Geophysical prospecting instrument is to use the benign conductivity, activation effect, radioactivity and other physical properties of groundwater to find the location, depth, water level and water yield of groundwater, also known as "water prospecting instrument" "water meter".

Principle of geophysical prospecting (water), with natural electric field as the source, in underground rock ore (groundwater) electrical difference, on the basis of measured natural electromagnetic field of the earth several different frequency electromagnetic fields produced by the change law of electric field and to study the different geological anomaly to solve geological problem of an electrical prospecting instrument.

At present, there are two kinds of geophysical water detector in China, one is nuclear magnetic resonance water detector, which is relatively expensive, the other is the common natural electric field water detector, which is cheap to the public, and it is the helper of well users to solve the problem of dry eyes. People usually say of drilling Wells for water meter is this, the instrument analysis of underground structure, variable layer fracture zone, is look not to come out of water, through the analysis of underground structures to water conditions, drilling users know made the layer is the best water conditions, combined with personal experience and the local geology condition with the consent of the lithology analysis, to determine how much out of water.

Domestic well water meter brand is not many, China Coal Group geological exploration equipment research institute water meter is a key into the chart of the instrument, suitable for the majority of well users to use.

This paper introduces the theoretical basis and design principle of the natural electric field geophysical instrument, and designs the earth electric field audio electric field signal of multiple frequency points based on the electromagnetic field theory, which is used to qualitatively understand the observation scheme of the typical structure of underground geological body. The weak signal detection technology is adopted in the design. The weak audio earth electric field signal is amplified, filtered, frequency selected and detected, integrated, and converted into digital signal after signal conditioning for analysis.

The instrument can observe the electric field signal of many frequency, and use a variety of reliable technology in hardware design and software development, so that the ability of anti-interference and the stability of the system have been strengthened. The instrument adopts multi-channel and multi-mode data collection, and carries out automatic analysis and processing on the collected data, saves the data in real time, draws the curve, and finds the broken belt through the curve.

Through the comparative analysis of field work examples, the natural electric field frequency detector can reflect the geological information within a certain depth of underground, and can be used for the rapid survey of geology and mineral resources, engineering geophysical exploration and water resources.