A Digital Lock-In Amplifier for Use at Temperatures of up to 200 °C

Abstract

Weak voltage signals cannot be reliably measured using currently available logging tools when these tools are subject to high-temperature (up to 200 °C) environments for prolonged periods. In this paper, we present a digital lock-in amplifier (DLIA) capable of operating at temperatures of up to 200 °C. The DLIA contains a low-noise instrument amplifier and signal acquisition and the corresponding signal processing electronics. The high-temperature stability of the DLIA is achieved by designing system-in-package (SiP) and multi-chip module (MCM) components with low thermal resistances. An effective look-up-table (LUT) method was developed for the lock-in amplifier algorithm, to decrease the complexity of the calculations and generate less heat than the traditional way. The performance of the design was tested by determining the linearity, gain, Q value, and frequency characteristic of the DLIA between 25 and 200 °C. The maximal nonlinear error in the linearity of the DLIA working at 200 °C was about 1.736% when the equivalent input was a sine wave signal with an amplitude of between 94.8 and 1896.0 nV and a frequency of 800 kHz. The tests showed that the DLIA proposed could work effectively in high-temperature environments up to 200 °C.

FPGA-Based Real-time T2 Spectrum Inversion Algorithm for LWD-NMR Logging with Periodic Thermal Management

“…The low thermal resistance of the system allows the internal electronic components to dissipate heat quickly [16]. The adoption of this technology can improve the temperature resistance of the hardware platform [17]; the high-temperature stability achieved in the design of the digital lock-in amplifier (DLIA) [18]. Honeywell made technical progress during a cooperative research agreement with the U.S. Department of Energy to develop a high-temperature reconfigurable data acquisition processor (RPDA).…”

FPGA-Based Digital Lock-in Amplifier With High-Precision Automatic Frequency Tracking

“…The detection of weak signals under complex background noise is a cutting-edge technology in scientific research, geological exploration, biomedical science, military, aerospace, and other fields [1][2][3]. Relevant scholars have done a lot of fruitful research in this key field and proposed a variety of detection methods, from the detection methods of linear theory such as the conventional time domain, frequency domain, and time-frequency domain, to the detection methods of nonlinear theory such as chaos and stochastic resonance [4][5][6].…”

Data acquisition and processing circuit for high-temperature logging up to 200°C

“…However, temperature increases with depth, and deep-well exploitation generally requires logging tools to operate for 4 h at temperature up to 200°C (Hyne, 2012; Shang et al , 2017). High temperature dramatically reduces the working lifetimes of electronic components, causes thermal noise and can damage chips in logging apparatus, eventually causing it to fail (Cheng et al , 2016; Sinha and Joshi, 2011; Watson and Castro, 2012; Werner and Fahrner, 2001). The use of active cooling systems to keep circuits cool in narrow-bore (< 15 cm) wells is problematic.…”