Abstract: A dual crystalline resonator package comprises either (1) two crystalline bodies, in adjoining cavities of which bodies a crystalline temperature resonator and a crystalline reference resonator are respectively connected and which bodies are directly connected together, or (2) such two crystalline bodies in conjunction with a third crystalline body which is connected directly between the two first-mentioned bodies and to opposite sides of which third body the resonators are connected so that the resonators extend therefrom into the cavities of the two first-mentioned bodies. Either of these embodiments can be used for generating temperature data signals in a high pressure, high temperature well wherein the respective embodiment is lowered and exposed to such high pressure and high temperature. A modification of the second embodiment eliminates one of the resonators and the respective body having the cavity into which the eliminated resonator would otherwise extend.