Method and device for measuring physical properties of fluid
Inventors
Kanno, Masahiro • Nagane, Yoshikazu
Assignees
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Publication Number
US-10352839-B2
Publication Date
2019-07-16
Expiration Date
Abstract
Provided are a method and device for improving a response speed in a measurement of viscosity of a fluid and obtaining a continuous smooth measurement graph. A viscometer includes a machine part that generates a shear rate in a sample, a machine drive, a shear rate changing means that outputs a target shear rate of the machine part, and a displacement detection sensor that measures displacement of the machine part, and performs feedback control to control a driving force of the machine drive so that an output value of the displacement detection sensor corresponds to the target shear rate and measures a viscosity of a sample, wherein a feedback gain is simply set for each measurement according to an optimum design or target shear rate.
Core Innovation
The invention relates to a tuning fork vibration viscometer that includes a pair of vibrators to be dunked in a sample, an electromagnetic drive for vibrating the vibrators, an amplitude value changing means outputting a target amplitude value of the vibrators, and a displacement detection sensor for measuring an amplitude of the vibrators. Feedback control is performed to control a driving current applied to the electromagnetic drive so that an output value of the displacement detection sensor corresponds to the target amplitude value, and the viscosity of the sample is measured based on a value of the driving current.
The invention addresses the problem of performing viscosity measurement in a manner that provides response speed improvement and a continuous smooth viscosity measurement graph while setting feedback gain appropriately to avoid oscillation of a measured viscosity value. The gain control means performs feedback gain setting by setting a feedback gain high at first in a state of a specific target amplitude value with respect to a sample having a specific viscosity, then reducing the gain until a limiting point that is just before a measured viscosity value starts oscillating is found.
After the limiting point is found, the gain at the limiting point is defined as an optimum feedback gain and the viscosity is measured using the optimum feedback gain. The measurement is performed every time the target amplitude value is changed, and the approach is extended using an oscillation field for staged gain selection and applied similarly to rotational viscometers using displacement sensing and a torque-to-viscosity proportional relationship.
Claims Coverage
The independent claim is clm-00001. It contains 3 inventive features comprising displacement-sensor feedback amplitude control, optimum feedback gain selection based on a limiting point just before measured viscosity oscillates, and repeated measurement when the target amplitude value changes.
Feedback amplitude control using displacement sensing
A tuning fork vibration viscometer that performs feedback control to control a driving current applied to an electromagnetic drive so that an output value of a displacement detection sensor corresponds to a target amplitude value, and measures viscosity of a sample based on a value of the driving current.
Optimum feedback gain selection by limiting-point oscillation threshold
A gain control means that sets a feedback gain high at first in a state of a specific target amplitude value with respect to a sample having a specific viscosity, reduces the gain until a limiting point that is just before a measured viscosity value starts oscillating is found, defines the gain at the limiting point as an optimum feedback gain, and performs a viscosity measurement using the optimum feedback gain.
Repeat measurement when target amplitude changes
The gain control means performs the measurement every time the target amplitude value is changed.
Overall, the claim coverage centers on a tuning fork vibration viscometer that uses displacement detection sensor feedback to drive the electromagnetic drive to a target amplitude and computes viscosity from driving current, combined with gain control that selects an optimum feedback gain using a limiting point just before viscosity oscillation and repeats measurement for each change in the target amplitude value.
Stated Advantages
Improves response speed of the viscosity measurement.
Produces a continuous smooth viscosity measurement graph.
Shortens overall measurement time.
Documented Applications
Uses the gain-control approach to perform viscosity measurement with a tuning fork vibration viscometer by updating the measurement when the target amplitude value is changed.
Extends gain control using an oscillation field and staged feedback gains to reduce hardware complexity.
Applies the gain-control approach to rotational viscometers using displacement sensing and a torque-to-viscosity proportional conversion relationship.
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