Fluid density sensing systems

Claim 2

In a vibration densitometer, the combination comprising: a structure including a vibratable member immersible in a fluid; a magnetostrictive driver mounted on said structure including a coil and a magnetostrictive body, said body being mounted in a position to vibrate said member; a detector mounted on said structure to produce an alternating output signal of a frequency equal to the frequency at which said member is vibrated; and means connected from said detector to impress a level shifted alternating voltage on said coil which is in phase with the output signal of said detector, said alternating voltage having an average value larger than zero and of an amplitude sufficient to keep the current in said coil flowing in one direction only.

Claim 3

The invention as defined in claim 1, wherein said means includes a first circuit to maintain the average current through said coil constant and independent of any change in the resistance of said coil.

Claim 4

The invention as defined in claim 1, wherein said means includes a first circuit to produce an output signal of a predetermined frequency approximately equal to the output signal of said detector and a phase approximately equal thereto, a second circuit to produce an output signal of said predetermined frequency and shifted in phase 90 degrees with respect to said first circuit output signal, and a third circuit connected from said first and second circuits to said coil to impress the alternating component of said level shifted voltage thereon, which component is directly proportional to the sum of a portion of the output of each of said first and second circuits.

Claim 5

The invention as defined in claim 3, wherein said second circuit includes a tracking filter, a fourth circuit connected from said crystal to the tracking filter input to impress thereon an alternating signal which is 90 degrees out of phase with the crystal output signal, said tracking filter including an amplifier, a first resistor and first and second capacitors, said first resistor being connected from said amplifier input to said amplifier output, said second capacitor being connected from the filter input to the amplifier input, said first circuit including a filter frequency control circuit and a phase detector, said control circuit being connected from said phase detector to the mutual junction of said capAcitors, said phase detector being connected from the input and output of said tracking filter, said first circuit output signal being provided over a connection from said mutual junction to said third circuit, said second circuit output signal being provided over a connection from the output of said amplifier to said third circuit.

Claim 6

The invention as defined in claim 4, wherein said third circuit includes an input junction, a second resistor connected from said mutual junction to said input junction, a third resistor connected from said amplifier output to said input junction, a fourth resistor connected from said input junction to a first point of first reference potential, said coil having first and second ends, amplifier means connected from said input junction to said first coil end, a fifth resistor connected from said second coil end to a second point of second reference potential different from that of said first potential, a sixth resistor connected from said second coil end to said input junction, a third capacitor and a seventh resistor connected in series from said coil end to said input junction.

Claim 7

The invention as described in claim 5, wherein said amplifier means produces an inverted output.

Claim 8

The invention as defined in claim 1, wherein said coil voltage impressing means includes amplifier means having an input connected from said detector and an output connected to one end of said coil, a first resistor having one end connected to the other end of said coil and the other end connected to a point of reference potential, a second resistor connected from said other coil end to said amplifier means input, and a feedback circuit connected from said one coil end to said amplifier means input, said feedback circuit including a series connected capacitor.

Claim 9

The invention as defined in claim 7, wherein said feedback circuit also includes a third resistor, said capacitor and said resistor being connected in series between the output and input of said amplifier means.

Claim 10

The invention as defined in claim 8, wherein said amplifier means has an inverted output.

Claim 11

The invention as defined in claim 9, wherein said third circuit includes a tracking filter, a fifth circuit connected from said crystal to the tracking filter input to impress thereon an alternating signal which is 90* out of phase with the crystal output signal, said tracking filter including an amplifier a first resistor and first and second capacitors, said first resistor being connected from said amplifier input to said amplifier output, said second capacitor being connected from the filter input to the amplifier input, said second circuit including a filter frequency control circuit and a phase detector, said control circuit being connected from said phase detector to the mutual junction of said capacitors, said phase detector being connected from the input and output of said tracking filter, said second circuit output signal being provided over a connection from said mutual junction to said fourth circuit, said third circuit output signal being provided over a connection from the output of said amplifier to said fourth circuit.

Claim 12

The invention as defined in claim 10, wherein said fourth circuit includes an input junction, a second resistor connected from said mutual junction to said input junction, a third resistor connected from said amplifier output to said input junction, a fourth resistor connected from said input junction to a first point of first reference potential, said coil having first and second ends, amplifier means connected from said input junction to said first coil end, a fifth resistor connected from said second coil end to a second point of second reference potential different from that of said first potential, a sixth resistor connected from said second coil end to said input junction, a third capacitor and a seventh resistor connected in series from said first coil end to said input junction.

Claim 13

The invention as defined in claim 1, wherEin said amplifier means produces an inverted output.

Claim 14

The invention as defined in claim 7, wherein said crystal is located approximately midway along the length of said vane.

Claim 15

In a vibration densitometer, the combination comprising: a structure including a vibratable member immersible in a fluid; a magnetostrictive driver mounted on said structure including a coil and a magnetostrictive body, said body being mounted in a position to vibrate said member; a detector mounted on said structure to produce an alternating output signal of a frequency equal to the frequency at which said member is vibrated; means connected from said detector to impress a level shifted alternating voltage on said coil which is in phase with the output signal of said detector, said alternating voltage having an average value larger than zero and of an amplitude sufficient to keep the current in said coil flowing in one direction only; said member being an approximately rectangular vane having a thickness small in comparison to its length or width, said vane being supported at its ends and being supported along its length at the edges thereof, said detector being a piezoelectric crystal positioned along one of said edges, said structure including inner and outer concentric cylinders, said vane being supported by said inner cylinder inside thereof, said outer cylinder having a hole therethrough 90 degrees from said crystal around said cylinders, said magnetostrictive body extending through said hole into engagement with said inner cylinder 90 degrees from said crystal around said cylinders, varying contact pressure of said body on said inner cylinder causing vibration of said vane when said means impresses said level shifted alternating voltage on said coil; said means including a first circuit to maintain the average current through said coil constant and independent of any change in the resistance of said coil due to a change in the temperature thereof or otherwise; said means including a second circuit to produce an output signal of a predetermined frequency approximately equal to the output signal of said crystal and a phase approximately equal thereto, a third circuit to produce an output signal of said predetermined frequency and shifted in phase 90 degrees with respect to said second circuit output signal, and a fourth circuit connected from said second and third circuits to said coil to impress the alternating component of said level shifted voltage thereon, which component is directly proportional to the sum of a portion of the output of each of said second and third circuits, said fourth circuit including an input junction, a first resistor connected from said third circuit to said input junction, a resistor connected from said second circuit to said input junction, a third resistor connected from said input junction to a first point of first reference potential, said coil having first and second ends, amplifier means connected from said input junction to said first coil end, a fourth resistor connected from said second coil end to a second point of second reference potential different from that of said first potential, a fifth resistor connected from said second coil end to said input junction, a capacitor and a sixth resistor connected in series from said first coil end to said input junction.

Claim 16

In a vibration densitometer, the combination comprising: a structure including a vibratable member immersible in a fluid; a magnetostrictive driver mounted on said structure including a coil and a magnetostrictive body, said body being mounted in a position to vibrate said member; a detector mounted on said structure to produce an alternating output signal of a frequency equal to the frequency at which said member is vibrated; means connected from said detector to impress a level shifted alternating voltage on said coil which is in phase with the output signal of said detector, said alternating voltage having an average value larger than zero and of an amplitude sufficient to keep the current in said coil flowing in one direction only; said member being an approximately rectangular vane having a thickness small in comparison to its length or width, said vane being supported at its ends and being supported along its length at the edges thereof, said detector being a piezoelectric crystal positioned along one of said edges, said structure including inner and outer concentric cylinders, said vane being supported by said inner cylinder inside thereof, said outer cylinder having a hole therethrough 90 degrees from said crystal around said cylinders, said magnetostrictive body extending through said hole into engagement with said inner cylinder 90 degrees from said crystal around said cylinders, varying contact pressure of said body on said inner cylinder causing vibration of said vane when said means impresses said level shifted alternating voltage on said coil; said means including a first circuit to maintain the average current through said coil constant and independent of any change in the resistance of said coil due to a change in the temperature thereof or otherwise; said means including a second circuit to produce an output signal of a predetermined frequency approximately equal to the output signal of said crystal and a phase approximately equal thereto, a third circuit to produce an output signal of said predetermined frequency and shifted in phase 90 degrees with respect to said second circuit output signal, and a fourth circuit connected from said second and third circuits to said coil to impress the alternating component of said level shifted voltage thereon, which component is directly proportional to the sum of a portion of the output of each of said second and third circuits, said fourth circuit including an input junction, a first resistor connected from said third circuit to said input junction, a resistor connected from said second circuit to said input junction, a third resistor connected from said input junction to a first point of first reference potential, said coil having first and second ends, amplifier means connected from said input junction to said first coil end, a fourth resistor connected from said second coil end to a second point of second reference potential different from that of said first potential, a fifth resistor connected from said second coil end to said input junction, a capacitor and a sixth resistor connected in series from said first coil end to said input junction.

Claim 17

The invention as defined in claim 14, wherein said amplifier means produces an inverted output.

Claim 18

A vibration densitometer comprising: a structure adapted to be substantially fixed in position; a member mounted on said structure in a position to be vibrated while exposed to contact by a fluid; a driver mounted on said structure in a position to vibrate said member when an alternating signal is impressed thereon; a sensor mounted contiguous to said member to produce an output signal of a frequency equal to the frequency of the vibration of said member; apparatus connected from said sensor to said driver to impress an alternating signal on said driver of an amplitude larger than The sensor output signal, but of the same frequency and phase, said apparatus including an amplifier, a first circuit connected from said sensor to the input of said amplifier, and a second circuit connected from the output of the amplifier to said driver; and self-start means connected to said amplifier input and actuable to impress an alternating self-start signal thereon which has a frequency that varies periodically and continuously over a predetermined band of interest.

Claim 19

A vibration densitometer comprising: a structure adapted to be substantially fixed in position; a member mounted on said structure in a position to be vibrated while exposed to contact by a fluid; a driver mounted on said structure in a position to vibrate said member when an alternating signal is impressed thereon; a sensor mounted contiguous to said member to produce an output signal of a frequency equal to the frequency of the vibration of said member; apparatus connected from said sensor to said driver to impress an alternating signal on said driver of an amplitude larger than The sensor output signal, but of the same frequency and phase, said apparatus including an amplifier, a first circuit connected from said sensor to the input of said amplifier, and a second circuit connected from the output of the amplifier to said driver; and self-start means connected to said amplifier input and actuable to impress an alternating self-start signal thereon which has a frequency that varies periodically and continuously over a predetermined band of interest.

Claim 20

A vibration densitometer comprising: a structure adapted to be substantially fixed in position; a member mounted on said structure in a position to be vibrated while exposed to contact by a fluid; a driver mounted on said structure in a position to vibrate said member when an alternating signal is impressed thereon; a sensor mounted contiguous to said member to produce an output signal of a frequency equal to the frequency of the vibration of said member; apparatus connected from said sensor to said driver to impress an alternating signal on said driver of an amplitude larger than the sensor output signal, but of the same frequency and phase, said apparatus including an amplifier, a first circuit connected from said sensor to the input of said amplifier, and a second circuit connected from the output of the amplifier to said driver; and self-start means connected to said amplifier input and actuable to impress an alternating self-start signal thereon which has a frequency that varies periodically and continuously over a predetermined band of interest, said self-start means including a first variable frequency oscillator connected from a second oscillator to said amplifier, said second oscillator having an oscillation frequency lower than that of said first oscillator.

Claim 21

A vibration densitometer comprising: a structure adapted to be substantially fixed in position; a member mounted on said structure in a position to be vibrated while exposed to contact by a fluid; a driver mounted on said structure in a position to vibrate said member when an alternating signal is impressed thereon; a sensor mounted contiguous to said member to produce an output signal of a frequency equal to the frequency of the vibration of said member; apparatus connected from said sensor to said driver to impress an alternating signal on said driver of an amplitude larger than the sensor output signal, but of the same frequency and phase, said apparatus including an amplifier, a first circuit connected from said sensor to the input of said amplifier, and a second circuit connected from the output of the amplifier to said driver; and self-start means connected to said amplifier input and actuable to impress an alternating self-start signal thereon which has a frequency that varies periodically and continuously over a predetermined band of interest, said self-start means including a first variable frequency oscillator connected from a second oscillator to said amplifier, said second oscillator having an oscillation frequency lower than that of said first oscillator.

Claim 22

The invention as defined in claim 17, including control means connected from the output of said amplifier for reducing the output of said self-start means when said member reaches resonance.

Claim 23

The invention as defined in claim 18, wherein the output signal amplitude of said self-start means is reduced to zero when said member reaches resonance.

Claim 24

The invention as defined in claim 19, wherein said control means includes a synchronous detector connected from the input and output of said amplifier to said self-start means.

Claim 25

The invention as defined in claim 20, wherein said self-start means also includes a gate, said first oscillator being connected to said amplifier input through said gate, the output of said synchronous detector being connected to said gate to open and to close the same depending upon the signal magnitude at the synchronous detector output.

Claim 26

The invention as defined in claim 21, including a switch to signal the lack of resonance connected from said amplifier output, the output of said synchronous detector being connected to said switch to operate it in accordance with whether or not resonance exists.

Claim 27

The invention as defined in claim 22, including an output circuit, said switch being connected to said output circuit said switch being adapted to hold the output signal of said output circuit to a magnitude outside the operating range thereof when there is no resonance.

Claim 28

The invention as defined in claim 23, wherein said switch holds said output circuit output signal constant when there is no resonance.

Claim 29

A vibration densitometer comprising: a structure adapted to be substantially fixed in position; a member mounted on said structure in a position to be vibrated while exposed to contact by a fluid; a driver mounted on said structure in a position to vibrate said member when an alternating signal is impressed thereon; a sensor mounted contiguous to said member to produce an output signal of a frequency equal to the frequency of the vibration of said member; apparatus connected from said sensor to said driver to impress an alternating signal on said driver of an amplitude larger than the sensor output signal, but of the same frequency and phase, said apparatus including an amplifier, a first circuit connected from said sensor to the input of said amplifier, and a second circuit connected from the output of the amplifier to said driver; and self-start means connected to said amplifier input and actuable to impress an alternating self-start signal thereon which has a frequency that varies periodically and continuously over a predetermined band of interest; control means connected from the output of said amplifier for reducing the output of said self-start means when said member reaches resonance.

Claim 30

A vibration densitometer comprising: a structure adapted to be substantially fixed in position; a member mounted on said structure in a position to be vibrated while exposed to contact by a fluid; a driver mounted on said structure in a position to vibrate said member when an alternating signal is impressed thereon; a sensor mounted contiguous to said member to produce an output signal of a frequency equal to the frequency of the vibration of said member; apparatus connected from said sensor to said driver to impress an alternating signal on said driver of an amplitude larger than the sensor output signal, but of the same frequency and phase, said apparatus including an amplifier, a first circuit connected from said sensor to the input of said amplifier, and a second circuit connected from the output of the amplifier to said driver; and self-start means connected to said amplifier input and actuable to impress an alternating self-start signal thereon which has a frequency that varies periodically and continuously over a predetermined band of interest; control means connected from the output of said amplifier for reducing the output of said self-start means when said member reaches resonance.

Claim 31

The invention as defined in claim 25, wherein said control means includes a synchronous detector connected from the input and output of said amplifier to said self-start means.

Claim 32

The invention as defined in claim 26, including a switch to signal the lack of resonance connected from said amplifier output, the output of said synchronous detector being connected to said switch to operate it in accordance with whether or not resonance exists.

Claim 33

The invention as defined in claim 27, including an output circuit, said switch being connected to said output circuit, said switch being adapted to hold the output signal of said output circuit to a magnitude outside the operating range thereof when there is no resonance.

Claim 34

The invention as defined in claim 28, wherein said switch holds said output circuit output signal constant when there is no resonance.

Claim 35

The invention as defined in claim 29, wherein the output signal amplitude of said self-start means is reduced to zero when said member reaches resonance.

Claim 36

The invention as defined in claim 25, wherein the output signal amplitude of said self-start means is reduced to zero when said member reaches resonance.

Claim 37

In a vibration densitometer, the combination comprising: a structure including a vibratable member immersible in a fluid; a magnetostrictive driver mounted on said structure including a coil and a magnetostrictive body, said body being mounted in a position to vibrate said member; a detector mounted on said structure to produce an alternating output signal of a frequency equal to the frequency at which said member is vibrated; and means connected from said detector to impress an alternating voltage on said coil which is in phase with the output signal of said detector; said member being an approximately rectangular vane having a thickness small in comparison to its length or width, said vane being unsupported at its ends and being supported along its length at the edges thereof, said detector being a piezoelectric crystal positioned along one of said edges, said structure including inner and outer concentric cylinders, said vane being supported by said inner cylinder inside thereof, said outer cylinder having a hole therethrough 90* from said crystal around said cylinders, said magnetostrictive body extending through said hole into engagement with said inner cylinder 90* from said crystal around said cylinders, varying contact pressure of said body on said inner cylinder causing vibration of said vane when said means impresses said level shifted alternating voltage on said coil.

Claim 38

In a vibration densitometer, the combination comprising: a structure including a vibratable member immersible in a fluid; a magnetostrictive driver mounted on said structure including a coil and a magnetostrictive body, said body being mounted in a position to vibrate said member; a detector mounted on said structure to produce an alternating output signal of a frequency equal to the frequency at which said member is vibrated; and means connected from said detector to impress an alternating voltage on said coil which is in phase with the output signal of said detector; said member being an approximately rectangular vane having a thickness small in comparison to its length or width, said vane being unsupported at its ends and being supported along its length at the edges thereof, said detector being a piezoelectric crystal positioned along one of said edges, said structure including inner and outer concentric cylinders, said vane being supported by said inner cylinder inside thereof, said outer cylinder having a hole therethrough 90* from said crystal around said cylinders, said magnetostrictive body extending through said hole into engagement with said inner cylinder 90* from said crystal around said cylinders, varying contact pressure of said body on said inner cylinder causing vibration of said vane when said means impresses said level shifted alternating voltage on said coil.

Claim 39

The invention as defined in claim 32, wherein said crystal is located approximately midway along the length of said vane.

Claim 40

In a vibration densitometer, the combination comprising: a structure including a vibratable member immersible in a fluid; a magnetostrictive driver mounted on said structure including a coil and a magnetostrictive body, said body being mounted in a position to vibrate said member; a detector mounted on said structure to produce an alternating output signal of a frequency equal to the frequency at which said member is vibrated; and means connected from said detector to impress an alternating voltage on said coil which is in phase with the output signal of said detector.

Claim 41

In a vibration densitometer, the combination comprising: a structure including a vibratable member immersible in a fluid; a magnetostrictive driver mounted on said structure including a coil and a magnetostrictive body, said body being mounted in a position to vibrate said member; a detector mounted on said structure to produce an alternating output signal of a frequency equal to the frequency at which said member is vibrated; and means connected from said detector to impress an alternating voltage on said coil which is in phase with the output signal of said detector.

Claim 42

In a vibration densitometer, the combination comprising: a structure including a vibratable member immersible in a fluid; a magnetostrictive driver mounted On said structure including a coil and a magnetostrictive body, said body being mounted in a position to vibrate said member; a detector mounted on said structure to produce an alternating output signal of a frequency equal to the frequency at which said member is vibrated; and means connected from said detector to impress an alternating voltage on said coil which is in phase with the outupt signal of said detector; said member being an approximately rectangular vane having a thickness small in comparison to its length or width, said vane being unsupported at its ends and being supported along its length at the edges thereof, said detector being a piezoelectric crystal positioned along one of said edges, said structure including inner and outer concentric cylinders, said vane being supported by said inner cylinder inside thereof, said outer cylinder having a hole therethrough 90 degrees from said crystal around said cylinders, said magnetostrictive body extending through said hole into engagement with said inner cylinder 90 degrees from said crystal around said cylinders, varying contact pressure of said body on said inner cylinder causing vibration of said vane when said means impresses said level shifted alternating voltage on said coil.

Claim 43

In a vibration densitometer, the combination comprising: a structure including a vibratable member immersible in a fluid; a magnetostrictive driver mounted On said structure including a coil and a magnetostrictive body, said body being mounted in a position to vibrate said member; a detector mounted on said structure to produce an alternating output signal of a frequency equal to the frequency at which said member is vibrated; and means connected from said detector to impress an alternating voltage on said coil which is in phase with the outupt signal of said detector; said member being an approximately rectangular vane having a thickness small in comparison to its length or width, said vane being unsupported at its ends and being supported along its length at the edges thereof, said detector being a piezoelectric crystal positioned along one of said edges, said structure including inner and outer concentric cylinders, said vane being supported by said inner cylinder inside thereof, said outer cylinder having a hole therethrough 90 degrees from said crystal around said cylinders, said magnetostrictive body extending through said hole into engagement with said inner cylinder 90 degrees from said crystal around said cylinders, varying contact pressure of said body on said inner cylinder causing vibration of said vane when said means impresses said level shifted alternating voltage on said coil.

Claim 44

The invention as defined in claim 35, wherein said crystal is located approximately midway along the length of said vane.

Claim 45

In a vibration densitometer, the combination comprising: a structure including a vibratable member immersible in a fluid; a magnetostrictive driver mounted on said structure including a coil and a magnetostrictive body, said body being mounted in a position to vibrate said member; a detector mounted on said structure to produce an alternating output signal of a frequency equal to the frequency at which said member is vibrated; and means connected from said detector to impress an alternating voltage on said coil which is in phase with the output signal of said detector.

Claim 46

In a vibration densitometer, the combination comprising: a structure including a vibratable member immersible in a fluid; a magnetostrictive driver mounted on said structure including a coil and a magnetostrictive body, said body being mounted in a position to vibrate said member; a detector mounted on said structure to produce an alternating output signal of a frequency equal to the frequency at which said member is vibrated; and means connected from said detector to impress an alternating voltage on said coil which is in phase with the output signal of said detector.