Unable to calibrate barometer in v 3.0.1

[AdamHI]

Hi all,

I've tried debugging this myself for a while, and i'm just not getting it.

Had weewx on my RPi on and off for about 2 years. Under weewx 2.x had a StdCalibrate Correction statement of

barometer = barometer - 0.03

This had always worked well to bring my reported barometric pressure (adjusted for elevation) within 0.01 inHg of the NOAA collection station about 3-4 miles away. (It's at sea level, i'm at 510 ft).

Last month my RPi died, and i replaced it.  I installed weewx 3.0.1 using the python tool, setup.py.

Now, the StdCalibrate correction doesn't seem to do anything. I've even tried really big numbers, wondering if it was using other unit (i kept US), but nothing seems to change what weewx spits out. Yes, i stop/start weewx to make sure it is loading, and have also run from the command line.

I set debug = 1

and here are a few iterations of loop data, including one with RECORD. I added a line between iterations for some ease in reviewing:

LOOP:   2015-01-19 08:49:09 HST (1421693349) {'heatindex': 71.78, 'outHumidity': 94.0, 'ptr': 14160, 'rainRate': 0.0, 'outTempBatteryStatus': 0, 'radiation': None, 'delay': 0, 'inTemp': 75.38, 'windGustDir': None, 'status': 0, 'barometer': 30.11163965582788, 'windchill': 71.78, 'dewpoint': 69.95589440129302, 'rain': 0.0, 'pressure': 29.57471943295925, 'rxCheckPercent': 100, 'rainTotal': 2.94, 'altimeter': 30.116327311912567, 'usUnits': 1, 'inDewpoint': 63.03521260110747, 'UV': None, 'dateTime': 1421693349, 'windDir': None, 'outTemp': 71.78, 'windSpeed': 0.0, 'inHumidity': 74.0, 'windGust': 0.0}

LOOP:   2015-01-19 08:50:09 HST (1421693409) {'heatindex': 71.78, 'outHumidity': 94.0, 'ptr': 14160, 'rainRate': 0.0, 'outTempBatteryStatus': 0, 'radiation': None, 'delay': 1, 'inTemp': 75.38, 'windGustDir': None, 'status': 0, 'barometer': 30.114646610057537, 'windchill': 71.78, 'dewpoint': 69.95589440129302, 'rain': 0.0, 'pressure': 29.57767277023036, 'rxCheckPercent': 100, 'rainTotal': 2.94, 'altimeter': 30.119325093674757, 'usUnits': 1, 'inDewpoint': 63.03521260110747, 'UV': None, 'dateTime': 1421693409, 'windDir': None, 'outTemp': 71.78, 'windSpeed': 0.0, 'inHumidity': 74.0, 'windGust': 0.0}

LOOP:   2015-01-19 08:51:10 HST (1421693470) {'heatindex': 71.78, 'outHumidity': 94.0, 'ptr': 14160, 'rainRate': 0.0, 'outTempBatteryStatus': 0, 'radiation': None, 'delay': 3, 'inTemp': 75.38, 'windGustDir': None, 'status': 0, 'barometer': 30.11163965582788, 'windchill': 71.78, 'dewpoint': 69.95589440129302, 'rain': 0.0, 'pressure': 29.57471943295925, 'rxCheckPercent': 100, 'rainTotal': 2.94, 'altimeter': 30.116327311912567, 'usUnits': 1, 'inDewpoint': 63.03521260110747, 'UV': None, 'dateTime': 1421693470, 'windDir': None, 'outTemp': 71.78, 'windSpeed': 0.0, 'inHumidity': 74.0, 'windGust': 0.0}

REC:    2015-01-19 08:50:00 HST (1421693400) {'outTempBatteryStatus': 0.0, 'outHumidity': 94.0, 'ptr': 14149.333333333334, 'rainRate': 0.0, 'heatindex': 71.65999999999998, 'radiation': None, 'delay': 1.5, 'inDewpoint': 62.919657765977206, 'inTemp': 75.38, 'status': 0.0, 'barometer': 30.111762012760316, 'windchill': 71.65999999999998, 'dewpoint': 69.83682855559749, 'rain': 0.0, 'interval': 5, 'pressure': 29.574719432959252, 'rxCheckPercent': 100.0, 'rainTotal': 2.94, 'altimeter': 30.116327311912567, 'usUnits': 1, 'UV': None, 'dateTime': 1421693400.0, 'windDir': None, 'outTemp': 71.65999999999998, 'windSpeed': 0.0, 'inHumidity': 74.0, 'windGust': 0.0, 'windGustDir': None}

LOOP:   2015-01-19 08:51:14 HST (1421693474) {'heatindex': 71.78, 'outHumidity': 94.0, 'ptr': 14160, 'rainRate': 0.0, 'outTempBatteryStatus': 0, 'radiation': None, 'delay': 3, 'inTemp': 75.38, 'windGustDir': None, 'status': 0, 'barometer': 30.11163965582788, 'windchill': 71.78, 'dewpoint': 69.95589440129302, 'rain': 0.0, 'pressure': 29.57471943295925, 'rxCheckPercent': 100, 'rainTotal': 2.94, 'altimeter': 30.116327311912567, 'usUnits': 1, 'inDewpoint': 63.03521260110747, 'UV': None, 'dateTime': 1421693474, 'windDir': None, 'outTemp': 71.78, 'windSpeed': 0.0, 'inHumidity': 74.0, 'windGust': 0.0}

=========================================================================================

The output onto the pages generated by weewx for the 08:50 report showed a Barometer reading of 30.112

My reads are consistently about 0.03 inHg higher than the readings of NOAA's Water Level Observation Station in Honolulu.

My weewx.conf has:

[StdCalibrate]

    # This section can adjust data using calibration expressions.

    [[Corrections]]

# For each type, an arbitrary calibration expression can be given.

# It should be in the native units of the weather station hardware.

# For example:

# outTemp = outTemp - 0.2

barometer = barometer - 0.03

Any help would be appreciated.

Weather page can be found at 

    http://adamhawaii.com/wx/index.html

Thanks.

--adam

[AdamHI]

Oops, forgot to post that this is a FineOffset WS2090.

--adam

[mwall]

hi adam,

apply the correction to 'pressure' instead of 'barometer'.

one of the changes in weewx v3 was the new StdWXCalculate service - it calculates derived quantities such as wind chill, heat index, and adjusted pressures.

the StdCalibrate service applies calibrations to raw data *before* the StdWXCalculate service runs.

for a fineoffset station, 'barometer' is a derived calculation.  it is calculated from the actual sensor reading, 'pressure', the temperature, 'outTemp', and the altitude.

so in your case, your barometer adjustment is ignored since there is no 'barometer' until StdWXCalculate runs.

note that other station hardware (te923, vantage) report 'barometer', so StdWXCalculate calculates 'pressure' from 'barometer' for those.

m

[AdamHI]

m,

That was it. Working well now - though the correction is painfully obvious in the graphs now - i may consider starting the database fresh. Or maybe not.

Thanks much.

--adam

[Brian Graham]

FWIW... I was facing this same issue with an Acurite 2032C with using v 3.2.1 on a RPi. 

Using 'pressure' instead of 'barometer' to adjust / calibrate / correct the barometer readings from my Acurite 2032C worked perfectly.

Cheers!

~brian