PRACTICAL: 2

AIM: Study of BLOOD FLOW METER

Material required

[1] Matrix trainer kit - BLOOD FLOW METER

[2] CRO

PROCEDURE:

Setup -

[1] Keep the Power switch in off condition.

[2] Connect power chord to mains (230 volt A.C).

Experiment

[1] Connect the sensor to the kit, place small quantity of jelly on the Vance of patient

where blood flow has to be measured.

[2] Put on the trainer & CRO & place ultrasound sensor on the Vance of patient

(smoothly touched not to much pressed with may block blood flow).

[3] Observe the output TEST point T1 & T3 w.r.t

[4] Connect Headphone to recording o/p socket.

[5] Herd the sound of blood flow if it is not hearable then change the pressure of

sensor ( Get periodic blood fiow sound).

[6] Block the Vance by band or by hand heard sound & note blood flow.

[7] Remove band quickiy and heard sound & note blood flow.

[8] Remove band quickiy and heard sound & note blood flow.

[9] Repeat for other patient.

Reading:

Sr

No

Display reading as blood flow

Liter/Minute

Observation:

Student observer their own observation.

BLOOD FLOW METER

INTRODUCTION:

It is not possible to conventional flow meter, such as the orifice or turbine. these type

of sensor required cutting the vessel & can cause formation of clots,So it is necessary

to develop electronics principle based flow meters those can measure blood flow with

only by touching particular vessel.

The ultrasonic flow meters can measure instantaneous. The ultrasound beamed

through the skin in blood vessel, reflected back by blood flow with modulation as

mechanical properties of blood flow. Therefore ultrasound flow meter also

measurement flow profile.

This type of flow meter consists of following block shown in fig.2.1

Stage1:- ULTRASOUND Sensor:

It is basically have two parts 1.transmitter & 2. Receiver of piezoelectric material.

This sensor converts electrical power from oscillator to acoustic form. The

piezoelectric material lead zirconate titanate is crystal has the highest conversion

efficiency used for sensor.

The near field extend a distance dnf given by dnf = D^2/4λ

Where the D=transducer diameter & λ=wavelength.

In the far filed the beam diverges, and the intensity is inversely proportional to

the square of the distance from the transducer. The angle of beam divergence

SinΦ = 1.2λ/D

Here in this trainer used sensor is operates on 8MHz frequency.

.

Fig.2.1: sensor equivalent circuit

Fig.2.2: sensor circuit diagram.

STAGE 2:-8 MHz oscillator:

Transistor Q1 & Q2 form astable Multivibrator.R2 C4 & R1 C2 set oscillation

frequency to 8 MHz TX1 primary & C1 form resonance circuit of 8 MHz. Converter

astable Multivibrator to 8 MHz sine wave . Secondary of TX1 energized transmitter

section of Sensor probe.

STAGE 3:-Receiver amplifier:

FET Q3 amplifier the received signal form RX section of probe.TX2 serve as

impedance Matching between sensor & input of amplifier Q3.

STAGE 4:-Demodulator:

Received output is amplitude modulated by blood flow. Hence to detect blood flow

information it is necessary to demodulate the output of amplifier Q3. D1 did this here

with R7 as load resistance. C10, C11, C13 filter detected information. This

information further amplify by three stage RC coupled amplifier. This amplifies

Output available for recording for further investigations about patient. This output

Also audible by headphone for proper setting of sensor. This output further average

by active filler circuit to produce constant blood flow volume.

STAGE 5:-Active rectifier:

Op-amp A1 and associate circuit form active filter.This active filter rectify eliminates

Junction loss of semiconductor diodes to recover true DC level of signal by

amplifying Input in proper portion. Further it is rectify by D4 & integrated by R26

&C24 to produce dc voltage proportional to blood flow. It is available at T3 w.r.t T4

(ground).

STAGE 6:-DIGITAL VOTLMETER with seven segment LED display:

This a digital counter count based on IC7017&display blood on 3 SEVEN

SEGMENT LED display by converting voltage level at T3 in digital form. Display

Shows blood flow readings in liter/minute.

Conclusion: