A barometer wiki

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start [2026/03/05 15:50] – adminstart [2026/05/14 20:28] (current) – [Barometer troubleshooting] admin
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 Barometers and their pressure readings and related calculations can be difficult to understand, so much so that until now, only a very small percentage of station owners have successfully managed to properly set-up or even use their barometers. However, this all changed with the introduction of Ecowitt's new automatic barometer firmware update in 2025. Barometers and their pressure readings and related calculations can be difficult to understand, so much so that until now, only a very small percentage of station owners have successfully managed to properly set-up or even use their barometers. However, this all changed with the introduction of Ecowitt's new automatic barometer firmware update in 2025.
  
-Ecowitt's new sea level pressure (SLP) firmware update is a radical departure from the previous algorithm, where sea level pressures were somewhat crudely approximated using a simple fixed offset. From now on, SLP (mean sea level pressure) will be automatically and continuously calculated based on changes in station pressure, outside temperatures and humidity. This new update will greatly increase the accuracy of sea level pressure calculations. It will also make the initial set-up of the barometer much easier, requiring the user to only input their barometer altitude above sea level. No more manual calculations required!+Ecowitt's new sea level pressure (SLP) firmware update is a radical departure from the previous algorithm, where sea level pressures were somewhat crudely approximated using a simple fixed offset. SLP (mean sea level pressure) is now automatically and continuously calculated based on changes in station pressure, outside temperatures and humidity. This new update greatly increases the accuracy of sea level pressure calculations. It will also make the initial set-up of the barometer much easier, requiring the user to only input their barometer altitude above sea level. No more manual calculations required!
  
  
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 </alert> </alert>
  
-One of its first important uses was for sailing ships more than three hundred years ago. Sailors noted that changes in atmospheric pressure were related to wind and gale.  Wind causes waves. Big waves sink ships and loses lives. Therefore, barometers became increasingly important. Even today, all ships still have analogue  +One of its first important uses was for sailing ships more than three hundred years ago. Sailors noted that changes in atmospheric pressure were related to wind and gale.  Wind causes waves. Big waves sink ships and loses lives. Therefore, barometers became increasingly important. Even today, ships still have analogue (dial type) barometers on board should all the electronics fail.
-(dial type) barometers on board should all the electronics fail.+
  
-In modern times, we now have aircraft and they too, have barometers aka "altimeters". And just like for ships, they can also save lives. Altimeters help maintain safe separation between aircraft and terrain.+In modern times, we now have aircraft and they too, have barometers aka "altimeters". And just like for ships, they can also save lives. Altimeters help maintain safe separation between other aircraft and terrain.
  
-Needless to say, in addition to weather forecasting purposes, barometers are safety-critical instruments for air, land and sea. Despite their importance, most people would have no idea (or care to know), how they work or how to use them.+Needless to say, in addition to weather forecasting purposes, barometers are safety-critical instruments for air, land and sea. Despite their importance, most people would have no idea how they work or how to use them.
  
 But the barometer is different. Unlike most weather sensors, it has predictive qualities, which is a key element of weather forecasting. But the barometer is different. Unlike most weather sensors, it has predictive qualities, which is a key element of weather forecasting.
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 ====Sea Level Pressure - visualizing a concept (Example #2)==== ====Sea Level Pressure - visualizing a concept (Example #2)====
 +**updated 07 March 2026**
  
 If you do a general search for a visual illustration of sea level pressure, you will undoubtedly find quite a few illustrations/drawings of mountains and weather stations at different elevations and calculated (but different) sea level pressures.  If you do a general search for a visual illustration of sea level pressure, you will undoubtedly find quite a few illustrations/drawings of mountains and weather stations at different elevations and calculated (but different) sea level pressures. 
 For a new weather station owner, these illustrations may not be all that helpful. For a new weather station owner, these illustrations may not be all that helpful.
  
-To better illustrate the <u>concept of sea level pressure</u> we will do something a bit different.+To better illustrate the concept of //sea level pressure,//we will do something a bit different.
  
 Rather than starting with station pressure and calculating sea level pressure, we will do the reverse. We will start with the sea - specifically the standard sea level pressure of 1013.25 hPa and work our way up into the atmosphere and calculate the appropriate temperature and station pressures at our weather stations using the standard model of the atmosphere.  Rather than starting with station pressure and calculating sea level pressure, we will do the reverse. We will start with the sea - specifically the standard sea level pressure of 1013.25 hPa and work our way up into the atmosphere and calculate the appropriate temperature and station pressures at our weather stations using the standard model of the atmosphere. 
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 1. STN "A"  ABS =1013.25, REL = 1013.25 @ 15C @ 0 m (sea level) 1. STN "A"  ABS =1013.25, REL = 1013.25 @ 15C @ 0 m (sea level)
 +
 2. STN "B"  ABS = 989.45, REL = 1013.25 @ 13.7C @ 200 m 2. STN "B"  ABS = 989.45, REL = 1013.25 @ 13.7C @ 200 m
-3. STN "C"  ABS = 954.61, REL = 1013.25 @ 11.75C @ 500 m+ 
 +3. STN "C"  ABS = 954.61, REL = 1013.25 @ 11.75C @ 500 m  
  
 ABS = measurement of absolute pressure/ station pressure ABS = measurement of absolute pressure/ station pressure
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 Since the sea level pressures are the same we could plot all three stations on a weather map and draw an isobar (lines of equal pressure) just like the meteorologists do.  Since the sea level pressures are the same we could plot all three stations on a weather map and draw an isobar (lines of equal pressure) just like the meteorologists do. 
  
-SUMMARY+**SUMMARY**
  
 We can now see what they mean by converting (normalizing) a station pressure to an equivalent sea level pressure. All three stations (A, B & C) have different station pressures, different altitudes and have different temperatures. Yet all of them yield the same sea level pressure of 1013.25. Because we have normalized or standardized all station pressures to a common altitude (sea level), we can now make valid comparisons between all three stations. We can now see what they mean by converting (normalizing) a station pressure to an equivalent sea level pressure. All three stations (A, B & C) have different station pressures, different altitudes and have different temperatures. Yet all of them yield the same sea level pressure of 1013.25. Because we have normalized or standardized all station pressures to a common altitude (sea level), we can now make valid comparisons between all three stations.
  
-What is the point of calculating sea level pressure if your weather station is not at sea level?+**What is the point of calculating sea level pressure if your weather station is not at sea level?**
  
 Meteorologists use barometer readings from thousands of weather stations in order to draw isobars. Isobars are the curving lines of equal mean sea level pressure. These lines (isobars) represent the familiar HIGH and LOW pressure systems we see every day on weather maps and forecasts. Drawing isobars is just a matter of connect-the-dots. See link below. Meteorologists use barometer readings from thousands of weather stations in order to draw isobars. Isobars are the curving lines of equal mean sea level pressure. These lines (isobars) represent the familiar HIGH and LOW pressure systems we see every day on weather maps and forecasts. Drawing isobars is just a matter of connect-the-dots. See link below.
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 Why devote an entire wiki to just one weather sensor? Why devote an entire wiki to just one weather sensor?
  
-Barometers, can be one of the most difficult weather sensors to set up properly. My informal annual survey of surrounding weather stations reveals that only a few percent of weather station owners have managed to successfully set up and calibrate their barometers. +Barometers, can be one of the most difficult and frustrating weather sensors to set up properly. My informal annual survey of surrounding weather stations reveals that only a few percent of weather station owners have managed to successfully set up and calibrate their barometers. 
  
 Hopefully, these guides, tutorials and how-to's will shed some light on the subject of barometers - what they are measuring, how to set them up and how to keep them calibrated and accurate, Hopefully, these guides, tutorials and how-to's will shed some light on the subject of barometers - what they are measuring, how to set them up and how to keep them calibrated and accurate,
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 ===== Barometer troubleshooting ===== ===== Barometer troubleshooting =====
-updated 23 Dec 2025+updated 14 May 2026
  
 Ecowitt rolled out a new firmware update in 2025 that dynamically calculates SLP (sea level pressure) factoring in elevation, station pressure,temperature and humidity. This new update is a radical departure from the previous algorithm, where sea level pressures were somewhat crudely approximated using a simple fixed offset. Ecowitt rolled out a new firmware update in 2025 that dynamically calculates SLP (sea level pressure) factoring in elevation, station pressure,temperature and humidity. This new update is a radical departure from the previous algorithm, where sea level pressures were somewhat crudely approximated using a simple fixed offset.
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 **Resources:**  **Resources:** 
  
-QFE calculator: This calculator uses the term QFE instead of station pressure. QFE is the aviation equivalent to station pressure. +QFE calculator: This calculator uses the term QFE instead of station pressure. QFE is the aviation equivalent to station pressure. Click on the QFE button to start and enter in your elevation and sea level pressure/QNH. 
-See example:https://www.sensorsone.com/elevation-station-qfe-sea-level-qnh-pressure-calculator/?ab=2&v0=300&f0=m&v1=975&f1=hPa&f2=hPa + 
 +See:https://www.sensorsone.com/elevation-station-qfe-sea-level-qnh-pressure-calculator 
  
 Note: For North America and jurisdictions that use altimeter setting instead of QNH, put the altimeter setting value of your airport into the QNH input box of the the calculator. Note: For North America and jurisdictions that use altimeter setting instead of QNH, put the altimeter setting value of your airport into the QNH input box of the the calculator.
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 We need to do the following to see if our ABS reading of 1000 hPa is accurate. We need to do the following to see if our ABS reading of 1000 hPa is accurate.
  
-If our barometric sensor is perfectly accurate, the we should have the same REL reading as the airport. The pressure reading at the airport is called the Altimeter (setting) or Altimeter.+If our barometric sensor is perfectly accurate, then we should have the same REL reading as the airport. The pressure reading at the airport is called the Altimeter (setting) or Altimeter.
  
 Suppose the current Altimeter reading at the airport is 1036.5 mb. However, our barometer REL shows 1035.5. They do not match. Suppose the current Altimeter reading at the airport is 1036.5 mb. However, our barometer REL shows 1035.5. They do not match.
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