Athmospheric pressure sensor calibration

[Tingsten]

Hello HW,

My OSTC 3 seems to be 5mBar off (always showing a value 5mBar lower than what is showing other OSTC or what official weathercast is saying). Is there anyway to offset it?

Thx you a lot!

[heinrichsweikamp]

5mbar are 5cm depth difference. That's acceptable.

But yes, you can offset the sensor with subsurface (Advanced Settings tab -> Pressure sensor offset).

regards,
Matthias

[Tingsten]

Hello Matthias,

thx you for this answer. I tried in subsurface and was able to modify the value. however it failed 3 or 4 time before working... Strangely sometime when i click write this parameters to the device it does it when when i redownload the parameters it was still giving me the old value.

any know issue with that? (or should the unit reboot beforereporting the proper value?

thx you,
Remi

[Tingsten]

Hello Matthias,

I retried today to setup properly pressure and temperature offset and i confirm that with subsurface and HWOS config it isn't possible:

-In subsurface when pressure offset is modified and data is downloaded to the device, the temperature offset is automatically set to pressure offset/10.
for exemple if you put -10mbar as pressure offset, the temperature offset is going to be -1°c
-In HWOS config, it is also not working but i wasn't able to exactly understand what it was reporting....

not sure whether it is a bug from the firmware or the Subsurface and HWOS config softwares. (i have last version of everything).

thx you for your help.

[Rob]

Hi Tingsten,

when you set the Value in HWOSConfig, after klicking the update button, the same value you set is shown?

i.e. if you set +5 in press. sensor offset, after klicking update the +5 is still shown?
If so, the setting of the Value is working.

When you klick on update, the value is set and after that hwosconfig reads the value again from the OSTC.

Regards
Rob

[Tingsten]

Hello Rob and thx you for your help.

Subsurface and HWOS Config are consistent regarding all the parameters (i have tested) but temperature and pressure offset. In this case (10mbar and +1°C reported by subsurface), HWOS Config is reporting 0 for both values....

When i change the value in HWOS it hasn't the expected effect on the value reported by the OSTC (on the screen). Also Subsurface is reporting a different value...

I have an OSTC 3+ with 2.7 firmware. Does it work fine in your case (ie change temp or pressure offset and check the value reported by the OSTC after reboot).

Rémi

[heinrichsweikamp]

Hi,

The hwOS accepts signed 8 bit "two's complement" values for these adjustments. When writing a +10mbar with hwOS config a get a .138 stored in the OSTC where it would accept a .10 for this setting.

This value of 138 is then ignored from the OSTC for being out of range.

So, an incompatibly between the hwOS and the hwOS Config/Subsurface.

Regards,
Matthias

[Rob]

Hi,

the Error is fixed in HWOSConfig.

Please download the latest Version of ostctools from my website.

Regards
Rob

[Tingsten]

HEllo All,

Recently realized that my OSTC3+ was still 10mbar off from the correct athmospheric pressure. Tried to change (via HWOS Config and Subsurface). Both are reading/writting consistent things inside the computer but it doesn't change the value reported by the OSCT on the main screen. Does it take time to change this value or should it change immediatly? If yes what could explain it doesn't change?

Thx you a lot and have a nice weekend all,
Tingste

[Tingsten]

By checking the HWOS code I saw that there is a 30 minute refresh time on this parameter. So the behavior seems normal.

Have nice weekend,
Tingsten

[glance]

FYI: The bug in subsurface was not that it wasn't writing it in "two's complement" , it was actually a copy-paste error, where it wrote pressureSensorOffset instead of tempSensorOffset. The bug fix is released in v4.6.0.