Devices Pulse and Inhale-Exhale. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Devices Pulse and Inhale-Exhale. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Electronics in medicine

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A photoelectric sensor is used to convert the pulse data into an electrical signal. The sensor consists of a light bulb from a flashlight L, (see Fig. ) and a photoresistor FS-K1, between which the finger of the patient under study is placed.

Devices Pulse and Inhale-Exhale

With each inflow of a portion of blood into the finger, its volume increases, which leads to a decrease in the amount of light passing through the finger and illuminating the light-sensitive surface of the photoresistor. In this case, the resistance of the photoresistor increases slightly. The photoresistor is connected according to the bridge circuit. The bridge is powered by a 1 V battery B150. From the output of the bridge, an alternating voltage corresponding to changes in the blood accumulation of the finger is fed through the capacitor C1 to the transistor amplifier. An MCA microammeter is included in the transistor collector circuit, the arrow of which oscillates in time with the pulse. The microammeter is used to control the correct installation of the sensor on the human finger. The sensor is mounted on the first phalanx of the finger against the nail in such a way that the nail faces the bulb and the fingertip faces the photoresistor.

Having installed the sensor, change the degree of pressing it to the finger, which is regulated by a screw. There is a certain pressure of the sensor on the finger, at which the sensor signal is greatest. In this case, the needle of the microammeter will fluctuate significantly.

The value of the sensor signal is strongly influenced by the state of the cardiovascular system of the subject and the temperature of the finger. For stable operation of the device, it is very important that the hand is warm. If the hand is cold, rub it to improve blood circulation.

Before working with a variable resistor K6, the microammeter pointer is set near division 40 of the microammeter scale. In this case, to darken the photoresistor, a piece of paper must be placed between it and the light bulb.

To transmit pulse data over a distance, a wired line is connected to the output terminals of the device, which goes to the researcher. A microammeter or recording device is connected to the line. When a microammeter is connected, the pulse is calculated by the number of oscillations of the microammeter needle per minute. In the case of using a recording device, in addition to the pulse, it is possible to determine the arrhythmia of heart contractions (if it exists).

Inhale-exhale device

The device "Breathing" (see the figure), designed by us, is intended for transmission over a distance by wires of data on the frequency of a person's respiration.

Devices Pulse and Inhale-Exhale

To convert the respiratory rate into an electrical signal, a wire sensor is used, which is an ordinary flashlight lamp, from which the glass bulb has been removed. The lamp is placed in a tube 150 mm long. The filament of the lamp is in a heated state due to the electric current passing through it. The tube is placed near the person's nose so that the flow of exhaled air passes through it. When inhaling and exhaling, due to the movement of air, the lamp filament cools down slightly, which leads to a decrease in its resistance.

The wire sensor is connected according to the bridge scheme. The bridge is formed by resistors R1, R2, R3 and a wire gauge. The bridge is powered by a galvanic cell B1. From the output of the bridge, a weak electrical signal is fed to a transistor amplifier. At the output of the amplifier, a milliammeter is switched on, the arrow of which oscillates in time with breathing.

To transmit data on the respiratory rate over a distance, a wire line is connected to the milliammeter using output clamps, at the end of which (at the researcher) a milliammeter or a recording device is connected. The recording device will allow you to obtain data not only on the frequency of breathing, but also on the duration of inhalation and exhalation and changes in the rhythm of breathing.

The initial position of the milliammeter needle of the device is set by a variable resistor R4. Resistor R1 in the manufactured device consists of eight parallel-connected resistors of the BC-0,5 type at 56 kOhm. You can also use a homemade wire resistor. To increase the stability of the lamp, the filament of the lamp must be soldered to its terminals. Otherwise, during operation, due to oxidation of the filament and the lamp leads, the contact resistance between them will increase, which may disrupt the normal operation of the sensor.

The device was developed and manufactured in the laboratory of automation and technical cybernetics of the Kyutsk State University of Siberian Branch of the USSR Academy of Sciences.

Author: A. Terskikh

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