IP gauges read 20psi different.

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tablesaw
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IP gauges read 20psi different.

Mon Jul 03, 2017 8:59 pm

I have two IP gauges that are the same and from the same online company but are off 20psi to each other. Is this common? I just rebuilt two MK2s and a MK200, one gauge says I'm set really high, the other says I'm a genius. Guess which one I like. Is there a preferred brand?

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antique diver
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Re: IP gauges read 20psi different.

Mon Jul 03, 2017 9:46 pm

Unfortunately that's a common problem with inexpensive gauges.

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Bryan
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Re: IP gauges read 20psi different.

Tue Jul 04, 2017 7:03 am

antique diver wrote:Unfortunately that's a common problem with inexpensive gauges.


If you have two gauges you can compare the difference and as long as you know how far the gauge is off and adjust for it it's not a big deal. The inexpensive gauges are susceptible to accuracy problems if dropped on hard surfaces. The ones in the store have the rubber cover and are pretty accurate and will let you know if there is a big problem or if you have excessive IP creep.
Doing it right should include some common sense, not just blindly following specs and instructions. .Gary D, AWAP on SB

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Herman
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Re: IP gauges read 20psi different.

Tue Jul 04, 2017 7:06 am

Its not unusual for inexpensive gauges to be off a good bit and when comparing 2 it may well be one is off low and the other high, giving the appearance of wider difference than actually exist. The good news is it really does not matter that much. The suggested IP is a range and anywhere within that range is still "in factory spec" but even outside of that range, the reg will perform fine. It may not meet all of the maximum specs, ie full flow volume might not be up to spec but that number is WAY above what any diver could possible inhale so it's a mute point. What is important is how stable and repeatable the IP is. In other words, does the IP get to the same value quickly and stay there, not creeping up over time. Any gauge, no matter how far off can do that. Bottom line, the gauge being off 10-15 psi is not really a big deal for a DIYer although I would suggest you pick one gauge as you "official" gauge rather than bouncing between several. That way, whatever the actual value is, you are using a consistent value to set up all your regs.
Herman

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Re: IP gauges read 20psi different.

Tue Jul 04, 2017 12:31 pm

if you're concerned you can order some nicer oil filled gauges and use the bcd connector.

I grabbed one of these in 300psi and it works really well. I bought mine 3 years ago and it appears that there may be some concerns with the newest ones. That said your bcd adapter is using a standard NPT thread so you can adapt it to normal gauges so go find one you trust and use that.
https://www.amazon.com/gp/product/B0080 ... UTF8&psc=1

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antique diver
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Re: IP gauges read 20psi different.

Tue Jul 04, 2017 4:22 pm

Ha... I read that and noticed one of the gauges is listed as being filled with "Food Grade" Glycerin. That's certainly an important benefit, as I have known two or three divers who have eaten their pressure gauges while having hunger pangs during very long dives. :roll:

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Re: IP gauges read 20psi different.

Tue Jul 04, 2017 6:37 pm

Thanks for the replies. The gauge that read 20psi high free flowed the second stage on the 3 regs I was servicing so I moved it to the bottom drawer. Going diving this weekend, I'll take the other one and compare it to my buddys shop gauge. He's a Scubapro tech so I'm sure it's perfectly accurate. :mrgreen:

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Re: IP gauges read 20psi different.

Tue Jul 04, 2017 11:17 pm

Despite the advantages of a oil filled gauge, I prefer a dry gauge for measuring i.p. I think it is important to be able to see the effect of a creeping i.p. without the oil (or glycerin) slowing the needle. I think a 300 psi gauge is the perfect graduation for an i.p. gauge.

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couv
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Re: IP gauges read 20psi different.

Thu Jul 06, 2017 12:10 pm

I smuggle my gauges into work for a comparison with a calibrated gauge. Then, I mark the glass with a Magic Marker (Sharpie for you kids) and apply a strip of clear tape over the mark. The mark indicates where 135 psi really is. With four at at home, I use the democratic process to decide which gauge needs another trip to work or a moving of the index mark.

I have one expensive gauge I use for gnat's ass adjustments (until I dropped it last week.) A few cheap gauges are modified by drilling out the snubbers to make them more responsive. It shortens the life of the gauge, but I want to see IP creep as it's happening.
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USdiver
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Re: IP gauges read 20psi different.

Sat Jul 08, 2017 12:04 pm

Ancient Chinese aphorism: "Man with one watch always know what time it is, man with two watches never sure."

Take one of those IP gauges and give it to a friend. Problem solved the ancient Chinese way...

Just Sayin' :wink:
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luis
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Re: IP gauges read 20psi different.

Sat Jul 08, 2017 3:03 pm

USdiver wrote:Ancient Chinese aphorism: "Man with one watch always know what time it is, man with two watches never sure."

Take one of those IP gauges and give it to a friend. Problem solved the ancient Chinese way...

Just Sayin' :wink:


Thanks... that is great. :lol: :lol:


The modern rebreather diver would say to get an odd number (in this case 3), average the ones with close readings and discard the value of any that falls far away from the general grouping. That is how some rebreathers rank O2 sensors.



I have one digital gauge that I verified against a calibrated precision gauge. I used that digital gauge to check all the others. I find most gauges in this range to be within 5 psi (or less) of my calibrated gauge. Since your gauges are that far apart, I am going to guess that one of your two gauges needs to be retired.

A 300 psi gauge that is off by 5 psi is good (1.6% error).
A 300 psi gauge that is off by 20 psi (6.6% error) is a paper weight IMO.
Luis

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antique diver
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Re: IP gauges read 20psi different.

Thu Jul 20, 2017 9:19 pm

pointer pullerIMG_2790.JPG
Many gauges can be calibrated if the lens is removable. I use this little pointer puller to remove the pointer from the inaccurate gauge. I find the true pressure with a gauge of known accuracy, (such as 150 psi) then apply the same pressure to the gauge to be calibrated... then carefully place the pointer back in place at the 150 psi reading. A light tap into place on the shaft and it's stuck there, ready to use.
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Bryan
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Re: IP gauges read 20psi different.

Fri Jul 21, 2017 7:25 am

Thanks for the post Bill....I need to look for one of those tools. I remember seeing one used years ago and completely forgot about it.
Doing it right should include some common sense, not just blindly following specs and instructions. .Gary D, AWAP on SB

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Herman
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Re: IP gauges read 20psi different.

Fri Jul 21, 2017 7:59 am

Bill,
What's the diameter of the tool? Guessing it's 1 to 1.5 inch
Herman

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antique diver
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Re: IP gauges read 20psi different.

Fri Jul 21, 2017 9:03 am

Hi Herman, you should be able to make these fairly easily. (I think I could even do it... but it wouldn't look so good, and it would take me all day!)

The outside diameter is one inch.

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