A method and device for estimating a density value .sub.m indicative of a true density or for estimating a viscosity value .sub.m indicative of a true viscosity of a fluid is disclosed. For this, a first resonance frequency f.sub.R of a first mechanical oscillator in a reference volume and a second resonance frequency f.sub.F of a second mechanical oscillator in contact with the fluid are measured. The estimated value .sub.m or .sub.m is then derived using these resonance frequencies f.sub.R and f.sub.F. During this derivation, at least one fluid-temperature- or fluid-pressure-dependent parameter of the fluid is used. Additionally or alternatively, the first (i.e. reference) mechanical oscillator is arranged in contact with a reference fluid. Thus, fundamental errors in the derivation of the estimated value .sub.m or .sub.m are reduced and the estimated value becomes more reliable.

A method and device for estimating a density value .sub.m indicative of a true density or for estimating a viscosity value .sub.m indicative of a true viscosity of a fluid is disclosed. For this, a first resonance frequency f.sub.R of a first mechanical oscillator in a reference volume and a second resonance frequency f.sub.F of a second mechanical oscillator in contact with the fluid are measured. The estimated value .sub.m or .sub.m is then derived using these resonance frequencies f.sub.R and f.sub.F. During this derivation, at least one fluid-temperature- or fluid-pressure-dependent parameter of the fluid is used. Additionally or alternatively, the first (i.e. reference) mechanical oscillator is arranged in contact with a reference fluid. Thus, fundamental errors in the derivation of the estimated value .sub.m or .sub.m are reduced and the estimated value becomes more reliable.

Some aspects of what is described here relate to analyzing a well cement slurry. In some aspects, a well cement slurry is mixed in a mixer under a plurality of conditions. The plurality of conditions correspond to a plurality of distinct Reynolds number values for the well cement slurry in the mixer. Power number values associated with mixing the well cement slurry in the mixer under the plurality of conditions are identified. Each power number value is based on an amount of energy used to mix the well cement slurry under a respective one of the plurality of conditions. Values for parameters of a functional relationship between power number and Reynolds number are identified based on the power number values and the Reynolds number values for the plurality of conditions.

A piezoelectric unit 1 includes a piezoelectric element that causes thickness shear vibration, a first electrode provided on one surface of the piezoelectric element, a second electrode and a third electrode which are provided on an opposite surface to the one surface which is provided with the first electrode of the piezoelectric element and are electrically insulated from each other, and a switching portion that is connected to the first electrode, the second electrode, and the third electrode, in which the switching portion can switch measurement modes between a mass/viscoelasticity measurement mode for measuring mass of a substance which is in contact with the piezoelectric element or viscoelasticity by vibrating the piezoelectric element, and an electrical characteristic measurement mode for measuring electrical characteristics between the second electrode and the third electrode.

A method to measure the vibrational characteristics of an oscillating system (1) uses a control system (6, 7a, 7b, 7c). The oscillating system comprises a resonator, at least one vibration exciter and at least one sensor. The resonator is excited by the vibration exciter, and the motion of the resonator is measured by the sensor. The control system uses the sensor to control the motion of the resonator by the vibration exciter. The motion of the resonator is a superposition of at least two harmonic motions, and the control system comprises at least two subcontrollers (7a, 7b, 7c). Each harmonic motion is controlled independently by one of the subcontrollers. The harmonic motions are controlled by the subcontrollers simultaneously. A corresponding device is also disclosed.

A method for fills and/or cleans the measurement cell of a measuring instrument, namely a viscometer and/or density measuring instrument, in particular of a rotational viscometer. A sample is introduced via a sample line into the measurement cell by a pump, and wherein a dynamic viscosity and/or density of the sample is determined in the measurement cell. A funnel-shaped, reversibly openable receiving container, in particular a filling funnel, for the sample, is arranged in the sample line, between the pump and the measurement cell. The receiving container is opened and the sample is introduced into the receiving container. The receiving container is connected to the pump via a pressure line in such a way that, when pressure is applied into the receiving container, a proportion of the sample is dispensed out of the receiving container and introduced into the measurement cell.

A method for fills and/or cleans the measurement cell of a measuring instrument, namely a viscometer and/or density measuring instrument, in particular of a rotational viscometer. A sample is introduced via a sample line into the measurement cell by a pump, and wherein a dynamic viscosity and/or density of the sample is determined in the measurement cell. A funnel-shaped, reversibly openable receiving container, in particular a filling funnel, for the sample, is arranged in the sample line, between the pump and the measurement cell. The receiving container is opened and the sample is introduced into the receiving container. The receiving container is connected to the pump via a pressure line in such a way that, when pressure is applied into the receiving container, a proportion of the sample is dispensed out of the receiving container and introduced into the measurement cell.

A hybrid free-space acoustic oscillator system and method for detecting perturbations in a free-space region by analyzing phase-induced frequency shifts. An acoustic transmitter is configured to emit signals at a preset oscillation frequency into the free-space region, where a sample under test induces phase shifts. An acoustic receiver captures the phase-shifted signals and converts them into electrical signals. A first and second feedback loop interconnect the receiver and transmitter, incorporating a first amplifier, a bandpass filter, and phase shifters to regulate signal characteristics. The system dynamically compensates for induced phase variations through controlled feedback adjustments. A detector measures the difference between the preset and new oscillation frequency to determine a property of the sample under test.

A system and method of determining a density of a drilling fluid in a wellbore. The system includes a drill string in the wellbore, the drill string including a downhole rotor. A drilling fluid flowing through the drill string in the wellbore causes the downhole rotor to rotate relative to the drill string. A brake is configured to apply a first brake torque to the downhole rotor to place the downhole rotor in a first state. A torque measurement system is configured to determine the applied first brake torque. A rotor speed measurement system is configured to measure a first downhole rotor speed of the downhole rotor having the drilling fluid flowing therethrough with the downhole rotor in the first state. A processor is configured to determine a density of the drilling fluid from the measured first downhole rotor speed, and the determined applied first brake torque.

A system and method of determining a density of a drilling fluid in a wellbore. The system includes a drill string in the wellbore, the drill string including a downhole rotor. A drilling fluid flowing through the drill string in the wellbore causes the downhole rotor to rotate relative to the drill string. A brake is configured to apply a first brake torque to the downhole rotor to place the downhole rotor in a first state. A torque measurement system is configured to determine the applied first brake torque. A rotor speed measurement system is configured to measure a first downhole rotor speed of the downhole rotor having the drilling fluid flowing therethrough with the downhole rotor in the first state. A processor is configured to determine a density of the drilling fluid from the measured first downhole rotor speed, and the determined applied first brake torque.