GB2099998A

GB2099998A - Ultrasonic viscosimeters

Info

Publication number: GB2099998A
Application number: GB8215195A
Authority: GB
Original assignee: VYZK USTAV MECH; VUMA Vyskumny Ustav Mechanizacie a Automatizacie
Current assignee: VYZK USTAV MECH; VUMA Vyskumny Ustav Mechanizacie a Automatizacie
Priority date: 1981-05-25
Filing date: 1982-05-25
Publication date: 1982-12-15
Also published as: DE3201724A1; CS235212B1; IT8219396A0; SE8203243L; FR2506457A1; JPS57196133A; IT1149537B

Abstract

In an ultrasonic viscosimeter utilizing a torsion resonator, a torsion rod (1) is fixed to a housing (5) in a nodal plane (2) and passes at nodal plane (3) through a pick-up coil (4). The housing (5) is electrically connected by conductor (6) to the upper end (7) of the torsion rod (1). An excitation transformer (8) has a primary winding in the form of a toroidal coil and a secondary winding formed by the housing (5) and torsion rod (1) so that when a current passes through rod (1), the resultant field causes the rod to twist. Damping of the torsion oscillations when the lower end of the rod is immersed in a liquid gives an indication of the viscosity of the liquid. <IMAGE>

Description

SPECIFICATION Improvements in and related to viscosimeters The invention relates to a probe for an ultrasonic viscosimeter with torsion resonator excited to torsion oscillations by a toroid coil.

A known ultrasonic torsion resonator for continuous measuring of viscosity comprises a half wave resonator fixed in its centre so that one free end is in contact with the liquid to be measured and the other end serves for exciting and picking up resonator oscillations. In another viscosimeter the torsion resonator is fixed at two nodal planes, one end part is immersed in the measured liquid, and on the other end part torsion oscillations are picked up.

Another resonator has a length equal to a half wave or to a multiple of a half wave of torsion oscillations of the respective material, it is fixed at one nodal plane and excited by a longitudinally oscillating transducer, tangentially fixed at an antinode, whereby a pick-up transducer with a 180 phase displacement against the exciting transducer is equally tangentially fixed.

A drawback of mentioned solutions is the relatively low output voltage on the pick-up coil due to the circumstance that torison oscillations are picked-u p beyond the nodal plane.

A probe according to the present invention for an ultrasonic viscosimeter with torsion resonator is provided with a torsion rod of a length B/2 . n where X is the characteristic wave length of the rod and n is an integer greater than 1, passing through a pick-up coil and through a toroidal coil forming a primary winding of a toroid transformer, the secondary winding of which is formed bya housing and bythe torsion rod, the main feature of which invention is in that the torsion rod is fixed firmly in a nodal plane to a housing and at the place of an n-th nodal plane it passes through a pick-up coil, the housing being electrically conductively connected to the upper end of the torsion rod at the place of its longitudinal axis.

The part of the torsion rod passing through the pick-up coil preferably consists of magnetostrictive material.

The pick-up coil may be connected via a primary winding of a separating transformerto a magnetizing current source.

By application of the probe for an ultrasonic viscosimeter with torsion resonator according to this invention the pick-up of torsion oscillations is accomplished within the range of a nodal plane, increasing thereby the voltage on the pick-up coil against other parts of the torsion resonator many times. If magnetostrictive material is used for the torsion rod solely at places where it passes through the pick-up coil, savings of special magnetostrictive material are obtained.

An examplary embodiment of a probe for an ultrasonic viscosimeter with torsion resonator is shown in the attached drawing in a longitudinal sectional view.

The probe for the ultrasonic viscosimeter with torsion resonator comprises a torsional oscillating rod 1 of a length B/2 . n, where n is an integer or whole positive number, for which holds true that n > 1 and k is the wave length propagated within the rod.

The torsion rod 1 consists of different materials. At the place of the first nodal plane 2 it is connected with a housing 5, at the place of the nodal plane 3, where the rod 1 passes through the pick-up coil 4 a part of the rod 1 is of magnetostrictive material. The torsion rod 1 together with the housing 5 and a conductor 6 form a secondary turn of an excitation transformer 8 which is a toroidal coil so that when a current passes through rod 1, the resultant field causes the rod to twist. The housing 5 is electrically conductively connected to the upper end 7 of the torsion rod 1 at the place of its longitudinal axis. The coils 4 and 8 are guided and fixed by the housing 5.

By a unidirectional or high frequency impulse a high frequency impulse is excited in the torsion rod 1 via the excitation transformer 8. In the course of passage of the current through the part consisting of magnetostrictive material an angular deviation of the torsion rod takes place due to magnetostriction due to the circular magnetic field. After the exciting impulse has ceased, the torsion rod continues to oscillate by dying-out oscillations at its own re sonantfrequency and these oscillations are pickedup by the pick-up coil 4 within the range of the nodal plane 3 where the maximum stress of the material is experienced and simultaneously a maximum magnetostriction occurs due to interaction with the longitudinal magnetic field of the pick-up coil excited by current from the current source 10.The alternating voltage on the pick-up coil 4 is proportional to the amplitude of torsion oscillations of the torsion rod 1. When a part of the resonator extending beyond the housing 5 is immersed in the measured liquid a damping of oscillations takes place corresponding to the magnitude of the product of viscosity and density of the liquid. The separating transformer 9 serves for separation of the alternating signal from the pick-up coil 4 and of the magnetizing current from the magnetizing current source 10.

A suitable magnetostrictive material for the magnetostrictive part of the rod 1 is an alloy of cobalt, iron, and vanadium of a ratio 49:49:2, the remaining part of the rod being of stainless steel.

1. A probe for an ultrasonic viscosimeter with torsion resonator comprising a torsion rod of a length 112 . n where X is the characteristic wave length of the rod and n is an integer greater than 1, the rod passing through a pick-up coil and through a toroidal coil forming a primary winding of an excitation transformer, the secondary winding of which is formed by a housing and the torsion rod, the torsion rod being firmly connected to the housing in a nodal plane and at the place of the n-th nodal plane it passes through the pick-up coil, the housing being electrically conductively connected to the upper end of the torsion rod at the place of its longitudinal axis.

2. A probe as claimed in Claim 1 wherein the part of the torsion -rod passing through the pick-up coil is of magnetostrictive material.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements in and related to viscosimeters The invention relates to a probe for an ultrasonic viscosimeter with torsion resonator excited to torsion oscillations by a toroid coil. A known ultrasonic torsion resonator for continuous measuring of viscosity comprises a half wave resonator fixed in its centre so that one free end is in contact with the liquid to be measured and the other end serves for exciting and picking up resonator oscillations. In another viscosimeter the torsion resonator is fixed at two nodal planes, one end part is immersed in the measured liquid, and on the other end part torsion oscillations are picked up. Another resonator has a length equal to a half wave or to a multiple of a half wave of torsion oscillations of the respective material, it is fixed at one nodal plane and excited by a longitudinally oscillating transducer, tangentially fixed at an antinode, whereby a pick-up transducer with a 180 phase displacement against the exciting transducer is equally tangentially fixed. A drawback of mentioned solutions is the relatively low output voltage on the pick-up coil due to the circumstance that torison oscillations are picked-u p beyond the nodal plane. A probe according to the present invention for an ultrasonic viscosimeter with torsion resonator is provided with a torsion rod of a length B/2 . n where X is the characteristic wave length of the rod and n is an integer greater than 1, passing through a pick-up coil and through a toroidal coil forming a primary winding of a toroid transformer, the secondary winding of which is formed bya housing and bythe torsion rod, the main feature of which invention is in that the torsion rod is fixed firmly in a nodal plane to a housing and at the place of an n-th nodal plane it passes through a pick-up coil, the housing being electrically conductively connected to the upper end of the torsion rod at the place of its longitudinal axis. The part of the torsion rod passing through the pick-up coil preferably consists of magnetostrictive material. The pick-up coil may be connected via a primary winding of a separating transformerto a magnetizing current source. By application of the probe for an ultrasonic viscosimeter with torsion resonator according to this invention the pick-up of torsion oscillations is accomplished within the range of a nodal plane, increasing thereby the voltage on the pick-up coil against other parts of the torsion resonator many times. If magnetostrictive material is used for the torsion rod solely at places where it passes through the pick-up coil, savings of special magnetostrictive material are obtained. An examplary embodiment of a probe for an ultrasonic viscosimeter with torsion resonator is shown in the attached drawing in a longitudinal sectional view. The probe for the ultrasonic viscosimeter with torsion resonator comprises a torsional oscillating rod 1 of a length B/2 . n, where n is an integer or whole positive number, for which holds true that n > 1 and k is the wave length propagated within the rod. The torsion rod 1 consists of different materials. At the place of the first nodal plane 2 it is connected with a housing 5, at the place of the nodal plane 3, where the rod 1 passes through the pick-up coil 4 a part of the rod 1 is of magnetostrictive material. The torsion rod 1 together with the housing 5 and a conductor 6 form a secondary turn of an excitation transformer 8 which is a toroidal coil so that when a current passes through rod 1, the resultant field causes the rod to twist. The housing 5 is electrically conductively connected to the upper end 7 of the torsion rod 1 at the place of its longitudinal axis. The coils 4 and 8 are guided and fixed by the housing 5. By a unidirectional or high frequency impulse a high frequency impulse is excited in the torsion rod 1 via the excitation transformer 8. In the course of passage of the current through the part consisting of magnetostrictive material an angular deviation of the torsion rod takes place due to magnetostriction due to the circular magnetic field. After the exciting impulse has ceased, the torsion rod continues to oscillate by dying-out oscillations at its own re sonantfrequency and these oscillations are pickedup by the pick-up coil 4 within the range of the nodal plane 3 where the maximum stress of the material is experienced and simultaneously a maximum magnetostriction occurs due to interaction with the longitudinal magnetic field of the pick-up coil excited by current from the current source 10.The alternating voltage on the pick-up coil 4 is proportional to the amplitude of torsion oscillations of the torsion rod 1. When a part of the resonator extending beyond the housing 5 is immersed in the measured liquid a damping of oscillations takes place corresponding to the magnitude of the product of viscosity and density of the liquid. The separating transformer 9 serves for separation of the alternating signal from the pick-up coil 4 and of the magnetizing current from the magnetizing current source 10. A suitable magnetostrictive material for the magnetostrictive part of the rod 1 is an alloy of cobalt, iron, and vanadium of a ratio 49:49:2, the remaining part of the rod being of stainless steel. CLAIMS

3. A probe as claimed in Claim 2 wherein the magnetostrictive material is an alloy of cobalt, iron and vanadium.

4. A probe as claimed in Claim 1 to 3 wherein the pick-up coil is connected via the primary winding of a separating transformer to a magnetizing current source.

5. A probe for an ultrasonic viscosimeterwith torsion resonator substantially as described with reference to the attached drawing.

6. A viscosimeter including the probe of any one of Claims 1 to 5.