The SRH3 in-duct Psychrometer is a great tool to properly charge fixed restrictor systems by quickly determining the target superheat, and to help determine optimum airflow across the evaporator with a target evaporator exit temperature Test. To assist hvacr professionals get the proper measurements, Fieldpiece engineered this in-duct Psychrometer to take measurements in the duct where they are supposed to be taken -- near the evaporator! made in United States. Manufactured by Fieldpiece instruments Inc.