DE1798100A1 - Device for speed measurement - Google Patents

Description

Device for measuring speed

The invention relates to a device for measuring speed especially of ijlut in its vessels, by means of Ultrasehall according to the Doppler effect method, with a pick-up that contains an ultrasound transmitter and receiver, as well as with a for the excitation of the transmitter provided high-frequency generator and with a, demodulator, the one of the difference frequency between corresponding to the transmitted transmission frequency and the received frequency forms proportional output signal.

In a known device of this type, there are two piezoelectric devices in the pick-up Arranged transducer, one of which works as an ultrasonic transmitter and the other as an ultrasonic receiver. Accordingly, the transmitter is connected to the high-frequency generator and the receiver to the demodulator. In this arrangement Continuous measurement is possible because the transmitter is continuous remain excited and the recipient can receive continuously. The disadvantage is that the consumer has two transducers (with its electrical Supply lines) and is therefore relatively large and expensive;

109845/0058

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However, it is also difficult to arrange the two transducers on one: Faun, side by side, electrically insulated, so that their directional characteristics (transmission and reception direction) match as closely as possible. It is possible only with great effort, two oscillators r.it except-calibrating exactly Ubereinstinmenden resonant frequencies to maintain (Choosing required!), Which in view of the fact that the transmission frequency will differ only slightly from the received frequency is w special .Bedeutung .

For these reasons, it was considered to be an ultrasound diagnosis to adopt the well-known principle, namely to use only one transducer, which alternates as a transmitter and receiver is working. To do this, a switchover device is required, which allows the The oscillator alternately connects to the high-frequency generator and the receiving electronics. Such switching devices should work extremely quickly and precisely, they are therefore expensive and there are transient and decay processes on the transducer that are undesirable in particular, measurements cannot be made during the transmission time and during these transient and decay processes, so that a considerable part of the measurements that can be recorded during permanent trench measurements Information is lost.

The invention is based on the object of the two described Opportunities to avoid inherent disadvantages. According to the invention this object is achieved in that when using a single one both as a transmitter and as a receiver Electro-acoustic converter, this converter is connected to the high-frequency generator and to the electrical demodulator at the same time is.

^{The solution according to the} invention is therefore particularly surprising, J ₁ ^ ₃ O OAS 1 09845 '°° 58 -3-

because it is already when using a transmitter transducer and one of them separate receiving oscillator is not easy to c? us the echo signals - by acoustic coupling of. Transmitter on the Er.pfangsschwinger reached - un. about three powers of ten to determine stronger transmission signals. It's thanks to the Inventor, to have nevertheless attempted to find a single! Input of the receiving electronics one by five to six powers of ten (compared to the kcho energy) there is greater gender energy; | this is insane. With a view to the fact that in ultrasound diagnostics the above-mentioned switching device is used a single transducer is used as transmitter and receiver and dar.it prevents transmission energy from being transferred to the receiver electro-acoustic oscillator comes to be valued as inventive knowledge.

The invention achieves a significant simplification and simplification of the device as well as a smaller size of the device. The subject of the invention is not just for them ^; 3lutflussn.essung, but quite 'generally for the flow measurement of media in lines permeable to ultrasound, suitable.

Details and further advantages of the invention emerge from the following description of an embodiment based on of two figures. Show it

1 shows a longitudinal section through a customer according to the invention during a flow measurement,

": ^? Fig. 2 shows the block diagram of the speed control measuring device according to the invention.

109845/0058. 4th

BATH ORIGINAL

In liig. 1 is rrdt 1 denotes a customer according to the invention, of the insulating material housing 2 and the: piezoelectric crystal 2 arranged therein as an electro-mechanical. or mechanical-electrical. 'Converter exists. With the, customer 1, who on the body surface 4 rests, the blood flow velocity (indicated by an arrow) in derr. Blood vessel 5 measured will.

™ The piezoelectric crystal 3 in the pick-up 1 is, as shown in FIG. 2, via the / amplifier 6 to the! ^: OchfrequenzüsziIlator 7 connected, by which it is continuously excited during the measurement for ultrasonic radiation to a frequency corresponding to the desired ultrasonic frequency ^f z.'i. 5 MHz). In addition, the piezoelectric crystal j5 is connected to the amplitude demodulator 9 via the amplifier '■;'. At the output of the amplitude demodulator 9, the loudspeaker 11, which makes the pulsation of the flow audible, can be connected by the switch 12 via the amplifier 10. The frequency detector IJ) is also connected to the output of the amplifier 10 via the amplifier 14, and the output signal of the frequency detector IJ is fed to the display device 15.

The frequency distortion between the ultrasound transmitted and received by the crystal JS as a result of the Doppler effect depends on the one hand on the transmission frequency, the velocity of sound propagation in the air and the angle between the transmission and reception direction of crystal 2 and the flow velocity in FIG. 1) and on the other hand on the size of the flow velocity. If it is assumed that the ^f jendefrequenz, the sound propagation speed in the blood and said angle are constant, it follows that the frequency rejection of the blood flow is proportional to speed. Dr die-

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se I frequency rejection in. "/ is very small compared to the frequency of the transmitted ultrasound, since the frequency of the ultrasound received by Crystal 3 deviates only slightly from the transmission frequency, is at the input of the amplifier I. because of the superimposition of the The transmitted and received ultrasound in: Crystal 3 a Gbwung, at which the frequency of the modulation voltage superimposed on the carrier voltage is proportional to the Tilut flow velocity the frequency of the modulation voltage is proportional to the blood flow velocity and the course of which can be made audible in the loudspeaker 11. The frequency detector 13 forms a direct voltage signal, the level of which is proportional to the frequency of the low-frequency alternating voltage and thus to the blood flow velocity. This signal controls the display device 15 'on which the blood flow rate can be read. The display device 15 can partly contain a tape recording device and / or an oscilloscope in a known manner.

The demodulator 9 contains a preloaded rectifier, where i the preload of the rectifier corresponds approximately to the amplitude of the applied transmission frequency. With this type of rectification, the beat frequency is obtained by itself; the downstream frequency detector then provides a DC voltage output signal which is proportional to the level of the frequency supplied to it.

The device is not only for measuring the speed of flowing Media (e.g. blood or the like), but also from organ movements (e.g. candle flaps).

109845/0058 _ ₆

ORIGINAL

Claims (3)

Claims 1. Apparatus for measuring the speed, in particular, of ', lut in its r; efässen, by means of' ltrasound according to the doubling effect method, rr.with a receiver, which contains a ltrasound transmitter and receiver and nit a DERS provided for the excitation of the üen- W high-frequency generator and rr.it a ·! demodulator which forms a difference frequency between the zugefürrten transmission frequency and the received frequency corresponding proportional Auegangssignal, characterized in that when using a single both As a transmitter as well as a receiver working electro-acoustic transducer, this transducer is connected at the same time to the high-frequency generator and to the electrical demodulator. 2. Apparatus according to claim 1, characterized in that the demodulator is an amplitude demodulator with a downstream frequency detector it is provided which frequency detector is one of the Frequency of the output voltage of the amplitude demodulator proportional Forms DC voltage signal. 3. Apparatus according to claim 2, characterized in that a biased diode is used as the amplitude demodulator, the bias of which corresponds approximately to the amplitude of the transmitted oscillation. 109845/0058 New lower "(A **« * «* ·» * · ¹ ** BATH ORIGINAL