Aneroid Barometer Accuracy - January 2017 Evaluation

For the month of January 2017 I compared the local pressure as measured once-per-day by my mercury barometer with the local pressure as measured by 22 different aneroid barometers. The aneroid barometers were all set for local pressure to eliminate any influence of the conversion to sea level pressure on the results. For each barometer, four statistics were calcualted:

1. The 'average error' is the average difference between the aneroid barometer pressure minus the mercury barometer pressure.
2. The 'standard deviation' is the standard deviation of the individual error values. 68% of the error values fall within +/- one standard deviation of the mercury barometer value. The average error can be reduced by recalibration of the aneroid barometer, while the standard deviation generally cannot, it is more inherent in the performance of the barometer.
3. The average drift was calculated. This is simply the slope of a straight line fitted to the the scatter of error data points plotted against day of the month. It is an indicator of how the error changes with time.
4. Finally, the average non-linearity was calculated. This is the slope of a straight line fitted to the scatter of error data points plotted against the mercury barometer local pressure, in mb per mb of barometric pressure. It is an indicator of how much the error changes on average with the local pressure.

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Most of my aneroid barometers are quite old and performance can be affected by the condition of the instrument as well as it's design. In general, I don't open or lubricate my barometers unless it is obvious that they are not working properly. It is not my intention to pass judgement on the design of the individual aneroid barometers. Take these results with a word of caution.

​My results are presented in the following table. The barometers are sorted from lowest standard deviation to highest standard deviation.

Aneroid Barometer Accuracy Evaluation - January 2017 Results

Several of the barometers were recalibrated following the December 2016 accuracy evaluation. Again the Changchun barometer performed surprisingly well. Again the Utsuki Keiki barometer did not perform well, despite recalibration. I will have to open it up and lubricate it.

There is, of course, error in the mercury barometer measurements. I did an evaluation of the accuracy of my mercury barometer, which may be found here. All of the measurements were made of the local pressure in my apartment, so that deviations from the outdoor pressure should not influence the results.

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