A capacitance sensing assembly comprising: an all-pass filter including an op-amp and a first capacitor with a first electrode of the first capacitor connected to a non-inverting input of the op-amp; and a complex impedance circuit connected between a second electrode of the first capacitor and a ground and including a variable capacitor having a terminal connected to the ground; wherein the complex impedance circuit increases a gradient of a phase to frequency response curve of the capacitance sensing assembly relative to that of the reversed all-pass filter with the second electrode of the first capacitor connected to ground without the complex impedance circuit.

An anomaly detection system according to the present disclosure includes: an optical fiber (10) configured to detect a state of a metal wire (20) affected by a magnetic force generated between a vehicle (60) and a guideway (50) of a magnetically levitated train; a reception unit (30) configured to receive, from the optical fiber (10), an optical signal including information indicating an effect of the magnetic force received by the metal wire (20); and a detection unit (42) configured to detect an anomaly of the vehicle (60) or the guideway (50) based on the information indicating the effect of the magnetic force received by the metal wire (20), the information being included in the optical signal.

An anomaly detection system according to the present disclosure includes: an optical fiber (10) configured to detect a state of a metal wire (20) affected by a magnetic force generated between a vehicle (60) and a guideway (50) of a magnetically levitated train; a reception unit (30) configured to receive, from the optical fiber (10), an optical signal including information indicating an effect of the magnetic force received by the metal wire (20); and a detection unit (42) configured to detect an anomaly of the vehicle (60) or the guideway (50) based on the information indicating the effect of the magnetic force received by the metal wire (20), the information being included in the optical signal.

An optomechanical gravimeter includes: a first and second accelerometer; and a spacer member interposed between the first accelerometer and the second accelerometer such that the first accelerometer and the second accelerometer independently include: a basal member; a test mass disposed on the basal member; a flexural member interposed between the basal member and the test mass such that the test mass is moveably disposed on the basal member via flexing of the flexural member; an armature disposed on the basal member and opposing the test mass and the flexural member such that: the armature is spaced apart from the test mass; a cavity including: a first mirror disposed on the test mass; a second mirror disposed on the armature, the spacer member providing a substantially constant distance of separation between a first measurement point of the first accelerometer and a second measurement point of the second accelerometer.

An optomechanical gravimeter includes: a first and second accelerometer; and a spacer member interposed between the first accelerometer and the second accelerometer such that the first accelerometer and the second accelerometer independently include: a basal member; a test mass disposed on the basal member; a flexural member interposed between the basal member and the test mass such that the test mass is moveably disposed on the basal member via flexing of the flexural member; an armature disposed on the basal member and opposing the test mass and the flexural member such that: the armature is spaced apart from the test mass; a cavity including: a first mirror disposed on the test mass; a second mirror disposed on the armature, the spacer member providing a substantially constant distance of separation between a first measurement point of the first accelerometer and a second measurement point of the second accelerometer.

Gravity surveys of subterranean formations may be based on the simultaneous measurement of gravity and its derivatives to produce a higher resolution formation map or wellbore log. For example, a method of performing a gravity survey may include positioning a matter wave interferometer relative to a subterranean formation; producing at least one cloud of atoms in the matter wave interferometer; producing a superposition of atoms in two different, spatially separated superimposed clouds from each of the at least one cloud of atoms; propagating the two different, spatially separated superimposed clouds along the matter wave interferometer as they with a gravitational field of the subterranean formation; combining the two different, spatially separated superimposed clouds with a Raman laser beam; measuring an interference produced by producing and combining the two different, spatially separated superimposed clouds; and calculating gravity for the gravitational field of the subterranean formation based on the interference.

Gravity surveys of subterranean formations may be based on the simultaneous measurement of gravity and its derivatives to produce a higher resolution formation map or wellbore log. For example, a method of performing a gravity survey may include positioning a matter wave interferometer relative to a subterranean formation; producing at least one cloud of atoms in the matter wave interferometer; producing a superposition of atoms in two different, spatially separated superimposed clouds from each of the at least one cloud of atoms; propagating the two different, spatially separated superimposed clouds along the matter wave interferometer as they with a gravitational field of the subterranean formation; combining the two different, spatially separated superimposed clouds with a Raman laser beam; measuring an interference produced by producing and combining the two different, spatially separated superimposed clouds; and calculating gravity for the gravitational field of the subterranean formation based on the interference.

The present invention discloses a MEMS gravimeter comprising: a spring-mass system, a displacement sensing structure, a displacement detecting circuit, a cavity body and a level adjustment base; the spring-mass system is disposed inside the cavity body and includes: a negative-stiffness spring, a positive-stiffness spring, a proof mass and an outer frame; the proof mass is connected to the outer frame by the negative-stiffness spring and the positive-stiffness spring, the negative-stiffness spring and the positive-stiffness spring are symmetrically disposed with respect to the proof mass, and the outer frame is fixedly connected to the cavity body; the displacement sensing structure is located on a surface of the proof mass, and the displacement detecting circuit is configured to detect a displacement signal from the displacement sensing structure; the spring-mass system realizes reduction in resonant frequency by matching of the positive and negative stiffness springs; and change in gravitational acceleration is detected by detecting a displacement of the proof mass. The MEMS gravimeter has high stability, small size and light weight, and thus can effectively reduce the production cost as well as the development difficulty of the signal detection unit and stable platform.

The present invention discloses a MEMS gravimeter comprising: a spring-mass system, a displacement sensing structure, a displacement detecting circuit, a cavity body and a level adjustment base; the spring-mass system is disposed inside the cavity body and includes: a negative-stiffness spring, a positive-stiffness spring, a proof mass and an outer frame; the proof mass is connected to the outer frame by the negative-stiffness spring and the positive-stiffness spring, the negative-stiffness spring and the positive-stiffness spring are symmetrically disposed with respect to the proof mass, and the outer frame is fixedly connected to the cavity body; the displacement sensing structure is located on a surface of the proof mass, and the displacement detecting circuit is configured to detect a displacement signal from the displacement sensing structure; the spring-mass system realizes reduction in resonant frequency by matching of the positive and negative stiffness springs; and change in gravitational acceleration is detected by detecting a displacement of the proof mass. The MEMS gravimeter has high stability, small size and light weight, and thus can effectively reduce the production cost as well as the development difficulty of the signal detection unit and stable platform.

A system method and computer-readable medium for correcting measurements obtained by a down hole tool for residual measurement errors is disclosed. A down hole tool having at least two directional field sensors is disposed in a borehole. The at least two directional sensors are substantially orthogonal to each other and to a longitudinal axis of the down hole tool. Measurements are obtained from the at least two directional sensors during rotation of the tool by at least 360 degrees around the longitudinal axis of the tool. Residual measurement errors are determined for the obtained measurements, and a quality level of the determined residual measurement errors selected. The determined residual measurement errors are applied to the obtained measurements when the determined residual measurement errors are consistent with the selected quality level. In various embodiments, the residual measurement errors are reduced from a first value that does not match the selected quality level to a second value that are consistent with the selected quality level.