Gauges all over the place

[broncobowsher]

Was putting together the rEvo to get back in the water. I had just redone the bailouts and pulled the button gauges and put the real gauges back on. Bailout read 2850 PSI, thought it would be worth it to bump it back up to full. Off to the booster. Start the math on filling it, put the DGX tank pressure checker on it, reads 3050. And the rabbit hole opened up.

Next thing I knew I was putting every pressure gauge I owned on this tank to try and figure it out.
2850 PSI - Hollis #1
3050 PSI - DGX pressure checker
2900 PSI - generic O2 high pressure gauge I put on quick connects so I can watch supply bottle pressure as I boost.
2825 PSI - Dwyer digital built into the booster
3050 PSI - Hollis #2 from the out bail out
199 BAR / 2884 PSI from the Shearwater transmitter on the rebreather
201 BAR, just past the 200 mark (converted to 2915 PSI with math) on the original DIL gauge from the rebreather
199 BAR, just under the 200 mark (converted to 2886 PSI with math) on the original O2 gauge from the rebreather
2825 PSI - Hollis #1 again after doing all those checks.

This probably explains why I have been struggling to get the mixes to dial in. Do the math based on starting with one gauge and filling to target pressures with a different gauge.
In the end I still don't know what I have. Something in the mid to high 2800 range would be my guess based what I am seeing. Without a standard to check the gauges against it is down to what gauges do I trust more, what numbers come up more often? The 3050s look like outlyers.
The 2 digital gauges only have a 59 PSI spread.

Left scratching my head on what is good and what needs to go away. Probably going to get some new gauges for Christmas from what I am seeing.

 

[mr_v]

Keep one gauge u like the most. Throw the rest away. Problem solved.

 

[iointerrupt]

I'd trust the Dwyer above all else, probably followed by the Shearwater.

Bourdon tube pressure gauges just have too many sources of error in them. You can dismiss pretty much any standard SCUBA SPG right from the start, not a single on of them is a precision instrument. If one of them reads correct, it is more by chance than by design.

Good instrument gauges state 1% error, but if you spend some time on eBay you can find older "3D Instruments" gauges good for 0.25%. But then, you can find Dwyer DPG-111s for cheap, with the same 0.25% error and none of the mechanical finickiness that comes from an analog gauge.

 

[Chris H]

If you are really into it, send the Dwyer to a metrology lab for calibration.

 

[broncobowsher]

If you are really into it, send the Dwyer to a metrology lab for calibration.

That is what I am thinking at the moment. Have a known good as a starting point. Filter the rest as needed. I might be able to get one into the calibration lab at work. Need to check how high they can go. Not sure they do over 1500 PSI.

The backup gauges for the rebreather, those will be close enough. As would be anything that just has to show a general level. Then decide on what to do with each that I want real numbers for.

 

[Tracy]

When you are mixing gases, you use one gauge. That is it. Only one. Ever.
No diving operation is spending the coin required for NIST certified gauges and the annual recalibration.
Accuracy of the gauge doesn't matter when it comes to blending. You are looking for precision and repeatability.

Finding two gauges that read the same is a mostly fruitless waste of your time. Sounds like the tank is full, dive it and worry about it when it isn't full.

 

[Eric802]

A man with one watch always knows what time it is. A man with two watches is never sure.

 

[ajchapman]

If you know the weight of an empty tank (including valve), the gas mix, and the temperature, you could weigh that and work out what the pressure should be. The conversion makes it more complicated though, and you might just end up with more numbers that don't quite match the others.

 

[lermontov]

Was putting together the rEvo to get back in the water. I had just redone the bailouts and pulled the button gauges and put the real gauges back on. Bailout read 2850 PSI, thought it would be worth it to bump it back up to full. Off to the booster. Start the math on filling it, put the DGX tank pressure checker on it, reads 3050. And the rabbit hole opened up.

Next thing I knew I was putting every pressure gauge I owned on this tank to try and figure it out.
2850 PSI - Hollis #1
3050 PSI - DGX pressure checker
2900 PSI - generic O2 high pressure gauge I put on quick connects so I can watch supply bottle pressure as I boost.
2825 PSI - Dwyer digital built into the booster
3050 PSI - Hollis #2 from the out bail out
199 BAR / 2884 PSI from the Shearwater transmitter on the rebreather
201 BAR, just past the 200 mark (converted to 2915 PSI with math) on the original DIL gauge from the rebreather
199 BAR, just under the 200 mark (converted to 2886 PSI with math) on the original O2 gauge from the rebreather
2825 PSI - Hollis #1 again after doing all those checks.

This probably explains why I have been struggling to get the mixes to dial in. Do the math based on starting with one gauge and filling to target pressures with a different gauge.
In the end I still don't know what I have. Something in the mid to high 2800 range would be my guess based what I am seeing. Without a standard to check the gauges against it is down to what gauges do I trust more, what numbers come up more often? The 3050s look like outlyers.
The 2 digital gauges only have a 59 PSI spread.

Left scratching my head on what is good and what needs to go away. Probably going to get some new gauges for Christmas from what I am seeing.

its a pain when mixing trimix as @Tracy said use one gauge to do all that stuff, its ratios of gas that counts -as far as the rEvo goes its easy to cross check PO2 for your expected dil so we're only talking about how full it is -as far as spg's go just work the most conservative reading

 

[happy-diver]

I've got the cheapest of cheap electronic gauges on each end of a booster for mixing and on special they were cheaper
This stuff gives great mixes partial pressure blending with fudge factors and witchcraft and most certainly close enough

But no cylinder rolling