Receiving circuit of transient field through casing resistivity logging system

Abstract

The invention discloses a receiving circuit of a transient field through casing resistivity logging system. The receiving circuit comprises a matching circuit, a filtering circuit, a pre-addition or subtraction amplification circuit, a lock amplifier, a multi-channel amplification circuit, an AD acquisition circuit and a DSP electrically connected in sequence; and the matching circuit comprises afront-end processing module and a signal clamping module electrically connected with each other, the front-end processing module is electrically connected with a receiving coil, and the signal clamping module is electrically connected with the filtering circuit. The receiving circuit of the transient field through casing resistivity logging system has the beneficial effects that a transient fieldthrough casing signal is a low frequency signal, a chopper modulation and amplification technology can effectively reduce interference of 1 / f noise at the low frequency on a received signal, the noise suppression ability of the circuit is enhanced, and the purpose of improving the signal-to-noise ratio of the received signal is achieved.

Description

technical field [0001] The invention belongs to the field of well logging systems, in particular to a receiving circuit of a transient field through-casing resistivity logging system in the field. Background technique [0002] Transient electromagnetic signals have a wide dynamic range and are difficult to be sampled. If the resolution of the instrument is improved by simply increasing the signal amplification factor, saturation is prone to occur. Compared Figure 1a and Figure 1b it can be discovered Figure 1a The signal is distorted due to excessive pre-gain, and part of the real signal is lost; in addition Figure 1b The tail signal is already very weak and not easy to detect. Moreover, the frequency of the measured signal is very low, close to the DC signal, and the 1 / f noise at the low frequency will cause great interference to the received signal. If a low-noise preamplifier is directly used, the circuit design is simple, but the noise of the receiving circuit itse...

AI Technical Summary

Problems solved by technology

[0002] Transient electromagnetic signals have a wide dynamic range and are difficult to be sampled. If the resolution of the instrument is improved by simply increasing the signal amplification factor, saturation is prone to occur

Compared Figure 1a and Figure 1b It can be found Figure 1a The signal is distorted due to excessive pre-gain, and part of the real signal is lost; in addition Figure 1b The tail signal is already very weak, it is not easy to detect

Moreover, the frequency of the measured signal is very low, close to the DC signal, and the 1 / f noise at the low frequency will cause great interference to the received signal. If a low-noise preamplifier is directly used, the circuit design is simple, but the noise of the receiving circuit itself and the 1 / f After the noise is amplified, it will appear at the output of the post-amplifier with a large amplitude. When the useful signal amplitude is small, it cannot be detected at all.

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