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Author Topic: Everspring ST814 temperature resolution  (Read 4500 times)

Offline Chris

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Everspring ST814 temperature resolution
« on: September 12, 2011, 05:07:58 pm »
Looking at the manual for the Everspring ST814 temperature/humidity sensor, it shows that the formulae for converting the temperature  should provide a resolution of 0.1 degrees C, but Vera only appears to show/record the resolution of 1 degree. Does anyone know if this can be changed to provide a sub 1 degree resultion?

Thanks
Chris

Offline Ap15e

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Re: Everspring ST814 temperature resolution
« Reply #1 on: September 13, 2011, 12:30:42 pm »
Vera doesn't support floating point data for sensors events. IIRC, MCV has no plans to implement floating point values ("too risky"). I stumbled upon it while implementing DAD: the earthquake magnitude event doesn't work as designed due to this bug.
« Last Edit: September 13, 2011, 05:41:08 pm by Ap15e »

Offline Chris

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Re: Everspring ST814 temperature resolution
« Reply #2 on: September 13, 2011, 12:39:43 pm »
Quote
Vera doesn't support floating point data for sensors. IIRC, MCV has no plans to implement floating point values ("too risky").
Thanks. That's a bit dissapointing since 1 degree resolution on temperature is actually pretty poor.  I'm a bit surprised that MCV don't intend to change this. I'm not sure why floating point is considered risky - it's meant to be the native number format for Lua (although as we know, it's broken due to the use of single precision floats instead of doubles).

Cheers
Chris

Offline Ap15e

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Offline Chris

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Re: Everspring ST814 temperature resolution
« Reply #4 on: September 18, 2011, 07:58:28 am »
On reading this further, this is problem is actually only relevant to events - not for variables in general. I've written a virtual device to display dewpoint and absolute humidity from a temp/humidity sensor, and it displays just fine.

I guess if I try setting an event or notification, it won't work correctly, but at least it is possible to use floats for variables, so it should be possible to display the temperature with a higher precision than 1 degree.

Offline parkerc

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Re: Everspring ST814 temperature resolution
« Reply #5 on: August 21, 2012, 03:21:04 pm »
Hi Chris

I'm looking at getting some of these sensors and would like to see the temperatures displayed down to one decimal point (e.g. 23.1).

You mentioned creating a virtual device to achieve that ? Are you able to share the files for this ?

Offline oTi@

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Re: Everspring ST814 temperature resolution
« Reply #6 on: September 13, 2012, 02:06:46 pm »
You mentioned creating a virtual device to achieve that ? Are you able to share the files for this ?
My guess is, it isn't for the ST814.
Dezwaved at the moment...

Offline Chris

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Re: Everspring ST814 temperature resolution
« Reply #7 on: September 13, 2012, 04:29:08 pm »
I'm looking at getting some of these sensors and would like to see the temperatures displayed down to one decimal point (e.g. 23.1).

You mentioned creating a virtual device to achieve that ? Are you able to share the files for this ?
The virtual device I mentioned was to display abolsute humidity and dew point from the data returned from a temp/humidity sensor. Unfortunately to improve the resolution display of the sensor requires MCV to change the internals of Vera.

Chris

Offline parkerc

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Re: Everspring ST814 temperature resolution
« Reply #8 on: September 19, 2012, 02:03:01 pm »
Thanks All

In the end, to get the accuracy I have gone with Oregon Scientific sensors with the RFXrtx plugin, as these go down to one decimal point, and for a temp/humidity sensor they're much cheaper to

Everspring ST814 = £45.
Oregon Scientific = £25 (£29 for LCD display)

Actually a little bird told me you can get just temperature ones (433mhz) for as little as £8, (€9, $14)
« Last Edit: September 23, 2012, 06:31:01 am by parkerc »