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Davis Extra Sensor Resolution - Really 0.6oC??

Posted: Tue 23 Dec 2014 12:08 pm
by Smithee
A quick question just to check i am not losing my mind - I have a Davis Extra Sensor plugged into my Cumulus set up and sending data to highcharts:

http://www.casa.ucl.ac.uk/cumulus/daygraph.htm

It seems to jump in 0.6oC units rather than the 0.1 i assumed - is this a limitation of the extra sensor? If so it seems a bit poor for a $180 bit of kit, our Netamo seems more accurate at the moment as a second sensor.

So just checking its a hardware limitation - if it is then does anyone have any recommendations for an better additional sensor i could run alongside within Cumulus?

Andy

Re: Davis Extra Sensor Resolution - Really 0.6oC??

Posted: Tue 23 Dec 2014 12:30 pm
by mcrossley
I think the extra sensor resolution is 1°F iirc.

Re: Davis Extra Sensor Resolution - Really 0.6oC??

Posted: Tue 23 Dec 2014 1:11 pm
by steve
AIUI, the sensor actually measures to 0.1F resolution, but the values are rounded to 1 degree F for the serial protocol between console and PC.

Re: Davis Extra Sensor Resolution - Really 0.6oC??

Posted: Tue 23 Dec 2014 4:41 pm
by prodata
steve wrote:AIUI, the sensor actually measures to 0.1F resolution, but the values are rounded to 1 degree F for the serial protocol between console and PC.
Yes indeed. In a little more detail: The sensor transmitter transmits temp data to 0.1F resolution, as you can verify if you pick up the transmitted data on an Envoy8X console (or a MeteoStick IIRC or even on a regular console with that transmitter being received as an ISS rather than a Temp station).

But if the receiving channel on a regular console has the transmitter assigned as Temp or Temp/Hum then the values stored and forwarded are limited to single byte values, hence integer degF values (remembering that all Davis internal temp values are stored as degF).