Oscillating viscometer

Claim 2

Apparatus for measuring fluid properties from controlled relative rotation between first and second viscometer elements having therebetween a fluid the properties of which are to be measured, said apparatus comprising: means for generating a drive signal having a waveform representing predetermined desired relative rotation between said viscometer elements; means for generating a torque signal in response to said drive signal; means for torquing said first element over a predetermined angular extent in response to said torque signal; means responsive to rotation of said first element for providing a position signal representative of angular position of said first element with respect to said second element through said predetermined angle; and means responsive to said position signal for providing position feedback control of said torque signal whereby said first viscometer element is torqued to maintain close relative angular correspondence with the waveform of said drive signal.

Claim 3

The apparatus for measuring fluid properties of claim 1 wherein: said drive signal is a triangle wave.

Claim 4

The apparatus for measuring fluid properties of claim 1 wherein said drive signal has an interval of constant amplitude whereby said torque signal is representative of fluid viscoelastic properties.

Claim 5

The apparatus for measuring fluid properties of claim 1 wherein said drive signal is a sinusoid thereby to permit phase measurements of Newtonian fluids and detection of nonlinear features of non-Newtonian fluids.

Claim 6

The apparatus for measuring fluid properties of claim 1 wherein said drive signal varies at a very slow rate to cause an angular rotation of said viscometer elements as slow as a few cycles per hour.

Claim 7

The apparatus for measuring fluid properties of claim 1 wherein said torque generating means is a DC torque generator.

Claim 8

The apparatus for measuring fluid properties of claim 1 further including means responsive to said torque and drive signals to provide a graphical representation of the variation of one with respect to the other and permit separate measurement of viscous and elastic fluid properties.

Claim 9

The apparatus for measuring fluid properties of claim 1 wherein: one of said viscometer elements is fixed; and means are provided to temperature control the fixed element so as to adjust the fluid temperature.

Claim 10

The apparatus for measuring fluid properties of claim 1 wherein: said position signal providing means includes means for providing an alternating current excitation signal thereto to provide said position signal as an alternating current signal; means are provided for demodulating said position signal to provide a direct current signal representative of the angle of rotation of said first element; said torque signal generating means further includes: means for differencing said drive signal and said demodulated position signal to provide a difference signal indicative of deviation in the angular position of said first element; and means for amplifying said difference signal to provide said torque signal from small relative differences between said demodulated position signal and said drive signal thereby to provide negative proportional feedback control over the relative rotation of said first viscometer element.

Claim 11

The apparatus for measuring fluid properties of claim 9 further including means for stabilizing said torque signal to provide quick response to said drive signal and said difference signal without permitting oscillation of said first element independent of said drive signal.

Claim 12

The apparatus for measuring fluid properties of claim 9 wherein said torquing means includes: an excitation source providing an excitation current to said torquing means with the resulting torque from said torquing means being representative of the magnitudes of said excitation current and said torque signal; and meAns for providing an output indication of the response of said first element as a combination of said torquing means excitation current and said torque signal.

Claim 13

The apparatus for measuring fluid properties of claim 9 further including: means for modulating said difference signal with said excitation signal; and means for exciting said torquing means with said excitation signal.

Claim 14

The apparatus for viscosity measurement of claim 1 further including means for selectively attenuating said torque signal as applied to said torquing means whereby said torque signal has a greater magnitude than necessary to torque said first element thereby to facilitate torque signal measurement.

Claim 15

The apparatus for measuring fluid properties of claim 1 including low friction, gas bearing support means for the first element of said viscometer to allow low friction rotation thereof with respect to the second of the elements of said viscometer.

Claim 16

In a viscometer of the type having first and second elements defining an annular cavity therebetween adapted to contain a fluid whose viscous properties are to be measured, a system for producing controlled rotation of said first viscometer element with respect to the other and comprising: means for supporting said second element against rotation; means for temperature controlling said second, stationary element; a function generator operative to provide an output drive signal having a predetermined waveform; means for sensing the angle of rotation of said first element and for producing an output position signal representative thereof; means for differencing said position signal and said drive signal to provide a difference signal representative of the deviation between actual angular position of said first element and the angular position represented by said position signal; means for amplifying said difference signal; an electromagnetic torque generator responsive to the amplified difference signal to apply a corresponding torque to said first viscometer element; fluid bearing means for rotationally supporting said first element; lead-lag means for applying damping to said difference signal to stabilize the response of said system; and means for providing a graphical representation of said difference signal as a function of said position signal.

Claim 17

In a viscometer of the type having first and second elements defining an annular cavity therebetween adapted to contain a fluid whose viscous properties are to be measured, a system for producing controlled rotation of said first viscometer element with respect to the other and comprising: means for supporting said second element against rotation; means for temperature controlling said second, stationary element; a function generator operative to provide an output drive signal having a predetermined waveform; means for sensing the angle of rotation of said first element and for producing an output position signal representative thereof; means for differencing said position signal and said drive signal to provide a difference signal representative of the deviation between actual angular position of said first element and the angular position represented by said position signal; means for amplifying said difference signal; an electromagnetic torque generator responsive to the amplified difference signal to apply a corresponding torque to said first viscometer element; fluid bearing means for rotationally supporting said first element; lead-lag means for applying damping to said difference signal to stabilize the response of said system; and means for providing a graphical representation of said difference signal as a function of said position signal.

Claim 18

The system for producing controlled rotation of claim 15 wherein said torque generator is a permanent magnet DC torque generator.

Claim 19

The system for producing controlled rotation of claim 15 further including means for selectively attenuating said difference signal whereby the relationship between the torque applied to said first element and said difference signal may be adjusted.