Undoubtedly, learning some watch knowledge can be centered on how to make a “real dive tables” problem, the water is deep and dark. Today our goal is not to resolve this dispute In this exercise, we will also ignore the dive computer, make sure it will end this article right here. We will also hold the watch for mixed gas diving. Instead, we will see what ISO think it can make a diving watch. The standard may raise some issues you have not considered. Once you know what’s what, you can decide how to make a diving watch, and if you need an ISO certified. ISO 6425 since 1996 due to the popularity of diving watches has been around in its current form, you would think that these standards will be well-known watch enthusiasts, but they are not, probably because they are not widely used as a standard COSC chronometer . They are also relatively long, a little technical, but also rarely reproduced in full. Official Guide meat is tested in the 6th and 7th find these spell the dive tables physical requirements and methods.
The watch must be equipped with a device that allows the user to pre-select a period of time of up to 60 minutes. This may be a rotating bezel or a digital display. The device must be protected from inadvertent manipulation. A bezel must have a scale showing 60 minutes with markings showing every 5 minutes. Markings on the dial must be coordinated with those on the pre-selecting device, and must be clearly visible. The time must also be clearly visible, and the minutes hand must be clearly distinguishable from the hour hand. (“Clearly” is a favorite ISO word.) The time set on the pre-selecting device must be clear, as must an indication that the watch is running. On analog watches, this is usually satisfied by placing luminous material on the seconds hand. Finally, battery-powered watches must have a visible low-battery indicator. Each of these must be visible at 25 cm, or about 10 inches, in the dark. There are also requirements governing salt-water resistance and reliability under water. The “resistance to salt water” test requires that the watch be placed in a sodium chloride solution of 30 grams per liter, which is about the same as seawater, and kept there for 24 hours at 18 to 25 degrees C, or about 64 to 77 degrees F.
The shock-resistance standard is intended to simulate the shock a watch receives if it is dropped from a height of one meter onto a hardwood floor. The test involves delivering two shocks – one to the 9 o’clock side of the case and one to the top or face of the watch. The shock is delivered by what looks like a croquet mallet suspended between vertical supports so that it swings like a pendulum. Between the supports, at the bottom, is what looks like a large, rubber golf tee. The mallet, which has a plastic head weighing 3 kg or about 6.6 pounds, is raised to a height of one meter and released. The head hits the watch, which sits on the rubber tee, at a speed of 4.43 meters per second, delivering a shock equal to about 5,000 Gs. To meet the ISO standard, after the test the watch must keep time to within +/-60 seconds per day, compared with its rate before the test.
The next requirements deal with resistance to external forces. The first test applies to the spring bars. With the strap closed, the inside of the strap is subjected to an outward force equal to 200 newtons in each direction. This subjects each spring bar to about 45 pounds of force. To make sure the crown and any other setting devices don’t leak, the watch is subjected to 125 percent of its rated depth pressure for 10 minutes while a force of five newtons, or a little over one pound, is applied to the top of the crown. Both before and after this test, the “hot-plate condensation test” described earlier is carried out to ensure that there is no leak. Note that the ISO guidelines do not explicitly require a screw-down crown. Any construction that passes the test is acceptable.
To meet the ISO 6425 guideline, this overpressure test must be performed on every watch. The other tests can be satisfied by testing a statistically significant sample of watches. This is an important difference compared with the less-stringent ISO 2281, used for watches that are merely “water resistant.” That ISO guideline does not require testing every watch to its rated depth, but only a sample. The next time you see an account of a watch rated to 100, 200 or even 300 meters failing at lesser depths, pay attention to whether the watch is an ISO 6425 diver or an ISO 2281 water-resistant model. Finally, the ISO standards include an optional test for air-tightness at an overpressure. The watch is subject to air pressure of two bar, or about 29 psi, and the flow of air entering the watch is measured. Comparable methods, for example using inert gasses, are permitted. The standard states, a bit vaguely, that “watches giving a high flow of air shall be eliminated from the test immediately.”
The ISO standards provide that a watch that passes all of the tests may be marked with the word “Divers” followed by the depth rating, for example “Divers 300m” (or similar terms in other languages). Watches that have not passed the ISO test may not be marked “Divers.” Note that the manufacturer is not required to put any specific mark or language on the watch to indicate that it satisfies ISO 6425.