Apparatus and methods for the continuous measurement of specific gravity or density of solids in a fluid medium are disclosed. A system for continuous measurement of density of a flowing medium comprises a cartridge connected in series to an inflow pipe and an outflow pipe, a displacement sensing device adapted to monitor displacement changes of the cartridge when a medium flows through the cartridge, a base configured to provide a support for the displacement sensing device, a pressure sensor, a temperature sensor, and a processor configured to calculate density of the flowing media based on measured displacement change, temperature and pressure.

A rheometer includes a drive shaft, a drag cup motor for rotating the drive shaft, a first measuring object supported by the drive shaft, a second measuring object, a linear position sensor, and processing and control electronics. The linear position sensor includes a target (e.g., an aluminum target) mounted to the drive shaft, and a pair of coils. The linear position sensor is configured to measure thermal expansion of the drive shaft based on a change in impedance of the coils resulting from a displacement of the target relative to the coils. The processing and control electronics are in communication with the coils and are configured to adjust a position of one of the measuring objects relative to the other based on a change in impedance of the coils resulting from a displacement of the target relative to the coils, thereby to maintain a substantially constant measurement gap therebetween.

A filter device includes a housing including a columnar portion having a columnar shape and provided at a filter device including a filtration member that filters a liquid, a pressure difference detection unit provided at the housing and configured to detect a pressure difference between a pressure upstream of the filtration member and a pressure downstream thereof, a viscosity sensor configured to measure viscosity of the liquid, and a temperature sensor configured to measure a temperature of the liquid are included. A hollow portion is provided inside the columnar portion, both ends of the hollow portion being covered, the hollow portion is provided with the viscosity sensor and the temperature sensor, and a communication hole that allows the hollow portion and a space outside the housing to communicate with each other is provided in the housing.

An apparatus for measuring properties of a thermosetting polymer includes a body having a first chamber and a second chamber each filled with the thermosetting polymer material. A first FBG sensor is disposed in the polymer material within the first chamber and a second FBG sensor is disposed in the polymer material within the second chamber. A first dielectric constant sensor is in the first chamber, and a second dielectric constant sensor is in the second chamber. A computing device is configured to measure properties of the thermosetting polymer based on wavelength data measured using the first FBG sensor and the second FBG sensor, and a loss coefficient of the polymer material measured using the first dielectric constant sensor and the second dielectric constant sensor, while the thermosetting polymer solidifies in the first chamber and the second chamber.