Today I upgraded the photos for all of the dial thermometers and dial hygrometers in the instrument collection section of the website.  I also added a large dial thermometer by the Amesbury Thermometer Company.  In the next few days I will upgrade the photos for the glass bulb thermometers and hygrometers.

Today I added a marine barometer made by R Fuess of Germany to the instrument collection website.  I believe it is older than 1976 since R Fuess went out of business in that year.  It was another acquisition from the ship breakers in India, and it works well.

I also upgraded the photographs for the remaining aneroid barometers on the website, except for the OTA barometer.  That barometer is currently disassembled on my workbench, awaiting repair.

Go to R Fuess Marine Barometer webpage.

​See Aneroid Barometer photographs.

Today I upgraded the photographs of the first 17 aneroid barometers in the instrument collection section of the website.  I bought a photographic copy stand with lighting for my digital camera, and the results are much better than before.  I will try to rephotograph the remaining aneroid barometers this weekend.

Today I added the calculated non-linearity of the aneroid and digital barometers based on December 2016 data.  This is based on calculated error values compared witrh my mercury barometer.  This may be found at:

• Barometric Calculations/Accuracy of Aneroid Barometers
• Barometric Calculations/Accuracy of Digital Barometers

In the next few days I will upgraded the photographs of the aneroid barometers on the website.
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Today I updated and expanded the web page on the accuracy of my digital barometers.  I compared daily simultaneous local pressure values from the digital barometers with values from my mercury barometer for the month of December 2016.  Values of the pressure error, the standard deviation of the pressure error, and the monthly average drift are presented.  

This may be found at 'Barometric Calculations/Accuracy of Digital Barometers'.

Go to 'Accuracy of Digital Barometers'

Today I added barometer/barograph drift data calculated for daily data from the month of December 2016.  The drift is calculated as the slope of a straight line fitted to the scatter of barometer pressure error data plotted against time.  The drift data was added to the following web pages:

• Barometric Calculations/Barograph Accuracy
• Barometric Calculations/Accuracy of Aneroid Barometers
• Barometric Calculations/Mercury Barometer Data Check

Tomorrow I will perform similar analyses for my digital barometers.

Go to  Barograph Accuracy webpage.

Go to Accuracy of Aneroid Barometers webpage

Go to Mercury Barometer Data Check webpage.

The Today I posted a new web page containing an analysis of the accuracy of my Friez ML-3A microbarograph for December 2016 daily data. The ML-3A is set to sea level pressure and its recorded data was compared with NWS airport data and data from my mercury barometer that was adjusted to sea level values. The analysis may be found at 'Barometric Calculations/Barograph Accuracy'.

I found that my ML-3A is very non-linear, it's accurate near the middle of the chart at 1020 mb but the error increases as the pen moves up or down. A possible cause is discussed in the analysis.

I plan to repeat this analysis in using January 2016 data for this barograph and for 3 other barographs:

• A Belfort Model 800A microbarograph
• A Friez Model 620 barograph
• A Weathertronics Model 7021 barograph

​The results will be posted in early February.

Go to Barograph Accuracy Analysis.

I have updated the web page on the accuracy of aneroid barometers with my daily data from December 2016.  Data was tabulated for 20 different aneroid barometers.  The aneroid barometer readings were compared daily with simultaneos readings from my mercury barometer.  All instruments were set to measure local pressure, not sea level pressure, so that the sea level correction does not influence the results.  The average error and standard deviation of the errors were calculated for each aneroid barometer.  The average error can be reduced somewhat by recalibration of the barometer, but the standard deviation of the errors is a more intrinsic indicator of barometer performance.  The results are sorted in a table from lowest standard deviation to highest standard deviation, and may be found at 'Barometer Calculations/Accuracy of Aneroid Barometers'.

Happy New Year!

Go to Accuracy of Aneroid Barometer webpage.

Today I performed a data check on the sea level pressure values calculated from my mercury barometer.  During the month of December 2016 I recorded daily values of the mercury barometer sea level pressure and simultaneous National Weather Service values from O'Hare Airport and Midway Airport, near me here in Chicago.  The analysis shows that the data from O'Hare averages 1.5 mb higher than from my barometer.  The data from Midway averages 2.5 mb higher.  Several causes may explain this difference.  These are all presented on a new webpage, which may be found under 'Mercury Barometer Data Check', which is under 'Barometric Calculations' on the home page.

Go to 'Mercury Barometer Data Check'.

Today I added three more aneroid barometers to the website:

• An Airguide desk barometer made by Fee & Stemwedel of the US.  I think it's from the 1940s, it has an attractive hardwood case.  Performance is mediocre.
• A GMP laboratory barometer from 1957 from the USSR.  I think GMP means Gidromet Pribor, or Hydrometeorology Instrument.  It still works pretty well.
• A Takahashi marine barometer from Japan.  I think it's from 1960.  Works fairly well.

I also made minor changes to the web page on printing your own instrument charts.  You'll find it on the home page.
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Have a Happy New Year!