Am 05.11.2013 18:35, schrieb Jeff Siddall:
>
> The logging is supposed to happen every minute so any minutes with no
> logs means the temperature data was invalid (probably null). But then
> there are readings like these three:
>
> 2013-11-05 04:41:10 ,Basement Fridge Thermometer, 85
> 2013-11-05 04:42:10 ,Basement Fridge Thermometer, 46.125
> 2013-11-05 04:43:10 ,Basement Fridge Thermometer, 7.4375
>
> I know for certain there is no way the temperature inside the fridge
> went from 85 C to 7 C in two minutes!
>
> So what is going on here?
>
85°C is the power-on value the device reports when there has been no
conversion done yet. As owfs inserts a sufficient delay after triggering
a conversion, a reading of 85°C usually means the device has been reset
during the conversion (usually because a lack of power).
May I guess these are "cooked" readings which are a median between a
number of adjacent raw readings? That would explain why there is
46.125°C in the log.
Power the sensors, check your cabling, use a thicker GND wire. 85°C
redings should go away. In your application, you may count it as a
problem indicator (note 85°C is *not* an error value!).
For other applications where 85°C may be a valid readout, I once posted
a way to tell the valid value away from the POR case:
* don't do 12-Bit conversions. This is the default in EEPROM, so it acts
as our POR flag.
a) do a 9, 10 or 11 bit conversion.
b) check the value returned
c) !=85 -> valid reading, return temperature
otherwise check further:
d) read scratchpad
c) byte 4 != 0x7f -> no POR -> valid reading, return temperature
otherwise
e) Power-On-Condition, need to repeat conversion.
If you really *need* to do 12-Bit conversions, you'll have to change the
default configuration register value in the EEPROM. There is currently
no way to do this with owfs, bus we could change that.
Kind regards
Jan
------------------------------------------------------------------------------
November Webinars for C, C++, Fortran Developers
Accelerate application performance with scalable programming models. Explore
techniques for threading, error checking, porting, and tuning. Get the most
from the latest Intel processors and coprocessors. See abstracts and register
http://pubads.g.doubleclick.net/gampad/clk?id=60136231&iu=/4140/ostg.clktrk
_______________________________________________
Owfs-developers mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/owfs-developers
