Helium Gas Analyzer

[Fort Collins Bob]

Hello All,

Can anyone lead me to some information about where I can get a helium sensor so I can make my own Helium analyzer?

I have been looking at TC sensors ( Thermal Conductivity ), but was thinking that maybe someone around here has built one?

I have built my own O2 analyzer, which I am very happy with.

ANY information or guidance would be great !

thanks all.

bob

[omar]

This is a little more advanced than an oxyhacker oxygen analyzer using a panel meter. You will need to put the TCC's into an appropriate circuit. The output of the cell will be dependent on the supply voltage or current depending on type of configuration used. The output will also be non-linear to the concentration of helium. This means that you will have to figure out a way to determine the calibration (response) curve, convert it into a digital signal and program it into a mircoprocessor to convert the output signal into the appropriate concentration (V/V%).

have fun.

omar

PS
The calibration gases, flow meters, circuit building & electronics gear and programmming stuff will cost a fair amount to get to the point that you can build one.

[Scuba_Vixen]

While we're on the thread of helium analysers, does anyone have experience or firsthand info on the heliox analyser from Dive Rite?
Seems like if it works well, as in accurate and reliable, and if it's not ridiculously expensive, It might be a worthwhile investment, especially for blending without dumping what's left in the tanks.
Thanks in advance for the feedback.

Darlene

[Cave Diver]

Scuba_Vixen once bubbled...
While we're on the thread of helium analysers, does anyone have experience or firsthand info on the heliox analyser from Dive Rite?
Seems like if it works well, as in accurate and reliable, and if it's not ridiculously expensive, It might be a worthwhile investment, especially for blending without dumping what's left in the tanks.
Thanks in advance for the feedback.

Darlene

Yes, I do. A buddy of mine has one and we borrowed it to double check our mixes during Trimix class. We analayzed both Oxygen and Helium contents to insure accuracy. Oxygen content was normally within about .3% and the Helium content was usually within about 2% of what our target mixes were supposed to be.

Memory serving me correctly it doesnt actually measure Helium content, but rather the thermal conductivity of the nix and compares it to a known value. I believe the acceptable margin of error is about 5% and the analyzer requires a 5 minute warm up (countdown is displayed on the screen) before using.

It is very simple to use; setup and usage is just like an O2 analyzer.

If you have any specific questions about it, I'll be glad to try and answer them for you.

[omar]

The Heliox requires a 90 second warmup period for the helium sensor. Either sensor or both (O2 & He) can be selected at Startup. The error for helium is +/- 1%. The error for oxygen is dependent upon the sensor used (typically 1-3%). The unit has a rechargeable battery that will provide a continuous readout up to 12 hours. You do not need to capture a gas sample and analyze it (hands free operation).

omar

[Braunbehrens]

I wonder how necessary it really is to have a He analyser. One of my LDS has one, and we use it to analyze the mixes. They are always spot on.

Since the important percentage is the oxygen anyway, and the other gasses can be calculated...why spend that much money on a He analyzer.

Also, there is always the voice test. Granted it's not that accurate, but all we really care about is that there is a good amount of helium in the tanks. Whether it's 35% or 42% doesn't make much difference.

I suppose after blowing up the tanks a few times, it might be nice to know exactly where one is at....but you could just as easily add a little more helium to make sure there is enough.

I think in general it is better to spend the money on other things to increase safety, at least for an individual. As a club I could see it as being a good purchase.

[Uncle Pug]

Without a helium analyzer I don't know how you could accurately continuous blend trimix.

Using a blender only requires having one Helium cylinder on hand at a time and you can take that down to 40~50 psi so there is no waste.

Plus blending on top of partial fills is easy.

[Charlie99]

Uncle Pug once bubbled...
Without a helium analyzer I don't know how you could accurately continuous blend trimix.

One could theoretically do it with two O2 sensors. Step one is to blend air and HE. Monitoring O2 would indirectly tell you the HE percentage. Step 2 is to then pass this through another CF blender to add O2 as necessary. Step 2 obviously affects the HE percentage a bit, but this is easy to precalculate.

Particularly if you are just making a few standard mixes, it shouldn't be too hard to get acceptable accuracy.

Charlie

[Charlie99]

Scuba_Vixen once bubbled...
While we're on the thread of helium analysers, does anyone have experience or firsthand info on the heliox analyser from Dive Rite?

I believe Dive Rite is selling the Atomox analyzer.

http://www.atomox.net/ has quite a bit of useful info and how it operates, as well as some other useful info and programs for gas mixing.

Charlie

[Uncle Pug]

Charlie99 once bubbled...
theoretically<<<<>>>> it shouldn't be too hard
I dunno Charlie... since I already have my flow gauges marked for various mixes I could probably get by if the helium analyzer went down but I don't know how easy it would be to get started without one.

What works in theory might not be so easy IRL.

[AquaTec]

I use the Dive Rite He analyzer

I love the simplicity of it, I can either plug it in or use batteries

It is great for top ups. and confirming exact gas mixes.

i want to be acurate with the amount of He and O2 i have
i don't like to guess or use some type of voice test.

[Fort Collins Bob]

[QUOTE]omar once bubbled...
[B]This is a little more advanced than an oxyhacker oxygen analyzer using a panel meter. You will need to put the TCC's into an appropriate circuit.

Hello all,

I was planning on using a single chip microproccessor ( PIC CHip)
to do all the magic with... and I have the programmer to do it with.

A little a/d conversion and I should be in the market.

I was hoping on finding some information about the cells ( TC's )
themselves. Manufacturer, spec's ...

Thx all ;-]

bob

[Uncle Pug]

ftcbob once bubbled...
Thx all ;-] bob
Bob.... forgot all about you Bob.... let us know how it works once you get it all figured out... ;-]

[Braunbehrens]

AquaTec once bubbled...
I want to be acurate with the amount of He

Not that there is anythign wrong with using a He analyzer or being accurate, but I'm just curious, why do you feel it's so important to be accurate with the amount of He?

[sheck33]

ftcbob once bubbled...
[QUOTE]omar once bubbled...
[B]This is a little more advanced than an oxyhacker oxygen analyzer using a panel meter. You will need to put the TCC's into an appropriate circuit.

Hello all,

I was planning on using a single chip microproccessor ( PIC CHip)
to do all the magic with... and I have the programmer to do it with.

A little a/d conversion and I should be in the market.

I was hoping on finding some information about the cells ( TC's )
themselves. Manufacturer, spec's ...

Thx all ;-]

bob

I am by no means an expert on this but i think the actual cell can really have a variety of shapes and sizes. However a small size is better. What could be done is put a thin filament, identical to the ones used in gas chromatographs, in the cell and flow the gas through the cell, the filament would be used in a Wheatstone Bridge configuration. How linear the resistance change would be with He content i dont know, but it can be calibrated.
Filaments are usually in the 30- 50 Ohm range with a maximum current of about 100 mA. The max current however very much depends on the rate of gasflow.

anyway, is this somewhere along the lines of what you were thinking about :confused:

[Charlie99]

Uncle Pug once bubbled...

I dunno Charlie... since I already have my flow gauges marked for various mixes I could probably get by if the helium analyzer went down but I don't know how easy it would be to get started without one.

What works in theory might not be so easy IRL.

I guess you haven't heard that Helium Analyzers Rot Yer Brain.

If you try running the He/air mixer output at 9%,and the final mix at 18%, you just might find yourself with 18/50.

You do need to fully mix the gases twice, but I hear Scott Koplin up in your area makes some pretty nice vortex mixing tubes.

Since all the gases are being blended at 1ATA, the nonlinearities of the pp mix methods are avoided. The only real downside is that a percent or two error in O2 in the first mix (air/He) turns into several percent error in He. In other words, if your first mix is 10% O2 rather than 9%, then you end up with 18/46 trimix, rather than 18/51.

Charlie

[Uncle Pug]

Charlie99 once bubbled...
I guess you haven't heard that Helium Analyzers Rot Yer Brain.
That must what happened alright Charlie. I don't figure in my poor state of mentation I could balance a stack of blenders.

Have you ever tried it IRL?

[Charlie99]

Nope, I never touch the devil's gas :mean:

Just hearsay.

[BigJetDriver]

Just as a note, I have an Atomox and the Qxycheq Expedition. Sure does make the job a lot easier!:)