Hi Pedro,
I looked at the HobbyBoards site and I think the humidity sensor is HIH-4000
based.
http://www.hobby-boards.com/catalog/product_info.php?cPath=24&products_id=54
I presume you are reading the HIH4000/humidity property.
My thought is to figure out which value is causing the sprious readings. The
calculation requires
VDD VAD and Temperature.
Possibly putting in a line line:
printf( "%g,%g,%g,%g\n", VAD, VDD, T, OWQ_F(owq) ) ;
before the return statement
File: owfs/module/owlib/src/c/ow_2438.c
Subroutine: FS_HUMID_4000
Line 372
// temperature compensation
temperature_compensation = 1.0546 - 0.00216 * T ;
OWQ_F(owq) = humidity_uncompensated / temperature_compensation ;
+ printf( "%g,%g,%g,%g\n", VAD, VDD, T, OWQ_F(owq) ) ;
return 0;
}
And running owserver in foreground piped to a file.
We'll get a CSV file that is easy to read in any spreadsheet. (Maybe some
fancy gnuplot script would do it too).
The columns will be VAD, VDD, Temperature and Humidity
Plotted out, it should be obvious if the outlier humidity readings
correspond to any outlier voltage or temperature readings.
Perhaps the reading needs a delay for the line to settle.
Paul Alfille
On Thu, Jul 7, 2011 at 7:02 AM, Pedro Côrte-Real <pedro@...> wrote:
> Hi,
>
> I have had a persistent bug reading from owserver that it will
> sometimes give me a very wild read (e.g., 135% humidity) from a sensor
> and then go right back to normal values. I've even built an outlier
> removal function into my saal package. I've had that happen today even
> more. My first thought was that there was something wrong with my
> owserver ruby client library but I did a tcpdump of the
> communications[1] and it seems I am indeed getting these values back
> from owserver. System logs don't show any owserver error messages.
>
> My setup is a USB dongle connected to a hobby boards hub that has 4
> hobby boards humidity+temp sensors attached to 4 ports and a daisy
> chain of other sensors attached to another port. The hub injects power
> so hopefully that's not an issue.
>
> I am doing uncached reads every minute to all the sensors in series.
> Any ideas of what could be wrong?
>
> Pedro
>
> [1] http://scratch.pedrocr.net/owserver.dump.bz2
>
>
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