[weewx-user] Re: SDR & FOWHx080 rain error

[Kalli]

Hallo

Das ist bei mir auch so.
sobalt es regnet .

cu. Kalli

Am Samstag, 11. August 2018 09:56:13 UTC+2 schrieb Gazza:
>
>
> It has just rained for the first time since I got my FOWH3080 clone 
> station working with the SDR FOWHx080 driver and  have just noticed Weewx 
> is showing the wrong value for rain.
>
> The loop data received from the station for rain_total is 0.3 per tip but 
> Weewx is reporting 3mm per tip.
>
> There is a comment in the FOWH1080Packet section of sdr.py about rain 
> being in "mm not cm" but there is nothing obvious in the section for the 
> FOWHx080 that relates to the value per tip.
>
>
> Gary 
>

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[weewx-user] Re: SDR & FOWHx080 rain error

[gjr80]

>
> On Monday, 13 August 2018 16:45:21 UTC+10, Gazza wrote:
>
>
>
> Given all this I think I'll leave the SDR driver alone and add any 
> conversion factors to the "StdCalibrate" section of weewx.conf.
>
>
Exactly what it is there for, saves creating an orphan.

Gary

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[weewx-user] Re: SDR & FOWHx080 rain error

[Gazza]

Thanks for that. 

On further testing I have found the built in plastic rain gauge on my 
station is not very reliable, it works when it tips one way but only 
randomly in the other and no amount of fiddling has improved it. So I have 
modified the station to use a semi commercial rain gauge I currently have 
connected to a stand alone counter.

The gauge is a solid old stainless steel unit with some sort of needle 
bearing arrangement on the tipping bucket but it is setup for points not mm 
or cm so I will need some other fudge factors to get the correct reading.

Given all this I think I'll leave the SDR driver alone and add any 
conversion factors to the "StdCalibrate" section of weewx.conf.


Gary

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[weewx-user] Re: SDR & FOWHx080 rain error

[gjr80]

Hi,

Not a SDR user but having a look at the 3080/x080 parsers it look like the 
x080 parser is taking the parsed rainfall value (presumably in mm) and 
putting it in a record that uses the METRIC unit system 
. Sounds great but the problem 
is that the METRIC unit system uses cm for rainfall units. So the rainfall 
value in mm is being interpreted by WeeWX as cm hence the factor of 10 
error. A couple of solutions come to mind; instead of creating a record 
with the METRIC unit system change it to create a record with a METRICWX 
punit system which does in fact use mm for rainfall, only problem is that 
METRICWX uses different wind speed units so we fix one issue (rainfall) and 
create another (wind speed). The other solution is to simply convert the 
rainfall in mm to cm in the x080 parser. Quite an acceptable approach 
though the name 'x080' indicates to me it is not just for 3080, so if some 
other station using this parser provides rain in cm this solution would 
break the driver for that station station. However, in my limited 
experience I have not seen too many stations whose sensors that natively 
report cm. 

Try making the following change (untested) to sdr.py, circa line 851 change:

pkt['rain_total'] = Packet.get_float(obj, 'rain')

to

_rain_total = Packet.get_float(obj, 'rain')
pkt['rain_total'] = _rain_total / 10 if _rain_total is not None 
else None

You will need to restart WeeWX for the change to take effect. Then wait for 
some rain or cycle your rain gauge with a known number of tips or 'rain'.

Gary

On Saturday, 11 August 2018 17:56:13 UTC+10, Gazza wrote:
>
>
> It has just rained for the first time since I got my FOWH3080 clone 
> station working with the SDR FOWHx080 driver and  have just noticed Weewx 
> is showing the wrong value for rain.
>
> The loop data received from the station for rain_total is 0.3 per tip but 
> Weewx is reporting 3mm per tip.
>
> There is a comment in the FOWH1080Packet section of sdr.py about rain 
> being in "mm not cm" but there is nothing obvious in the section for the 
> FOWHx080 that relates to the value per tip.
>
>
> Gary 
>

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