4th Cell/VR3 link odd behaviour

daveroo

GDay All

I am diving a Classic Inspiration. I have recently installed an APV 4th cell and have hooked it up to my VR3 (7 pin connector - software v3.0.3c). It all works, but there is an odd quirk. I carry out calibration of the fourth cell as per the manual, and the VR3 reading tracks the handsets perfectly from 21% to 100% O2 at ambient. When I go for a dive, again the unit tracks fine in shallow water. However, when I descend below about 20m, the VR3 reading starts to climb. Typically the handsets will be steady on 1.3, but the VR3 will read upwards of 1.45. However, after about 10mins or so, the VR3 reading begins to drop, and after about 20mins, it tracks the handsets perfectly, and behaves itself beautifully thereafter. I thought there was some issue with the cell, but both used and new cells (R22-2BUD) show the same behaviour.

It seems to be some sort of equilibration issue. However, ambient and water temperature are currently the same here (18-20C), so perhaps it is a pressure or humidity thing? I am not using HIDs or other potential sources of electrical interference. Electrical contacts are very clean and the mV reading from the fourth cell is very stable during calibration.

My next move is to try some AI cells.

Has anyone seen similar, or have any suggestions?

Thanks and regards

Dave

AndyP

Which 4th cell holder is it. I have seen something similar with the one from DeltaP

Andrew

gbmay

Here is an answer I received from DeltaP regarding odd behaviour of 02 sensor "First go into the DVo screen and make sure XFunc is switched on with X O2 on. Then I think you need to first turn on NX99 as the only gas and flush with O2 and calibrate it in the O2 screen and see what it reads, then turn off NX99 and activate AIR and see what it reads in air. You can also if you wish try an air calibration in the O2 screen and see what it reads in Air." Proper calibration of the VR3 is key to good "readings".

Try this it worked for me.

George

daveroo

Dear All

Thanks for the responses to my questions. The fourth cell holder is the Delta P one. In terms of the calibration procedure, I have followed this carefully, and I think I am doing it right as the tracking in ambient and shallow water is fine. It is also fine (initially) when I descend - but then creeps up after a few minutes. This is on a time scale too long to be simply a matter of a slowly responding cell. Also after it has had its 20mins of reading high it comes back down to correct values and behaves itself after that. All of which suggests that the calibration is OK, but the cell/VR3 is having some kind of conniption.

Thanks and regards

Dave

daveroo

Just a postscript to my original email. The problem was with the VR3. There is a parameter called the pO2 offset, and mine had reverted to default. Resetting it is usually done at the factory. If you get this problem contact Delta P.

Regards

Daveroo