Setting Temperature...

[cheeseandjamsandwich]

Hi,

When changing a setting from the 'OSTC Download' dialog box in Diver Log 5... does pressing the "Save changes to OSTC" then ALSO calibrate the Temperature Sensor each time? (to say 20°C, the default), even if i haven't touched the Temperature calibration value?

I don't have a thermometer handy at the moment, so i've got it in a big bowl of icecubes (remembered physics lessons at school!) and its reading 1.5-2°C
So i was wondering if i'd unknowingly calibrated it with the wrong ambient temperature set...
And it seemed to be reading a couple of degrees higher than the other diver's computers in the lake on saturday.

Is there a way of setting the temperature from the menu, i.e. when in the water?
If not, can there be in the future?
Would be handy to have the option to do it in the water.

Cheers
Rich.

[PeterK]

Rich, it is not correct to expect the temperature of melting ice to be at 0°C.

The freezing point of water under certain conditions is zeo degrees centigrade. But this applies to distilled water and normalized air pressure only.

The liquid generated by molten ice is certainly quite cold, but it will be very difficult to get to zero degrees.

If you want to check the accuracy of your unit it will be better to compare with a device with known precision. Maybe a clinical thermometer can be used but this will work around 37°C, only.

[swissdiving]

There is not temperature calibration value I would know of and neither is there a CF to adjust "temperature". With CF21 you can change the sampling rate, that's all.

And even if there was, why would you want to change the temperature under water? As far as I know temperature is not included in the deco calculation of the OSTC. Even if it was a difference of a degree or two would most certainly not make a shred of difference.

[cheeseandjamsandwich]

PeterK Wrote:
-------------------------------------------------------
> Rich, it is not correct to expect the temperature
> of melting ice to be at 0°C.
>
> The freezing point of water under certain
> conditions is zeo degrees centigrade. But this
> applies to distilled water and normalized air
> pressure only.
>
> The liquid generated by molten ice is certainly
> quite cold, but it will be very difficult to get
> to zero degrees.
>
> If you want to check the accuracy of your unit it
> will be better to compare with a device with known
> precision. Maybe a clinical thermometer can be
> used but this will work around 37°C, only.

But any impurities in water will lower the melting point... and we're only talking about tap water, so pure enough.
And i seem to remember from physics lessons that we were comparing thermometers by using melting ice and boiling water... i don't remember them being far out at all..
I did have a LOT of ice cubes in a plastic bowl.

my OSTC was reading a couple of degrees plus...


BUT YES... a thermometer would the most obvious /accurate solution! Above was a workaround...

And being able to set it in that water would be handy...

[cheeseandjamsandwich]

swissdiving Wrote:
-------------------------------------------------------
> There is not temperature calibration value I would
> know of...

When you plug it in to download with Diving Log, the dialog box which allows setting the date/time, CFs, etc includes a temperature calibartion setting...

[swissdiving]

What setting are you talking about?

The only setting in relation to temperature is CF21 and that has nothing to do with temperature calibration.

[swissdiving]

I stand corrected. You are right, there is the possibility of calibration.

I still don't see any value in adjusting temperature under water. To be able to do that a CF which allows an adjustment would have to be added.

But as it is the calibration in an "controlled" environment above water would seem a lot more sensible.

[JeanDo]

No, there is no temperature calibration feature in the OSTC. The sensor is factory-calibrated. And should not change over time.

What most of us experience, is that the OSTC is a bad at measuring temperature. Imagine a precision sensor at the center of a tight plastic (bad to conduct heat) case, stuffed with a power consuming display (producing heat), a processor (also), a battery (also). Everything filled with epoxy (nice to retain heat too) just to make sure you won't have surprise at 13 bar...

A good thermometer design would be a small temperature probe, at the end of a long isolating pin, enclosed into a nice metal radiator... Not practical as a dive computer.

I guess you got the idea...

[cheeseandjamsandwich]

swissdiving Wrote:
-------------------------------------------------------
> I stand corrected. You are right, there is the
> possibility of calibration.

No probs

> I still don't see any value in adjusting
> temperature under water. To be able to do that a
> CF which allows an adjustment would have to be
> added.
>
> But as it is the calibration in an "controlled"
> environment above water would seem a lot more
> sensible.

In water could be considered a controlled environment... Water temp is pretty* stable, good thermal conductivity to the temperature transducer... and there's often a few other divers around with computers around to check against...
When plugged it, would the unit warm up when charging?
Yes it'd need a new CF or menu entry...

And the primary question: Does the calibration happen each time we press 'Save changes to OSTC' in Diving Log?

* Allowing for warm surface layer and thermoclines...

[cheeseandjamsandwich]

JeanDo Wrote:
-------------------------------------------------------
> No, there is no temperature calibration feature in
> the OSTC.

There is in the Download dialog box in Diving Log software though...

[divinglog]

As far as I know there was a temperature calibration in the OSTC 1 (you could do it from the Diving Log dialog), but I'm not sure if this is still necessary for the latest OSTC, I'll have to ask Matthias. The "Write to OSTC" button will however not calibrate or influence the temperature, it will only write the custom functions back to the OSTC.

[cheeseandjamsandwich]

divinglog Wrote:
-------------------------------------------------------
> As far as I know there was a temperature
> calibration in the OSTC 1 (you could do it from
> the Diving Log dialog), but I'm not sure if this
> is still necessary for the latest OSTC, I'll have
> to ask Matthias. The "Write to OSTC" button will
> however not calibrate or influence the
> temperature, it will only write the custom
> functions back to the OSTC.

Cheers Sven.

[swissdiving]

@cheeseandjamsandwich

Even if it was possible to adjust temp, I still cannot see any value in doing it under water if you can do it easily with the PC.

[scubatinoo]

As long as the temperature is not used for any calculation i don't see any value in calibrating the temperature... I would say: 10 divecomputers = 10 different temperatures logged.

[heinrichsweikamp]

Hi,

Measuring accurate temperature (+/- 0.1°C) is tricky and requires a much better temperature sensor and a different mechanical design in which the sensor is installed.

@Sven: The calibration option is no longer available, the uart/USB command "f" which was used for this has no effect. The single point calibration did not increase the accuracy enough to justify the amount of email support we had to serve to people who miss-calibrated their sensors.

Regards,
Matthias

[swissdiving]

Thanx Matthias!

[divinglog]

Thanks Matthias, then I'll remove the option in the next Diving Log update to avoid any confusion.

[cheeseandjamsandwich]

heinrichsweikamp Wrote:
-------------------------------------------------------
> Hi,
>
> Measuring accurate temperature (+/- 0.1°C) is
> tricky and requires a much better temperature
> sensor and a different mechanical design in which
> the sensor is installed.
>
> @Sven: The calibration option is no longer
> available, the uart/USB command "f" which was used
> for this has no effect. The single point
> calibration did not increase the accuracy enough
> to justify the amount of email support we had to
> serve to people who miss-calibrated their
> sensors.
>
> Regards,
> Matthias

Cheers Matthias.