Do you have to calibrate dive computer depth guages?

[purbeast]

I purchased a Suunto Vyper Novo second hand from someone who only had about 8 dives on it and I used it for the first time during my first 3 OW certification dives. I noticed that the depth it was reading was completely different/wrong compared to the depth gauge that was on next to my SPG.

When we were at 20 feet according to my depth gauge next to my SPG the computer was reading 14 or 13 feet. We were clearly closer to 20 feet than 14 or 13 feet too. I was on my knees at this point too so while my wrist wasn't on the ground, it was like 1-2 feet from the ground around this time.

Is this pretty common that these things aren't that accurate? Or is there some kind of calibration needed?

This is my first experience with a dive computer so I have no clue.

 

[JackD342]

First, here is a link to your very own copy of the Suunto Vyper Novo User's Guide.
https://ns.suunto.com/Manuals/Vyper_Novo/Userguides/Suunto_VyperNovo_UserGuide_EN.pdf

Now, as a general rule, I would expect a DC to be consistently more accurate than an analog depth gauge. You will really need to either measure that depth, or better yet bring a couple more instruments along the next time to determine which is right and which is wrong.
There should be no "calibration" of depth for a DC. Many/most/all will have a configurable or automatic altitude setting, but that would only explain a difference if the Vyper said you were deeper than the analog. Also, many computers can be set for fresh or salt water. I don't see that mentioned in the Vyper Novo manual, so that is probably following the EN13319 standard that uses one setting that kind of splits the difference between the densities of fresh and salt. Again, that difference is nowhere near enough to explain a difference of 30%.

Also, Suunto analog depth gauges have a feature I have not seen on other brands that does allow you to calibrate the depth gauge. (the intention is to allow calibration for altitude) If your analog is the one that is wrong it might not be defective, it might just require adjustment.

 

[tursiops]

And Suunto dive computers are surprisingly often mentioned here on ScubaBoard as having faulty depth sensors.

 

[JackD342]

And Suunto dive computers are surprisingly often mentioned here on ScubaBoard as having faulty depth sensors.

If this is related to that issue, it will be the first instance I have heard of it manifesting itself in that way. The failures I am aware of have you at hundreds of feet down when on the surface - nonsensical readouts versus questionable readouts.

Still it could be, but I am inclined to think it is something else.

 

[purbeast]

Another thing (that may or may not matter) is that I changed the battery prior to using it and noticed that it reset all of the settings on the watch.

I just went back and looked at the logs of the dives to verify that it didn't save the logs as the correct depth versus what I saw and it is showing the same that I saw, which is around 14-15 feet pretty much the whole dives.

I also contacted Suunto and asked them about this via a message so I'll see what they say back.

 

[tursiops]

You did 3 OW dives at that depth, whatever it was?

 

[purbeast]

You did 3 OW dives at that depth, whatever it was?

Yes they were all around the same depth where we were pretty much on the bottom doing skills.

 

[Centrals]

Blindly trust computers?

Have the computer check properly.
Ask the person who sold you the computer on the matter.

 

[tursiops]

We

Yes they were all around the same depth where we were pretty much on the bottom doing skills.

Well, in a perverse way I hope your computer is wrong, because the OW dives must be deeper than 15 ft to meet standards!

 

[Bob DBF]

And folks wonder why I hang on to my capillary depth gauge.


Bob