Abstract: A quad-gate demodulator circuit for capacitive transducers in which analog gate devices replace the diodes of a prior art diode-quad bridge circuit. This improvement eliminates the temperature and ratiometricity errors associated with the diode-quad circuit.

Abstract: In an apparatus for testing lubricating or material properties, two clamping assemblies are pressed together. Each clamping assembly has a clamping surface facing the clamping surface on the other assembly. The first clamping surface has two annular roller paths with the axes of the paths spaced apart. The second clamping surface has one annular roller path intersecting the roller paths on the first clamping surface. Four balls roll in the roller path of the second clamping surface with two of the balls rolling in one of the roller paths of the first clamping surface and the other two balls rolling in the other roller path of the first clamping surface. The clamping assembly with the second clamping surface oscillates back and forth relative to the clamping assembly with the first clamping surface. The pulling force developed by the movement of the balls is measured as an indication of the properties of a lubricant filled into the roller paths or of the materials of the balls and the roller paths.

Abstract: A novel transducer able to detect ultrasonic surface waves over a wide frency band. The transducer is essentially a grid or series of bars connected in parallel or series. The sensitivity of the transducer increases proportionally with frequency for constant surface wave amplitude. The transducer detects surface waves by providing a resistance change across the transducer output terminal proportional to the surface wave strain. The output voltage can be calibrated to give a direct reading of the surface wave amplitude. The coupling problems which are inherent in most transducer configurations are drastically reduced for this strain sensitive detector. The modulation of the grid excitation voltage provides a means for mixing two signals by giving the direct product of the signals in time. Complicated filtering functions can be built into the grid detector by varying the bar spacing in a manner analogous to the piezoelectric interdigital grid transducer.

Abstract: In the preferred and illustrated embodiment of the disclosed apparatus, a constant pressure cylinder is set forth. Improvements included therewith are a vortex mixer for mixing the accumulated sample or specimen therein. The mixer is slidably mounted on a stainless steel centered rod to avoid damage to the cylinder wall surrounding said vortex mixer. The vortex mixer is slidably mounted on an elongate rod centered and aligned in the cylinder. Moreover, the device additionally incorporates a clear acrylic tracker tube receiving a piston tracker magnetically attracted to the piston for indicating to an observer the elevation of the piston in the constant pressure cylinder.

Abstract: A rheometer for measuring the extrudate swell of polymeric solutions. The eometer has an upper and lower transparent reservoir with a capillary tube therebetween. The flow of solution between reservoirs from upper to lower is provided by gas pressure. Initially, the swell is photographed and the lower reservoir is then filled with an immiscible Newtonian fluid. In sequence the flow is again started and a second photograph is taken. The first and second swell are measured, and the results applied to a formula to determine the first normal stress difference of the polymeric solution.