Inline SPG?

[Fish in a Barrel]

Does anyone make an inline SPG? By that I mean a gauge that has not just an input for the HP line, but also an output? As a line diagram:
(1st stage) ----> (SPG) ----> (AI computer)

Basically, I want a backup SPG without adding yet another hose to my rig. Also, when on the surface, my computer does not display pressure unless you tell it to. This confuses anyone who attempts to check my gear.

So is there such a product? Is there a better solution I'm missing? Am I noobishly over-thinking this?

 

[aikiguy]

You could put a button pressure gauge on a spare hp port on your first stage. Or you could switch to a wireless computer and install a separate spg. Or you could use a HP t and a button gauge in the line to the computer, however it would be clunky, cumbersome, and add three more points of potential failure to the system.

Guy

 

[ereediver]

I'm not an engineer, but I think just they way SPG's work, they have to be a dead end. If not they could not read the pressure. The air would just pass through. Anyone know if it's even possible to make a pressure gauge that lets air past?

 

[DevonDiver]

The SPG needs to be closed.

I've never heard of an 'in-line' system. Besides, the most common failure would be a blow-out of the SPG. If it was 'in-line' that'd disable both of your pressure monitoring systems.

 

[redacted]

It would not be much of an engineering problem but I suspect the demand for such a device is extremely low. Do you really believe your HP hose can be trusted but not your AI computer?

 

[RJP]

Basically, I want a backup SPG without adding yet another hose to my rig. Also, when on the surface, my computer does not display pressure unless you tell it to. This confuses anyone who attempts to check my gear.

You don't really need an SPG to backup an AI computer during any given dive, because if the computer craps out, you're ending the dive at that point irrespective of tank pressure. Backup makes sense, but keep the SPG in your save-a-dive kit and swap it for the computer on the next dive (along with a depth gauge and timing device of course.)

 

[Fish in a Barrel]

Aikiguy, I did first consider adding a button SPG to my spare HP port, just to make it easier to do pre-dive checks. But then I thought, "hey, if I'm going to add another gauge, I might as well put it somewhere that might be useful in a pinch."

I suspect I'm over-thinking it.

 

[RJP]

This confuses anyone who attempts to check my gear.

PS - who needs to check your gear?

 

[DevonDiver]

Within technical diving, when considering gear configurations, there is a mindset that compares the value of an item against the potential risks that it poses. This is especially true when the issue of necessary redundancy is raised. This 'best practice' technical diving methodology can also be useful when determining kit configurations for recreational diving.

In the case of SPGs, the assessment could go like this...

1) Need for redundancy (Potential Benefits).

The SPG or AI Computer fulfills a vital function. You must be able to monitor your air throughout the course of a dive. However, in a recreational open water dive the standard operating procedure for any critical equipment failure is to immediately abort the dive and surface. If the SPG or AI computer failed, then you would immediately end the dive and ascend to the surface. You would be ending the dive early.... therefore you would have enough air to make the ascent anyway. If the SPG/AI Computer failure led to a loss of gas, then have a spare wouldn't help you...or give you more gas. If the air ran out on ascent, then only a redundandant air source or air-sharing buddy would give you more. Otherwise it would be time to CESA. Either way, a redundant SPG would provide you with no tangible benefit.

2) Potential Risks.

Any component in a scuba configuration is at risk of failure. The more components, the greater the overall risk of failure occurance. These are often referred to as 'failure points'. Take stock of your equipment; identify and be aware of those failure points. Seek to minimise those points of failure within your configuration, without detracting from your base requirements to dive safely.

If you add an extra SPG to your kit, then there are more points that may fail. The most likely failures in a scuba configuration occur at joints,seams and hoses. Joints in the HP system are particular weaknesses. Adding further joints or hoses into the HP system weakens the integrity of the system.

Benefits versus Risks

Zero practical benefits.
Increased risk of failure.

Solution: Item not practical for inclusion.

 

[Fish in a Barrel]

PS - who needs to check your gear?

Why, my buddy, of course! We all do buddy checks before hitting the water, right? My dive instructor wasn't lying to me about that, was he?

DevonDiver, having thought about it, I agree with your CBA of this. No practical gain while adding another single-point failure.

OK, OK, you guys have convinced me! Diving is a new hobby for me, and I have a tendency to go a little gadget crazy whenever I pick up a new hobby. Left unchecked I'd be diving with more ornaments than a Christmas tree. I had a feeling I was going a little overboard with this (no pun intended), so thanks for the reality check!

I'm going to consider putting a compact console in my save-a-dive kit instead. More useful in the event of a computer failure, and really not that much more expensive.