Nitrox Analyzer

[rob.mwpropane]

An issue I HAVE noticed, is that if I get partial pressure fills, the reading I get at home is very different when compared to what I checked at the shop, if I don't roll the tanks around a bunch before checking them at the shop. I've seen differences of several percent, which is enough to cause trouble. After the home check, if I go back to the shop, the second shop check is pretty close to my home reading. The ride home seems to mix things up well enough.

I have filled a set of doubles not knowing that best practice is to pp blend in one post, and fill through the same post (makes sense, lol).... I got very different readings from each post... I laid them on there sides and within 24 hrs they evened out, thankfully, as I had a wreck dive planned that weekend.

My buddy said if I showed up to the boat with different mixes marked on each tank I was gonna get it from everyone on the boat starting with him

 

[BlueTrin]

I have filled a set of doubles not knowing that best practice is to pp blend in one post, and fill through the same post (makes sense, lol).... I got very different readings from each post... I laid them on there sides and within 24 hrs they evened out, thankfully, as I had a wreck dive planned that weekend.

My buddy said if I showed up to the boat with different mixes marked on each tank I was gonna get it from everyone on the boat starting with him

Also I was told that if you have different mixes on each side, they won’t mix if you have the same pressure on each side and you open the manifold afterwards.

 

[rjack321]

The Analox has a ‘sensor saver’ cap you can buy that seals off the sensor when not in use and thus extends the life of the sensor.

Also, the life expectancy of the Analox sensor is rated at 4 yrs.

It is marketed as a "sensor saver" but reality is they dont do squat.

 

[rjack321]

Also I was told that if you have different mixes on each side, they won’t mix if you have the same pressure on each side and you open the manifold afterwards.

That is correct. If you have air 2 mixes in either side at the same pressure they will never mix (it'll be years).

If you reopen the isolator and analyze both sides you can get similar readings, but that's "mixing on the fly" as some gas is being drawn from each side. Leave the manifold isolator open at all times. If there is any hint of it being closed when they were out of your sight at the shop, then analyze both sides with the isolator open and closed. Those 4 readings should be the same, if not someone has been messing with your gas.

 

[BlueTrin]

That is correct. If you have air 2 mixes in either side at the same pressure they will never mix (it'll be years).

If you reopen the isolator and analyze both sides you can get similar readings, but that's "mixing on the fly" as some gas is being drawn from each side. Leave the manifold isolator open at all times. If there is any hint of it being closed when they were out of your sight at the shop, then analyze both sides with the isolator open and closed. Those 4 readings should be the same, if not someone has been messing with your gas.

I didn’t realise it’d mix on the fly, it makes perfect sense when you think about it.

 

[sprockjohnson]

It is marketed as a "sensor saver" but reality is they dont do squat.

Agree. Also, the sensors, if truly capped off or placed into environments without ambient o2 levels, need to "wake-up" by being exposed to ambient o2 levels again before giving accurate readings on your mix. This is mostly relevant to high o2 percentages such as ppo2 in a rebreather but could factor into your readings if you were testing something higher than, say, 50%.

 

[rjack321]

Agree. Also, the sensors, if truly capped off or placed into environments without ambient o2 levels, need to "wake-up" by being exposed to ambient o2 levels again before giving accurate readings on your mix. This is mostly relevant to high o2 percentages such as ppo2 in a rebreather but could factor into your readings if you were testing something higher than, say, 50%.

They do keep the membrane protected and clean, but puncturing those is super rare anyway. A little pelican like case is a better investment than the sensor cap IMO.

 

[rob.mwpropane]

That is correct. If you have air 2 mixes in either side at the same pressure they will never mix (it'll be years).

If you reopen the isolator and analyze both sides you can get similar readings, but that's "mixing on the fly" as some gas is being drawn from each side. Leave the manifold isolator open at all times. If there is any hint of it being closed when they were out of your sight at the shop, then analyze both sides with the isolator open and closed. Those 4 readings should be the same, if not someone has been messing with your gas.

So I had a set of doubles. I added 100% to one side to PP blend (with isolator open), then filled from the opposite post. I got pretty different readings from either side. Isolator open the whole time. After 24 hrs everything had settled out to the same %. Obviously I should pick a post to do everything with, but it doesn't make sense to me why they were so different.

I started @ zero psi, filled with O2, then topped off with the compressor. To me I should not of gotten different readings, but maybe I should wait like ~ hr to analyze or something?

 

[rjack321]

So I had a set of doubles. I added 100% to one side to PP blend (with isolator open), then filled from the opposite post. I got pretty different readings from either side. Isolator open the whole time. After 24 hrs everything had settled out to the same %. Obviously I should pick a post to do everything with, but it doesn't make sense to me why they were so different.

I started @ zero psi, filled with O2, then topped off with the compressor. To me I should not of gotten different readings, but maybe I should wait like ~ hr to analyze or something?

This is a different scenario than a "closed then reopened" situation

Both sides had the same volume of o2 added. Then the same volume of air added. Neither side was well mixed after your filling so you got different results. They mostly stratify due to temperature. Lay them on their side (exposing the maximum surface area to mix across) and leave them a couple hours.

 

[rob.mwpropane]

This is a different scenario than a "closed then reopened" situation

Both sides had the same volume of o2 added. Then the same volume of air added. Neither side was well mixed after your filling so you got different results. They mostly stratify due to temperature. Lay them on their side (exposing the maximum surface area to mix across) and leave them a couple hours.

I understand it was different than a closed isolator.

That's what I did, laid them on the side. It all worked out after a day or so. I'll do everything from the right post from now on instead of either or.

Thanks.