VR3 PO2 Monitoring vs Uwatec Aladin Air ZO2 with the Oxy2

tamorgen

Hi all,
Last month I took my new VR3 with the Dräger O2 monitoring cable for a spin down in the Florida Keys. I was diving with two other Dolphin divers, and they had the Oxy2 & Aladin setup for their O2 monitoring.

We started up with the same mix in our bottles, same oriface, pretty much the same rig with the exception of the electronic montoring. When we were diving, the O2 reading on my VR3 seemed to be considerably higher than the readings from their Oxy2/Aladin. Before I started diving, I calibrated the sensor to Air as per the directions in the VR3 manual. At a few points, I noticed that the reading was actually higher than the mix in my bottle (not sure how that is possible). I was thinking the reading may be slightly higher with the VR3 because the VR3 sensor is on the P-port on the counterlung, vs inline with the hose on the Oxy2.

Am I doing something wrong? Does the Oxy2/Aladin setup display the information differently than the VR3? I'd appreciate any help or advise anyone can give me.

JonORunde

I would try to calibrate the VR3 on pure O2. (Goes for the Oxy2's too)

Other then that, I have dived with both monitoringsolutions, and found them to be within 0.little of eachother

jon o

tamorgen

So theoretically they should have the same readings? I was starting to think that the VR3 might display it differntly somehow. The two guys on their Oxy2's kept looking at my VR3, like it was from another planet, and something was really weird. I guess it is just a calibration issue.

tamorgen

I read another post with a similar topic, so I guess I wanted to bring this topic back up. The VR3, when attached to a SCR reads FO2. Is this correct? It doesn't make much sense to me, since when you start diving the reading should be at presure, and therefore be PO2. Am I missing something?

PO2 = ATM * FO2

Am I missing something?

What does the Aladin read?

Lake_Tahoe_Diver

True when the VR3 is in SCR mode it returns Fo2, when it is CCR mode it returns Po2.

__________________
Scuba Diving,the only sport where it is good to be in over your head....

tamorgen

Okay, cool. I'm then I presume Aladin is reading FO2 as well, but since they read it from a different location in the loop, their readings would be slightly different than mine, being more elivated than theirs.

PaulTG2

Hello,

There shouldn't be a consistant difference between what is in the inhalation counterlung and the inhalation hose. The hose pulls from the counterlung so I can't see where there should be a lower concentration of O2 in the hose.

You also can't have a higher F02 in the lung than what is in the tank.

A calibration error on the VR3 or a difference in computed linearity would explain it.

--p

tamorgen

I knew there could be a higher FO2 than what was in the tank. It just wasn't making sense. It has to be some sort of calibration error, but I haven't been able to figure it out. I followed the directions to a T, but something is still obviously wrong. I guess I'll have to play around with it next time I go diving, see if I can get it to calibrate. I was calibrating off of air, so maybe that is my problem. Someone had suggested using O2 to calibrate, but I generally do not carry an O2 bottle around for SCR.