Vt 3

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xanyas

xanyas

Registered
Scuba Instructor
Messages
32
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Location
Nagahama, Yomitan, Okinawa, Japan
# of dives
Hello all,

I have a question concerning the VT 3 safety stop feature. Mine is set at 15ft, but the count down always starts around 20-25 ft? Any info on this would be greatful.

Shawn
 
Hello Shawn,

As you know the safety stop feature setting options are 10ft, 15ft and 20ft. The pressure transducers are set to perform at plus or minus 1 ft to 100 ft. In other words if your setting is 15 ft the countdown should not start until 14ft -16ft. Double check it next time you dive, if in fact the stop is set at 15 ft and the unit is counting down in the 20-25 ft range then if definetly needs to come back to Oceanic to recalibrate the pressure transducer. Hope this helps.

Regards,
Darryl Bowerman
AERIS/Oceanic Regional Manager
 
Gentlemen,

Thank you for your quick response, but now I am confused.... I am asuming both of you are Oceanic reps, but are giving different reasons for the countdown starting early. I dove last night and it was in fact programed for 15ft, and it started the countdown at 20ft. If the countdown starts 5ft prior to the setting, what is the reason behind this? Thank you for the help.
 
Is it using the RGBM model? If so, it might be a deco stop at 25ft, then a safety stop at 15ft (very doubtful, but possible, depending on your diving profile). Sorry, I don't use that model of diving computer, so i'm not going to be alot of help here - sorry.

-----

Mike.
 
Midnight Star:
Is it using the RGBM model? If so, it might be a deco stop at 25ft, then a safety stop at 15ft (very doubtful, but possible, depending on your diving profile). Sorry, I don't use that model of diving computer, so i'm not going to be alot of help here - sorry.

-----

Mike.
Click to expand...

Not RGBM, Modified Haladane from DSAT
 
cerich:
Not RGBM, Modified Haladane from DSAT
Click to expand...

Thanks :) - I wasn't sure if, for some reason, it was doing a deco stop along with a mandantory safety stop.

It almost sounds like the calibration of the DC is off. From what I understand, most "off gassing" of N occurs at reduced pressures (around 10-15'), which, given 25' is a bit deeper, to me, implies that a 3 minute stop WONT expell as much N as at 10-15', increasing the risk of DCS when pushing the limits of either model.

Any word on whether this is a setting (sounds strange to be such), or a calibration issue? Is the depth sensor damaged? How does the depth reading compare to other DC's?

-----

Mike.
 
Ok. Got a clarification. Spoke with Doug at length yesterday regarding this setting. While it is true that the calibration is set at plus/minus 1 foot for the depth reading the stop is set to begin at 5ft deeper than the set point. So at 15ft the set point countdown will begin at around 20ft. This is to allow a little variance in the divers actual depth. We all know how hard it is to ascend to 15ft on the nose and not ascend to 10 ft. or descent to 20ft. So you start slowing your ascent at 20 ft and if you are within that 15 to 20ft window the countdown will be running.

Darryl
 
Darryl Bowerman:
Ok. Got a clarification. Spoke with Doug at length yesterday regarding this setting. While it is true that the calibration is set at plus/minus 1 foot for the depth reading the stop is set to begin at 5ft deeper than the set point. So at 15ft the set point countdown will begin at around 20ft. This is to allow a little variance in the divers actual depth. We all know how hard it is to ascend to 15ft on the nose and not ascend to 10 ft. or descent to 20ft. So you start slowing your ascent at 20 ft and if you are within that 15 to 20ft window the countdown will be running.

Darryl
Click to expand...
Is the 25' depth where the countdown started, then considered the decompression "floor", and 5' above that (the actual setting) the "ceiling"? This would definately make sense to allow for wave motion and diver depth variances during a deco (or safety) stop.

-----

Mike.
 
Hey Mike,

The countdown would start at 25ft if your setting is 20ft. Should not start deeper than 5ft. So if the deco stop depth setting is 15ft then at 20ft the coundtdown would start. This computer has the option of setting the stop at 10ft, 15ft or 20ft.

Darryl
 
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