can not get weewx to process this formula

[Mks Mk]

we want to improve the accuracy of our home energy monitor and we added new sensor to read the main line voltage so we got two sensors and the data is logged in weewx database.

    [[sensor_map]]

        ampere = current.***.EfPacket
        linevoltage = payload5.*****.RadioHeadASKPacket

the database have these columns which we created

consumption
ampere
linevoltage
pf

we want to calculate the energy consumption so we added this correction

[StdCalibrate]

    [[Corrections]]
        # For each type, an arbitrary calibration expression can be given.
        # It should be in the units defined in the StdConvert section.
        # Example:
        foo = foo + 0.2
pf = 0.88
        consumption = ((ampere * linevoltage) /1000) * pf

unfortunately weewx did nothing nor it complained about it. can weewx process such formula?

thanks

[Tom Keffer]

The only symbols that can be used in the [[Corrections]] formula are other types in the archive record. So unless 'ampere', 'linevoltage', and 'pf' all appear in the record, the correction will not work.

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[Mks Mk]

Hi Tom

we run weewx directly and found that 'ampere' & 'linevoltage' are in different loop because the data are coming from two different sensors by sdr.py driver.
how we can combine these loops into one so weewx can process this formula, or what can we do to get this calculation done.?

Thank you for your support

[gjr80]

So what does

consumption = ((ampere * linevoltage) /1000) * 0.88

do?

Gary

[Tom Keffer]

Even if all types don't appear in the LOOP packets, they should all be appearing in the archive records. Run weewxd directly from the command line and see exactly what's in the archive record.

I apologize that the error diagnostics for [[Corrections]] are pretty crappy. Still, is there anything in the log?

Your other option is to write a weewx service that caches values.

To view this discussion on the web visit https://groups.google.com/d/msgid/weewx-user/43ebabf0-db3e-4715-99a8-14f1ac7927f8n%40googlegroups.com.

[Mks Mk]

Hi Gary

it all started here

https://groups.google.com/g/weewx-user/c/ltOVkcY1fKc/m/7sQSVGN_AQAJ

we were using fixed value for the incoming grid line to calculate the consumption but it was not accurate enough so we added new sensor to read the grid incoming line voltage.

earlier this formula worked consumption = ampere * 117 / 1000 * 0.88

but  consumption = ampere * linevoltage / 1000 * 0.88 did not work

the linevoltage input comes from different sensor than ampere,  these two reading are generated in different loops, so based on Tom advice the weewx correction will not work

thank you

[Mks Mk]

from database

dateTime usUnits interval consumption          ampere                linevoltage      pf
1697583060 1            1                        90.84233333          141           0.9
1697583120 1            1                        110.3686667          141           0.9
1697583180 1            1                        77.51766667          140.5           0.9
1697583240 1            1                        101.4843333          141           0.9
1697583300 1            1                        100.0026667          141           0.9
1697583360 1            1                        4.977666667          141           0.9
1697583420 1            1                        4.907666667   142           0.9
1697583480 1            1                        4.927666667   141.5           0.9
1697583540 1            1                        4.886          141.3333333   0.9
1697583600 1            1                        4.867666667          141            0.9
1697583660 1            1                        4.877666667          141            0.9
1697583720 1            1                        78.94533333          141            0.9
1697583780 1            1                        90.26166667          140.6666667     0.9

[Tom Keffer]

Just had a thought. 

I assume that weewxd is using software record generation. Check in the log. If so, [[Corrections]] does not apply the corrections to archive records because, in theory, the correction should have already been applied in the LOOP packets. Obviously that's not happening here.

I've created issue #895 to track.

In the meantime, what you can do is create a simple service to do the calculation. It would look something like this (NOT TESTED):

from weewx.engine import StdService

class Power(StdService):

  def __init__(self, engine, config_dict):

    super(Power, self).__init__(engine, config_dict)

    self.bind(weewx.NEW_ARCHIVE_RECORD, self.new_archive_record)

  def new_archive_record(self, event)

    ampere = event.record.get('ampere')

    linevoltage = event.record.get('linevoltage')

    if ampere is not None and linevoltage is not None:

      event.record['consumption'] = ampere * linevoltage

    else:

      event.record['consumption'] = None

This will work provided that linevoltage and ampere do not vary too much over the archive interval. Because you are using short intervals (60 seconds), this is probably not much of a problem.

    

To view this discussion on the web visit https://groups.google.com/d/msgid/weewx-user/fa342793-222a-4773-9bde-5bf97cf88dddn%40googlegroups.com.

[Mks Mk]

there is nothing in the log file related to the correction

we tried the service but it failed twice

1st run failed with error:

Oct 18 06:37:20 debian weewx[3413] CRITICAL __main__:     ****    File "/usr/share/weewx/user/myservice.py", line 10
Oct 18 06:37:20 debian weewx[3413] CRITICAL __main__:     ****      def new_archive_record(self, event)
Oct 18 06:37:20 debian weewx[3413] CRITICAL __main__:     ****                                         ^
Oct 18 06:37:20 debian weewx[3413] CRITICAL __main__:     ****  SyntaxError: invalid syntax
Oct 18 06:37:20 debian weewx[3413] CRITICAL __main__:     ****  Exiting.

changed to

def new_archive_record(self, event):

run weewx again but failed with error


Oct 18 06:42:20 debian weewx[3603] CRITICAL __main__:     ****    File "/usr/share/weewx/weewxd", line 148, in main
Oct 18 06:42:20 debian weewx[3603] CRITICAL __main__:     ****      engine = weewx.engine.StdEngine(config_dict)
Oct 18 06:42:20 debian weewx[3603] CRITICAL __main__:     ****    File "/usr/share/weewx/weewx/engine.py", line 93, in __init__
Oct 18 06:42:20 debian weewx[3603] CRITICAL __main__:     ****      self.loadServices(config_dict)
Oct 18 06:42:20 debian weewx[3603] CRITICAL __main__:     ****    File "/usr/share/weewx/weewx/engine.py", line 161, in loadServices
Oct 18 06:42:20 debian weewx[3603] CRITICAL __main__:     ****      obj = weeutil.weeutil.get_object(svc)(self, config_dict)
Oct 18 06:42:20 debian weewx[3603] CRITICAL __main__:     ****    File "/usr/share/weewx/user/myservice.py", line 8, in __init__
Oct 18 06:42:20 debian weewx[3603] CRITICAL __main__:     ****      self.bind(weewx.NEW_ARCHIVE_RECORD, self.new_archive_record)
Oct 18 06:42:20 debian weewx[3603] CRITICAL __main__:     ****  NameError: name 'weewx' is not defined
Oct 18 06:42:20 debian weewx[3603] CRITICAL __main__:     ****  Exiting.

[Mks Mk]

added import weewx to the top of file

it worked

[Mks Mk]

Thank you Tom

the service file is doing exactly what we needed.

GOD bless you

[Tom Keffer]

Final note on this: Commit a978796 allows one to apply corrections to only archive records, even if they came from software. So, you could do

 [[Corrections]]

pf = 0.88
        consumption = ((ampere * linevoltage) /1000) * pf, archive

This is not precisely what you want, because it is applying the expression to the product of the average amperage times the average linevoltage, but it would get you close.

-tk