Coriolis-type mass flowmeter circuitry

A signal processing and control method for a Coriolis-type mass flowmeter having several oscillating conduit sections, comprising

• oscillating a conduit section, detecting the displacements of the respective ends of said section and producing two corresponding complementary sensor outputs, each including a drive component and a Coriolis component,
• recovering the drive component from the two sensor outputs,
• controlling the oscillation of each conduit in accordance with the drive signal derived from the recovered drive component by applying complementary forms of said drive signal to complementary force drivers at opposite ends of each section, and
• compensating for drive force imbalance between the drivers at opposite ends of each section of said conduit.

In a Coriolis-type mass flowmeter having at least one oscillating conduit section, the combination comprising

• an oscillation drive system coupled to one conduit section to oscillate said section,
• a detector system arranged to sense the displacement of the ends of said section producing corresponding complementary sensor outputs, each including a drive component and a Coriolis component,
• a signal processing circuit connected to receive said sensor outputs for recovering said drive component,
• said oscillation drive system including a pair of drivers coupled to opposite ends respectively of each conduit section, said drive signal being applied in complementary forms to said drivers respectively,
• an error signal generator responsive to said output signals and having an output indicative of drive force imbalance, and
• a drive force matching circuit adapted to compensate for imbalance between the drivers at opposite ends of a conduit section.

A correction system for a Coriolis mass flowmeter, comprising

• at least one conduit,
• a pair of force drivers at opposite ends respectively of a section of said conduit,
• a pair of sensors at opposite ends of said section of said conduit arranged to sense the displacement of the ends of said section producing two corresponding sensor outputs,
• a drive signal generator having an output forming a drive signal,
• means for applying of said drive signal to said drivers respectively,
• a perturbation signal generator having an output forming a perturbation signal out-of-phase with said drive signal,
• a combining circuit having said perturbation signal and said drive signal as inputs and having an output forming a composite drive signal representing an algebraic combination of said input signals,
• a combination circuit connected to receive both sensor outputs and having an output representing a combination of said sensor outputs,
• a detector connected to receive the output of said combination circuit and having an output indicative of any remaining artifact due to said perturbation signal which did not cancel out in said combination circuit because of an imbalance in said drivers.

A Coriolis-type mass flowmeter, comprising

• at least two nominally parallel conduit sections each having a similar resonant frequency of vibration,
• a pair of drivers at opposite ends of each section, each driver capable of forcing the respective end in either lateral direction in response to a drive signal,
• a drive circuit connected to said drivers, responsive to said resonant frequency, having first and second drive signal outputs,
• two of said drivers located at corresponding ends of said sections being connected to receive said first drive signal output,
• two other drivers at opposite corresponding ends of said sections being connected to receive said second drive signal output,
• corresponding ones of said drivers being interconnected such that the same drive signal applied to corresponding drivers forces the corresponding ends of the sections toward or away from each other.

A Coriolis-type mass flowmeter, comprising

• at least two nominally parallel conduit sections each having a similar resonant frequency of vibration,
• a pair of drivers at opposite ends of each section, each driver capable of forcing the respective end in either lateral direction in response to a drive signal,
• a pair of sensors at opposite ends of each section, each sensor having an output indicative of the magnitude of displacement of the corresponding end,
• a drive circuit connected to said drivers, responsive to said resonant frequency, having first and second drive signal outputs,
• two of said drivers located at corresponding ends of said sections being connected to receive said first drive signal output,
• two other drivers at the opposite corresponding ends of said sections being connected to receive said second drive signal output, said drivers being interconnected such that the same drive signal applied to corresponding drivers forces the corresponding ends of the sections toward or away from each other, and
• a signal processing circuit having first and second signal inputs and an output indicative of mass flow, the outputs of sensors at corresponding ends of the respective sections being coupled to said first signal input, the outputs of sensors at the opposite corresponding ends of said sections being coupled to said second signal input.