Calibrating the VR3 O2 Sensor

tamorgen · 28th April 2008, 15:39

I just got a response from Al Wright at Delta P. He seems to confirm my suspicions that once you set the C4 code, you must calibrate as if you have a CCR. You can set the calibration gas to Air and do the calibration, but you have to go into CCR mode to set the gas and perform the calibration. I'll let everyone know how it works. Thanks all for your input.

Dinspiration · 28th April 2008, 17:13

Hi,

I just did the calibration on my VR3 in OC(SCR) and CCR Mode.

In OC/SCR Mode the computer is using the current active gas for calibration. This means, if you would like to calibrate the O2 sensor with air, you will need to active air as active gas on your VR3 - The display should say : AIR. After that select O2 and do the complete calibration in air. After the calibration the Display should say: X Air, or X NX22 and the bottom line: AIR. This makes sure, that you did the calibration correctly.

Now you should switch the active gas to that, what should be within your breathing loop (FO2). E.g. you are using an NX50 and NX50 dosage block - set it to NX45. Now you are ready do dive.

Why OC/SCR Mode: There is no official OC/SCR mode on the VR3. If you are using the VR3 with an SCR the computer is in standard OC mode as the decompression is the same for OC and SCR's. If you have an external O2 cell and Xdec switched on it will calculated the decompression based on the O2 cell reading. But the complete decompression calculation is still based on OC.

DINspiration

tamorgen · 28th April 2008, 17:20

Quote: (Originally Posted by Dinspiration)

Hi,

I just did the calibration on my VR3 in OC(SCR) and CCR Mode. It seems to be correct, that the computer remembers the selected CAL GAS entered in the CCR Mode.

I switched the computer to CCR Mode and selected a NX 25 as CAL GAS. After that I switched back to OC Mode (Which is the correct mode for SCR's) and did the calibration in Air. After the calibration in AIR the VR3 showed me 25.0 % O2 or X NX 25.

This means, if you have a C4 VR3 and plan to calibrate the computer in OC (SCR) Mode you will need to set the CAL GAS first in CCR Mode to AIR. After that you can switch back to OC/SCR and do the complete calibration. With an SCR it is not needed to switch back and forward between OC/CCR modes. After you defined the GAL GAS to AIR you can do everything in OC/SCR Mode.

Why OC/SCR Mode: There is no official OC/SCR mode on the VR3. If you are using the VR3 with an SCR the computer is in standard OC mode as the decompression is the same for OC and SCR's. If you have an external O2 cell and Xdec switched on it will calculated the decompression based on the O2 cell reading. But the complete decompression calculation is still based on OC.

DINspiration

Thanks DINspiration, it seems that we have come up with the same answer. I haven't been able to test it yet (I'm at work), but I plan on trying again tonight. Having to set the CAL gas in CCR mode I think was the missing link in my calibration, and it does make sense, once you wrap your brain around it, but Delta P doesn't come out and explicitly say it. I suspect my attempt tonight will be much more successful. I still may calibrate with O2, as some have said that it tends to be more accurate, but it's nice to know the procedure however I decide to do it.

sdussault · 28th April 2008, 18:08

I use the VR3 with my Dolphin. I must admit it took awhile to get everything working OK. First and foremost do you have NEW O2 cell? Having more than one cell is a good idea. My early problems were do to bad cells. When you calibrate with air the output of the cell should be between 9mV - 13mV. I typically see about 10mV. Make sure there is no corrosion / discoloration on the connector. If so clean the connections and try again. I just came back from a week long diving trip where the VR3 with Dolphin worked flawlessly.

Regards,

Steve

tamorgen · 28th April 2008, 18:14

Quote: (Originally Posted by sdussault)

I use the VR3 with my Dolphin. I must admit it took awhile to get everything working OK. First and foremost do you have NEW O2 cell? Having more than one cell is a good idea. My early problems were do to bad cells. When you calibrate with air the output of the cell should be between 9mV - 13mV. I typically see about 10mV. Make sure there is no corrosion / discoloration on the connector. If so clean the connections and try again. I just came back from a week long diving trip where the VR3 with Dolphin worked flawlessly.

Regards,

Steve

Hi Steve,
I just had bought 2 new sensors before diving this weekend. I had tried them both. As I discovered, the problem wasn't the sensors, it was getting it calibrated correctly. Since I bought the VR3 with the C4 code, I discovered today that you must calibrate it as if you are calibrating it in CCR mode, and set the calibration gas. If you only have the C1 or C2 code, you can calibrate it in OC mode, and it defaults to Air for the calibration gas. The problem is that the VR3 manual just isn't written very well, and it may say things, but only in shades of grey. You really have to read between the lines to figure this sort of thing out. Now that I know, I don't expect to have any further issues.

28th April 2008, 15:39	#11 (permalink)
tamorgen Gadget guru extrordinaire Current Rebreather/s: Dolphin Other Rebreather/s: Dolphin Join Date: Apr 2006 Location: Columbia, MD Posts: 183	Re: Calibrating the VR3 O2 Sensor I just got a response from Al Wright at Delta P. He seems to confirm my suspicions that once you set the C4 code, you must calibrate as if you have a CCR. You can set the calibration gas to Air and do the calibration, but you have to go into CCR mode to set the gas and perform the calibration. I'll let everyone know how it works. Thanks all for your input.
(Offline)

28th April 2008, 17:13	#12 (permalink)
Dinspiration Custom Title Allowed! Current Rebreather/s: Inspiration Classic Other CCR Other Rebreather/s: Not Bought Yet Other CCR Join Date: Dec 2005 Location: Switzerland Posts: 197	Re: Calibrating the VR3 O2 Sensor Hi, I just did the calibration on my VR3 in OC(SCR) and CCR Mode. In OC/SCR Mode the computer is using the current active gas for calibration. This means, if you would like to calibrate the O2 sensor with air, you will need to active air as active gas on your VR3 - The display should say : AIR. After that select O2 and do the complete calibration in air. After the calibration the Display should say: X Air, or X NX22 and the bottom line: AIR. This makes sure, that you did the calibration correctly. Now you should switch the active gas to that, what should be within your breathing loop (FO2). E.g. you are using an NX50 and NX50 dosage block - set it to NX45. Now you are ready do dive. Why OC/SCR Mode: There is no official OC/SCR mode on the VR3. If you are using the VR3 with an SCR the computer is in standard OC mode as the decompression is the same for OC and SCR's. If you have an external O2 cell and Xdec switched on it will calculated the decompression based on the O2 cell reading. But the complete decompression calculation is still based on OC. DINspiration Last edited by Dinspiration : 28th April 2008 at 17:31.
(Offline)

28th April 2008, 17:20	#13 (permalink)
tamorgen Gadget guru extrordinaire Current Rebreather/s: Dolphin Other Rebreather/s: Dolphin Join Date: Apr 2006 Location: Columbia, MD Posts: 183	Re: Calibrating the VR3 O2 Sensor Quote: (Originally Posted by Dinspiration) Hi, I just did the calibration on my VR3 in OC(SCR) and CCR Mode. It seems to be correct, that the computer remembers the selected CAL GAS entered in the CCR Mode. I switched the computer to CCR Mode and selected a NX 25 as CAL GAS. After that I switched back to OC Mode (Which is the correct mode for SCR's) and did the calibration in Air. After the calibration in AIR the VR3 showed me 25.0 % O2 or X NX 25. This means, if you have a C4 VR3 and plan to calibrate the computer in OC (SCR) Mode you will need to set the CAL GAS first in CCR Mode to AIR. After that you can switch back to OC/SCR and do the complete calibration. With an SCR it is not needed to switch back and forward between OC/CCR modes. After you defined the GAL GAS to AIR you can do everything in OC/SCR Mode. Why OC/SCR Mode: There is no official OC/SCR mode on the VR3. If you are using the VR3 with an SCR the computer is in standard OC mode as the decompression is the same for OC and SCR's. If you have an external O2 cell and Xdec switched on it will calculated the decompression based on the O2 cell reading. But the complete decompression calculation is still based on OC. DINspiration Thanks DINspiration, it seems that we have come up with the same answer. I haven't been able to test it yet (I'm at work), but I plan on trying again tonight. Having to set the CAL gas in CCR mode I think was the missing link in my calibration, and it does make sense, once you wrap your brain around it, but Delta P doesn't come out and explicitly say it. I suspect my attempt tonight will be much more successful. I still may calibrate with O2, as some have said that it tends to be more accurate, but it's nice to know the procedure however I decide to do it.
(Offline)

28th April 2008, 18:08	#14 (permalink)
sdussault New Member Current Rebreather/s: Dolphin Other Rebreather/s: Dolphin Join Date: Nov 2005 Location: NH Posts: 10	Re: Calibrating the VR3 O2 Sensor I use the VR3 with my Dolphin. I must admit it took awhile to get everything working OK. First and foremost do you have NEW O2 cell? Having more than one cell is a good idea. My early problems were do to bad cells. When you calibrate with air the output of the cell should be between 9mV - 13mV. I typically see about 10mV. Make sure there is no corrosion / discoloration on the connector. If so clean the connections and try again. I just came back from a week long diving trip where the VR3 with Dolphin worked flawlessly. Regards, Steve
(Offline)

28th April 2008, 18:14	#15 (permalink)
tamorgen Gadget guru extrordinaire Current Rebreather/s: Dolphin Other Rebreather/s: Dolphin Join Date: Apr 2006 Location: Columbia, MD Posts: 183	Re: Calibrating the VR3 O2 Sensor Quote: (Originally Posted by sdussault) I use the VR3 with my Dolphin. I must admit it took awhile to get everything working OK. First and foremost do you have NEW O2 cell? Having more than one cell is a good idea. My early problems were do to bad cells. When you calibrate with air the output of the cell should be between 9mV - 13mV. I typically see about 10mV. Make sure there is no corrosion / discoloration on the connector. If so clean the connections and try again. I just came back from a week long diving trip where the VR3 with Dolphin worked flawlessly. Regards, Steve Hi Steve, I just had bought 2 new sensors before diving this weekend. I had tried them both. As I discovered, the problem wasn't the sensors, it was getting it calibrated correctly. Since I bought the VR3 with the C4 code, I discovered today that you must calibrate it as if you are calibrating it in CCR mode, and set the calibration gas. If you only have the C1 or C2 code, you can calibrate it in OC mode, and it defaults to Air for the calibration gas. The problem is that the VR3 manual just isn't written very well, and it may say things, but only in shades of grey. You really have to read between the lines to figure this sort of thing out. Now that I know, I don't expect to have any further issues.
(Offline)

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