PERDIX or PERDIX AI?

[doctormike]

Why LP leak is more serious?

The rate that a tank empties is much more dependent on the orifice size than the pressure gradient.

The HP port on a regulator has a tiny orifice because it just has to transmit pressure, it doesn't have to supply gas. The LP port is much larger because it has to supply you with enough gas to breathe.

Here's a good example of that. Cut the HP hose, an AL 80 will drain in 22 minutes. Cut the LP hose, 81 seconds.

 

[doctormike]

This is just your opinion so also meaningless as a datapoint.

I don't understand. Are you saying that the point that I made was wrong? Or are you saying that you aren't interested in it?

Let's stop hijacking the OP's thread.

Yeah, I can see how a discussion of the reliability of hoseless AI would be irrelevant to the OP, who asked about the pros and cons of hoseless AI.

 

[doctormike]

Please define HAI and DC

HAI = Hoseless air integration, like on the Perdix. As opposed to an air integrated computer in a console, in which the computer shows pressure information, but it's connected by a hose. I used to say WAI (wireless AI), but at one point we had a lengthy discussion of that term, and it was concluded that console AI computers are connected by a hose, not a wire.

DC = Dive Computer

 

[guruboy]

I don't understand. Are you saying that the point that I made was wrong? Or are you saying that you aren't interested in it?

I'm saying that your point is just your opinion and, without any statistical evidence to support it, is worthless as a datapoint.

 

[doctormike]

I'm saying that your point is just your opinion and without any statistical evidence to support it, is worthless as a datapoint.

It's not a "datapoint", it's a fairly simple observation that a device with a high failure rate will always have a lot of good reviews, because the majority of users won't have a problem with it. I don't know what statistics you would be looking for to back up that simple observation.

I mean, if you could tell me why you don't think that I am correct, that would be an interesting discussion. I'm always happy to learn.

 

[guruboy]

It's not a "datapoint", it's a fairly simple observation that a device with a high failure rate will always have a lot of good reviews, because the majority of users won't have a problem with it. I don't know what statistics you would be looking for to back up that simple observation.

As I said before, without actual statistics, that is just your opinion. It has no value besides being your opinion. Someone else can make the exact opposite observation and their opinion would be just as valid as yours.

First off, you need to know how many total purchasers there are. Then you need to know how many of them actually left a review.

Just because 10/10 reviews are negative does not mean it is 100% failure. Maybe none of the satisfied purchasers left a review. For all you know only 10/1000 failed. It just so happens the 10 failures posted reviews while the 990 successes did not.

The opposite scenario can also be true.

Without numbers, opinions are just opinions.

I think I made my point clear and will stop hijacking the OP's thread.

 

[doctormike]

As I said before, without actual statistics, that is just your opinion. It has no value besides being your opinion. Someone else can make the exact opposite observation and their opinion would be just as valid as yours.

First off, you need to know how many total purchasers there are. Then you need to know how many of them actually left a review.

Just because 10/10 reviews are negative does not mean it is 100% failure. Maybe none of the satisfied purchasers left a review. For all you know only 10/1000 failed. It just so happens the 10 failures posted reviews while the 990 successes did not.

The opposite scenario can also be true.

Without numbers, opinions are just opinions.

I think I made my point clear and will stop hijacking the OP's thread.

You are right, that's a good point! You can't conclude a failure rate by counting posts.

I think that my observation was that the statistical power of a given positive review - in the absence of a denominator - is extremely low, because there are always going to be vastly more positive reviews than negative reviews for something with a relatively low failure rate.

So getting back to the OP's question (for whom this discussion IS relevant), I would say that I wouldn't dive HAI without an SPG because of the frequency with which people report failures. But strictly speaking, you are correct that given a large enough population of divers with working HAI but who don't post, those negative reports could be pushed to statistical insignificance.

So since we don't have that denominator to give us accurate statistics, we should not discuss reliability at all when discussing the pros and cons of HAI, right?

 

[kaaralex]

Here's a good example of that. Cut the HP hose, an AL 80 will drain in 22 minutes. Cut the LP hose, 81 seconds.

Wow. This looks like a great piece of information. Now i know better, thanks!

 

[KentB]

What's the price difference between the non AI and AI computers without the transmitter $100?

Buying new I'd buy the AI computer for sure and the transmitter later on if it's not in the budget right now. If the AI doesn't interest you, then I'd agree with the person above who said buy a used non AI from someone looking to grab an AI one.

 

[stuartv]

I do deco on most of my dives.

Knowing this, I would say that you would want to have an SPG (unlike what I said about recreational diving, earlier).

For my deco diving, I use back mount doubles. I have an SPG on the left post and my AI transmitter on my right post. The 1st stage orientation allows me to have the transmitter pointing down, so it's not in any danger of getting broken or entangled.

I like collecting my gas consumption data on deco dives, but I also like the fact that if I have a problem and have to shut down my left post, I will still be able to know how much gas I have left in my right cylinder. That could, for example, be the difference between doing a completely normal ascent versus knowing I will have to share air with my buddy or possibly change my computer settings to GF99/99 to try and get to my first gas switch as quickly as possible. All pretty unlikely, of course, but I don't see the downside of having the transmitter there as a significant risk. It only has 1 O-ring that could cause me to lose gas - a lot less than the number of O-rings in an SPG setup that could cause me to lose gas.