Well, yeah :-) For pressure, I ignore all but the Tempest now, except when someone asks.
About time - I have a GPS-disciplined Temperature Controlled Oscillator as an NPT Stratum 1 source, and all but two of the 18 "time display units" in my house, our pre-internet stoves, are synced to that or WWVB (NIST Radio time). I know what time it is down to a few hundred milliseconds or better. And while we're on that subject, is everyone ready for The Epochalypse Project — Time Integrity & Epoch Rollover Risk (2036/2038) <https://epochalypse-project.org/en/>? On Tuesday, July 7, 2026 at 8:56:28 PM UTC-7 Tom Keffer wrote: > Clay, you're the perfect example of the saying, "Give a man a watch and he > knows what time it is. Give him two and he has no idea." > > On Tue, Jul 7, 2026 at 8:10 PM Clay Jackson <[email protected]> wrote: > >> Pardon me for jumping in here; but I've done a lot of fiddling and >> research on just this topic. >> >> Some background, I currently have THREE pressure sensors within a 600' >> radius, and Acurite 5-n-1, the pressure sensor that comes with an >> "original" PurpleAire Outdoor unit and the sensor in my Tempest >> WeatherFlow. At one time or another I've had as many as five pressure >> sensors. Being in the US, I typically display pressure as inHg; but when >> fiddling, I use millibars. Right now, my Tempest WeatherFlow is reporting >> 29.736 inHG, my purpleair is reporting 29.08 inHG and the Accurite is >> reporting 29.63 inHG. I've NEVER seen agreement on any 2 sensors, let >> alone 3 or 4 and I've seen differences as much as .5 inHG >> >> I'm 3 miles and about 100 feet lower than S40 (our nearest airport) which >> is reporting 29.81. But I'm also reporting a CORRECTED (to a NIST >> traceable sling psychrometer) temp of 94.2 as opposed to 86 at S40. For >> what it's worth, the purpleaire is reporting a temp of 104, because the >> sensors are inside a small non-ventilated case. >> >> I also participate in the NOAA Citizen's Weather Observer Program, and >> here's what they say over the last 30 days. >> Average barometer error: 0.1 milliBars >> Error standard deviation: 0.4 milliBars >> >> When I first started w/CWOP, I went crazy trying to correct stuff and >> actually did correct my Acurite to SLP; but Based on the current CWOP data, >> which is taken from the Tempest, when I installed that 3 years ago and >> observed the differences daily for a month, I gave up trying to "calibrate" >> it. I do check once or twice/week and have never seen anything but two >> "thumbs up" out of CWOP except during frontal passes. It's also been my >> experience that even 3 miles and 100 ft can make a large difference, a few >> tenths inHG, especially when you consider temperature as well. >> >> Bottom line: >> 1) With "consumer grade" equipment, you're never gonna get NIST >> reliabilty or traceabilty >> 2) Different sensors will report different results. Pick one, get it to >> approximate either Sea Level Pressure or "altitude corrected" pressure and >> then observe it for a while. >> >> And as far as what WeeWx does, "What Tom and the documentation say". >> >> On Tuesday, July 7, 2026 at 2:11:16 AM UTC-7 Tomasz Lewicki wrote: >> >>> Please help me understand the workflow for pressure/barometer >>> calculations in Weewx. >>> >>> Here’s the situation. Let’s say my barometer reads 970 hPa. Setting >>> aside how the reduced pressure is calculated, I know that it underestimates >>> the pressure by 6 hPa. I’d like to inform Weewx of this without using the >>> weather station console—that is, without physically entering corrections >>> into the console. In other words, I want to do this in weewx.conf. >>> >>> I’ve made the following changes: >>> [[[Units]]] >>> [[[[Groups]]]] >>> group_pressure = hPa >>> >>> [StdCalibrate] >>> [[Corrections]] >>> pressure = pressure + 6.0 >>> >>> [StdWXCalculate] >>> [[Calculations]] >>> barometer = WHAT SHOULD BE HERE? >>> pressure = AND HERE? >> >> -- >> > 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 visit >> https://groups.google.com/d/msgid/weewx-user/1fcc87ca-6e24-48f5-bf3a-358fc983c915n%40googlegroups.com >> >> <https://groups.google.com/d/msgid/weewx-user/1fcc87ca-6e24-48f5-bf3a-358fc983c915n%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 visit https://groups.google.com/d/msgid/weewx-user/ce22f6e0-02d6-49a3-b9bc-64bf7eb86ae4n%40googlegroups.com.
