Inexpensive Digital Gauge

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Actually @Tracy I had a ? So i was mixing for 38% for an upcoming dive. I filled all tanks to the required psi of O2. Plenty of time for them to cool.. actually double checked all tanks to make sure. Then I went to fill. I know that when I run my compressor I need to overshoot by some so they cool down to what I want. About 3-400psi. So 3500 get 3900, etc.

Now I went to test the next day and I've got 36% across the board.. the only thing I can figure is I should PP blend for 3900.. even though I know it will cool to 3500?

I'm a little stumped.. I know all systems are different, but there has to be a mathematical answer...yeah? Thoughts?
The mathematical solution is complex.

Control the fill rate carefully and room temp. note the difference. You should be able to dial it in from that data. Each tank will react differently.

10% overfill will only get you there with very slow fill rates.
 
@rob.mwpropane, I’m out in the shop blending now and just using an 8" perma-cal as a gauge on the fill whip. I would give you a good deal on it. Send me a DM if interested. It is accurate to 0.25% of full scale (only +/- 10psi). When I was doing PP blending using Baltic blender used to get within a few 10ths on O2%. Just following exactly what that calculator says. My PP whip has an 800psi 6" perma-cal which is +/-4psi. By the way, the PP whip is for sale too now that I’m mixing in the compressor.

My 4inch cheapo gauge for my compressor. Tends to be quite accurate.
But probably take some practice to blend on it...
But a 12"gauge.... nice!!!! Any pictures so I can drool.

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Actually @Tracy I had a ? So i was mixing for 38% for an upcoming dive. I filled all tanks to the required psi of O2. Plenty of time for them to cool.. actually double checked all tanks to make sure. Then I went to fill. I know that when I run my compressor I need to overshoot by some so they cool down to what I want. About 3-400psi. So 3500 get 3900, etc.

Now I went to test the next day and I've got 36% across the board.. the only thing I can figure is I should PP blend for 3900.. even though I know it will cool to 3500?

I'm a little stumped.. I know all systems are different, but there has to be a mathematical answer...yeah? Thoughts?
What did you add? Should be around 800 psi oxygen if you are shooting for 3600ish.
I have never tried to make 38%, but that should be damned close.
 
@rob.mwpropane, I’m out in the shop blending now and just using an 8" perma-cal as a gauge on the fill whip. I would give you a good deal on it. Send me a DM if interested. It is accurate to 0.25% of full scale (only +/- 10psi). When I was doing PP blending using Baltic blender used to get within a few 10ths on O2%. Just following exactly what that calculator says. My PP whip has an 800psi 6" perma-cal which is +/-4psi. By the way, the PP whip is for sale too now that I’m mixing in the compressor.



View attachment 725293
I appreciate the offer, but I don't think my issue is that I don't have enough gauges, I'm just not experienced enough just yet.
What did you add? Should be around 800 psi oxygen if you are shooting for 3600ish.
I have never tried to make 38%, but that should be damned close.

I added 775psi to get 38% @ 3600psi using the app "CCR Mixer". Then filled the tanks to 3900 warm and they cooled to 3500. I thought that if anything my O2 readings would be a hair high, but I'm obviously not understanding something because I got 36%.

I'm fine with 36%.. it works, I can do the dive, just trying to understand why I ended up where I did.

I am in the works of building a mixing stick, but since I don't dive a lot of nitrox it just gets put on the back burner in favor of other things.
 
Have you tried adjusting #5 in the picture? Should take away the bounce....
Just a thought....
Funny how the more accurate we get the more we worry or want to be precise.... there is something to be said of analog gauges....

I could not find any instructions that came with mine, but it does have this function / feature. I went from 03 to 07 so I'll see what that does. Thanks!!

(any idea what yours is set to that works for you? I'm just guessing at 07)
 
I haven't used that style gauge yet... just a spare.. for a customer that uses it on an exavator for installing post piles, to read torque. I have a different one on my air system...
Can't recommend a setting.
 
I could not find any instructions that came with mine, but it does have this function / feature. I went from 03 to 07 so I'll see what that does. Thanks!!

(any idea what yours is set to that works for you? I'm just guessing at 07)
Every sensor has an output that is not stable, if your gauge reading does not move around a bit, it is software doing that. I typically don't put filters on systems I build so you can see if there is noise. If a motor or other source of electrical interference in present, you can see it.

You should consider adding an analog gauge. You can be plenty accurate with them and it is way easier to determine fill rate with them vs digital. Digitals give you that warm feeling of a definite number but analog gives a better representation when things start moving.
 
Every sensor has an output that is not stable, if your gauge reading does not move around a bit, it is software doing that. I typically don't put filters on systems I build so you can see if there is noise. If a motor or other source of electrical interference in present, you can see it.

You should consider adding an analog gauge. You can be plenty accurate with them and it is way easier to determine fill rate with them vs digital. Digitals give you that warm feeling of a definite number but analog gives a better representation when things start moving.

I actually have multiple analog on my system.. one is on 2nd and 3rd stage and then another on the tower itself. One digital gauge is @ a T right before the fill whips.. this seems to work good, I've actually caught two leaks that I otherwise wouldn't hear with the racket of the small diesel engine. Losing a few psi when it should be building tipped me off right away. I don't think I would have caught that as quick with an analog gauge.

This other digital gauge is on my whip for going between tanks or O2 tanks, this is that gauge. It's nice to be able to deal with a little digital gauge, and even the swings that it makes aren't a huge deal... playing with the setting should fix it, but even if it doesn't it really does work for my system.

Edit: I'll probably switch this over to the whips as I can always reference it with the analog gauge on the tower and the other one is less bulky, so better for a mobile whip.
 

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