A short calibration study of the Vantage Pro Plus weatherstation Francis Massen, meteoLCD  vantage_calibration.html  version 1.0  16 Feb 2003

1.     Operational procedures

A new (never used) Vantage Plus Pro weatherstation ( wireless model, to be used by Prof. A. Kies, Physics Lab, Centre Universitaire, Luxembourg) was mounted at the meteoLCD site and operated for the period from 17 Jan 2003 to 5 Feb 2003 for comparison and calibration factors (sampling interval = 30 minutes). The sensors used as a reference are those of meteoLCD (see the description).

The aim of the study is to check if the rather inexpensive and easy to setup Vantage Pro Plus, manufactured by Davis in the USA, could qualify as a valid weatherstation compared to the professional-grade sensors of meteoLCD.

 Due to an operator glitch, the rain-sensor was operational only from 26 Jan, 16:00 on. The wind direction sensor was not calibrated, so it will not be used in this study. All data were imported into Statistica 6.1. for analysis and graphing; the Excel file test_davis1a.xls corresponds to these data.When calibrating the Vantage Pro Plus, an xy graph with x-axis = Vantage Pro Plus, y-axis = meteoLCD, was used; the linear regression line gives the mathematical function to apply to the Vantage readings to obtain the (assumed) correct meteoLCD values.

2.     Correlation matrix

  The correlation coefficients are all significant at the alpha = 0.05 level; many are 1.

3.     Outside (air-) temperature: (click on small picture to get full size)

4.  Outside (air) relative humidity

5.  Air pressure

6. Wind velocity

  7.  Solar radiation

8. Effective (erythemal) UVB irradiation

The Vantage Pro applies a multilayered filter to approximate the UVB sensors output to the CIE (Diffey) erythemal spectrum; this approximation may be acceptable, but there exist notable deviation in the 310-320 nm region (see Davis info).
Fine reading the specifications shows that Davis applies a (non-European) definition of

1 MED = 220 J/m²

This should be adjusted for European comparisons, where 1 MED = 250 J/m². The uncorrected UVI-reading of the Vantage Pro should probably be multiplied by 220/250 (Vantage UVI ‘s are probably too high: 1 UVI is 1/40 W/m² effective UVB; depending on the computation of the UVI (from eff. power? from MED ?)).
There also is some confusion regarding the UVB sensor readings: what Davis calls DOSE ( in the .pdf info-flyer) is a dose-rate in MED/hr. Only if the sampling interval is 1 hour, dose and dose-rate are expressed by the same number. The data column UVB shows readings that the author is incapable to decipher: it is not effective power, as one could think. Thus the comparison is done using the column called DOSE as representing the dose-rate, and comparing to the output of the UVB 501A Biometer of meteoLCD.

 This short comparison shows that the Vantage Pro Plus delivers excellent to good quality data, compared to professional-grade sensors. One should not expect too much from the rather simple solar and UVB sensors: certainly their accuracy is way too low to detect minor long-time trends in these parameters. If the solar sensor is used to measure global (monthly or yearly) irradiance (for instance to check the available local yearly solar-energy ), the  accuracy is good enough. This can also be said for the UVB sensor, which should be taken as an inexpensive and sufficient accurate mean to gather UVI’s (which as a matter of fact are always rounded to integer numbers).

The Vantage Pro Plus is a good buy for an easy to setup weatherstation to be used in the field (as a temporary station during a research project) or at home.

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