Davis Temperature and Humidity Sensor Sensitivity.

KI5OMM Weather Station

I’ve replaced the Temp/Hum sensor several times over the years as they seem to last about 3 or 4 years before they start showing signs of inaccuracy. The current sensor that I am using now is a Sensiron SHT31 that I purchased from Scaled Instruments in Fl.

This is the latest generation of temperature/humidity sensors that Davis is using currently in their VPII weather stations and so far, I am impressed. The specifications are good and accuracy is dependable;

Temperature – ±0.3°C (±0.5°F) across entire range
Humidity – ±2% across entire range

For unknown reasons the sensors that I have used in the past have all failed with different issues, therefore no clear failure pattern has emerged to help implement a solution. The one common thing that I have noticed is that each failed sensor would continue to operate normally as long as temperature extremes were avoided. But if for example, the ambient temperature rose above 98 degrees F. the sensor would suddenly indicate a reading of 150 degrees.

I currently have this new sensor mounted in the Cotton Region Shelter with a homemade FARS unit gently blowing ambient air on it during the sunny days.

Fan Aspirated Shield

Time will tell how reliable it will be as compared to the previous versions.

One rather humorous note about the new sensor’s sensitivity. Recently I was using my riding tractor lawnmower to trim the grass around the instrument shelter. I was careful to not bump the shelter with the mower to avoid any damage to the unit. What I did not realize was that each time I had drove by the shelter with the lawn tractor, the exhaust from the engine was blowing right into the FARS fan intake. The sensor would register a small temperature spike for each pass with the tractor! I noticed it later while looking at the website temperature graphs where each spike could be clearly seen. At least I know it’s sensitive to small changes in ambient temperature.



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