I dive with two computers, each displays different tank pressures ?

[master_diver_UJ]

I dive with two dive computers. My primary is an Atomic Cobalt & I use an Oceanic OC1 (w/ transmitter) as a backup. I get different tank pressure readings from the two - usually the OC1 reads a few hundred PSI's higher than the Cobalt. I've owned both for a couple years & the pressure difference has always been there.

Which do you think is more accurate - the air integrated Cobalt or the wireless OC1 ? Just curious...

Thanks !

John

 

[decompression]

Just difference in sensors. I would really just use an analog gauge as a back up, but that's just my opinion.

 

[PACKRMAN]

You could compare your computers to a certified gauge or breath a tank down to zero.

 

[master_diver_UJ]

Thanks for the feedback - both good ideas. I'm diving next week - I'll compare my computers with the gauges at the dive ops' fill center.

 

[KDAD]

All good ideas but packrman is spot on. Comparing the PDC to a gauge at the dive shop is good but if that is not certified it may be off as well. A certified gauge has been compared against a standard with greater accuracy. Therefore you can have greater confidence that what you are comparing against is accurate.

Ideally you would compare with the tank full and again with say 500 psi to assess the accuracy of the gauge.

 

[Steve_C]

Used to use a LDS that claimed one of their gauges was off by 400psi. I checked it against others and it was.

 

[DiveNav]

..... My primary is an Atomic Cobalt & I use an Oceanic OC1 (w/ transmitter) as a backup. I get different tank pressure readings from the two .........

It depends on how the high pressure sensor on each dive computer (or transmitter in the case of the OC1) was calibrated at the factory.

Let's if RonR responds to this one

 

[dmaziuk]

I dive with two dive computers. My primary is an Atomic Cobalt & I use an Oceanic OC1 (w/ transmitter) as a backup. I get different tank pressure readings from the two - usually the OC1 reads a few hundred PSI's higher than the Cobalt. I've owned both for a couple years & the pressure difference has always been there.

Which do you think is more accurate - the air integrated Cobalt or the wireless OC1 ?

Dunno about accuracy but go by the cobalt because if you're down to 0 and it's wrong you'll have a reserve. If you go down to 0 by oceanic and it's wrong, you're OOG.

 

[divad]

Dunno about accuracy but go by the cobalt because if you're down to 0 and it's wrong you'll have a reserve. If you go down to 0 by oceanic and it's wrong, you're OOG.

LOL

 

[RonR]

John,
The Cobalt is very easy to re-calibrate for HP using a built in utility and a good pressure gauge. In our experience it is very rarely necessary. I will send you instructions in a PM.

The advice to check against a known HP gauge is good- most dive shops will have a large gauge associated with a fill station or in the repair department. You could use a just-filled tank as an accurate enough source, connect your reg, and note the readings. Measuring at low pressures, near empty, will be much less accurate- high pressure sensors aren’t as accurate at low pressures. You will find many dive computers just drop to zero below some point to be safe. The Cobalt’s sensor should be accurate to between 10 and 20 psi, if temperature is stable.

Ron