A Sensor Signal Digitalization Module for High-Temperature Environment Applications

The electronic instrumentation which operates in the high-temperature environment of an oil well should be specially designed. Analog-to-digital converters are critical components in well-logging applications with only few high-temperature-rated commercial components on the market. Our objective is to realize a custom A/D conversion module for multichannel well-logging applications following the smart-sensor concept and using proven, reliable and available electronic components. This paper presents a simple and robust digitalization module which utilizes a pulse-width modulator in combination with a phase-locked loop. We are presenting results of a high-temperature functional evaluation of a demonstration prototype implemented using commercial- and industrial-grade integrated components in combination with high-temperature rated passive components. The module´s operating range is defined by the 5V unipolar supply voltage. The effective number of bits of the digitalization module is between 10 and 13 over the temperature range 25-175degC