weewx vantage pressure calculation null every day, twice a day during a short period

[Rodrigo Scuissiato]

Hi, 

two times a day, the pressure from mu davis vantage vue is beeing calculated as null

here is the mysql archive:

MariaDB [weewx]> select from_unixtime(datetime),barometer,pressure,altimeter from archive order by datetime desc limit 50;
+-------------------------+--------------------+--------------------+--------------------+
| from_unixtime(datetime) | barometer          | pressure           | altimeter          |
+-------------------------+--------------------+--------------------+--------------------+

| 2023-04-27 18:36:00     |             30.035 |               NULL |               NULL |
| 2023-04-27 18:35:00     |             30.035 |               NULL |               NULL |
| 2023-04-27 18:34:00     |             30.034 |               NULL |               NULL |
| 2023-04-27 18:33:00     |             30.034 |  26.58821997477311 | 30.160739007773113 |
| 2023-04-27 18:32:00     |             30.034 | 26.588551871590237 | 30.161106590655088 |

it happens every day near down and dusk

i couldnt find anything in the logs

wee_device --current is reading the barometer OK

[gjr80]

To understand what could be going wrong you need to understand how WeeWX obtains the three pressure values. For Davis stations the vantage driver emits WeeWX field barometer and WeeWX then calculates pressure and altitude. pressure is calculated first using values for barometer, outTemp and outHumidity as well as outTemp 12 hours ago. If any of these values do not exist pressure is not calculated. WeeWX then calculates altimeter using the just calculated pressure value and station altitude. If either of theses values do not exist then altitude is not calculated.

Given that you have no missing barometer data it is quite possible the lack of pressure and altimeter is due to missing outTemp or outHumidity. If both outTemp and outHumidity are present it could be missing outTemp from 12 hours ago. Try adding outTemp and outHumidity to your query, if both fields are present look at outTemp 12 hours (or 43200 seconds) ago.

Hopefully this should reveal the final part of the reason why pressure and altimeter are not being calculated, but it won't show the underlying cause. I cannot think of a reason why any of the obs concerned 'disappear' at/near sun rise/set. Is this repeatable, ie happens every day or is it sporadic? If every day then try stopping the WeeWX daemon and run WeeWX directly before sunset and observe the loop packets (LOOP: lines) and archive records (REC: lines) on the console and see what obs disappear when. 

You do have a very short archive interval of one minute, though your station should be emitting loop packets every two odd seconds so WeeWX should be seeing multiple loop packets each archive period. On top of that each loop packet should contain outTemp, outHumidity and barometer (unlike some stations that do not include all obs in each loop packet). So whilst short, I don't think your archive interval is contributing to the problem.

Gary

[Rodrigo Scuissiato]

Hi,

YES, I'm not receiving the outTemp and outHumidity , so as you said, that's why pressure and altimeter is not being calculated.

Now I have to investigate why these sensors are not working.

Thank you for your help

+-------------------------+--------------------+--------------------+--------------------+-------------------+
| from_unixtime(datetime) | barometer| pressure  | altimeter  | outTemp | outHumidity |
+-------------------------+--------------------+--------------------+--------------------+-------------------+
| 2023-04-28 13:23:00     | 30.059 |  26.58 | 30.15 |  60.6 |  88 |
| 2023-04-28 13:22:00     | 30.06 | 26.58 | 30.16| 60.7 | 89 |

...

| 2023-04-28 10:44:00     | 30.014 |  NULL |  NULL |  NULL | NULL |
| 2023-04-28 10:43:00     | 30.01 |  NULL |  NULL |   NULL | NULL |

...

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[Rodrigo Scuissiato]

for some reason, is not working again