Divers like to carry small amounts of oxygen tanks in order to reduce weight underwater, but the amount of oxygen is related to the size of the tank, so those familiar with dive gear carry devices to measure oxygen levels, and dive watches reinforce this need in due course. The rotating bezel is arguably the most important feature of a dive watch, serving as a reminder of dive time. The rotating bezel is marked on a scale of 15, 30, 45, as oxygen tanks generally only last 45 minutes, and some are marked on a 60 minute scale. The first 15 minutes are colored or specially marked because divers strictly observe a 15-minute safety stop during ascent to completely release the nitrogen absorbed from the cylinder. Usually you can tell the time spent on a dive by turning the bezel so that the 0 mark on the bezel is aligned with the minute hand, and then watching the minute hand move against the scale on the bezel. Of course you can also use a countdown timer by first knowing your dive time, turning the bezel to align the minute scale with the minute hand, and then the minute hand goes to the 0 scale at exactly the time of your dive, which means the 0 scale position is your dive limit time.The external bezel is designed to rotate in a single counterclockwise direction, which is designed to ensure that only more time is counted, not less, and to prevent the danger of prolonging the time by mistake. The scales and numerals are professionally coated with luminescence to facilitate clear display in dim underwater light. In recent years, the new built-in chronograph bezel has no restriction on the direction of rotation, as the crown controlling the bezel must be locked before going underwater. The Aquatimer Cousteau, for example, has a built-in chronograph bezel that guarantees the indication without the need for a separate hole in the case. Another advantage is that there is no need to clean the mud from the case joints of those bezels after going out of the water. In fact, only 5 out of 1000 people who buy a dive watch will have the chance to dive to a depth of 50 meters, and more players love the crisp sound of the bezel when it is rotated than the nominal number. OMEGA’s Ploprof Co-Axial Diver’s rotating bezel is operated by an orange button attached to the top right side of the case and can be rotated in either a clockwise or counterclockwise direction, a rare design that allows the bezel to rotate in both directions. The bezel is not much of a work of art, but Blancpain’s 50 series model with its single rotating bezel is different. The designers used sapphire crystal to cover the luminescent scale (instead of the usual high-tech ceramic), and spent several years developing and patenting a glue to bond the luminescent scale material to the sapphire bezel and metal bezel. Rolex uses a patented PVD technology to fill the rotating bezel with platinum, and thanks to a new luminescent material that emits a bright blue light, the triangular zero indication on the outer ring of the scale is visible for longer at night or in the deep sea. All dive watches are equipped with eye-catching luminescent hands and scales because divers are often in deep, dark waters, so the hands, scales or surfaces of dive watches are often coated with luminescent material and deliberately enlarged to make reading the time easier for the user.
The early luminescent material was radium (Radiomir), which was discontinued due to its excessive radioactivity. The most commonly used luminescent materials today are Super-LumiNova and tritium tubes, and Super-LumiNova is a new material that absorbs gamma particles from light to store light for more than 10 hours, but the intensity of the light will fade after a certain period. Tritium tube luminous (also called “gas lamp”) is a great leap forward in modern luminous technology. The use of tritium gas tube is a glorious tradition of Ball (Ball). The advantage is that self-illumination is not only bright, but also long-lived – it is said that the service life of up to 25 years. The principle is to fill a mineral glass tube coated with a phosphorescent substance inside with gaseous tritium, using the B-rays of tritium to excite the reaction of the phosphorescent substance to produce a cold light source, which has no dazzling light and heat emission, and will not burn or explode. The wall of the tube can isolate B-rays and is harmless as long as the tritium tube does not break. Tritium tubes do not require external energy or reflections from external light sources and can maintain a stable and long-lasting light for 10 to 20 years. The tritium tube luminescence is marked on the back cover of the watch case with the letters 3H illumination and mbmicrotec, and on the hands and scales of all Ball watches (also temperature and seconds hand). The only disadvantage of this is that the hands are heavier, especially the second hand, which should have a slight impact on the watch’s timing. To maintain balance, the second hand on Ball watches has a “long tail” or a “flower tail” composed of two RRs. The luminous effect of the dial of the Panerai Radiomir is achieved by applying a special coating to the markers and indicators, a mixture of zinc sulfide, radium bromide and new thorium. This compound, invented and formulated by Panerai, was previously also a feature of the aiming and observation instruments produced by Florentine. The powerful luminescence allows the instrument to illuminate itself in total darkness without the need to borrow auxiliary lighting that might be detected by the enemy.
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