check the checksum statistics and check if you have short circuits bad
checksums and others problems
2013/11/5 Jan Kandziora <[email protected]>
> 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
>
>
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--
Roberto Spadim
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