CN2372684Y

CN2372684Y - Liquid density sensor by ultrasonic wave

Info

Publication number: CN2372684Y
Application number: CN 99230869
Authority: CN
Inventors: 蔡绍皙; 吕霞付; 邓明晰; 舒红宇; 段铭; 吴西
Original assignee: Chongqing University
Current assignee: Chongqing University
Priority date: 1999-01-26
Filing date: 1999-01-26
Publication date: 2000-04-05
Anticipated expiration: 2009-01-26

Abstract

The utility model relates to an ultrasonic liquid density sensor, which is a medical sensor. A pair of interdigital transducers and a side plate are used for forming a closed measuring cavity body; the interdigital transducers are arranged on plates which are oppositely parallel; interdigital electrodes on the interdigital transducers are arranged oppositely and are staggered with each other; the interdigital electrodes in the measuring cavity have anticorrosion performance; the surface of a piezoelectric crystal, which is in contact with liquid which is prepared for measurement has a layer of a metal film; the interdigital electrodes are respectively connected with an ultrasonic generator and a phase detector by electrode lead wires. Because the volume of the measuring chamber is small, the utility model is suitable for dynamically measuring the density of micro liquid, and is especially suitable for dynamically measuring the density of blood. Because the phase detection technology is adopted, the measuring resolution is high.

Description

Ultrasonic liquid density sensor

The utility model belongs to medical energy converter, and it is a kind of electro-acoustic element, is a kind of sensitive element of measuring a kind of sensitive element, particularly dynamic measuring density of blood of fluid density.

At 1989 " sound material effects magazine " the 4th volume 1-3 (Journal of Wave-MaterialInteraction on the phase, Vol4, No1-3,1989) delivered and be entitled as " typical microwave sound fluid sensor ", this sensor is by interdigital transducer, and strict with it parallel glass plate and acoustic absorbant composition, respectively there is one group of interdigital electrode at the two ends of interdigital transducer, testing liquid is strapped between glass plate and the interdigital transducer by capillary action, its weak point is: it can only the static measurement fluid density, owing to adopt the acoustic duct mode, require the two sides strict keeping parallelism relative, and very high smooth finish must be arranged with contacted interdigital transducer of liquid and glass plate, make difficulty, after repeatedly reflecting, it is very big to decay, not the viscous liquid of energy measurement such as blood in liquid for ultrasound wave.

The purpose of this utility model is to provide a kind of Measurement Resolution height, and the testing liquid volume is little, measures response soon, can be used for the fluid density kinetic measurement, particularly the Ultrasonic liquid density sensor of density of blood kinetic measurement.

For achieving the above object, the technical solution of the utility model is on the basis of existing technology by paired interdigital transducer [1], [2] and side plate [7] sealing that constituted liquid measure cavity, interdigital transducer is contained on the relative parallel-plate with acoustic absorbant [4], interdigital electrode on it relatively also staggers mutually, interdigital electrode is positioned at measures the chamber, the both sides of cavity are connected with the intubate [8] that liquid flows into and flows out, end on each interdigital transducer piezoelectric crystal is manufactured with the interdigital electrode [5] with antiseptic property, on the surface of piezoelectric crystal up and down in liquid measure chamber layer of metal film is arranged.An interdigital electrode connects ultrasonic generator [9] through contact conductor [3], and another interdigital electrode connects phase detectors [10] through contact conductor [3].

For achieving the above object, the measure that the utility model is taked is that the thickness of piezoelectric crystal is 0.5 to 1.5 millimeter, and the finger logarithm of interdigital electrode is 50 to 200, and the electrode cycle is 40 to 100 microns, vertical range between two transducers is 0.5 to 2 millimeter, side plate [7] be shaped as arc.

The utility model has following advantage compared to existing technology: the Measurement Resolution height, greater than the 10-6 grams per milliliter, blood volume to be measured is little, less than 0.2 milliliter, it is fast to measure response, is not subjected to the restriction of sample frequency, and used ultrasonic signal frequencies is lower, be suitable for the kinetic measurement of fluid density kinetic measurement, particularly density of blood.

Fig. 1 is the A-A sectional view of Fig. 2;

Fig. 2 is the B-B sectional view of Fig. 1; Among Fig. 1, Fig. 2: [1] and [2] respectively is interdigital transducer, and [3] are contact conductor, and [4] are acoustic absorbant, and [5] are interdigital electrode, and [6] are piezoelectric crystal, and [7] are side plate, and [8] are intubate, and [9] are ultrasonic generator, and [10] are phase-sensitive detector.

Be described as follows below in conjunction with accompanying drawing 1,2:

During the utility model work, the high-frequency signal de-energisation input interdigital transducer of ultrasonic generator output 23.5MHz, by reasonably selecting the material of piezoelectric crystal, thickness, cutting mode and tested blood thickness, the ultrasound wave that the input interdigital transducer is produced is mainly propagated in blood, the piezoelectric crystal material that the utility model adopts is a lithium niobate, the thickness of piezoelectric crystal is 0.5 to 1.5 millimeter, wherein 1 millimeter is optimum thickness, the cutting mode of piezoelectric crystal is the YZ cutting, be that Y is to cutting Z to propagation, the finger logarithm of the interdigital electrode of making on the piezoelectric crystal is 50 to 200, wherein the best refers to that logarithm is 100, the electrode cycle is 40 to 100 microns, wherein the optimum electrode cycle is 60 microns, and the vertical range (i.e. degree for the treatment of) between two interdigital transducers is 0.5 to 2 millimeter, and wherein optimal spacing is 1.5 millimeters, when being propagated in blood by the ultrasound wave of input interdigital transducer generation, the variation of ultrasonic signal phase place and density of blood have definite relation.Ultrasonic signal after blood is propagated arrives and receives interdigital transducer, and the output that receives interdigital transducer enters phase-sensitive detector through lead-in wire, and that phase-sensitive detector records is the phase difference relevant with density of blood, can try to achieve density of blood to be measured through converting.Have corrosive liquid medium like this for resembling blood, adopted interdigital electrode,, carried out the metal coating processing with the surface of contacted two piezoelectric crystals of fluid to be measured for eliminating of the influence of electrolyte solution intermediate ion to acoustic propagation with antiseptic property.For testing liquid is flowed with layer flow mode, adopted arc side plate.Owing to adopted undersized interdigital transducer, the measurement chamber capacity that it and side plate constitute is very little, be generally less than 0.2 milliliter, be particularly suitable for dynamic measuring density of blood, adopted the phase-detection technology, the resolution of measurement is very high, has adopted the mode of a transmission of sound wave, the acoustic propagation decay is very little, measures response soon.

Claims

1. Ultrasonic liquid density sensor, comprise interdigital transducer [1], [2], contact conductor [3], acoustic absorbant [4], interdigital transducer [1], [2] be meant and on the surface of piezoelectric crystal [6], be manufactured with interdigital electrode [5], it is characterized in that by paired interdigital transducer [1], [2] and side plate [7] sealing that constituted liquid measure cavity, interdigital transducer is contained on the relative parallel-plate with acoustic absorbant [4], interdigital electrode on it relatively also staggers mutually, interdigital electrode is positioned at measures the chamber, the both sides of cavity are connected with the intubate [8] that liquid flows into and flows out, end on each interdigital transducer piezoelectric crystal is manufactured with the interdigital electrode [5] with antiseptic property, on the surface of piezoelectric crystal up and down in liquid measure chamber layer of metal film is arranged.An interdigital electrode connects ultrasonic generator [9] through contact conductor [3], and another interdigital electrode connects phase detectors [10] through contact conductor [3].

2. Ultrasonic liquid density sensor according to claim 1, the thickness that it is characterized in that piezoelectric crystal is 0.5 to 1.5 millimeter, the finger logarithm of interdigital electrode is 50 to 200, the electrode cycle is 40 to 100 microns, vertical range between two transducers is 0.5 to 2 millimeter, side plate [7] be shaped as arc.