The present disclosure discloses a coupling evaluation geophone, comprising piezoelectric ceramic crystal 1, 2 and 3, a geophone 4 and a relevant supplying circuit. Three piezoelectric ceramic crystals 1, 2 and 3 are respectively provided on the top and two lateral sides of the geophone 4. By processing measurement data derived from the coupling evaluation geophone, a ground-geophone coupling effect is obtained at a corresponding embedment point of the coupling evaluation geophone. An effect of the ground-geophone coupling on an earthquake data can be eliminated by calculation. Data detected by the coupling evaluation geophone is improved in fidelity, Signal/Noise ratio and resolution.

A closed loop broadband geophone which is made by using a high performance method to measure a mechanical vibration is disclosed. All coil portions of the two or more coil sets are located in at least 4 separate recesses of the bobbin. Each coil portion of these coil sets has an individual magnetic field magnitude using Faraday's Law and Lorentz's Law. This mathematic method, significantly improves the accuracy of both measuring the mechanical vibration and providing feedback control to the sensor coils. These coil sets are connected to an electronic device which processes the measuring signal and a feedback signal to the sensing coil as a precision digital forcing signal for a reference position.

In one aspect, an apparatus is disclosed comprising: a housing; a proof mass movable within the housing; an optical element mounted on one of the housing and the proof mass; a reflective element on the other one of the housing and the proof mass; a light source configured to illuminate grating and minor; and one or more detectors configured to detect light incident from the reflective element and the diffractive element and generate a signal indicative of the relative displacement of proof mass and the housing.

Vibration transducers, sensors including the vibration transducers, and methods for manufacturing the same. The vibration transducer may include a magnet. The vibration transducer may include a bobbin disposed about the magnet. The vibration transducer may include a first coil disposed about the bobbin. The vibration transducer may include a controllable damping coil disposed about the bobbin. The first coil is movable relative to the magnet. The magnet is polarized with respect to the axis of the vibration transducer.

A seismic sensor for a downhole tool positionable in a wellbore penetrating a subterranean formation. The seismic sensor includes a sensor housing, a bobbin supported in the sensor housing along an axis thereof, at least one coil wound about the bobbin (the coil movably supportable within the sensor housing by at least one spring), at least one magnet positionable about the bobbin to generate a magnetic field with the at least one coil whereby seismic vibrations are detectable, and a filler fluid disposed in the sensor housing to buoy the at least one coil whereby gravitational effects may be neutralized.

The present disclosure relates to fault detection at a geophone unit (1).

The geophone unit comprises a housing (2, 20), and a a geophone sensor arrangement (7) arranged in the housing (2, 20), wherein the geophone sensor arrangement (7) is configured to detect vibrations transferred from the test surface and provide a first sensor output (O1) based thereon, and wherein the geophone sensor arrangement (7) comprises a coil (5) and a magnet (4) configured to move relative to each other when the geophone (1) is subjected to said vibrations so as to provide the first sensor output (O1). The geophone unit moreover comprises a further sensor (ACC), wherein the further sensor comprises an electronic accelerometer configured to sense vibrations and provide a second sensor output (O2) based thereon. When detecting faults, a test signal (T1) is provided. so as to induce the geophone sensor arrangement (7) to provide a first test response (O1, O3) from the geophone sensor arrangement (7). a second test response (O2) from the further sensor (ACC) is provided in response to a vibration caused by the test signal (T1),

Data is processed so as to determine if a fault indication has occurred at the geophone unit (1), wherein said processed data is based on at least reference data (REF) and information retrieved from the second test response (O2). If a fault indication is determined to occur, a fault indication output (S6, S56, S66) representing an indication of a fault at the geophone unit (1) is provided.