SU1364294A1 - Tone sensor - Google Patents

Abstract

The invention relates to medical technology. To increase the sensitivity, the sensor consists of a housing 1, a lid with a central opening 2, a bimorph piezo-ceramic element 3, located in the housing parallel to the lid and connected with its edges to the housing through a cuff 4, matching device 5, pilot 6, fixed at the center of the piezoelectric element and placed in the hole so that its end side is located in the same plane with the outer surface of the housing cover, and an elastic element 7 located along the perimeter of the piezoelectric element (sensor). 1 il.

Description

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The invention relates to medical technology and is intended to indicate Korotkoff tones when measuring blood pressure by the Korotkov method.

The purpose of the invention is to improve the registration of weak signals of Korotkov tones by rotating the sensitivity of the sensor.

The drawing shows the sensor section.

The sensor consists of a housing 1, a lid 2 with a central hole, a bimorph piezoceramic element 3 located in the housing parallel to the lid and connected with its edges to the housing through the cuff 4, matching device 5, latch 6 fixed in the center of the piezoelectric element and placed in the hole so that its end side is located in the same plane with the outer surface of the housing cover, and an elastic element 7 located along the perimeter of the piezoelectric element (sensor).

The sensor works as follows.

The sensor is fitted under the compression cuff on the inside of the human forearm. The sound vibrations that occur in the tissues when the pressure in the cuff changes, are perceived by the pilot 6 and converted by the piezoceramic element 3 into an electrical signal, which is then amplified by an amplifier at the field effect transistor.

Example. A bimorph piezo element is used (two piezo elements with a diameter of 30 mm and a thickness of 0.3 mm from piezoceramics-PZT-: 19, glued together with epoxy resin). The sensor is connected according to a circuit, its sensitivity is measured, for which the sensor is installed on a device in which a sound pressure of 114 dB is created using a loudspeaker, which is monitored with a sound pressure meter PI-6, and you

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the output voltage from the drain of the field effect transistor is measured with a millivoltmeter.

The gain of the transistor is measured in advance. The sensitivity of the piezoelectric element is defined as h-tstno from dividing the output voltage from the drain of the transistor to the gain of the field-effect transistor. Sensitivity measurements are made at frequencies of 20–200 Hz (normalized frequency range for Korotkoff tone sensors). An elastic element in the form of a cut ring made of spring steel is installed on the piezoelement (1.5 mm wide strip with a thickness of 0.2 mm). Rings set with a diameter of less than 30 mm, and then quenched. The force with which the ring compresses the piezoelectric element is determined by stretching the ring (using equilibria) to a diameter of 30 mm.

Claims (1)

After installing the elastic element, the sensitivity is again determined. Invention Formula A tone sensor, comprising a housing, a lid with a central hole, a piezoceramic element located in the housing parallel to the lid and connected to the edges with the housing through a cuff, matching device, a pilot fixed in the center of the piezoelectric element and placed in the opening located in the same plane with the outer surface of the housing cover, characterized in that, in order to improve the detection of weak signals of Korotkov tones by increasing the sensitivity of the sensor, the sensor is provided with a split a circular element located around the perimeter of the piezoelectric sensor.