CA1224060A - Vibrating needle viscosity meter - Google Patents
Vibrating needle viscosity meterInfo
- Publication number
- CA1224060A CA1224060A CA000476700A CA476700A CA1224060A CA 1224060 A CA1224060 A CA 1224060A CA 000476700 A CA000476700 A CA 000476700A CA 476700 A CA476700 A CA 476700A CA 1224060 A CA1224060 A CA 1224060A
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- end portion
- viscosity
- coil
- viscosity meter
- measuring
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Abstract
ABSTRACT
Vibratinq needle viscosity meter A viscosity meter comprises a straight metal rod having an end portion immersed in a fluid whose viscosi-ty is determined. An intermediate portion of the rod is secured against movement and the other end portion is driven into transversal flexure oscillation by a coil.
The coil is fed with an A.C. current at the natural fre-quency of the rod and the magnitude of the oscillation is measured.
Vibratinq needle viscosity meter A viscosity meter comprises a straight metal rod having an end portion immersed in a fluid whose viscosi-ty is determined. An intermediate portion of the rod is secured against movement and the other end portion is driven into transversal flexure oscillation by a coil.
The coil is fed with an A.C. current at the natural fre-quency of the rod and the magnitude of the oscillation is measured.
Description
Vibratinq needle viscosity meter BACKGROUND AND SUMMARY OF T~IE INV~NTION
The invention relates to viscosity meters of the type having a probe consisting of a straight needle which is adapted to be partially immersed in the fluid whose viscosity is to be measured. An intermediate portion of the needle is secured against movement to constitute a node and a portion of the needle remote from the immersed portion is provided with drive means for vibrating the needle transversally and with pick up means for delivering a signal representative of the am-plitude of the vibration.
Viscosity meters of the above-defined type have been known for score of years (French 899,057). However, it was found that they are not suitable for use when a high accuracy is required or/and under circumstances where the viscosity may vary in a substantial range;
consequently U-shaped probes rather than needles are used in the present day mechanical vibration viscosity meters (French 2,353,847). On the other hand, the increased complexity of the viscosity meters using a U-shaped probe represents a definite drawbnck.
The inventors have now found that the main defi-ciencies of the prior art needle type viscosity meters may in fact be removed if they are driven at the natural or resonance frequency of the needle; a difficulty then occurs, which is the variation of that frequency if the length of the irnmersed portion or the viscosity changes.
It is an object of the invention to provide a viscosity meter which retains the simplicity in desig associated with a needle probe and substantially improves upon the accuracy, ease of use and ranye oF
operation of the prior art viscosity meters~ It is an ancillary object to provide a viscosity meter whose res-ponse rnay be rendered substantially independent of the ~r ~:2~
temperature variation in a broad range.
According to the present invention, there is provided a viscosity meter for measuring the viscosity of a fluid comprising:
stationary base means, a straight metal rod extending along a predeter-mined axis, having a first end portion adapted to be immersed in the flui.d whose viscosity should be determined, a second end por-tion and an intermedia-te portion mechanically connec-ted to said base means, drive means for maintaining said metal rod in transversal oscillation, having stationary coil means opera-tively associated with said second end portion and having circuit means for energizing said coil, and pick up means arranged to deliver an electri-cal signal representative of the amount of movement of said second end portion of said rod from a res-t position, wherein said circuit means are connected to receive said electrical signal and to energize said drive means at a frequency which is equal to the natural oscilla-tion frequency of the rod.
According to the presen-t invention, there is also provided a viscosity meter for measuring the viscosity of a fluid comprising:
stationary base means, a straight metal rod extending along a predetermined axis, having a first end portion adap-ted to be immersed in a fluid whose viscosity should be determined, a second end portion carrying a ferromagnetic element and an interme-diate portion mechanically connected to said base means, drive means for maintaining said metal rod in transversal flexure oscilla-tion, having stationary coil means operatively associated with a magnet carried by said second end portion and having circuit means for energizing said coil, and tempera-ture compensated pick up means arranged to deliver an alternating electrical signal representative of the amount of movement of said ferromagnetic element, wherein said circuit means are connec-ted to receive said electrical signal and to energize said drive means at a frequency which is substantially equal to the natural transversal oscillation frequency of the rod.
According to the present invention, there is also provided a viscosity meter for measuring the viscosity of a fluid comprising:
stationary base means, a straight metal tube extending along a predeter-mined axis, having a first end portion adapted to be immer-sed in a Eluid whose viscosi-ty should be determined and a second end portion secured to said base means, a straight metal necdle coaxial to said me-tal tube, having an external portion sealingly pro~ecting -through said firs-t end portion of said metal tube and an internal end portion freely projecting through said second end portion out of said metal -tube.
drive means for maintaining said metal needle in transversal flexure oscillation, having stationary coil means opera-tively associated with a ferromagnetic element carried by said second end portion and having cirGuit means for energizing said coil, and pick up means arranged to deliver an alterna-ting electrical signal representative of the amount of move-ment of said second end portion of said needle, wherein said circuit means are connected to receive said electrical signal to energize said drive means at a frequency which is subs-tantially equal to the natural oscillation frequency of an assembly consisting of said tube and needle, whereby said assembly exhibits transversal flexure vibrations about a node located along said predeter-mined axis at a point between said first and second end ..
6~
-2b-portions.
Expexience has shown that the response of a viscosity meter according to the invention is such -that it is suitable for use in a very wide viscosity range, typi-cally of from 1 to lO cpo. An ancillary advantage is alife duration much increased as compared with the systems in which a probe is oscillated by a ro-ta-ting cam and follo-wer mechanism.
A needle will typically be secured in an end wall of a tube section (the needle and the tube is referred to as the rod) whose opposite end is secured to a stationary plate. Then the vibration node will usually be between the ends of the tube section.
A measure of the viscosity of the fluid may be the magnitude of an electric signal delivered by the pick up means when a predetermined elec-trical power is ap-plied to the drive coil. The pick up means (e.g. Hall ele-ments) provide a voltage which is in direct relation to the amount of vibration. In another embodiment, the elec-trical current applied to the drive means may be adjustedfor maintaining the amplitude of the output from the pick up means at a constant value and the power is measured for providing an indication of the viscosity.
The output from the pick up means, as well as the movement of the needle is approximately sine shaped.
It is however preferable to deliver a square wave signal to the coil. It can be generated by amplifying and .,,. ., ~
:~2~
clipping the signal delivered by the pick up. With that approach, the vibration starts without an axternal action when power is applied.
SHORT DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic representation of the mechanical part of a viscosity meter according to an embodiment of the invention, in cross section along an axial plane;
Figure 2 is a block diagram of the energi~ing and measuring circuit of the viscosity meter of Figure l;
Figures 3 and 4 are block diagrams illustrating possible modifications of Figure 2 DETAILED DESCRIPTION OF PREFERRED EM~ODIMENT~
Referring to Figure 1, the mechanical parts of a viscosity meter comprise a base member 10 adapted to be secured onto a vessel or pipe containing the li~uid or pasteous product whose viscosity is to be measured. A
tube 12 of resilient metal (typically of stainless steel) is secured in an axial opening of the base member by appropriate means, for instance by force fitting and welding. A cylindrical needle 14 located along the axis of tube 12 projects from both ends of the tube 12. An intermediate portion of the needle is secured to an end portion of the tube remote from the base member. The rod may be secured by silver welding or electron beam welding. Means are provided for inducing a transversal flexure vibratory movement of the assembly 16 consisting of needle 14 and tube 12, which will -thereafter be referred to as a rod. As shown, the means for driving the rod into oscillation comprises a permanent magnet 18 carried by the end of the rod which is remote from the portion adaptecl to be deeped into the product. Magnet 18 is located in the air gap of an electromagnet 2û having a driving coil 22 and carried by a frame 24 fixed to the base plate 10. The frame 24 also carries a displacement ~2~
pick up 26, which may be a ~lall probe cooperating with a magnet 28 carried by the needle. The mflgnets may be carried by a cap retained on the needle by a screw.
A protective casiny 3û removably connected to the base plate lO accomodates the mechanical components.
The casing is formed with an opening through which the electrical components are connected to outside circuits.
~ finned sleeve ~4 may be located around the casing for heat dispersal.
That arrangement makes it possible to use a simple construction. For instance, satisfactory results have been obtained with a stainless steel tube 12, 50 mm long and 0.25 mm thick, having an internal diameter of mm. The length oF tlle needle is 150 mm and the diameter 3 mm. The length or diameter of the needle will be selected at a value which is all the more greater as the viscosity is lower.
Referring to Figure 2, there is illustrated a circuit which may be associated to the components of Figure l. The circuit of Figure 2 is adapted to measure the amount of damping, and consequently the viscosity, by determining the magnitude of the oscillation when a constant driving power is applied. The circuit is asso-ciated with a D.C. power source (not shown). It delivers driving signals as square signals having a constant voltage as long as the operating temperature remains unchanged. If the operating temperature range is large, the circuit can include means for compensating the variation in resistance of the coil 22 as a function of temperature.
In a first embodiment, the pick up probe 26 consists oF a Hall probe of a type which is currently available in the trade as a unit provided with its own temperature compensation circuit (Honeywell 92 SS 12-2*
for instance). That probe delivers a sine shaped signal whose amplitude is in direct relation with th~t of the * Honeywell 92 SS 12-2 is a trade mark ,d `~'I'b 06~
magnitude of the oscillation in a large range. The out-put of pick up probe 26 i5 applied to a measuring leg and a driving leg, which energizes coil 22.
The driving leg has an open loop Dperational amplifier 36 having a high gain. Two zener diodes 38 in opposed series relation connected between the output of amplifier 36 and ground clamp the signal for transforming it into square pulses. The zener diodes may be diodes having a triggering voltage of 5,1 Volt, for instance BZX 46C whose characteristics hardly vary with temperature.
The square signal is applied to a second oper-ational amplifier 40 acting as follower. As illustrated in Figure 2, amplifier 4û drives a summing amplifier 42 whose function will appear later. The output signal of amplifier 42 is applied to coil 22 through an operat-ional amplifier 44 having an adjustable gain, which is used for manual gain adjustment.
As illustrated in Figure 2, the circuit has temperature compensation means for delivering square signals, at the output frequency of pick up probe 36, whose amplitude is variable in proportion to the temper-ature variation of the coil. The compensation means will not be described in detail, since they are quite conven-tional in nature and consist of operational amplifiers.One of the inputs of compensation means 46 receives a signal from the output of amplifier 40 and a temperature representative signal delivered by a probe 48 in close proximity to coil 22. The temperature probe 48 may for instance be a platinum resistance probe available from the firm THERMO-EST under reference K 2015.
A network of resistors 50, 52 connected to the inverting input of operational amplifier 42 i5 used for summing the output signals from the amplifier 40 and from the compensation mear-s 46.
The measuring leg of the circuit includes an 6~1 operational amplifier 54 connected to an output circuit - having a rectifying diode 56 and a storage capacitor 5~, whereby it operates as a rectifier-integrator. The D.C.
voltage across capacitor 58 drives an impedance adapt-ation amplifier 60, connected as a follower. The output signal of amplifier 60 is applied to a recorder 62 which may be oF any appropriate type.
It will be appreciated that the viscosity meter of the invention provides For excitation of the rod at its natural frequency, whatever the viscosity oF the product. It has also attendent advantages: the amplitude of the oscillating movement is measured without mecha-nical contact; there is no appreciable wear of the driving mechanism; the system is not sensitive to perturbations of the A.C. network, since it uses a D.C.
power source. It may operate in any angular position and it is of reduced bulk.
Since operation of the viscosity meter results from the description, it will not be analyzed in detail.
The viscosity meter is so located that the unit consis-ting of the tube 12 and that part of needle 14 which projects from the tube is immersed in the product. Elec-trical power is applied. Operation occurs immediately, without any need for an outside excitation. The elec-tronic part may be located at a distance. When thecasing should be airtight, a grommet may be located in the opening of casing 30, with passages for the wires (two wires for coil 22, three wires for the Hall probe 26 and three wires for the temperature compensation probe).
As already indicated, detectors other than a Hall probe may be used. Each particular type of detector will generally require a temperature compensatior- cir-cuit which is particular to that detector. Referring to S5 Figure 3, there is shown the head portion of a circuit which makes use of an electromagnetic detector 2fia. A
capacitor 64 is connected across the detector for filtering purposes. The signal from detector 26a is applied to a closed loop operational amplifier 40a which drives an open loop operational amplifier 36a. Then, temperature compensation may use a coil 66 subjected to the same temperature as detector 26a and connected bet-ween a line toward the measuring leg and ground.
The thermal compensation circuit associated with the driving coil 22 may sometimes be omitted by oper-ating it at a constant current value. Referring toFigure 4, there is illustrated a circuit which may be substituted to the final portion of the energizing leg of Figure 2. The drive coil 22 is inserted in a feedback loop of operational amplifier 42. A capacitor 68 across the terminals of coil 22 may be used for adjusting resonance. The feedback loop is connected to ground by a resistor 70 which increases safety by limiting the value of the current. The operational amplifiers may be of type LM 324 or TL 084. A Schmitt trigger (for instance 4093 of National Semiconductors) may be located upstream of amplifier 44 for shaping the signal.
The invention relates to viscosity meters of the type having a probe consisting of a straight needle which is adapted to be partially immersed in the fluid whose viscosity is to be measured. An intermediate portion of the needle is secured against movement to constitute a node and a portion of the needle remote from the immersed portion is provided with drive means for vibrating the needle transversally and with pick up means for delivering a signal representative of the am-plitude of the vibration.
Viscosity meters of the above-defined type have been known for score of years (French 899,057). However, it was found that they are not suitable for use when a high accuracy is required or/and under circumstances where the viscosity may vary in a substantial range;
consequently U-shaped probes rather than needles are used in the present day mechanical vibration viscosity meters (French 2,353,847). On the other hand, the increased complexity of the viscosity meters using a U-shaped probe represents a definite drawbnck.
The inventors have now found that the main defi-ciencies of the prior art needle type viscosity meters may in fact be removed if they are driven at the natural or resonance frequency of the needle; a difficulty then occurs, which is the variation of that frequency if the length of the irnmersed portion or the viscosity changes.
It is an object of the invention to provide a viscosity meter which retains the simplicity in desig associated with a needle probe and substantially improves upon the accuracy, ease of use and ranye oF
operation of the prior art viscosity meters~ It is an ancillary object to provide a viscosity meter whose res-ponse rnay be rendered substantially independent of the ~r ~:2~
temperature variation in a broad range.
According to the present invention, there is provided a viscosity meter for measuring the viscosity of a fluid comprising:
stationary base means, a straight metal rod extending along a predeter-mined axis, having a first end portion adapted to be immersed in the flui.d whose viscosity should be determined, a second end por-tion and an intermedia-te portion mechanically connec-ted to said base means, drive means for maintaining said metal rod in transversal oscillation, having stationary coil means opera-tively associated with said second end portion and having circuit means for energizing said coil, and pick up means arranged to deliver an electri-cal signal representative of the amount of movement of said second end portion of said rod from a res-t position, wherein said circuit means are connected to receive said electrical signal and to energize said drive means at a frequency which is equal to the natural oscilla-tion frequency of the rod.
According to the presen-t invention, there is also provided a viscosity meter for measuring the viscosity of a fluid comprising:
stationary base means, a straight metal rod extending along a predetermined axis, having a first end portion adap-ted to be immersed in a fluid whose viscosity should be determined, a second end portion carrying a ferromagnetic element and an interme-diate portion mechanically connected to said base means, drive means for maintaining said metal rod in transversal flexure oscilla-tion, having stationary coil means operatively associated with a magnet carried by said second end portion and having circuit means for energizing said coil, and tempera-ture compensated pick up means arranged to deliver an alternating electrical signal representative of the amount of movement of said ferromagnetic element, wherein said circuit means are connec-ted to receive said electrical signal and to energize said drive means at a frequency which is substantially equal to the natural transversal oscillation frequency of the rod.
According to the present invention, there is also provided a viscosity meter for measuring the viscosity of a fluid comprising:
stationary base means, a straight metal tube extending along a predeter-mined axis, having a first end portion adapted to be immer-sed in a Eluid whose viscosi-ty should be determined and a second end portion secured to said base means, a straight metal necdle coaxial to said me-tal tube, having an external portion sealingly pro~ecting -through said firs-t end portion of said metal tube and an internal end portion freely projecting through said second end portion out of said metal -tube.
drive means for maintaining said metal needle in transversal flexure oscillation, having stationary coil means opera-tively associated with a ferromagnetic element carried by said second end portion and having cirGuit means for energizing said coil, and pick up means arranged to deliver an alterna-ting electrical signal representative of the amount of move-ment of said second end portion of said needle, wherein said circuit means are connected to receive said electrical signal to energize said drive means at a frequency which is subs-tantially equal to the natural oscillation frequency of an assembly consisting of said tube and needle, whereby said assembly exhibits transversal flexure vibrations about a node located along said predeter-mined axis at a point between said first and second end ..
6~
-2b-portions.
Expexience has shown that the response of a viscosity meter according to the invention is such -that it is suitable for use in a very wide viscosity range, typi-cally of from 1 to lO cpo. An ancillary advantage is alife duration much increased as compared with the systems in which a probe is oscillated by a ro-ta-ting cam and follo-wer mechanism.
A needle will typically be secured in an end wall of a tube section (the needle and the tube is referred to as the rod) whose opposite end is secured to a stationary plate. Then the vibration node will usually be between the ends of the tube section.
A measure of the viscosity of the fluid may be the magnitude of an electric signal delivered by the pick up means when a predetermined elec-trical power is ap-plied to the drive coil. The pick up means (e.g. Hall ele-ments) provide a voltage which is in direct relation to the amount of vibration. In another embodiment, the elec-trical current applied to the drive means may be adjustedfor maintaining the amplitude of the output from the pick up means at a constant value and the power is measured for providing an indication of the viscosity.
The output from the pick up means, as well as the movement of the needle is approximately sine shaped.
It is however preferable to deliver a square wave signal to the coil. It can be generated by amplifying and .,,. ., ~
:~2~
clipping the signal delivered by the pick up. With that approach, the vibration starts without an axternal action when power is applied.
SHORT DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic representation of the mechanical part of a viscosity meter according to an embodiment of the invention, in cross section along an axial plane;
Figure 2 is a block diagram of the energi~ing and measuring circuit of the viscosity meter of Figure l;
Figures 3 and 4 are block diagrams illustrating possible modifications of Figure 2 DETAILED DESCRIPTION OF PREFERRED EM~ODIMENT~
Referring to Figure 1, the mechanical parts of a viscosity meter comprise a base member 10 adapted to be secured onto a vessel or pipe containing the li~uid or pasteous product whose viscosity is to be measured. A
tube 12 of resilient metal (typically of stainless steel) is secured in an axial opening of the base member by appropriate means, for instance by force fitting and welding. A cylindrical needle 14 located along the axis of tube 12 projects from both ends of the tube 12. An intermediate portion of the needle is secured to an end portion of the tube remote from the base member. The rod may be secured by silver welding or electron beam welding. Means are provided for inducing a transversal flexure vibratory movement of the assembly 16 consisting of needle 14 and tube 12, which will -thereafter be referred to as a rod. As shown, the means for driving the rod into oscillation comprises a permanent magnet 18 carried by the end of the rod which is remote from the portion adaptecl to be deeped into the product. Magnet 18 is located in the air gap of an electromagnet 2û having a driving coil 22 and carried by a frame 24 fixed to the base plate 10. The frame 24 also carries a displacement ~2~
pick up 26, which may be a ~lall probe cooperating with a magnet 28 carried by the needle. The mflgnets may be carried by a cap retained on the needle by a screw.
A protective casiny 3û removably connected to the base plate lO accomodates the mechanical components.
The casing is formed with an opening through which the electrical components are connected to outside circuits.
~ finned sleeve ~4 may be located around the casing for heat dispersal.
That arrangement makes it possible to use a simple construction. For instance, satisfactory results have been obtained with a stainless steel tube 12, 50 mm long and 0.25 mm thick, having an internal diameter of mm. The length oF tlle needle is 150 mm and the diameter 3 mm. The length or diameter of the needle will be selected at a value which is all the more greater as the viscosity is lower.
Referring to Figure 2, there is illustrated a circuit which may be associated to the components of Figure l. The circuit of Figure 2 is adapted to measure the amount of damping, and consequently the viscosity, by determining the magnitude of the oscillation when a constant driving power is applied. The circuit is asso-ciated with a D.C. power source (not shown). It delivers driving signals as square signals having a constant voltage as long as the operating temperature remains unchanged. If the operating temperature range is large, the circuit can include means for compensating the variation in resistance of the coil 22 as a function of temperature.
In a first embodiment, the pick up probe 26 consists oF a Hall probe of a type which is currently available in the trade as a unit provided with its own temperature compensation circuit (Honeywell 92 SS 12-2*
for instance). That probe delivers a sine shaped signal whose amplitude is in direct relation with th~t of the * Honeywell 92 SS 12-2 is a trade mark ,d `~'I'b 06~
magnitude of the oscillation in a large range. The out-put of pick up probe 26 i5 applied to a measuring leg and a driving leg, which energizes coil 22.
The driving leg has an open loop Dperational amplifier 36 having a high gain. Two zener diodes 38 in opposed series relation connected between the output of amplifier 36 and ground clamp the signal for transforming it into square pulses. The zener diodes may be diodes having a triggering voltage of 5,1 Volt, for instance BZX 46C whose characteristics hardly vary with temperature.
The square signal is applied to a second oper-ational amplifier 40 acting as follower. As illustrated in Figure 2, amplifier 4û drives a summing amplifier 42 whose function will appear later. The output signal of amplifier 42 is applied to coil 22 through an operat-ional amplifier 44 having an adjustable gain, which is used for manual gain adjustment.
As illustrated in Figure 2, the circuit has temperature compensation means for delivering square signals, at the output frequency of pick up probe 36, whose amplitude is variable in proportion to the temper-ature variation of the coil. The compensation means will not be described in detail, since they are quite conven-tional in nature and consist of operational amplifiers.One of the inputs of compensation means 46 receives a signal from the output of amplifier 40 and a temperature representative signal delivered by a probe 48 in close proximity to coil 22. The temperature probe 48 may for instance be a platinum resistance probe available from the firm THERMO-EST under reference K 2015.
A network of resistors 50, 52 connected to the inverting input of operational amplifier 42 i5 used for summing the output signals from the amplifier 40 and from the compensation mear-s 46.
The measuring leg of the circuit includes an 6~1 operational amplifier 54 connected to an output circuit - having a rectifying diode 56 and a storage capacitor 5~, whereby it operates as a rectifier-integrator. The D.C.
voltage across capacitor 58 drives an impedance adapt-ation amplifier 60, connected as a follower. The output signal of amplifier 60 is applied to a recorder 62 which may be oF any appropriate type.
It will be appreciated that the viscosity meter of the invention provides For excitation of the rod at its natural frequency, whatever the viscosity oF the product. It has also attendent advantages: the amplitude of the oscillating movement is measured without mecha-nical contact; there is no appreciable wear of the driving mechanism; the system is not sensitive to perturbations of the A.C. network, since it uses a D.C.
power source. It may operate in any angular position and it is of reduced bulk.
Since operation of the viscosity meter results from the description, it will not be analyzed in detail.
The viscosity meter is so located that the unit consis-ting of the tube 12 and that part of needle 14 which projects from the tube is immersed in the product. Elec-trical power is applied. Operation occurs immediately, without any need for an outside excitation. The elec-tronic part may be located at a distance. When thecasing should be airtight, a grommet may be located in the opening of casing 30, with passages for the wires (two wires for coil 22, three wires for the Hall probe 26 and three wires for the temperature compensation probe).
As already indicated, detectors other than a Hall probe may be used. Each particular type of detector will generally require a temperature compensatior- cir-cuit which is particular to that detector. Referring to S5 Figure 3, there is shown the head portion of a circuit which makes use of an electromagnetic detector 2fia. A
capacitor 64 is connected across the detector for filtering purposes. The signal from detector 26a is applied to a closed loop operational amplifier 40a which drives an open loop operational amplifier 36a. Then, temperature compensation may use a coil 66 subjected to the same temperature as detector 26a and connected bet-ween a line toward the measuring leg and ground.
The thermal compensation circuit associated with the driving coil 22 may sometimes be omitted by oper-ating it at a constant current value. Referring toFigure 4, there is illustrated a circuit which may be substituted to the final portion of the energizing leg of Figure 2. The drive coil 22 is inserted in a feedback loop of operational amplifier 42. A capacitor 68 across the terminals of coil 22 may be used for adjusting resonance. The feedback loop is connected to ground by a resistor 70 which increases safety by limiting the value of the current. The operational amplifiers may be of type LM 324 or TL 084. A Schmitt trigger (for instance 4093 of National Semiconductors) may be located upstream of amplifier 44 for shaping the signal.
Claims (9)
1. A viscosity meter for measuring the viscosity of a fluid comprising:
stationary base means, a straight metal rod extending along a predeter-mined axis, having a first end portion adapted to be immersed in the fluid whose viscosity should be deter-mined, a second end portion and an intermediate portion mechanically connected to said base means, drive means for maintaining said metal rod in transversal oscillation, having stationary coil means operatively associated with said second end portion and having circuit means for energizing said coil, and pick up means arranged to deliver an elec-trical signal representative of the amount of movement of said second end portion of said rod from a rest position, wherein said circuit means are connected to receive said electrical signal and to energize said drive means at a frequency which is equal to the natural oscillation frequency of the rod.
stationary base means, a straight metal rod extending along a predeter-mined axis, having a first end portion adapted to be immersed in the fluid whose viscosity should be deter-mined, a second end portion and an intermediate portion mechanically connected to said base means, drive means for maintaining said metal rod in transversal oscillation, having stationary coil means operatively associated with said second end portion and having circuit means for energizing said coil, and pick up means arranged to deliver an elec-trical signal representative of the amount of movement of said second end portion of said rod from a rest position, wherein said circuit means are connected to receive said electrical signal and to energize said drive means at a frequency which is equal to the natural oscillation frequency of the rod.
2. Viscosity meter according to claim 1, wherein said circuit comprises feedback means for maintaining the amplitude of oscillation of said rod at a constant value and means for measuring an electric power deliver-ed to said coil by said circuit as an indication of the viscosity.
3. Viscosity meter according to claim 1, wherein said circuit comprises feedback means for maintaining an electric power delivered by said coil means at a cons-tant value and means for measuring the magnitude of the output signal from the pick up means.
4. Viscosity meter according to claim 3, wherein said circuit includes:
a measuring leg including said means for measuring the magnitude of the output signal, and an energization leg including said feedback means and having a high gain amplifier, clamping means connected to the output of said amplifier and delivering square pulses of a predetermined amplitude and at the frequency of said output signal and impedance matching and amplification means between said clamping means and said coil means.
a measuring leg including said means for measuring the magnitude of the output signal, and an energization leg including said feedback means and having a high gain amplifier, clamping means connected to the output of said amplifier and delivering square pulses of a predetermined amplitude and at the frequency of said output signal and impedance matching and amplification means between said clamping means and said coil means.
5. Viscosity meter according to claim 4, wherein said impedance matching and amplification means include a summing amplifier connected to receive said square pulses of predetermined amplitude and a compensation signal consisting of square pulses at the frequency of said output signal and of an amplitude which is in rela-tion with the temperature of said coil means.
6. A viscosity meter according to claim 4, wherein said means for measuring the magnitude of the output signal have an integrating amplifier connected to receive said output signal and delivering a D.C. signal whose value is in direct relation with said magnitude.
7. A viscosity meter according to claim 1, wherein said pick up means are a temperature compensated Hall probe.
8. A viscosity meter for measuring the viscosity of a fluid comprising.
stationary base means, a straight metal rod extending along a predeter-mined axis, having a first end portion adapted to be immersed in a fluid whose viscosity should be deter-mined, a second end portion carrying a ferromagnetic element and an intermediate portion mechanically connec-ted to said base means, drive means for maintaining said metal rod in transversal flexure oscillation, having stationary coil means operatively associated with a magnet carried by said second end portion and having circuit means for energizing said coil, and temperature compensated pick up means arranged to deliver an alternating electrical signal representative of the amount of movement of said ferro-magnetic element, wherein said circuit means are connected to receive said electrical signal and to energize said drive means at a frequency which is substantially equal to the natural transversal oscillation frequency of the rod.
stationary base means, a straight metal rod extending along a predeter-mined axis, having a first end portion adapted to be immersed in a fluid whose viscosity should be deter-mined, a second end portion carrying a ferromagnetic element and an intermediate portion mechanically connec-ted to said base means, drive means for maintaining said metal rod in transversal flexure oscillation, having stationary coil means operatively associated with a magnet carried by said second end portion and having circuit means for energizing said coil, and temperature compensated pick up means arranged to deliver an alternating electrical signal representative of the amount of movement of said ferro-magnetic element, wherein said circuit means are connected to receive said electrical signal and to energize said drive means at a frequency which is substantially equal to the natural transversal oscillation frequency of the rod.
9. A viscosity meter for measuring the viscosity of a fluid comprising:
stationary base means, a straight metal tube extending along a prede-termined axis, having a first end portion adapted to be immersed in a fluid whose viscosity should be determined and a second end portion secured to said base means, a straight metal needle coaxial to said metal tube, having an external portion sealingly projecting through said first end portion of said metal tube and an internal end portion freely projecting through said second end portion out of said metal tube.
drive means for maintaining said metal needle in transversal flexure oscillation, having stationary coil means operatively associated with a ferromagnetic ele-ment carried by said second end portion and having cir-cuit means for energizing said coil, and pick up means arranged to deliver an alter-nating electrical signal representative of the amount of movement of said second end portion of said needle, wherein said circuit means are connected to receive said electrical signal and to energize said drive means at a frequency which is substantially equal to the natural oscillation frequency of an assembly con-sisting of said tube and needle, whereby said assembly exhibits transversal flexure vibrations about a node located along said predetermined axis at a point between said first and second end portions.
stationary base means, a straight metal tube extending along a prede-termined axis, having a first end portion adapted to be immersed in a fluid whose viscosity should be determined and a second end portion secured to said base means, a straight metal needle coaxial to said metal tube, having an external portion sealingly projecting through said first end portion of said metal tube and an internal end portion freely projecting through said second end portion out of said metal tube.
drive means for maintaining said metal needle in transversal flexure oscillation, having stationary coil means operatively associated with a ferromagnetic ele-ment carried by said second end portion and having cir-cuit means for energizing said coil, and pick up means arranged to deliver an alter-nating electrical signal representative of the amount of movement of said second end portion of said needle, wherein said circuit means are connected to receive said electrical signal and to energize said drive means at a frequency which is substantially equal to the natural oscillation frequency of an assembly con-sisting of said tube and needle, whereby said assembly exhibits transversal flexure vibrations about a node located along said predetermined axis at a point between said first and second end portions.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000476700A CA1224060A (en) | 1985-03-15 | 1985-03-15 | Vibrating needle viscosity meter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000476700A CA1224060A (en) | 1985-03-15 | 1985-03-15 | Vibrating needle viscosity meter |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1224060A true CA1224060A (en) | 1987-07-14 |
Family
ID=4130043
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000476700A Expired CA1224060A (en) | 1985-03-15 | 1985-03-15 | Vibrating needle viscosity meter |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1224060A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108827831A (en) * | 2018-06-07 | 2018-11-16 | 深圳市鸿曙科技有限公司 | Oscillatory type viscosity apparatus and its Detection Method of Liquid Viscosity |
-
1985
- 1985-03-15 CA CA000476700A patent/CA1224060A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108827831A (en) * | 2018-06-07 | 2018-11-16 | 深圳市鸿曙科技有限公司 | Oscillatory type viscosity apparatus and its Detection Method of Liquid Viscosity |
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