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.

Abstract: A rotational rheometer is provided with a heat control cup located around a measuring cup having a wall thickness decreasing gradually from the bottom of the cup to its outer rim. Temperature of the heat control cup is maintained by a heat pump. The heat controlled cup has a wall thickness which is narrow at or adjacent the open end than the thickness adjacent the base of the cup.

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:

Abstract: A rheometer has temperature control means which include a bath through which liquid is circulated, so that it will completely immerse both the upper and lower probes or plates between which a sample, whose rheological are being investigated, is located. This allows the temperature of the sample to be closely controlled to within 0.2.degree. C. of a selected temperature. The rheometer is particularly suitable for measuring the properties of bitumous materials which are extremely temperature sensitive.