Hi Ashley,
I think you presented your station already in 2006 in the weewx group
The relevant portion of your station for the weewx context here are two
pieces:
the legacy WH25 indoor T&HP sensor (nowadays WN32P) and the Fine Offset
WH2600 LAN gateway also known as observer IP.
The pressure readings come from the WH25 sensor and the WH2600 sends the
absolute pressure in inHg via the custom server string (which the
interceptor driver intercepts and evaluates).
The WH2600 cannot post any relative pressure unless you calibrated it
before providing a local pressure/sea level pressure offset. Default
value is zero.
The value you enter depends on your unit system configured in the
console (WH2600, the black box).
When you set both offsets to zero on the "Calibration" page by the help
of the "Weather Logger" software, the value provided via baromin should
be your local pressure, station pressure, what your WH25 reads at its
position. By entering e.g. a value like "22" into the relative pressure
offset field (and not forgetting to save) will give you the answer which
value is sent via the custom server string: abs or rel. - if rel. it
should adopt the 22 change for the baromin value. Even if you think you
know, no harm in testing that. 😉
The way the interceptor driver is programmed it looks as if it knows how
an ObserverIP module sends data.
If only rel pressure is provided, then the weewx.conf settings in
[StdWXCalculate] should be like below
[StdWXCalculate]
[[Calculations]]
# How to calculate derived quantities. Possible values are:
# hardware - use the value provided by hardware
# software - use the value calculated by weewx
# prefer_hardware - use value provide by hardware if available,
# otherwise use value calculated by weewx
pressure = software
barometer = prefer_hardware
barometer is the supposed to be relative or sea level pressure value =>
take what the interceptor driver provides (console provides rel pressure
only)
pressure is the station pressure which is not provided and weewx has to
re-calculate (pressure = software) from the relative pressure, the
station altitude (=barometer=WH25 altitude) and the temperature
HOWEVER, to have the ObserverIP post the proper relative pressure, you
have to calculate your offset and enter it into the relative pressure
offset field.
You can use https://www.starpath.com/barometers/baro_cal.php
<https://www.starpath.com/barometers/baro_cal.php>
Make sure you are using the proper units - and the
altitude asked for is the height of your WH25 above ground plus the
ground elevation
https://meshka.eu/Ecowitt/dokuwiki/lib/exe/detail.php?id=start&media=altitude-elevation-height.jpg
in the picture the airplane corresponds to your WH25.
A potential issue may be that the interceptor driver (interceptor.py)
asks in line 1391
--- code start ---
if fw == 'WH2600GEN_V2.2.5' or fw == 'WH2650A_V1.2.1':
--- code end ----
as you are running firmware 2.2.8, you may need to change that line to
--- code start ---
if fw == 'WH2600GEN_V2.2.5' or fw == 'WH2650A_V1.2.1' or fw ==
'WH2600GEN_V2.2.8':
--- code end ----
as the driver only asks for 2.2.5
good luck
On 14.11.2024 16:33, [email protected] wrote:
Oops..sorry just saw that you already did the firmware update. I would
try Aercus support and troubleshoot the receiver for
power/disappearing/random changing settings.
On Monday, November 11, 2024 at 12:59:18 PM UTC-5 Ashley Hinton wrote:
Thanks for your reply.
The station is a weathersleuth professional, apologies I should
have been clearer. When I bought it I figured because of weewx I
didn't need, or want, an indoor screen.
https://www.aercusinstruments.com/aercus-instruments-weathersleuth-professional-ip-weather-station-with-direct-real-time-internet-monitoring/
Setting the station:
Absolute pressure offset = 0
Relative pressure offset = 0
The LCD screen in the barometer transmitter is showing the same
value as both absolute & relative pressure on the live data webpage.
If I stop weewx and listen for the data on the relevant tcp/ip
port this is what the station sends:
sudo nc -l 7890
GET
/weatherstation/updateweatherstation.php?ID=***&PASSWORD=***&tempf=53.6&humidity=76&dewptf=46.2&windchillf=53.6&winddir=31&windspeedmph=0.00&windgustmph=0.00&rainin=0.00&dailyrainin=0.00&weeklyrainin=0.00&monthlyrainin=0.00&yearlyrainin=29.46&solarradiation=110.48&UV=0&indoortempf=67.3&indoorhumidity=61/&baromin=30.59/&dateutc=now&softwaretype=WH2600%20V2.2.8&action=updateraw&realtime=1&rtfreq=5
HTTP/1.0
The /baromin/ value is the relative pressure. It doesn't send any
other pressure values.
If I offset in hardware it works and weewx reports barometer
correctly compared to local reliable sources but it doesn't
(always!) survive a power outage. Whats worse is the relative
offset doesn't even stay defaulted to 0 - give it a few minutes
and it does its own thing, literally a random minus value based on
no other setting I can find, unless I manually change the offset
value again but it only stays until it loses power.
My thoughts were to map /baromin /(relative pressure) from the
station to /pressure /in weewx, leave the station relative
pressure offset at zero and let weewx calculate barometer as you
suggest, of course double checking the altitude value in
weewx.conf is correct. Now I know it won't work after a power cut,
and I suspect even if I manually set zero offset and kill the
power it will initially return with zero and then change to a
random value.
Station firmware is up to date - v2.2.8 is the last available.
However I'm starting to think I could get the pressure reading
from elsewhere. I'm running an Arduino in the greenhouse which is
providing some extra sensor data picked up by weewx using the
Weewx MQTT Subscribe extension.
Adding a barometric sensor to the Arduino should be pretty easy,
mapping its output to /pressure /in weewx.
Either that or read the station live data webpage into weewx but
it seems a lot of hassle compared to a buying a relatively cheap
sensor. The one I've just looked at claims an accuracy of 0.01mbar.
Maybe that's the solution - map an incoming MQTT topic
"greenhouse/absolutepressure" to pressure in weewx.
[[[greenhouse/absolutepressure]]] #mqtt topic sent from Arduino
name = pressure #weewx database table
.. and under
[[Calculations]]
Change /prefer_hardware/ in the following entries to:
pressure = hardware
altimeter = software
barometer = software
Which I think would ignore the station relative pressure
(barometer) and since its not sending absolute pressure anyway I
need not worry about a conflict between the station and what the
Arduino would be sending.
Also apologies again, I should have mentioned in my original post:
Weewx v5.1.0 (installed via pip/venv)
Raspberry Pi 4
Raspian (Debian) v12 Bookworm (arm64)
Aercus Instruments Weathersleuth Professional station.
On Friday 25 October 2024 at 12:03:49 UTC+1 [email protected] wrote:
--Hmm..if Absolute pressure and relative pressure = 0 (zero)
your barometer was not set up correctly and not calibrated
correctly. II absolute pressure = 0, you would be living in a
vacuum! Or are you referring to both offsets = 0?
Your station is the weathersleuth IP? If so, you have an
outside array, a Wi-Fi gateway and a separate LCD indoor
sensor with a barometer sensor: Thermo-hygrometer-barometer
transmitter (temperature/humidity/pressure).
If your barometer is working, it should be reading the current
atmospheric pressure at your elevation (the elevation of your
barometer). In your calibration screen, you should see an
absolute pressure offset and a relative pressure offset. These
fields are used to adjust your absolute pressure and relative
pressure, respectively.
It is best to start over from scratch. Set both offsets back
to zero in the calibration screen. Verify that the pressure
showing on the LCD screen of the external
Thermo-hygrometer-barometer transmitter is equal to the
absolute pressure on your console. Maybe it's under the Live
data tab?
You will have to calculate your relative pressure offset which
depends on your elevation.
Your weather station appears to be similar to an Ecowitt or
Ambient weather station therefore calibration procedures
should be the same. Read the barometer wiki to set your
elevation and calibrate your barometer:
http://meshka.eu/Ecowitt/dokuwiki/doku.php?id=barometer#calibration_wi-fi_gateways
Your other question relates to WeeWX. You definitely do not
want to pass on your weather station's REL to WeeWX. Your
weather station uses a single fixed offset amount to do an
estimate of sea level pressure. It can be a reasonably close
approximation but your readings will drift at times. You would
be far better off relying on WeeWX "barometer" pressure
reading because it uses an actual algorithm to calculate sea
level pressure much more accurately. To obtain the WeewX
"barometer" reading you do not need to configure anything.
WeeWX will automatically calculate "barometer" from your
absolute pressure. BTW, the WeeWX "barometer" reading refers
to SLP (sea level pressure) that you might see on
meteorological isobar charts/surface analysis maps. If you
follow the wiki's tutorials, your REL (relative pressure) on
your station's console should be an approximation of the
Altimeter setting.
On Tuesday, October 22, 2024 at 4:43:24 AM UTC-4 Ashley Hinton
wrote:
Hi Michael
Thanks for your reply.
I did indeed read it which made me realise the issue is
what WeeWx is receiving (in relation to what its
displaying on the webpage) & that it needs to be
calibrated somewhere.
I will first calibrate the hardware & then check what
value from the hardware is being displayed on the webpage.
I'm pretty certain at the moment Relative Pressure from
hardware = Barometer on the webpage but will double check
so I know in future.
Thanks again,
On Monday 21 October 2024 at 04:56:31 UTC+1
[email protected] wrote:
Hello, as a first step, did you read the following:
https://weewx.com/docs/5.1/usersguide/troubleshooting/meteo/
After that, do you know the pressure mappings console
<=> weewx? Then, which of the values (pressure,
altimeter, barometer) is displayed on the webpage? If
you know all these things, calibrate your hardware
according to the manual and choose your desired
obs_type to be displayed on the webpage.
Ashley Hinton schrieb am Sonntag, 20. Oktober 2024 um
22:08:57 UTC+2:
Hello
I've noticed my Barometer reading is different
from other local sources: the airfield just up the
road from me, the local weather report, my phone
weather app - you name it, my readings did not
agree. WeeWx was reporting too high.
I'm using an Aercus IP weather station and WeeWx
is using the Interceptor driver.
The weather station itself has its own calibration
settings page, it has two fields for calibrating
pressure:
Absolute Pressure (was, and is, set to 0)
Relative Pressure (was set to 30.00hpa which I'm
sure was arbitrary, now set to 0)
If I change the Relative Pressure offset the
Barometer value reported on the resulting
WeeWx-generated webpage changes, so I'm confident
that Relative Pressure is what's sent to WeeWx.
My question is what to do - calculate and set the
calibration in hardware, or in WeeWx? What is
generally preferred or considered the best option?
Thanks!
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