When considering our favorite spy movies and kin that involve deep-sea diving, we’d generally expect to see some high-end watch that costs thousands of dollars and is specially engineered to withstand the immense pressures kilometers below the ocean’s surface. Yet what about a humble Casio F91W that can be bought for about $15 if it’s the genuine article and not one of the millions of fakes? Over at the Watches of Espionage site they figured that they’d dress up one of these famous watches to give it the best possible shot at surviving the crushing pressures at a depth of 5 km.
The actual modification to the F91W was pretty mild, involving nothing but a ‘hydro-mod’ whereby oil is used to replace the air inside the watch case. Since oil is incompressible, nothing bad should happen to the watch. Theoretically at least. The Watch-Under-Test (WUT) was strapped to a US Navy’s CURV 21 remotely operated vehicle and dunked into the ocean before starting its descend into the inky darkness of the deep sea.
Although only hitting a measly 4,950 m, the watch survived just fine, showing that even if you’re a secret US operative on a deep-dive espionage mission, all you really need is one of these Casio watches.
“a measly 4,950 km”
Wut?? Picture shows meters not km
sighs
You tired bro?
Hi there! In Western Europe we use commas as separators.
So 4,950 km means 4.950 km (4950 m)
Still, for clairity it would have been better to just say 4950 m.
That’s fairly confusing…
Oooh, if that’s confusing then you better not look at how other countries handle large numbers. Or dates and time, for that matter. Stay parochial!
It’s also confusing with pocket calculators (the physical ones).
They’re meant for international market and use a dot usually, whereas we use commas in school.
Also, we usually don’t use commas as separators for thousand.
Instead of 1,000 or 1 000 we do write just 1000.
The gaps between the zeros aren’t/weren’t allowed in school.
We have/had to write numbers such as 1,000,000,000 as 1000000000.
As a workaround, we sometimes use/used a pencil and do write faint dots in order to not get lost (1000.000.000).
In exams, we used an rubb, er, eraser to get rid of the dots when we were finished, if memory serves.
As a precaution, so the teacher wouldn’t complain about it.
Or maybe it was just in my time/my school?
Nowadays, students in school use notebooks, tablets PCs and whatnot.
So I’m speaking under correction here.
In online banking of today, the IBAN numbers are being split into groups, though, for better readability.
The HP41C lets you choose the decimal character, and (independently) lets you choose whether or not to include the thousands separator: it’s a couple of flags.
+1 for HP-41C reference!
RPN forever!
If anything it would fit the definition of “parochial” to use very old and regional methods of punctuation and notation whereas most of the world (and computing) has moved to using a period as a decimal. It is nice to know what a milliard is for trivia’s sake, but to say that instead of “billion” in the 21st century would just be needlessly insular and stubborn.
There is only one correct order for dates and it’s yyyy-mm-dd.
There are other languages than English. English is actually a minority language in Europe with about 500 million people speaking something else. The use of the short scale is in fact far less common around the entire world, making the situation much like imperial vs. metric.
The Spanish have millardo, French milliard, German milliarde… and they all translate to “billion” in English. Meanwhile, billion translates to “trillion” in English, so you get double confusion. This is why the metric system uses its own prefixes.
Eh? In England we use commas as separators too, but not for decimal places!
So 4,950 km means 4950 km.
If you wanted say 4950050 m that would be 4,950.05 km
Out of curiousity, if you use the , for decimal place what do you do for separators?
. [dot] IIRC
or space, I’ve seen both. Space is more common
Source: I read a lot of foreign tech documentation
Interesting, I didn’t know that.
I have to admit I wasn’t thinking about England in first place when I wrote “Western Europe”, sorry about that. :D
In my home country on right side of the Rhine 4,950 km means 4 km and 950m.
And in school we didn’t officially use any dots or commas for groups of three. Gaps weren’t used, either, I think.
Some students/pupils did of course use a pencil and added markers of some sort, but it wasn’t wise to do so in math exams.
Later in university it might have been different, not sure.
My father claims that they had used dots for the thousands/groups of three.
Eww gross.
Unless you also end sentences with ‘,’ and use ‘.’ for pauses then I disagree with that choice.
Hard pass.
The article headline has “5,000 meters” and the body of the article has “4,950km” – I understand that different systems are used, but they are not mutually compatible
I just realized that I did not know the exact history of the adoption of a period as decimal point and grouping three digits with commas. Just posting this in case anybody finds the backstory interesting.
That’s interesting, thank you.
In the distant past, I just barely came across this topic when tinkering with the nationality settings in Windows 3 Control Panel! 😅
It had offered different formats for hours/date, currency symbols and decimals.
Interestingly, in (english) South Africa we were taught in public school the comma decimal separator. That was a half century ago though; things have changed a lot since then.
surprised that the clock crystal doesn’t get crushed
Yeah, this. At 5 km, 500 atm, 50 MPa , the force on that 1-2 mm^2 crystal endcap is 50-100 N (isn’t the metric system easy?). Not crazy, but that’s still a lot for a thin bit of aluminium or phenolic to endure.
Since the pressure on the crystal should be perfectly uniform, I would expect it to just shrink a tiny bit.
[in place of an edit] I now realize you’re referring to the quartz crystal, not the glass on the front of the watch (also commonly referred to as a crystal). I guess the same applies, but I don’t know much about the guts of quartz crystal components.
The instant a drop of oil touches the crystal the oscillation will cease and the watch will stop. The watch’s operation depends on the crystal staying dry and oil-free. The only barrier protecting the crystal is the little phenolic plug in the end of the crystal can and the crimp holding it there. It’s kind of astonishing it will keep the oil out under 500 atm of pressure.
I wonder which specific package of oscillator it uses… I was also picturing the classic long, cylindrical can with two bent leads on one end, but I found this image of the watch’s guts:
https://www.crowdsupply.com/img/7cd2/06194802-93bb-4500-92fc-e540b4257cd2/sensorwatch-lite-update-with-watch-01_jpg_aa-md.jpg
I could imagine that surface-mount part with a soldered can as being a lot more pressure-resistant, but still impressive to hold up under five kilometers of water. My next question would be: did they remove that reset button? Actually I guess that thing could fill up with silicone oil with no problems
Nevermind, that photo I posted earlier is an aftermarket replacement. Still having trouble finding the stock oscillator… Perhaps it is the old-school can after all? I thought that would be more era-appropriate anyway.
It may change the frequency of the crystal significantly though. I wonder how it affected the accuracy of the watch.
The big question is how long the plastic case survives the oil. Or did they use silicone oil perhaps?
Silicone oil “super lube” is apparently the go to thing for these mods.
It also seems to reduce reflections from the glass from the G-Shock I’ve seen.
Presumably also preserves the o-rings too.
Mineral oil seems common, too. Some gaskets are silicone, which could cause problems with silicone oil.
It survives a looooot deeper than your unprotected body will survive… But here’s the real kicker: it leaves you with a greasy wrist. Hope you brought some paper towels!
Oil is not comprensible?. I has understood It was…
If oil were compressible, it would be very hard to make hydraulical equipment.
oil is compressible like everything else, it just isn’t very much
It is, and even more so than water:
https://en.wikipedia.org/wiki/Properties_of_water#Compressibility
“When considering our favorite spy movies and kin that involve deep-sea diving, we’d generally expect to see some high-end watch that costs thousands of dollars and is specially engineered to withstand the immense pressures kilometers below the ocean’s surface.”
No, not really. No one is going to wear a watch in the water at that depth, because no one will be in the water at that depth. One would be in some submersible, at atmospheric pressure, where any all watch will suffice.
I spent most of my professional career in the ROV business.
When it all started, all the electronics where in 1 atmosphere reverse pressure vessels. Over the years, it was figured out that a lot of electronic components can withstand significant external pressure.
The challenge was, to do enjoy testing to see what worked and what didn’t. Manny things surprised us by either failing in a spectacular manner, or working very well.
All the electronics on an ROV now are houses in junction boxes full of hydraulic oil, compensated to about 5psi over ambient.
Works just fine.
The challenge is to keep the water out as most ROV’s operate at elevated voltage to minimize resistive losses from a very long umbilical.
Geeze, sorry about all the fat fingering….
The ability to edits posts after the fact would help us appear less addled….
‘jus sayin’