FPGA-only MVT digitizer for neutron downhole applications. (April 2023)

• Record Type: Journal Article
• Authors: Zhao, Siyuan; Wang, Zhen; Li, Muyao; Zhang, Pu; Cheng, Jingjing
• Is Part Of: Measurement. Volume 211(2023)
• Publication Date: 2023-04
• Subjects: Neutron logging instrument -- Peak power detection -- Multi-voltage threshold -- Temperature compensation -- FPGA; Weights and measures -- Periodicals; Measurement -- Periodicals; Measurement; Weights and measures; Periodicals; 530.8
• DOI: 10.1016/j.measurement.2023.112649
• Languages: English
• ISSNs: 0263-2241

Abstract

Abstract: The multi-voltage threshold (MVT) digitization method has been widely used in peak power detection, thanks to its property of direct sampling fast pulse signals and cost efficiency, but it is not specifically designed to operate over a wide temperature range. In downhole exploration in the oil and gas industry, electronics for instrumentation are required to operate at wide temperature ranges. In our approach, we first used an intrinsic temperature compensation method, which is performed using the temperature characteristics of the FPGA's internal delay lines, it solves the problem of the internal delay line time drifting of the TDC. Then the pulse reconstruction based on the least-squares fitting method is realized in FPGA by using the look-up table method, and the computing speed is accelerated to meet the real-time requirements. This study provides a novel idea for the peak power detection of nanosecond pulses when operating in a wide temperature range. Highlights: The MVT digitization method is realized by FPGA. A temperature compensation method is proposed, it solves the problem of the internal delay line time drifting of TDC. An energy spectrum measurement circuit and a neutron logging instrument were designed. This study provides a new idea for the peak power detection of nanosecond pulses when operating in a wide temperature range.