If you’ve ever purchased a wristwatch, there is a good chance it was advertised with something like “water resistant up to 5 meters.” That’s deeper than most people will ever go. The exceptions, of course, are divers. They need special dive watches that are rated for much deeper water. As depth increases, so does pressure. You would think that a watch rated for a depth of 300 meters could easily withstand the pressure of a simple shower, but is that true? There is a common myth that dive watches can be damaged by a shower or even just swimming, and Kristopher Marciniak decided to use technology to put that myth to the test.
Just like a submarine, a dive watch relies on mechanical fortitude to keep out the water and avoid crushing under pressure. A dive watch’s housing is made from stiff metal, the crystal is strong, and seals prevent water from pushing through the cracks. But the myth says that the pressure from falling water in a shower, or the movement of your arm, can be enough to allow water to squeeze past those seals. To test that, Marciniak needed a way to monitor the pressure inside of a dive watch while it was subjected to various high-pressure situations. To do that, they used an ESP8266 and some components from Adafruit.
First, Marciniak found a very compact ESP8266 module. They then connected that to a BMP280 pressure and temperature sensor from Adafruit. Those are powered by a tiny 150mAh LiPo battery, also from Adafruit. The whole package was just barely small enough to fit inside of an Invicta Grand Diver watch housing. The ESP8266 was programmed to send out both pressure and temperature readings, because temperature affects pressure.
Right off the bat, Marciniak noticed that a small amount of pressure was created just from squeezing the air while sealing the watch. Next, they found that cold water decreased the pressure, effectively creating a soft vacuum. In a 100psi pressure vessel, simulating 70 meters of depth, barely any increase in pressure was registered — the watch didn’t let any water in and hardly deflected under the pressure. Finally, the watch was subjected to a 2800psi pressure washing. Once again, the internal pressure change was minor. This soundly busts the shower myth, and proves that it’s okay to take your dive watch into the shower as long as your seals are good.