Abstract: A set point pressure control circuit is disclosed for controlling pressure in a high pressure environment. The circuit includes a high pressure communicating, low pressure actuated valve. The valve includes a housing in which a valve member is disposed. The valve member has an axial passageway defined therethrough for communicating a high pressure port across a piston of the valve member to an opposite high pressure chamber which is placed in communication with a low pressure port when the valve member is in an open position.

Abstract: A fluid testing apparatus comprises a container for holding a fluid to be tested and a member disposed within the container so that the member is rotatable within a fluid to be tested within the container. The container has a wall defining a cavity into which the member extends. A magnetically responsive rotor is mounted on this end of the member. Immediately adjacent the outside surface of this wall, a plurality of stator poles are secured so that a field generated in the stator poles directly interacts with the rotor across the wall to rotate the member. The rotor and stator poles are preferably of a stepper motor.

Abstract: An appartus and method for testing characteristics of a substance, such as a cement slurry to be used within an oil or gas well, are provided. The apparatus includes a single drive motor which can be actuated in either a dynamic mode or a static mode to measure, in the preferred embodiment, either consistency or static gel strength of the substance. A single display is switchably connectible to one of two scaling circuits which scale a single transducer output signal to provide the desired measurement.