watch. On the other hand, the International Standards Organization (ISO) stipulates that diving watches must be waterproof to 100 meters. All of these depth levels are significantly higher (or lower, if you prefer) than the depth at which non-professional divers can dive. Casual divers are no more than 40 meters (130 feet) deep. In addition, they have entered the technical diving field, which requires a lot of training, special mixed gas breathing, long-term decompression stop and special equipment. The reason for the difference is that when the factory tests the waterproofness, the watch is in an artificial environment, which is very different from the environment faced by the watch during actual diving. For testing, the mechanical diving watch is completely static, the gasket is brand new and is a newly assembled housing so it does not affect its water resistance. The test machine does not take into account the additional pressure of the wearer jumping or diving into the water; or the temperature and pressure change as the diver rises and falls, which causes the housing to contract or expand. In addition, the aging of the watch's gasket will reduce the waterproof performance of the watch. Knocking and other rough handling may cause the components of the case to fit more closely together than when the watch is brand new. What features make the watch not enough to dive? Some features are needed to make the watch unable to penetrate the dive. In almost all dive watches, the case has a screw-in crown and crown. O-rings are used to seal the crown, the case back and the crystal. The case and crystal are thicker than the non-diving watch. Top-grade mechanical diving watches designed for deep diving often have additional compression characteristics, such as dome-shaped crystals or steel rings for reinforcing the case (such as the Rolex Deep Sea). What are the other functions of the mechanical diving watch? Most dive watches have a rotating bezel to measure elapsed time. They also have illuminated hands and markers that can be read underwater. ISO Standard 6425 requires the dive watch to have a "time preselection device" (rotating bezel meets this requirement) and a dial that can be read at a distance of 25 cm in the dark. The ISO also states that the watch must have an indicator light to show at a glance whether the watch is still running. The second hand meets this requirement. Most dive watches have steel or titanium bracelets or rubber straps, although some straps are made of nylon or a variety of composite materials. Some diving bracelets and shoulder straps are equipped with an extension that allows the watch to be mounted on a diving suit. Some diving watches have helium valves and/or depth sensors. What is a helium valve? A device used to balance the pressure inside and outside the case when the mechanical dive watches is worn in the dimple. Indoors, the diver breathes a mixture of gases containing helium. The ruthenium molecule is very small, so it can penetrate the case and accumulate inside it. During decompression, the pressure inside the chamber drops faster than the pressure inside the housing. This may cause the watch crystal to pop up. In order to prevent this, some watches have a valve on the side of the casing that allows helium to escape from the casing during decompression, so that the pressure inside and outside the casing is the same. Most mechanical diving watches do not have helium valves because they are only used for saturated diving when the diver spends time in the diving room.