Bluebuddy Temperature Calibration

[BFRedrocks]

Hi Guys,

I took my Bluebuddy out for a couple of night dives tonight and noticed that the temperature recorded by the Bluebuddy is not consistent with mine or my dive buddy's computer. I dove with two computers (a new Petrel 2 and a Suunto Vyper Air) and both recorded minimum temperatures of 61 degrees and 67 degrees, respectively. However, for the same dives, the Bluebuddy recorded minimum temperatures of 58 and 64 degrees, respectively. Based on those dives, the Bluebuddy appears to be off by -3 degrees, consistently. I have noticed this with other dives as well, where the Bluebuddy is consistently "colder" than my dive computer (and my dive partner's computer). Is it possible that the unit is out of calibration or there is something wrong with the temperature sensor? I just want the Bluebuddy to record similar data to my computers.

Thanks!

 

[DiveNav]

Most of the dive computers in the market use a pressure / depth sensor made by the same company that we use.
The temperature accuracy of the sensor used in bluebuddy is +/- 1.4F, so a difference of 2.8F between 2 different devices that use the same sensor is within the specs.

The other factors that can influence temperature reading are the thermal resistivity and the thermal hysteresis of the overall system and the location of the unit.

In general a dive computer consumes way more power (and generates more heat) and has a bigger hysteresis of our sensor.

 

[RJP]

The temperature accuracy of the sensor used in bluebuddy is +/- 1.4F, so a difference of 2.8F between 2 different devices that use the same sensor is within the specs.

Watch collectors have a saying:

A man with one watch knows exactly what time it is. A man with two watches is never really sure.

 

[BFRedrocks]

The temperature accuracy of the sensor used in bluebuddy is +/- 1.4F, so a difference of 2.8F between 2 different devices that use the same sensor is within the specs.

In general a dive computer consumes way more power (and generates more heat) and has a bigger hysteresis of our sensor.

Technically that is true, but one device has to be -1.4F consistently and one has to be +1.4F consistently for the devices to be off by 2.8F, consistently. Not really the intent of the +/- designation, but still "technically" within the spec.

Based on your last sentence then, would you say (forgetting for a second which device you make) that the BB is more accurate with regards to the actual water temperature than a dive computer because it generates less internal heat?

Being a scientist, I'm always interested in the most accurate data.

Thanks!

 

[DiveNav]

....Being a scientist, I'm always interested in the most accurate data.....

Being an engineer I like to calculate / measure things ....

.... would you say (forgetting for a second which device you make) that the BB is more accurate with regards to the actual water temperature than a dive computer because it generates less internal heat?....

What I am saying is that
IF 2 devices use the same pressure/temperature sensor and the same filtering/calibration algorithm (as recommended by the manufacturer of such pressure/temperature sensor),
THEN, the device that generates less internal heat should be more accurate.

Having said that, the only way to know for sure is to perform a thermal analysis of each system (location of the heat sources, power consumption, location of the sensor, thermal resistance (water/sensor and sensor/heat sources) ....).

Lastly, precision thermometers have the sensor far away from the electronics ...