SU1647370A1 - Device for measuring electric conductance of biological media - Google Patents

Abstract

The invention relates to a measurement technique and can be used to measure the electrical conductivity parameters of liquid media, including biological fluids. The purpose of the invention is to improve the accuracy, reliability and sensitivity of measurements. A device for measuring the electrical conductivity of biological media contains a multivibrator, a sensor, and an indicator unit. The introduction of two triggers, a current transformer and a pulse shaper into the device allows optimal matching of the information and exciting signals of the measuring circuit and the sensor. 2 Il.

Description

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The invention relates to a measurement technique, in particular, to devices for measuring the electrical conductivity of fluid parameters, including biological fluids.

The aim of the invention is to improve the accuracy and reliability of measurements.

Fig. 1 shows a block diagram of a device for measuring the electrical conductivity of biological media: Fig. 2 shows timing diagrams explaining the operation of the device.

A device for measuring the electrical conductivity of biological media contains multivibrator 1, first trigger 2, current transformer 3, pulse shaper 4, second trigger 5, indicator unit 6 and sensor 7. Multivibrator 1 shaper pulse 4 are made on discrete elements, for example, CMOL structures, triggers 2 and 5 are selected from the same chip series (device assembled on K 176 series chips).

The device works as follows.

Multivibrator 1 controls the operation of trigger 2, which in the counting mode divides the initial pulse frequency into two (this eliminates the constant component of the current in the sensor). This signal through the transformer 3 current and the sensor 7 excites the test medium and through the driver 4 pulses turn on the output trigger 5 on the counting input. Turning off the aforementioned trigger 5 is produced by the signal from the inverse output of trigger 2 to

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setup R input. This makes it possible to obtain an output signal from trigger 5, depending on the magnitude of the signal propagation delay through the transformer, the impedance of which, in turn, depends on the conductivity of the medium.

In the initial (unloaded) state of sensor 7, the signal from trigger 2 to trigger 5 passes with a maximum delay, while changing the frequency of the multivibrator 1. sets the resonance mode, which is indicated by short pulses at the output of trigger 5. whose average level is perceived as zero. the impedance of the medium, noted by the loaded sensor 7, leads to a change in the group delay time of a signal with a complex spectral composition on the current transformer 3. The delay is reduced due to the shunting effect of the secondary the second winding of the current transformer 3 with a loaded sensor 7, which leads to an increase in the duration of the output signals, therefore, to a proportional change in the duty cycle of the output signals of the trigger 5, which can be used to judge the value of the conductivity of the medium. Averaging the output signals of the trigger 5 and proportional conductivity of the test medium, occurs in the indicator unit 6, for example in a switch instrument.

Timing diagrams (Fig. 2) depict information signals, respectively, in unloaded and loaded states during measurement, respectively. The signal from multivibrator 1 (Fig. 2a) after dividing by frequency into two trigger 2

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(Fig. 2b) is delayed by the current transformer 3 (Fig. 2b) and at the output of the trigger 5 generates a signal with a variable duty cycle (Fig. 2d), the average level of which carries information (Fig. 2e) about the conductivity of the medium. A device for measuring the electrical conductivity of biological media makes it possible, using simple means, to coordinate the sensor with the measuring transducer, to solve the main problems that affect the accuracy and reliability of the measurement: to reconcile the sensor and the excitation elements, to limit the voltage on the sensor, to use

group delay times to form the output signal, provide a galvanic isolation and ground the device sensor.

Claims (1)

Invention Formula A device for measuring the electrical conductivity of biological media containing a multivibrator, a sensor and an indicator unit, characterized in that, in order to improve accuracy, reliability and measurements, the first and second triggers, the current transformer and the pulse shaper are introduced, the output of the multivibrator is connected to the counting input of the first trigger the direct output of which through the primary winding of the current transformer and pulse shaper is connected to the counting input of the second flip-flop, the installation input of which is connected to the inverse output of the first flip-flop output The second trigger is connected to the indicator unit, the sensor is connected to the secondary winding of the current transformer, which is connected to the common busbar on one side. a 5 at g L / g 2