Underground Engineering Parameters For Testing The Small-signal Amplifier Design

This paper aims to study and realize high precise amplification ofμV level voltage signals in high-temperature condition. According to practice of project, when the drilling well-engineering parameters are mixed with a variety of noise caused by the high temperature, high pressure and strong vibration, the useful signals are submerged in various noises. Only on condition that noise is restrained, SNR is strengthened, the useful signals can be picked up. So it is very necessary to study the reason and discipline that caused noise and the route of its transmission, then effective measures can be carried out. The development of technology of weak signal amplification is fast, and it has been widely used in various fields such as astronomy, geology, petroleum exploration and military affairs.The small signal amplifier based on the drilling well-engineering parameters measurement respectively adopts TLC2652 advanced Lin-CMOS precision chopper-stabilized operational amplifiers of TI corps, AD8552 zero-drift rail-to-rail operational amplifiers and OP07 high-precision ultra-low offset voltage operational amplifiers as the core of pre-amplifier. Contrasted by a series of experiments, a better pre-amplifier TLC2652 is chosen. The paper deeply studied on the small signal amplifier's noise characteristics, parts choosing, hardware debugging, anti-interference performance, and so on.This paper deeply analyzed the noise sorts, characteristics, transmitting mechanism, the noise models of some electronic parts and quantitatively calculated noise indicators. Combined with the noise parameters, it suggests a list of design principles such as low noise, low drift, and accomplish the work of circuit parameters calculation, electronic parts choosing.In aspect of amplifying-circuits design, the characteristics of main chips used in the system are introduced. The hardware circuit takes TLC2652 as the core of the pre-amplifier, and takes OP07 as the core of the active low-pass filter, high-pass filter, notch filter and so on. And adopt various anti-interference measures such as power supply filtering, shielding and grounded. Then the high-quality Printed Circuit Board is produced. Finally, the hardware test and data analysis is performed under different temperature conditions.The results of experiments show that, the small signal amplifier could realize high precise amplification of 50μV voltage signal in high-temperature condition, and has the characters of good filter performance, small solidity and stability. So it has good practical value, and satisfies the design requirements.