Are dive computers making bad divers?

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jvogt

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@Wibble hit one of my favorite parts of RB diving with multiple PDCs, one dive plan for the entire trip. You just have to know the maximum limits of your bailout.
 

jvogt

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As for the actual thread subject:

Tables and PDCs are the same tool for the job. One is manual, one is electronic. Neither inparts more knowledge of decompression theory than the other. The only way to know deco theory better is to study it and calculate the algorithm yourself.

PDCs make better biginer divers all things equal. Because most didn't bother with the tables until PDCs became mainstream.
 

Belzelbub

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PDCs make better biginer divers all things equal. Because most didn't bother with the tables until PDCs became mainstream.
Agreed, and they also help to keep beginner divers safer. If a beginner is using tables, they may find out after the dive that they violated something. If they’ve got a computer with them, and actually use it, they should be alerted to an approaching limit before they actually exceed that limit.

I learned with tables, and used them for many years before finally deciding to get a computer. One of the things I learned quickly was that my ascents before then had likely been a bit too fast. I was taught to follow the smallest bubbles on ascent. On my first dive with a computer, I still did that and got a slow down warning. I was just ascending a bit too fast, but until the computer told me, I thought it was fine.
 

CT-Rich

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Dive tables won’t tell you whether you are diving safely or or luckily. With tables you get back on the boat aren’t bent, you have no certainty. A computer will let you know with rigid certainty. Back diving tables, you *thought* you were okay and planned around that. If you were wrong, you never knew, unless you got a hit.

Computers reduce task load and remove human mental calculations from the process. It makes diving easier and safer. The flip side is it can allow less experienced divers do more challenging dives where what you don’t know what you don’t know becomes a bigger factor.
 

leavenotrace

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CCCP failed to consider graphite is extremely conductive and in a capsule with no ventilation and analog circuitry this could cause serious problems.

They have many shortcomings such as this, look at how they construct night vision equipment.
 

Akimbo

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Many people may be wondering why recreational divers were not bent at very high rates in the pre-computer era. I think this will help explain it.
  • Tables designed for square profiles are very conservative on most recreational dives where a small percentage of bottom time is spent at max depth.
  • Most tables limited repetitive dives to one in the fine print — two dives/day.
  • Very few divers (in the US anyway) were using doubles/packing enough gas to get very far into decompression. Those that did tended to be very experienced and plan dives very carefully.
  • Decompression diving was limited by thermal protection in many parts of the world. The first modern drysuits were not available until the last half of the 1960s after NASA invented the waterproof zipper.
  • For the most part, divers were much more concerned about getting DCS. Treatment options were very limited both by facilities and knowledge. For all practical purposes, DCS treatment meant a naval facility.
  • Basic Scuba training included decompression and repetitive dive tables, not just no-decompression tables.
Analog decompression meters were available from the early 1960s. They were unfairly nicknamed Bend-O-Matics but were actually pretty close to many of the European navies' tables. I used one for over 30 years and can't recall anyone I personally knew getting bent using one.

Here is an image from the 1964 Healthways catalog. It was actually manufactured in Italy like a lot of dive gear in the US.

1656782347020.png


AUTOMATIC DECOMPRESSION METER​
catalog no. 1973​
price $29.95​
With Healthways Automatic Decompression Meter there is no need to worry; you can always be sure. The precision instrument that functions automatically like an "electronic brain" - continuously memorizing repetitive and multiple depth dives. The Automatic Decompression Meter takes the guess work out of planning your dive. It records the two essential elements for each dive-TIME and DEPTH, automatically calculates these two factors and immediately indicates the necessary decompression time. The Automatic Decompression Meter reproduces the physiology of the body by duplicating the rate at which the nitrogen goes into and out of solution in the blood stream. Keeping an exact record of the dive completed and of the time you spent on the surface between dives, it uses the diving time as well as the surface time to automatically calculate and prescribe the decompression time necessary on the next dive. This process of memorizing continues for 6 hours after the last dive you make. The compact unit can be worn on the arm or attached to your harness.​

From the modern viewpoint, "The precision instrument that functions automatically like an "electronic brain" - continuously memorizing repetitive and multiple depth dives." is misleading. Today, that implies data logging including depth, and time displays. It only displayed decompression obligations.

It was nothing more than a Nitrogen filled flexible bag, a porous material the leaked gas at a set rate, and a Bourdon tube pressure gauge with a specially calibrated face. That leakage rate and the custom pressure gauge face came out pretty close to No-D, repetitive, and decompression tables.

The $30 cost was fairly high when you consider low-end regulators were $35 and depth gauges were around $12. Many of the dive pros and more affluent divers were using them by the late 1960s.
 

Akimbo

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But according to this inflation calculator, it's just under $200 today, which is about what the cheapest computers cost.

True, but a typical dive kit didn't include a computer, BC, SPG, Octopus, or flash light so an inflation adjusted $200 represents a greater percentage of the set. A well equipped diver had:
  • Mask
  • Fins
  • Snorkel
  • Tank with a harness or maybe a backpack
  • Regulator
  • Weight belt
  • Wetsuit aided by corn starch or talcum power
  • Depth gauge
  • Watch
  • BFKnife
  • Surplus store seabag to pack it all except the tanks
  • Clamp-on pressure gauge (not submersible)
The only inflatable marker buoy I ever saw was on Sea Hunt. Defog solution was spit.
 
https://www.shearwater.com/products/swift/

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