Trihunter 6000 helium analyzer: how it works?

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Arus

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Treviso
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hi everybody!
I’d like to learn more about the system used to get the helium percentage using just 2 oxygen sensors and no helium analyzers at all, in this mixing stick i’m using at the moment for the blending.

I couldn’t find much on their website...
Anybody can give me a full explaination about how it works?

Thanks
 
full explanation will take a while.
Short explanation is when you program the gas mix into the brain box, say 21/35, the coding says that in "stage 1" at the first O2 sensor, it has to add O2 until the ppO2 reads 32% so it fires the solenoid until it hits 32%. In "stage 2" at the second O2 sensor, it knows it has to dilute that mix back down to 21%, so it opens the helium sensor until the ppO2 reads 21%.
No different than pp blending with only an O2 analyzer.
 
So it does calculations to get the blend but without a trimix analyzer you have no way of testing the final product to see if it worked? Sounds like a workable system for the blending part but you still need a helium analyzer to check it?
 
So it does calculations to get the blend but without a trimix analyzer you have no way of testing the final product to see if it worked? Sounds like a workable system for the blending part but you still need a helium analyzer to check it?

eh, trimix has been blended for decades in this exact manner for decades without helium analyzers and still is blended this way in many parts of the world including cave country. No real point in a He analyzer if you use standard gases.
If you know the fO2 going in, you know the fO2 coming out, and the only other thing that went in there was helium, then you know the balance is helium. The stick knows fO2 "going in" based on the first sensor, and it knows fO2 "coming out" based on the He sensor. Analyze the fO2 of the tank since there may be some He leakage in the system, but it's going to be close enough
 
What Tom said. And since you're really only concerned with the accuracy of the FO2, a little helium here or there isn't going to make much of a difference now that it's been fairly well demonstrated that the "helium penalty" doesn't really exist in any appreciable manner. A couple points here or there isn't going to affect your END to the point where you're going to be concerned, and in this case inert gas is inert gas, so your decompression isn't going to be affected to any serious degree.

I still leave my computer set with the desired amount of helium, as it has been posited that the "penalty" makes us do the right amount of deco, just for the wrong reason. However, I am unconcerned with actual accuracy of helium content as long as it's marginally close.
 
In our case i’m pretty sure that is injecting the helium first, because today, blending a 17/45 the first sensor read something around 9 and the second one around 17.
So the amount of helium is calculated, based on the oxygen variation after the injection... correct?

full explanation will take a while.
Short explanation is when you program the gas mix into the brain box, say 21/35, the coding says that in "stage 1" at the first O2 sensor, it has to add O2 until the ppO2 reads 32% so it fires the solenoid until it hits 32%. In "stage 2" at the second O2 sensor, it knows it has to dilute that mix back down to 21%, so it opens the helium sensor until the ppO2 reads 21%.
No different than pp blending with only an O2 analyzer.
 
@Arus I can't remember which order they inject in, but the same principal applies yes.
In that case it has 3 ppO2 values to work with. Starting is 20.8 for air. Second is after dilution to helium which is calculated based on the mix you sent, then it "brings it back" to the set point by adding O2.
Probably a more accurate way to do it, though the concept is arguably easier to understand with adding O2 first as it's the way we partial pressure blend
 
Actually i always add helium first in partial pressure blending.
And that’s also what most of the blending app suggests for what i know. Some you choose, ok.

Thanks for the explaination anyway. :)
 
The explanation isn't quite accurate. Tbone's giving the unit a little more power than it actually has. The solenoids are only safeties, they are closed with power off and open with power on. You start your compressor then adjust the knobs on the unit until the gas hits the %'s you want. You will have to toy with it to keep it at say 21/35. I found it not to be super-precise, so you do have to stand over it as the %'s fluctuate more than on my nitrox stick. The unit is only using oxygen analyzers, but the brain box then converts the % drop in oxygen on the first (helium) sensor into an estimated helium percentage on the screen. If your % of oxygen goes over a certain amount ( I believe 40%) the solenoids get automatically shut to avoid too much oxygen going in the system. The solenoids can not act to maintain your current % dialed in on the screen.
 
@rddvet how new is yours? I've seen the newer ones that don't have fiddle knobs anymore. He released it at DEMA last year IIRC. The old ones were just needle valves with shutoff solenoids, but the ones he showed me last year were fully automatic
 
https://www.shearwater.com/products/teric/

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