Recommendations: Cylinder pressure gauge (surface, not submersible)

[Wibs]

Tired of inaccurate surface pressure gauges. Would like to buy a new gauge which is within spitting distance of the pressure. Wouldn't object to buying a digital one either as it'll be better for blending. A larger 3"/75mm would be nice. I have the DIN connector and pressure relief valve from an old gauge that consistently reads 10% low.

I realise that yer gets what yer pays for.

So, to start off, are there any "quality" brands which are generally good?

Digital gauges. These vary a lot in price. Would buying the eBay advertised "Digital DIN cylinder contents pressure check gauge 0 - 400 Bar 0.5% Accuracy" be a waste of the ~£120? Or going for the Narked one for a lot more?

Any other recommendations?


TIA

[notdeadyet]

Try SMP in Preston.

[colinicky]

I seem to remember way back when having a conversation with John @ narked & at that time being told that analogue gauge was more accurate than digital, be interested to know if that is still the case

[MikeF]

Undersea 100mm gauge. 275 bar 1%fsd should be good enough.

Doesn’t matter if it’s digital or analogue just so long as it’s (relatively) accurate. My digital transducer is 0.7% fsd but the more truly accurate you get the more you spend. Though the most accurate gauges also come with a calibration cert so you can compensate for the inaccuracy of the accurate gauge.

[graham_hk]

Use the same gauge for all parts of the filling and you’ll get way better results … I can fill using a scuba spg and nail the mixes but when I use multiple gauges (even expensive /accurate) it takes a while to learn the peculiarities and get dialed in. But at the end of the day - you’re in a rebreather - it doesn’t matter

[N Bailey]

Another yes for Undersea

[Energy58]

Standard quality pressure gauges typically measure to 1% of FSD, you can get calibrated gauges that will do +/-0.25% at a known temperature but in reality can anyone do anything we do with greater precision than 1 bar in 200 or even read a normal gauge to that kind of accuracy? I think you are probably kidding yourself if you think you can. Chuck your 10% wrong one in the bin and replace it with a new one from a decent supplier, using the same gauge for each step of the process will help.

[Wibs]

Undersea 100mm gauge. 275 bar 1%fsd should be good enough.

That seems like the one. Good enough and not stupidly expensive.

I'm not after amazing absolute accuracy, but would like to know within a few percent, especially for bailouts.

For mixing, would use the whip gauge. This is the one I'm thinking of getting a digital gauge as whilst it might not be accurate to absolute pressure, it should be accurate to changing pressure, e.g. adding in 20 bar of O2 on top of, say, 150bar of absolute pressure. (Digital isn't more accurate, it's just easier to read a specific figure than an analogue gauge with or without a mirror)


Minor thread question: do 'standard' SPGs use 1/4BSP? What's the thicker thread size which both of my hand-held pressure gauges use? Measured the male thread to 0.54"; is that 9/16 (=0.5625)? Asking as I'll probably need the 1/4 female to 9/16 male adapter.

[MikeF]

the ones on your hand held gauges are most likely G1/4 which is 1/4 BSPP, major diameter is 0.518".

the undersea 100mm gauge is G1/2.

spg's are 7/16 UNF as far as I recall

[notdeadyet]

spg's are 7/16 UNF as far as I recall

Yes, both ends of the HP hose are 7/16-UNF. You can, in theory, screw an SPG directly into the HP port on a reg without using a hose if you stick an oring on it. It doesn't seat very well though.