Temp/Humidity Offset


Our new Davis Vantage Pro2 with 24 hour fan-aspirated radiation shield has been in service for 1 week today. Therefore, I have another question for all the Davis experts.

Since I have other temperature and humidity gauges, I have taken the time to cross check the temperature and humidity readings on the Vantage Pro2 unit .......... several times. Everything seems to be running relatively close. However, I do not know which of my gauges are the most accurate. In your opinion, are the Vantage Pro2 units extremely accurate or should I expect that I will need to enter some offets? Outside temperature readings on the Vantage Pro2 are running about 2 degrees lower than my DTH-1A (A.W.Sperry unit) and lab thermomoter. Outside humidity is running about 8% higher on the Vantage Pro2 as compared to my DTH-1A (A.W.Sperry unit). Inside temperature and humidity readings are almost identical on the console unit and the lab thermometer and DTH-1A (A.W.Sperry unit)!

Since the Vantage Pro2 is new and probably was calibrated before leaving the factory, I'm thinking it is the more correct and I probably shouldn't be entering offsets! Any thoughts?

So, thanks again!

Tony Lunn
Get the old fashioned sling psychometer and check your humidity readings! :p J/K

Temperature will vary between devices. It's a given. If you have 3 devices that are all off from each other by a degree or two, you can (A) Not worry about the differences, or (B) take the average between the three and go with that.

I always used my local airport readings to guage against what I had, but then I had a mobile set up too. With your stationary set up and the fast it's in an asperated shield, that will make some difference right there. Air movement and cover as opposed to less movement and no shade.

I used a sling psychrometer on mine and it needed no offsets (other than elevation for barometer). Temp/dewpoint are always within one degree of the Lee's Summit ASOS which is 2 miles away and the SLP is always dead on.

Agree with John, get a nice sling. You can probably pick one up on Ebay cheap -- not sure if their rules allow the transport of mercury ones though...