Closed loop rheometer
AssigneeBohlin Instruments Limited
InventorsNigel Evans, John Wilkinson
Life of this patent
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Abstract
The invention provides a method for operating a controlled stress rheometer in a controlled strain mode to follow a demand strain Xd in a sample having applied thereto a variable demand force Td, inducing an actual strain X including the steps of: monitoring the actual strain X; continuously comparing the actual strain X with the demand strain Xd and calculating the difference; calculating in real time, using an appropriate algorithm, the value of Td necessary to adjust the strain from X to Xd, and adjusting Td to the calculated value so as to effect this strain adjustment. The method may be performed by a computer software algorithm installed in a digital signal processor forming part of the controller system of the rheometer.
Claims15
A method for operating a controlled stress rheometer in a controlled strain mode to follow a demand strain Xd in a sample having applied thereto a variable demand force Td inducing an actual strain X including the steps of:
- monitoring the actual strain X;
- continuously comparing the actual strain X with the demand strain Xd and calculating the difference;
- and
- calculating in real time, using an appropriate algorithm, the value of Td necessary to adjust the strain from X to Xd;
- and adjusting Td to the calculated value so as to effect this strain adjustment,
- wherein the algorithm employs a transfer function based on a third order solution to the Butterworth approximation.
A method for operating a controlled stress rheometer as a torque measuring device to follow a variable demand force Td in a sample subjected to a pre-selected demand strain Xd, said method comprising the steps of:
- monitoring the actual strain X;
- continuously comparing the actual strain X with the demand strain Xd and calculating the difference;
- adjusting the actual strain X to equal the demand strain Xd, and
- calculating in real time, using an appropriate algorithm, the value of Td necessary to adjust the strain from X to Xd.
- wherein the algorithm employs a transfer function based on a third order solution to the Butterworth approximation.
A controlled stress rheometer comprising a controller as claimed 14.
Dependencies are inferred from the claim text.