ISO 6425 or DIN 8306: What must a diver’s watch be able to do?

Not every watch that looks like a diver’s watch can really be used for diving. A watch that looks like a diver’s watch but is only splash-proof should definitely stay above the surface of the water. Above all, it is important that the watch can withstand the water pressure of the desired diving depth. So that a diver’s watch can also be used as a backup for a dive computer, if necessary, it must meet certain requirements that are specified in the German diver’s watch standard DIN 8306 and the international standard ISO 6425.

Circula diver’s watch AquaSport II Automatic

DIN 8306 or ISO 6425: The characteristics of a diver’s watch

The following points are hidden behind the diver’s watch standard DIN 8306 and the international standard ISO 6425:

• Pressure-resistant up to 20 ATM (≈ 200 m) (the diver’s watch must remain in this water depth for two hours and then another three hours at three meters – the diver’s watch must still work during and after 20 minutes of water pressure at the specified depth)
• Rotating bezel, which for safety reasons can only be rotated counterclockwise and which can still be operated in 30 centimeters of water
• Continuous minute markings and every 5 minutes a clearly legible, offset line marking as well as a luminous triangular mark on the bezel (or, depending on the design, on the dial) with which the immersion time is marked
• Clear readability of the diver’s watch from a distance of 25 cm in the dark, which is why the markings on the bezel, hands and indices are provided with light sources
• Luminous second hand, which shows that the watch is running
• Antimagnetic according to DIN 8309 (accuracy of ± 30 seconds per day in three positions under a direct current magnetic field of 4,800 amps per meter)
• Shockproof according to DIN 8308 (the deviation may not exceed ± 60 seconds per day after an impact at 4.43 m/s)
• Rust-resistant in sea water (the diver’s watch must withstand 24 hours in warm salt water without damage)
• Fixed strap (nothing should come loose or bend if the bracelet is loaded with 40 kilograms for one minute)
• The average rate variation may only be between -4 and +6 seconds per day (only applies to DIN 8306)
• Pressure-resistant crown (this is 25 percent above the specified pressure resistance (at 20 ATM this is 25 ATM) for ten minutes with 0.5 kilograms)
• Resistant to temperature fluctuations (the watch is first brought to 40 degrees Celsius for ten minutes, then ten minutes to five degrees Celsius, then ten minutes to 40 degrees Celsius in a water depth of 30 centimeters)
• Resistant to pressure (the diver’s watch must withstand 25 percent above the specified depth for one hour, then one hour at 0.3 bar negative pressure)

In the case of a type test, all tests must be completed; in the case of the individual test, only the test for tightness must be carried out at 25 percent above the specified depth.

Circula diver’s watch SuperSport Automatic

Other diver’s watch features beyond ISO 6425 or DIN 8306

In order for a diver’s watch to be easy to read under water from the side and in the event of reflections, the cover glass should have an anti-reflective coating, at least on the inside. Diving watches usually also have a screw-down crown so that it cannot be accidentally pulled out while diving, preventing water to penetrate the watch and to damage the movement.

Rubber straps have also proven themselves in diving practice, as they adapt perfectly to the changing pressure conditions under water. But metal watch straps and textile straps are also very popular on diving watches.

A helium valve, on the other hand, is only necessary if the watch is to be taken on dives to several hundred meters and the diver is in a pressure chamber during the decompression phase. This usually only applies to professional divers.

A helium valve is not necessary for amateur divers. On the contrary: a helium valve is then just an additional opening with a risk of leaks.

Circula diver’s watches and ISO 6425 or DIN 8306

The diving watches from Circula (AquaSport II and SuperSport) meet almost all points of the ISO 6425 and DIN 8306 standards – however, they are not certified. Only the points “Antimagnetic according to DIN 8309”, “Shockproof according to DIN 8308” and the mean rate deviation of -4 and +6 seconds per day (only DIN 8306) do not apply. However, both watches are suitable for diving and the wearer can still enjoy the watches for a long time after the dive.

Circula diver’s watch AquaSport II Automatic