DescriptionRH80 and RH90 Series thermo-hygrometers are compact in size and easily fit into your shirt pocket. The cover protects the sensor and also acts as a handy pocket clip. Model RH81 is a digital thermo-hygrometer with min/max data storage, data hold and auto power off features. Models RH83 and RH92 have all of the features of the RH81 and also measure dewpoint and wet bulb temperature. The RH92 also features a twist-close sensor protection cap. Optional test salts and an external temperature probe are also available for the model RH92.