In the past I have had a feeling my Fine Offset weather station has not been recording all of our rainfall. Then when we had a storm today, my weather station recorded about 5mm less than my manual weather gauge so I knew I’d better look into it. I knew that the weewx software had limits set for various readings to eliminate spurious readings so I thought I’d start there. I couldn’t find anything that made sense though.

Time for Google! I eventually found an obscure reference to max_rain_rate in the file fousb.py having a maximum rate to stop strange readings which the Fine Offset stations are apparently prone to. The default is 24cm/hr so any rainfall over this is ignored.

All of my data for the day was still in the console so I disconnected it from the Raspberry Pi and plugged it into a Cumulus setup on my laptop and downloaded the data. I found one entry at a rate of 288mm/hr or 28.8cm/hour. This started to make sense. Obviously the location the weewx software is written doesn’t experience the downpours SE Qld is prone to in our summer storms. A bit more googling  and checking out the comments in fousb.py and I had the answer. I had to enter some code in the setup file weewx.conf to override the default.

##############################################################################

[FineOffsetUSB]
    # This section is for the Fine Offset series of weather stations.
    
    # The station model, e.g., WH1080, WS1090, WS2080, WH3081
    model = WH1080
    
    # The polling mode can be PERIODIC or ADAPTIVE
    polling_mode = PERIODIC
    
    # How often to poll the station for data, in seconds
    polling_interval = 60
    
    # The pressure calibration offset, in hPa (millibars)
    pressure_offset = 0
	
	max_rain_rate = 36 # cm/hr, default is 24, changed because heavy rain not being measured.
    
    # The driver to use:
    driver = weewx.drivers.fousb

##############################################################################