Devices for analysis of a fluid
An ultrasonic transducer is described, including a piezoelectric element, a fluid medium contact layer, a matching layer between the piezoelectric element and the fluid medium contact layer, and a backing layer. Ultrasound sensor devices utilising the ultrasonic transducer are also described, for use in systems for analysing a fluid such as milk.
1. An ultrasonic transducer including:
a piezoelectric element, wherein the piezoelectric element has an acoustic impedance of between 15 to 22 MRayls;
a fluid medium contact layer, wherein the fluid medium contact layer is a polymer layer;
a matching layer between the piezoelectric element and the fluid medium contact layer, wherein the matching layer has an acoustic impedance of between 4 to 10 MRayls; and
a backing layer, wherein the backing layer has an acoustic impedance of between 15 to 20 MRayls.
2. The ultrasonic transducer of claim 1 , wherein the piezoelectric element is a lead metaniobate piezoelectric element.
3. The ultrasonic transducer of claim 1 , wherein the polymer layer is polysulfone.
4. The ultrasonic transducer of claim 1 , wherein the thickness of the fluid medium contact layer is configured to delay reflections of an acoustic signal from an interface between the fluid medium contact layer and a fluid in contact with the fluid medium contact layer by a predetermined number of wavelengths, or part wavelengths, of the acoustic signal.
5. The ultrasonic transducer of claim 4 , wherein the thickness of the fluid medium contact layer is greater than two wavelengths of the acoustic signal.
6. The ultrasonic transducer of claim 1 , wherein the matching layer is a hydrocarbon ceramic laminate layer.
7. The ultrasonic transducer of claim 1 , wherein the matching layer has an acoustic impedance of between 5 to 8 MRayls.
8. The ultrasonic transducer of claim 1 , wherein the thickness of the matching layer is configured to provide quarter wave matching with the acoustic signal.
9. The ultrasonic transducer of claim 8 , wherein the thickness of the matching layer is between 0.2 to 0.3 wavelengths of the acoustic signal at the centre frequency of the ultrasonic transducer.
10. The ultrasonic transducer of claim 1 , wherein the matching layer is a circuit board layer.
11. The ultrasonic transducer of claim 10 , wherein the circuit board layer provides electrical connections to the piezoelectric element.
12. The ultrasonic transducer of claim 1 , wherein the backing layer has an acoustic impedance substantially that of the piezoelectric element.
13. The ultrasonic transducer of claim 1 , wherein at least one of the following is true:
the backing layer is a tungsten composite layer;
the tungsten composite of the tungsten composite layer includes first tungsten particles of a first size, and second tungsten particles of a second size;
the first tungsten particles are a granulated tungsten powder, and the second tungsten particles are a fine tungsten powder;
a ratio of granulated tungsten powder to fine tungsten powder in the tungsten composite is about 56:7;
the backing layer comprises a graduation in density of the first tungsten particles and the second tungsten particles; and
any combination thereof.
14. The ultrasonic transducer of claim 1 , wherein the ultrasonic transducer has a centre frequency of one of: between 1 to 10 MHz, between 3 to 5 MHz, 3.5 to 4 MHZ, and about 3.75 MHz.
15. The ultrasonic transducer of claim 1 , wherein the ultrasonic transducer has a −6 dB percentage bandwidth greater than 60%.
16. The ultrasonic transducer of claim 1 , wherein the −6 dB bandwidth is between 2 to 3 MHz.
17. The ultrasonic transducer of claim 1 , wherein at least one of the following is true:
the ultrasonic transducer further includes a housing having a main body, wherein a portion of the main body provides the fluid medium contact layer;
the main body includes a projection through which an acoustic pathway of the ultrasonic transducer passes;
the ultrasonic transducer further includes a piezoelectric assembly, the piezoelectric assembly including the piezoelectric element and the matching layer;
the piezoelectric assembly includes an element holder having an aperture in which the piezoelectric element is located;
wherein the element holder is made of a circuit board material;
the matching layer spans the aperture of the element holder;
the piezoelectric assembly includes an electrical contact on an opposing side of the piezoelectric element from the matching layer;
the main body includes a slotted portion configured to receive the piezoelectric assembly, wherein the ultrasonic transducer further includes a cap configured to be secured to the main body to hold the piezoelectric assembly in place within the slotted portion; and
any combination thereof.
18. A system for analysing a fluid, including:
a ultrasound sensor device comprising an ultrasonic transducer as claimed in claim 1 ,
a sample delivery device configured to deliver a sample of fluid from a fluid carrying and/or storing system to the ultrasound sensor device; and
at least one processor configured to determine a characteristic of the sample of fluid based at least in part on a signal output from the ultrasound sensor device.
19. The system of claim 18 , wherein the fluid is one of: a liquid, a solution including a liquid, and milk.
20. An ultrasound sensor device, including:
an elongate hollow body configured to receive a fluid to be analysed;
a first ultrasound transducer, provided at a first end of the hollow body, wherein the first ultrasound transducer includes:
a piezoelectric element, wherein the piezoelectric element has an acoustic impedance of between 15 to 22 MRayls;
a fluid medium contact layer, wherein the fluid medium contact layer is a polymer layer;
a matching layer between the piezoelectric element and the fluid medium contact layer,
wherein the matching layer has an acoustic impedance of between 4 to 10 MRayls; and
a backing layer, wherein the backing layer has an acoustic impedance of between 15 to 20 MRayls.
21. The ultrasound sensor device of claim 20 , further including a second ultrasound transducer of the same configuration as the first ultrasound transducer, wherein the second ultrasound transducer is provided at a second end of the hollow body and facing the first ultrasound transducer.
22. The ultrasound sensor device of claim 21 , wherein a length of the respective fluid medium contact layers of the first ultrasound transducer and the second ultrasound transducer is less than 15% of the overall path length.
23. The ultrasound sensor device of claim 21 , wherein a path length between the respective piezoelectric elements of the first ultrasound transducer and the second ultrasound transducer is one of: greater than about 25 mm, between 25 mm to 100 mm, and about 70 mm.
24. The ultrasound sensor device of claim 20 , wherein the hollow body is made of a metal.
25. The ultrasound sensor device of claim 20 , wherein the hollow body comprises an acoustically reflective surface, wherein the first ultrasound transducer faces the acoustically reflective surface.
26. The ultrasound sensor device of claim 25 , wherein a total return path length between the piezoelectric element of the first ultrasound transducer and the acoustically reflective surface is one of: greater than about 25 mm, between 25 mm to 100 mm, and about 70 mm.