ALC crystal oscillators based pressure and temperature measurementintegrated circuit for high temperature oil well applications

摘要

An application specific integrated circuit for the pressure andntemperature measurement at the high temperature oil well bottomnconditions is presented in this paper. The circuit is mainly composed ofnthree high performance automatic level controlled (ALC) oscillatorncircuits, which drive three external crystals (the sensitive elements),nas well as mixing and filtering stages. The integrated circuit wasnsuccessfully tested up to 220°C, showing a frequency resolution ofn0.0003 ppm (0.0007 psi, for the pressure measurement) and a drift of 1.5nHz/month (0.5 psi/month) concerning, respectively, the short- andnlong-term measurement stability. A drastic reduction of the wholenmeasurement tool size and cost was then allowed by means of thisnapplication specific BiCMOS integrated circuit