I bought this to measure temperature and moisture in garden soil (advertised for use in soil although further reading describes its use in air). It was once placed in the ground and seemed to respond to soil moisture. He was on a lab bench to test the battery life of a portable microcontroller-based remote soil tester. During this time, the humidity sensor worked for about a month before reporting a relative humidity above 100%. The only extreme he was presented with was being placed in dry ice to see the temperature range. The seller refunded me the money for the purchase, but I believe that this is not what you need if you want to put it in the ground.
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