Author Topic: Barometric Pressure Calibration  (Read 4576 times)

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Offline gpbarth

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Barometric Pressure Calibration
« on: April 09, 2017, 02:45:14 PM »
Just installed my new 5-in-1 station, and everything went extremely well. Few problems connecting to Weather Underground, but before long, everything seemed to be in place. I then started to check everything out as far as accuracy, and noticed that my display was reading in the 30's for barometric pressure. Checking my Dashboard, I realized that the pressure has gone from a low of 29.24 to a high of 29.79. And that's what is being reported.

So, following the calibration procedure, I switched the display to "Manual" for the pressure, and changed the read-out to mirror what is on my Dashboard, 29.75. So far, so good. Now I also assumed (yeah, I know...don't assume anything) that after I adjusted the read-out, I should revert to the "Automatic" mode for the pressure. But when I did, the display reverted to the old 30.43 readout. So I switched back to manual mode to get the desired display.

My question now - do I leave the display in the "Manual" mode for pressure to get the right readout? What does the "Automatic" mode do that the "Manual" mode does not? The weather sensor seems to be transmitting the correct pressure (although when I look at several other area WU stations, they all seem to read 29.99, along with mine), so why is the "Auto" mode reading high?

And in other stuff, why is my WU sticker not working? I followed the instructions in copying the code from WU, and it still appears in my signature as raw code.

Thank y'all in advance.
« Last Edit: April 09, 2017, 02:46:56 PM by gpbarth »
-= Gary =-

Offline worachj

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Re: Barometric Pressure Calibration
« Reply #1 on: April 14, 2017, 02:00:29 PM »
I too am a new owner in early April of a 5-in-1 Pro+ and Display(06039M) and was having problems understand barometric pressure.

I thought the pressure reading was taken in the sensor. But it turns out that it's taken in the display unit, and/or in the smartHUB if you have one. The auto mode of the display takes a pressure reading as if you were at sea level. It needs to be put in manual mode and adjusted for elevation. Some sites like Wunderground will automatically do the elevation adjustment for you when you send them the readings.

So you need to understand which device is taking the pressure reading and how that reading is sent to the different web sites like My AcuRite and Wunderground.

From my Display manual:
Quote
*To change from AUTO to MANUAL pressure mode and vice versa, press
AND HOLD the “ ” button for 5-7 seconds. The display indicates the
current pressure mode selected, “AUTO” or “MANUAL”. The “ ” icon will
appear next to the barometric pressure to indicate that MANUAL mode has
been activated. Press and HOLD the “ ” button for 5-7 seconds to return to
AUTO mode.

How calibrations are sent:
Quote
For smartHUB use only - readings sent to Weather Underground do not have calibrations applied. This is due to sensor readings are sent directly from the smartHUB.

For PC Connect Display only - when the calibrate readings settings are set directly in the PC Connect software, the readings are sent with calibrations to Weather Underground and My AcuRite.

NOTE
How to set the reading calibration of barometric pressure is based on the device.

smartHUB only- set in the profile of the smartHUB.

PC Connect Display only- required to be set in the PC Connect software.


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Offline gpbarth

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Re: Barometric Pressure Calibration
« Reply #2 on: April 14, 2017, 09:09:22 PM »
Another question then - if the Smart Hub is registering 29.99 and the display is registering 29.96, which pressure reading needs to be used? If the Hub is sending the pressure to WU and My AcuRite, where is the display calibrated? Is the display getting the reading from the 5n1 or from the Hub?
-= Gary =-

Offline haroldashe

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Re: Barometric Pressure Calibration
« Reply #3 on: April 15, 2017, 01:12:17 AM »
The display has its own barometric pressure sensor, as does your hub.  The outdoor sensor does not have a baro sensor at all.

Offline worachj

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Re: Barometric Pressure Calibration
« Reply #4 on: April 15, 2017, 08:04:48 AM »
You are using the pressure reading from your SmartHUB. On "My AcuRite" if you go under the device menu and edit your smartHUB profile you will see two settings for Barometric Pressure (Adjusted Pressure & Station Pressure).

Adjusted Pressure: will take your smartHUB reading and adjust it for elevation. WU will do the same thing.

Station Pressure: Will use your smartHUB reading without any adjustment for elevation.

You can calibrate your smartHUB pressure reading by changing the elevation in the smartHUB profile.

I calibrate both my display reading and smartHUB readings. I change my display pressure to match my smartHUB.
« Last Edit: April 15, 2017, 08:07:54 AM by worachj »


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Offline gpbarth

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Re: Barometric Pressure Calibration
« Reply #5 on: April 15, 2017, 03:49:45 PM »
Well, I went and readjusted everything. Used my GPS altitude read-out to get the elevation (478'), and adjusted the pressure type to "Adjusted Pressure." Then went and adjusted the resulting pressure read-out on my Dashboard to my display. Everything is now reading the same.

Thanks, all! I'm a happy camper!
-= Gary =-

Offline gpbarth

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Re: Barometric Pressure Calibration
« Reply #6 on: April 26, 2017, 02:03:22 PM »
Well, this is fun! I moved my display to the same room as my Smart Hub, and once again, calibrated my display with my hub. The hub and display are probably less than 5 feet apart. Three days later, and the hub is reading 29.91 while the display is reading 29.93. Okay, I can re-calibrate this thing again, but is this going to be a constant thing? BTW, I am using a computer logged into MyAcurite's dashboard to do the comparison.

Likewise, the hub temp readout is showing 65.2ºF, while the display (which doesn't read 10ths) is reading 67ºF. Going on the supposition that the hub is the correct source, I have re-calibrated the display temp to match the hub. Am I going in the right direction? And is this calibration stuff going to continue on a weekly basis? I'm thinking of getting a manual barometer and going out to the sensors to get a more accurate read-out. Is that necessary?

Sorry for 20 questions, but I'm still playing with this, and I want to get it fine-tuned.
-= Gary =-

Offline Beaudog

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Re: Barometric Pressure Calibration
« Reply #7 on: April 26, 2017, 07:12:50 PM »
Where are you getting the HUB readings from?    If you are getting them from acurite.com everything may not be on the same exact time.   The Hub may be showing readings that are older or newer than the console.

I don't think updates to the console and to acurite take place at the exact same time. And, you have to allot time for processing.

It is just like WU your reading will vary depending on which exact page you are looking at.

Trying to keep them exactly synchronized is going to an exercise in futility.

Offline gpbarth

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Re: Barometric Pressure Calibration
« Reply #8 on: April 26, 2017, 07:45:34 PM »
The hub readings are coming from Acurite (myacurite.com dashboard), and it's constantly open here on my desk. The console is sitting here, too. I'm not going to chase these readings all over the place, but I'd like to get them fairly sync'ed before relying on them altogether. I guess I'll be happy with what I have now.

What I would like to do is get an analog barometer, and check it against the hub. I do have a pretty good idea of my station altitude from my GPS, so I'd like to know how accurate the hub is now. Other than that, I guess with this station, it's more for my personal enjoyment than as some reporting facility for NWS.  8-) Next, I have to find out the best wifi camera for my weather cam.
-= Gary =-

Offline alanb

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Re: Barometric Pressure Calibration
« Reply #9 on: April 26, 2017, 08:27:04 PM »
The hub readings are coming from Acurite (myacurite.com dashboard), and it's constantly open here on my desk. The console is sitting here, too. I'm not going to chase these readings all over the place, but I'd like to get them fairly sync'ed before relying on them altogether. I guess I'll be happy with what I have now.

What I would like to do is get an analog barometer, and check it against the hub. I do have a pretty good idea of my station altitude from my GPS, so I'd like to know how accurate the hub is now. Other than that, I guess with this station, it's more for my personal enjoyment than as some reporting facility for NWS.  8-) Next, I have to find out the best wifi camera for my weather cam.
Does your GPS have a barometric altimeter? It is my understanding that the the GPS altimeters based on satellite reception (like automotive navigators) are notoriously inaccurate and can fluctuate by 50' or more. And even the barometric altimeters (like on Garmin Oregon series) need to be calibrated regularly. I used a topo map to determine the elevation of my property. By overlaying the street map on the topo I was able to get a pretty accurate estimate (within 5') at the street. The topo lines were in 10' increments, so I could interpolate to get the elevation estimate of my street, then use that to estimate the elevation of each floor in my house. I actually use that elevation to calibrate the altimeter/barometer on my Garmin Oregon 550.
« Last Edit: April 26, 2017, 08:40:19 PM by alanb »
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Offline gpbarth

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Re: Barometric Pressure Calibration
« Reply #10 on: April 26, 2017, 08:54:38 PM »
Well, I used a topo map and re-adjusted my altitude to 399' from 485', so the GPS was definitely off. I don't think it's worth adding another 10' for my 2nd floor room. Funny, but WU had the correct altitude from the beginning - they must have the lat/lon info built into their app. Thanks for the suggestion.
-= Gary =-

Offline alanb

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Re: Barometric Pressure Calibration
« Reply #11 on: April 26, 2017, 11:34:36 PM »
I am new at this, so maybe one of the experts will correct me ... but I would set the elevation for where the barometer sensor is mounted. If your street elevation is 399' and the floor of your 2nd story is 10' higher and your have your barometer mounted 5' up on the wall of the 2nd story, that would make the elevation of the barometer 414'. From some of the barometric pressure charts I have looked at that could make a difference of ~.01 Hg. Not a big deal, but I guess I am kind of perfectionist.

I think some people make a mistake of using the elevation of their ISS (including height of the pole) when the barometer is actually in the console or smarthub. But again, I am just learning, so I could be completely wrong.
Alan - Ambient WS-2000, WH31E x5, WH31L, Ecowitt WN32(WH32E)
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Offline gpbarth

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Re: Barometric Pressure Calibration
« Reply #12 on: April 27, 2017, 12:05:05 AM »
I guess that being on the second floor, I could set the elevation to 409' (or even 412, since the hub is sitting on a table about 3' tall) but I think that's getting too critical. My best idea would be to use a analog barometer sitting next to the hub, and set the hub to the same setting. That would negate any elevation differences. So I think I will see if I can find an analog barometer and try that. I know you can buy them, but unless you get a high-end model, they can't be counted on to be all that accurate.
-= Gary =-

Offline haroldashe

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Re: Barometric Pressure Calibration
« Reply #13 on: April 27, 2017, 03:52:34 AM »
GPBARTH, if  cone up with a good weather cam, let us know.  I'm looking for one, too.

Offline gpbarth

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Re: Barometric Pressure Calibration
« Reply #14 on: April 27, 2017, 09:30:17 AM »
I will definitely let you know if and when I find a weather cam. But I'll tell you right now, mine won't be day/night and weather-proof - I plan on mounting it in a 2nd floor window, against the glass, with a clear view of downtown and the mountain 1/2 mile away. All I need is WiFi capability, because I'm not running any wires.
-= Gary =-

Offline gpbarth

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Re: Barometric Pressure Calibration
« Reply #15 on: April 28, 2017, 03:51:24 PM »
Me again! Just call me a pest and be done with it. As previously noted, I now have my console and my Smart Hub in the same room, about 6' apart. When I brought the console upstairs, I re-calibrated it with the Hub using my on-line AcuRite dashboard. Set the console to read the same pressure as the Hub. And it was tracking nicely all day.

This morning, I came into the room, and my dashboard is reading 30.06, while the console is reading 30.15. So I go to my WU station, and it's reporting 29.92. Altitude on all 3 is the same - 399'. Pressure is set to "manual" on the console.

I'm getting the idea that I have to leave this thing alone, and stop comparing the 3 different read-outs, because it just isn't going to ever match. Probably if I had bought a more expensive station, I could expect more. But being what it is, I give up. Guess I'll depend on the console and shut down the AcuRite dashboard, unless I have to change something. And how WU is coming up with the pressure is beyond me.
-= Gary =-

Offline CW2274

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Re: Barometric Pressure Calibration
« Reply #16 on: April 28, 2017, 05:17:48 PM »
how WU is coming up with the pressure is beyond me.
WU knows best and supposedly "corrects" everybody to MSLP. I quit trying to get them to leave my altimeter setting alone..... ](*,)

Offline CW2274

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Re: Barometric Pressure Calibration
« Reply #17 on: April 28, 2017, 07:41:54 PM »
I am new at this, so maybe one of the experts will correct me ... but I would set the elevation for where the barometer sensor is mounted. If your street elevation is 399' and the floor of your 2nd story is 10' higher and your have your barometer mounted 5' up on the wall of the 2nd story, that would make the elevation of the barometer 414'. From some of the barometric pressure charts I have looked at that could make a difference of ~.01 Hg. Not a big deal, but I guess I am kind of perfectionist.

I think some people make a mistake of using the elevation of their ISS (including height of the pole) when the barometer is actually in the console or smarthub. But again, I am just learning, so I could be completely wrong.
No sir, you're on it. Just for further clarification, .01 inches of Hg equates to 10 feet in elevation, so to go from 399' to 414' would be .015 hg., all things being equal.

 

anything