Louis - thanks for restoring my sanity!! Yes, it is a FineOffset which I have got. In the summer I see the issue when I turn the AC on and in winter when I light the kerosene stoves!! So, it's a faulty station design - which was, I will admit, a conclusion I was coming to following Tom's patient answer. I suspect the issue is that the sensor is not insulated well enough - but if the same sensor is used for temperature - which would not require the same insulation - the issue is unresolvable!! Maybe I will try and get a separate pressure gauge and take readings from that instead!!
On Sunday, 14 January 2018 21:35:33 UTC+2, Louis De Lange wrote: > > As a previous owner of a Fine Offset station I can confirm that I noticed > this same behavior. Living in Canada where our homes are heated, I could > clearly see the altimeter reading (my station did not support barometer > correction to sea level) seesaw with the furnace operating and shutting > down. > > Reading up on the issue it appeared that the Fine Offset hardware was > doing a temperature correction internal to the indoor unit, but that quick > changes to the indoor temperature threw the reading off. There is no way > that you can correct for that with calibration - it is a flaw in the > hardware. > > This and other quirks in the Fine Offset hardware eventually drove me to > buy a Vantage Pro and be done with it. If you are a stickler for accuracy > you will save yourself o lot of frustration by getting a Vantage Pro > > On Sunday, 14 January 2018 07:17:31 UTC-8, Greg Troxel wrote: >> >> >> Andrew Milner <andrew.s...@gmail.com> writes: >> >> > I ask the question because whenever I put the heating on I see a change >> to >> > the barometer readings on my graphs which implies to me that the >> pressure >> > is changed (it appears to fall as the temperature rises). My console >> is >> >> This seems like a sign of trouble. I see no effect on pressure readings >> due to inside temperature changes or heating system on/off (with a >> Vantage Pro 2), and I wouldn't expect any. (I just looked at last >> night's data, and the heating system behavior is obvious from inside >> temperature.) >> >> > 2/3 up the wall (too high to even read, but good for sensor reception!) >> and >> > so warms quite rapidly as the hot air from the heating rises making the >> > pressure change quite noticeable. I have always put it down to being a >> > quirk of FineOffset and have ignored barometer changes which appeared >> to be >> >> That is a good theory :-) >> >> > indoor temperature change related. However the variation does lead on >> to my >> > conclusions re compensating indoor pressure readings to match outdoor >> > temperatures. Maybe I need to investigate this more and try and >> correlate >> > 'pressure' to indoor temperature directly ....... I suspect it may be >> > related to temperature differentials between temperature inside the >> > pressure sensor and temperature outside the sensor ie if the >> temperature is >> > uniform all is fine but when there is a difference the pressure reading >> is >> > erroneous >> >> There are two things to understand about your situation. >> >> One is if the inside pressure and the outside pressure are actually >> different. This seems very unlikely. Surely someone on this list has >> set up pressure sensors in and out and compared them - hopefully they'll >> admit to that and share results :-) >> >> The other is which device is doing the reduction to sea level pressure >> and if it is doing it correctly. This is about the weight of the air >> and is related to the outside temperature only. It seems this is done >> by weewx. >> >> https://github.com/weewx/weewx/wiki/Barometer,-pressure,-and-altimeter >> >> So I don't understand why you are having trouble. I would look at the >> raw station pressure data. If that is changing correlated with the >> heating system, then either it really is changing or your station is >> behaving funny. >> >> It might help to post graphs of computed baromtric pressure and inside >> and outside temperate, along with barometric presssure reported by a >> nearby station. >> > -- 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 weewx-user+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
