Am 04.12.2016 um 12:07 schrieb Martin Patzak (GMX):
>
> I am experiencing delays and also time-outs when reading temperatures of
> very very close to and equal to 85 degrees Celsius.
>
This is a complicated situation as 85°C is the default power-up value
the sensor uses. When you have power failures during the conversion, you
cannot tell it apart from a valid 85°C reading.
>
> I have 25 DS18B20, which are powered.
>
That's good, as the most problems arise from supplying insufficient
parasite power (aka 4.7k pullup to 3.3V)
> My application is a heating system, where a wood burning oven heats up
> two 800l buffer containers of water to a max temperature of 95 degree
> Celsius.
>
> Every 30s simultaneous is written, followed by a two second wait, before
> starting reading back the temperatures sequentially.
>
Please update to owfs-3.1p4. It has a new "latesttemp" node, which is
meant for exactly this setup. Trigger simulatenous/temperature, wait a
second in your user program, then read all the temperature values
sampled from the "latesttemp" node.
>
> I am aware that the 18S20 did report an error with 85 deg C, but the
> 18B20 should not do this.
>
> Is there something in owfs that would re-read in case a value of exactly
> 85 deg C would be returned by a sensor?
>
Yes, there is a try-again-mechanism when you read the "temperature" and
"temperatureXX" nodes. Update and use "latesttemp" instead.
Please see the updated manpages, too.
Kind regards
Jan
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