Unit groups pose no limitations on what data can be stored in any database field. All WeeWX numeric fields in the db schemas shipped with WeeWX are of type real so can handle positive and negative numbers. What the unit groups do is set the default formatting and default unit label when the field is used in a WeeWX report tag. The unit group also sets what units the value can be converted to/from. The default formatting and labels associated with a unit group can be (and are) changed by the user either via config file or programatically. Default formatting can be overridden on a tag by tag basis through use of the .format() tag. Unit conversion options available with a given unit group can also be changed (eg more available units added), though this is normally done programmatically and is not something that can be done via tags in reports.
You will find that group_direction and group_angle will both allow you to store your positive/negative angle values; the difference will be in the default formatting, default unit label and available unit conversion options. Since you have positive/negative values I expect you will be, at the very least, wanting to use a format in reports that is different to the default used by both unit groups (refer to my previous post for the default formats). Depending on requirements this might be as simple as using the .format() tag in reports. Sorry if I seem to be belabouring the point, but I think it important to be clear that unit groups have no effect on what/how data is stored in the database; unit groups only affect the presentation of data. If it was me I would be use group_angle , mainly because the unit group name is a better fit and the availability of conversion to radians if required. I would use either .format() to change tag formatting in reports or override the default formatting in skin.conf/weewx.conf if I frequently use the field in tags. Gary On Monday, 25 September 2023 at 05:46:48 UTC+10 [email protected] wrote: > Because tilt can be a negative number I think we have to rule out > group_direction which I think has a range of 0 to 360. Not sure about > group_angle, do you know if it allows for positive and negative angles? > > Craig > > On Saturday, September 23, 2023 at 6:30:28 PM UTC+12 gjr80 wrote: > >> Remember, unit groups are for picking an appropriate unit for a >> field/observation (including allowing for conversion between applicable >> units) and providing a suitable format and label. Your description brings >> to mind two possible suitable unit groups; group_direction and >> group_angle. Both of these unit groups support fields/observations in >> degrees (degree_compass for group_direction and degree_angle for >> group_angle. Both provide (default) unit labels of the degree symbol, >> both offer similar (default) formats (%03.0f v %02.0f). group_angle >> facilitates unit conversion between degrees and radians, which may or may >> not be something you use now or in the future, group_direction does not >> support this conversion. >> >> We tend to re-use unit groups where we can, only creating new unit groups >> where there is no other suitable unit group. Remember, default unit group >> formats and labels are only defaults and can be altered or overridden in a >> tag using .format() (eg for tilt you might want to always display a sign >> and format to one decimal place so you might decide to alter the default or >> override the default format using .format() with the format string ' >> %+02.1'). >> >> Gary >> On Saturday, 23 September 2023 at 14:40:36 UTC+10 [email protected] >> wrote: >> >>> Signal4 and Signal 5 are sensor tilt measurements in degrees. For >>> example, if the sensor is tilted 1.5 degrees in the N/S direction the value >>> for Signal4 = 1.5 degrees. Looking at units.py and defaults.py I see >>> groups for degrees temperature, degrees direction, but not degrees tilt. >>> Should a new group "group-tilt" be added through the driver or should this >>> be added to weewx files to be made available to everyone? >>> >>> On Saturday, September 23, 2023 at 4:06:25 PM UTC+12 Craig Young wrote: >>> >>>> I will add the assignments in the driver. >>>> >>>> On Saturday, September 23, 2023 at 12:38:22 PM UTC+12 Tom Keffer wrote: >>>> >>>>> Good advice! >>>>> >>>>> On Fri, Sep 22, 2023 at 5:35 PM gjr80 <[email protected]> wrote: >>>>> >>>>>> The other other variation on Tom's advice to use extensions.py, >>>>>> particularly if you are (still keen on) writing your own driver, is to >>>>>> include the unit group assignments in the driver file. They statements >>>>>> only >>>>>> need to be somewhere where they are executed each time WeeWX starts. If >>>>>> the >>>>>> fields are inextricably linked to the driver having everything in one >>>>>> place >>>>>> can be of benefit. I've used this approach with some of the drivers I >>>>>> have >>>>>> written. >>>>>> >>>>>> Gary >>>>>> >>>>>> On Saturday, 23 September 2023 at 10:11:16 UTC+10 [email protected] >>>>>> wrote: >>>>>> >>>>>>> Exactly. >>>>>>> >>>>>>> Or, alternatively, you can assign them to appropriate unit groups >>>>>>> <http://www.weewx.com/docs/customizing.htm#Assigning_a_unit_group> >>>>>>> in the file user/extensions.py: >>>>>>> >>>>>>> *import weewx.units* >>>>>>> >>>>>>> *weewx.units.obs_group_dict['signal1'] = 'group_radiation'* >>>>>>> *weewx.units.obs_group_dict['signal2'] = 'group_temperature'* >>>>>>> *weewx.units.obs_group_dict['signal3'] = 'group_radiation'* >>>>>>> >>>>>>> >>>>>>> Then you would not need to specify a format and label. It would also >>>>>>> allow you to do things like >>>>>>> >>>>>>> *The temperature is $current.signal2.degree_C >>>>>>> ($current.signal2.degree_F)* >>>>>>> >>>>>>> >>>>>>> to publish the temperature in both ºC and ºF. >>>>>>> >>>>>>> -tk >>>>>>> >>>>>>> On Fri, Sep 22, 2023 at 4:38 PM Craig Young <[email protected]> >>>>>>> wrote: >>>>>>> >>>>>>>> Thanks Tom. Signal1 for my station is the signal voltage from a >>>>>>>> pyrgometer. Signal2 is the temperature of the pyrgometer sensor (C) >>>>>>>> and >>>>>>>> Signal3 is the long wave intensity (W/m2) calculated by the >>>>>>>> datalogger. So >>>>>>>> if I understand correctly, the weewx engine will pass these values >>>>>>>> untouched through the various services and add to the DB as real >>>>>>>> numbers. >>>>>>>> I can then deal with them manually when creating the report. >>>>>>>> >>>>>>>> On Saturday, September 23, 2023 at 11:00:54 AM UTC+12 Tom Keffer >>>>>>>> wrote: >>>>>>>> >>>>>>>>> Signals are for ill-defined measurements. >>>>>>>>> >>>>>>>>> Unit groups exist for two reasons: >>>>>>>>> >>>>>>>>> 1. To pick an appropriate unit for a type of measurement. For >>>>>>>>> example, ºC for temperatures. >>>>>>>>> 2. To pick an appropriate format and label. >>>>>>>>> >>>>>>>>> Signals don't fit neatly into these reasons. They don't take a >>>>>>>>> unit, and it's not obvious what format and what label they should >>>>>>>>> use. So, >>>>>>>>> they were left out of units.py and defaults.py. >>>>>>>>> >>>>>>>>> You can use the signal types without adding them to a unit group. >>>>>>>>> You just won't be able to convert them to a different unit (which >>>>>>>>> they >>>>>>>>> don't have anyway), and there will be no automatic formatting and >>>>>>>>> labelling. If you need a format, use a .format() suffix. If you need >>>>>>>>> a >>>>>>>>> format, just add it on. For example: >>>>>>>>> >>>>>>>>> *$current.signal1.format("%d") widgets* >>>>>>>>> >>>>>>>>> >>>>>>>>> Alternatively, if your signal is actually some kind of counter, >>>>>>>>> you could assign them to group_count. Then they would use "%d" for >>>>>>>>> the >>>>>>>>> format, and an empty string for the label. >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> On Fri, Sep 22, 2023 at 3:22 PM Craig Young <[email protected]> >>>>>>>>> wrote: >>>>>>>>> >>>>>>>>>> In the wview_extended.py schema there is a group of types for >>>>>>>>>> signals (signal1, signal2, .. signal8) and stored in the DB as >>>>>>>>>> reals. I >>>>>>>>>> looked in units.py but did not see signals listed. >>>>>>>>>> >>>>>>>>>> On Saturday, September 23, 2023 at 9:40:17 AM UTC+12 Craig Young >>>>>>>>>> wrote: >>>>>>>>>> >>>>>>>>>>> What units group do the observation type Signals fall under? >>>>>>>>>>> Or, if I use a signal do I need to update a configuration file to >>>>>>>>>>> place it >>>>>>>>>>> into a units group. >>>>>>>>>>> >>>>>>>>>> -- >>>>>>>>>> You received this message because you are subscribed to the >>>>>>>>>> Google Groups "weewx-user" group. >>>>>>>>>> To unsubscribe from this group and stop receiving emails from it, >>>>>>>>>> send an email to [email protected]. >>>>>>>>>> To view this discussion on the web visit >>>>>>>>>> https://groups.google.com/d/msgid/weewx-user/b9fa5024-38c9-4d95-8e4b-5c9bb4f0ddb8n%40googlegroups.com >>>>>>>>>> >>>>>>>>>> <https://groups.google.com/d/msgid/weewx-user/b9fa5024-38c9-4d95-8e4b-5c9bb4f0ddb8n%40googlegroups.com?utm_medium=email&utm_source=footer> >>>>>>>>>> . >>>>>>>>>> >>>>>>>>> -- >>>>>>>> You received this message because you are subscribed to the Google >>>>>>>> Groups "weewx-user" group. >>>>>>>> To unsubscribe from this group and stop receiving emails from it, >>>>>>>> send an email to [email protected]. >>>>>>>> >>>>>>> To view this discussion on the web visit >>>>>>>> https://groups.google.com/d/msgid/weewx-user/2dd9fe34-ffde-4e8f-aaf6-b205009b76a7n%40googlegroups.com >>>>>>>> >>>>>>>> <https://groups.google.com/d/msgid/weewx-user/2dd9fe34-ffde-4e8f-aaf6-b205009b76a7n%40googlegroups.com?utm_medium=email&utm_source=footer> >>>>>>>> . >>>>>>>> >>>>>>> -- >>>>>> You received this message because you are subscribed to the Google >>>>>> Groups "weewx-user" group. >>>>>> To unsubscribe from this group and stop receiving emails from it, >>>>>> send an email to [email protected]. >>>>>> >>>>> To view this discussion on the web visit >>>>>> https://groups.google.com/d/msgid/weewx-user/bfef0c77-5e59-4d78-b1a8-f557b0dddaa6n%40googlegroups.com >>>>>> >>>>>> <https://groups.google.com/d/msgid/weewx-user/bfef0c77-5e59-4d78-b1a8-f557b0dddaa6n%40googlegroups.com?utm_medium=email&utm_source=footer> >>>>>> . >>>>>> >>>>> -- You received this message because you are subscribed to the Google Groups "weewx-user" group. 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