Viscometer

Details Viscometer Viscometer

1987-04-23

1988-08-23

Levy, Stewart J.

Measuring and testing

Liquid analysis or analysis of the suspension of solids in a...

Viscosity

G01N 1114

Patent

active

047651806

DESCRIPTION:

BRIEF SUMMARY
This invention relates to viscometers, and in particular to an improved sensing arrangement and control arrangement therefor.
The measurement of viscosity is important in many production processes, and there have been a large number of proposals for viscosity measuring apparatus.
One previous proposal is that of my own earlier United Kingdom patent application No. 2 058 341, which used a continuously rotated, resiliently mounted bob immersed in the test liquid; the change in angular position of a detection arm connected to the bob with change in liquid viscosity was recorded once each bob revolution by detector means, conveniently optical detector means.
An alternative arrangement is that disclosed in U.S. Pat. No. 4,448,061 in which a transducer is provided with a stator included in the drive of a resiliently yieldable connection subject to a constant speed drive, and having a rotor which turns relative to the stator as the connection yields or recovers in response to viscosity changes; the transducer provides a continuous signal, the strength of which changes with viscosity changes, and which is continuously delivered to a digital display or readout which is responsive thereto.
It is an object of my invention to provide a viscometer having an intermittent signal delivered to a recorder e.g. a visual display, but with an accuracy at least equal to that of known apparatus with continuously delivered signals.
Thus according to one feature of my invention I provide a viscometer in which the angular position of an element responsive to the viscosity of a test liquid is sensed by a magnetoresistive sensor. Preferably the sensor indicates the relative angular positions of two rotatable elements, one of which is responsive to the liquid viscosity. Thus I provide a viscometer for use in monitoring the viscosity of a liquid, which includes a rotatable support element, drive means to rotate said support element, a rotatable driven element coaxial with said support element and having a part which is to be immersed in a liquid the viscosity of which is to be monitored and which is to be subjected to a viscous drag which changes as the viscosity of the liquid changes, resilient means connecting the elements and which yields with variation in the relative angular position of the elements as the viscous drag increases, electrical means to sense the variation in the relative angular position of the elements and to provide an electrical output signal of a magnitude dependent upon said relative angular position, and electronic means communicating with the electrical means and arranged to record the variation in angular position characterised in that the electrical means is a magnetoresistive sensor mounted to rotate with one of the elements and responsive to magnetic flux producing means mounted to rotate with the other of the elements, in that the electronic means is connected to the electrical means by an analogue to digital converter, and in that the electronic means is a microprocessor system adapted to derive intermittent electronic signals from the electrical means by intermittent sampling of the output of the analogue to digital converter.
In order that the viscometer of the present invention can provide rapid updates of any change in viscosity, I arrange my magnetoresistive sensor to provide several indicator signals each second, usually at least 10 signals per second and conveniently 20 signals per second.
As is well known, the electrical resistance of thin ferromagnetic, layers depends on the angle between the direction of the electrical current flowing in the layers and the direction of the imposed magnetisation (the magnetoresistive effect). For my ferromagnetic layer I prefer an alloy of 80% nickel and 20% iron, since such an alloy has a significant resistance charge of between 2% and 3%, whilst having stable and repeatable characteristics over a wide temperature range; though in alternative embodiments I may use an alloy having between 70% and 90% nickel. Thus such a material is particularly useful as a senso

REFERENCES:
patent: 2587174 (1952-02-01), Lanz
patent: 3533275 (1970-10-01), Zemp
patent: 4175425 (1979-11-01), Brookfield
patent: 4373147 (1983-02-01), Carlson, Jr.

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