Does everyone really need an SPG? (w/transmitter)

[Bruce_Partridge]

I have a question. Over the years I have had a couple of SPGs fail. Both of them failed by not going all the way back to 0. It's not hard to detect by just paying attention when you take your gauges off, but I wonder if that is a common failure mode.

 

[Belzelbub]

I have a question. Over the years I have had a couple of SPGs fail. Both of them failed by not going all the way back to 0. It's not hard to detect by just paying attention when you take your gauges off, but I wonder if that is a common failure mode.

I’ve never seen that behavior with mine. PPS transmitter with Oceanic VT 4.1 and now with a Perdix AI. I usually do watch the pressure reduce to zero after I turn off the gas and purge the lines.

Edit: Oops. Read that as transmitters, not SPGs. Disregard.

 

[wetb4igetinthewater]

I have a question. Over the years I have had a couple of SPGs fail. Both of them failed by not going all the way back to 0. It's not hard to detect by just paying attention when you take your gauges off, but I wonder if that is a common failure mode.

The two SPGs that I had fail, failed mid dive stuck at a different value each. I noticed it within a couple minutes as I saw that "hey, the needle didn't move". My transmitters were both working (ugly to have both an SPG and transmitter), so I did keep diving (solo, photography).

 

[J-Vo]

You might not "blame" it on the tech, but that issue is inherent to the tech. SPGs have their own inherent issues. That's why many divers dive with redundant systems - to reduce the likely hood that the inoperability of one system would cause you to abort your dive, or worse. For all the BS that's been spat of this thread I've not heard one good reason why you absolutely should avoid carrying a redundant air supply measuring device, whether you have an AI or not. Plenty of reasons for carrying it, though......

I don't have a problem with redundancy, just with blaming the technology for operator laziness.

I used transmitters and SPGs for several years before I was confidant enough to ditch the SPGs. Now it's transmitters only even for deep deco and cave dives. All my deco and stage rigs have SPGs however.

 

[shopguy]

I work in technology/computers and I’ll probably keep my mechanical SPG because of how many idiots and stupid business practices I see in the industry. I’d be less worried about my computer dying as it giving me wrong numbers. I’m sure facts would prove me wrong though, probably computers are as reliable as mechanical, but diving is a lot about peace of mind and confidence also.

As far as having to end your dive if your computer fails... I agree mostly, but if I’m diving in my home area in a protected bay with max depth of 30’ and planning a 20’ depth for 45 minutes max... I will not dive without my SPG, but would have no issue diving without my computer. If I was diving 100+ depth I’d have two SPGs, digital or analog, probably one of each.

 

[Mike1967]

All my deco and stage rigs have SPGs however.

Is that because you own a Shearwater?

 

[wetb4igetinthewater]

I work in technology/computers and I’ll probably keep my mechanical SPG because of how many idiots and stupid business practices I see in the industry. I’d be less worried about my computer dying as it giving me wrong numbers. I’m sure facts would prove me wrong though, probably computers are as reliable as mechanical, but diving is a lot about peace of mind and confidence also.

As far as having to end your dive if your computer fails... I agree mostly, but if I’m diving in my home area in a protected bay with max depth of 30’ and planning a 20’ depth for 45 minutes max... I will not dive without my SPG, but would have no issue diving without my computer. If I was diving 100+ depth I’d have two SPGs, digital or analog, probably one of each.

Unless you drive a really old one, you have a lot of firmware running in your car.

For companies like Shearwater or Divesoft, I believe they have the competence of a high degree of reliability. Transmitters are really low tech and super simple to read. We are talking about pretty low data rates.

In our area, people who technical dive on OC have a single SPG for their back gas, single SPG on each deco bottle. People who technical dive OC on sidemount have just an SPG per cylinder.

 

[Blackcrusader]

I work in technology/computers and I’ll probably keep my mechanical SPG because of how many idiots and stupid business practices I see in the industry. I’d be less worried about my computer dying as it giving me wrong numbers. I’m sure facts would prove me wrong though, probably computers are as reliable as mechanical, but diving is a lot about peace of mind and confidence also.

As far as having to end your dive if your computer fails... I agree mostly, but if I’m diving in my home area in a protected bay with max depth of 30’ and planning a 20’ depth for 45 minutes max... I will not dive without my SPG, but would have no issue diving without my computer. If I was diving 100+ depth I’d have two SPGs, digital or analog, probably one of each.

Don't need to end the dive if my Shearwater failed and not exceeding NDL. If I was doing a planned deco dive I could just end dive and do the deco stop. I dive with this SPG....So yes I have Perdix AI and SPG.

 

[J-Vo]

Is that because you own a Shearwater?

I have two Shearwaters, so I could use 4 transmitters. I don't know about the reliability of coming back to a staged transmitter at the end of a dive, and when SHTF, I think it's more important to know what's left in my stage/deco bottles then in my bottom gas. If I was diving back mount where monitoring gas was less frequent and more accessible, I doubt I would use a transmitter.

 

[Lostdiver71]

I have a question. Over the years I have had a couple of SPGs fail. Both of them failed by not going all the way back to 0. It's not hard to detect by just paying attention when you take your gauges off, but I wonder if that is a common failure mode.

It is the Bourdon Tube inside the SPG that expands and eventually loses elasticity and does not return to zero, I have seen it many times on older rental equipment which is one of the reasons most busy dive shops change out their equipment on a yearly basis.