RU179919U1 - Simulator for metrological verification and testing of electrocardiographs - Google Patents

Abstract

The utility model relates to medical equipment, namely to the electrocardiographic technique for recording the biopotentials of the heart on the surface of the human body, and is intended to provide metrological verification, certification and production tests of electrocardiographs in test centers, laboratories and "on the spot". The technical result of the proposed technical solution is to increase the ergonomics of the simulator when it is used autonomously (outside a computerized stand). This technical result is achieved due to the fact that, in a well-known simulator for metrological verification and testing of electrocardiographs, containing a universal USB 2.0 serial bus interface for communication with a personal computer, a memory unit and a display connected to the microcontroller, the fourth and fifth outputs of which are connected, respectively, to the sound indication unit, and to the first input of the 8-channel digital-to-analog converter (DAC), as well as the stabilized reference voltage generating unit, the output of which is is single with the second input of the 8-channel DAC, each of whose outputs is connected to the input of the corresponding channel of the 8-channel low-pass filter, 8-channel patient equivalent connection block and 8-channel open circuit simulation block are introduced in series, 8 outputs of which are simulator outputs intended for connecting to the electrodes L, F, C1 - C6, respectively, as well as sequentially connected 2-channel unit for connecting the patient's equivalent and 2-channel unit for simulating open circuit, the outputs of which are They are simulator outputs intended for connecting to the N electrode and the R reference electrode, respectively, while both inputs of the 2-channel patient equivalent connection block are connected to analog ground. 3 s.p. f-ly, 5 ill.

Description

The utility model relates to medical equipment, namely, electrocardiographic equipment (ECT) for recording the biopotentials of the heart on the surface of a person’s body, and is intended to provide metrological verification, certification and production tests of ECT in testing centers, laboratories and "on the ground" at all stages life cycle (development, mass production, operation).

In the Russian Federation today there are a number of standards that regulate the technical requirements for ECT, methods of its certification tests, as well as recommendations on metrology that establish the verification procedure for this type of equipment (GOST R IEC 60601-2-51-2008. Medical electrical products. M: Standartinform , 2009, R 50.2.009-2001, Recommendations on metrology, Electrocardiographs, electrocardioscopes, electrocardiological analyzers, Calibration Methods, Moscow: Publishing House of Standards, 2001). The verification procedure is very laborious and takes about 6 hours for one device. Of considerable interest is also the possibility of assessing the current state of ECT during equipment maintenance during its operation by the engineers and technicians of medical institutions. This makes it possible to carry out pre-verification preparation of equipment, to carry out monitoring of its condition "on the ground", which, undoubtedly, significantly increases the reliability of patient diagnosis. At the same time, the existing technical and methodological support for the metrological assessment of the state of ECT cannot be used to solve this problem, in view of the high complexity of the assessment, the complexity of the equipment used and the high qualifications of the performers of these works. Therefore, the development of a system for metrological verification and certification tests of electrocardiography that meets the requirements of GOST R IEC 60601-2-51-2008 and allows to reduce material and labor costs for conducting metrological verification procedures and certification tests due to the integrated automation of the main processes, remains very relevant challenge.

There are proposals on the creation of an information system for metrological verification and certification tests of electrocardiological equipment (Proceedings of the IV International Scientific and Technical Conference ITNOP-2010, K.V. Podmasteriev, A.V. Kozyura, UDC 006.91: 615.47: 004.91) aimed at solving this urgent problem . The specified system contains an operator-driven test signal generator connected via a universal USB 2.0 serial bus interface to a personal computer (PC). The output of the test signal generator through the connection circuit is connected to the test electrocardiographic device (ECP). The test signal generator can work both autonomously, using the built-in database (DB) of test signals, and in the mode of collaboration with a PC. In this mode, in particular, software (software) for automation of metrological verification of electrocardiographic equipment registered by the authors of these proposals (Certificate on state registration of computer programs No. 20099613815 of 04/13/2009) can be used. The key link of this system is a PC-controlled generator of test ECG signals, the structure of which is given in the article "Generator for metrological verification and certification testing of cardio equipment" ("Fundamental and applied problems of engineering and technology", OGTU, 2010, No. 1279, p. 82-87).

As shown in this article, the characteristics and functionality of the test ECG signal generator are determined by the test methods and test signals regulated by the harmonized standard GOST R IEC 60601-2-51-2008.

To test such basic functional hardware characteristics of electrocardiographs and software designed for ECG analysis, such as accuracy in measuring amplitude, accuracy in measuring absolute intervals and durations of teeth and others, it is necessary to ensure the formation of so-called calibration and analytical ECG signals. A specific feature of such ECG signals is the proximity of their forms to the forms of real biological ECG signals. To conduct certain types of tests, the ECG signal for each of the leads may be different from the others. The base of test signals contains about 125 different types of analytical ECG signals in order to provide the ability to verify the functional characteristics for each type of test described in GOST IEC 60601-2-51-2011. Adding new analytical ECG signals that the generator can reproduce allows you to better evaluate the performance of POS and software, as well as supplement the test list.

The generator must have a built-in base of test signals necessary for all types of tests. This function, together with an autonomous power supply from galvanic cells, provides greater mobility of use compared to the use of generators requiring connection to a PC on which the appropriate software that controls the generator must be installed. In this case, the generator of test ECG signals is more correctly called a simulator for metrological verification and ECT testing.

From a review of the foreign market of devices used in certification and production tests of ECT and capable of reproducing signals regulated by GOST R IEC 60601-2-51-2011, it follows that the ADElektronik PSI 300 simulator satisfies these requirements to the greatest extent.

There is a known scheme of a domestic simulator that surpasses the specified foreign counterpart in its functionality described in the article "Generator for metrological verification and certification tests of cardio equipment", "Fundamental problems of engineering and technology", OGTU, 2010, No. 1/279, p. 4), The circuit contains a computing and control device (microcontroller) connected to a USB 2.0 port for interaction with a PC, with a storage device and a display. A keyboard is connected to the control input of the microcontroller, an audio alarm unit is connected to the audio output, and digital-to-analog converters (DACs) are connected to the channel outputs.

In the signal generation mode, data from the storage device necessary for reproducing signals of a given shape are read and processed by the microcontroller and fed to the inputs of these DACs, which interact with the microcontroller using the serial interface of peripheral devices (SPI). Using this interface, a bus configuration is organized, which allows you to quickly switch the DAC and, accordingly, provide the required speed for transmitting the DAC for the subsequent formation of test ECG signals with the required sampling frequency at the corresponding outputs of the simulator. Two DACs and eight channels, respectively, are used to form test ECG signals, which are then converted to test ECG signals of the corresponding electrodes used to obtain standard leads. In the third DAC, three channels are used - for the formation, respectively, of triangular, rectangular and sinusoidal signals of a given amplitude. The reference voltage source is connected in parallel to the reference inputs of all three DACs. After digital-to-analog conversion, the signal is fed to smoothing low-pass filters. The cutoff frequency in these filters is determined by the frequency of the DAC clock pulses.

Smooth signals from eight outputs used to generate test ECG signals are fed to passive attenuators with an adjustable division factor to provide the required output signal level, and then to the ECG signal preprocessing circuit, the implementation and parameters of which must satisfy the requirements of the aforementioned GOST R IEC 60601- 2-51-2011. A galvanic cell is used as a source of supply voltage. This allows you to use the simulator autonomously, as well as reduce the level of interference from an industrial network of 50 Hz.

The minimum capacity of the microcontroller is determined by the capacity of the DAC. The speed of the microcontroller should be sufficient to work with the LCD display and the DAC.

In contrast to the aforementioned foreign analogue, the simulator described above has great potential for generating various types of test signals, making it possible to generate rectangular, triangular and sinusoidal signals of a given amplitude necessary for testing.

The disadvantage of the closest analogue is that the ability to sufficiently fully meet the requirements of GOST R IEC 60601-2-51-2011 is achieved only when it is combined with a PC equipped with appropriate specialized software, for example, a program for the automation of metrological verification of cardiac equipment registered for No. 20099613815 from 05/18/09. In the absence of the possibility of such interaction, the productivity of the operator performing metrological verification or EPC testing drops sharply, due to the fact that manual operations are necessary to switch channels and switch to different test modes. Accordingly, the complexity, measured by the amount of time spent by the operator for each operation, increases significantly.

As you know, the effectiveness of automated processes, which include procedures for metrological verification and ECT testing, is defined as “ergonomics”, which means the possibility of achieving the highest labor productivity with the least probability of error. Accordingly, the expected technical result of the proposed device can be formulated as improving the ergonomics of the simulator when it is used autonomously.

This technical result is planned to be achieved due to the fact that a well-known simulator for metrological calibration and testing of electrocardiographs contains a universal serial bus interface USB 2.0 port for communication with a personal computer, a memory unit and a display connected to a microcontroller, the fourth output of which is connected to the sound unit indications, and the fifth - to the first input of the 8-channel digital-to-analog converter, to the second input of which the output of the stabilized voltage generating unit is connected a transistor configured to be connected to external power devices, with each of the eight outputs of an 8-channel digital-to-analog converter connected to the input of the corresponding channel of an 8-channel low-pass filter, 8-channel patient equivalent connection block and 8-channel simulation unit are connected in series open circuit, the outputs of which are the outputs of the simulator, designed for parallel connection of eight signal electrodes L, F, C1 - C6, respectively, as well as sequentially the included 2-channel patient equivalent connection block and the 2-channel open circuit simulation block, the outputs of which are simulator outputs for connecting the N and R electrodes, respectively, while both inputs of the 2-channel patient equivalent connection block are connected to analog ground.

In a possible embodiment of the construction of the indicated simulator, each channel of the 8-channel and 2-channel patient equivalent connection blocks is made in the form of parallel-connected resistor R and capacitor C, the ratings of which satisfy the requirements of GOST R IEC 60601-2-25 2016, in parallel with which the circuit breaker is turned on , while the input and output of the specified channel are the connection points, respectively, of the output of the corresponding channel of the 8-channel low-pass filter and the input of the corresponding channel of the 8-channel simulation unit bryva chain. At the same time, each channel of the 8-channel and 2-channel circuit break simulation blocks is made in the form of a circuit breaker, one contact of which is the connection point to the output of the corresponding channel of the 8-channel circuit break simulation, and the other contact is used to connect the corresponding signal electrode.

The stabilized voltage generating unit of the simulator can be made in the form of series-connected power control unit, voltage converter unit, voltage stabilizer unit and reference voltage driver, the output of which is the output of the stabilized voltage generating unit, and also include a galvanic cell connected to the control unit, for example , a battery, and a voltage inverter connected between the second output of the voltage converter unit and the second input of the unit Single voltage stabilizers.

The essence of the proposed technical solution is illustrated in FIG. 1 - FIG. 3.

In FIG. 1 shows a structural diagram of the proposed simulator for metrological verification and testing of electrocardiographs.

In FIG. Figure 2 shows a possible embodiment of a patient equivalent connection channel.

In FIG. 3 shows a possible embodiment of a stabilized voltage generating unit.

In FIG. 4 and FIG. Figure 5 shows photographs confirming the possibility of practical implementation of the proposed simulator on the existing elemental base, respectively:

- photo of the board with electronic components located on it.

- A photograph of a general view of the simulator in the body.

The considered simulator for metrological verification and testing of electrocardiographs contains a universal serial bus interface - USB 2.0 port 1 for external communication with a PC, a memory unit 2 and a display 4 connected to the microcontroller 3, the fourth and fifth outputs of which are connected, respectively, to the sound indication unit 6 and to the first input of the 8-channel DAC 5, as well as the stabilized voltage generating unit 7, the output of which is connected to the second input of the 8-channel DAC 5, each of the outputs of which is connected to the input correspondingly about the channel of the 8-channel low-pass filter 8, the output of which is connected in series with the channel of the 8-channel block 9 connecting the patient’s equivalent and the channel of the 8-channel block 10 simulating an open circuit connected to the output of the simulator intended for connection to the signal electrodes L, F, C1 - C6, respectively. The simulator under consideration also includes a 2-channel unit 12 for connecting the patient’s equivalent and a 2-channel block 13 for simulating an open circuit connected in series, the outputs of which are the outputs of the simulator, intended to be connected to the electrodes of the N electrode and the reference R electrode, respectively, with inputs 2 -channel block 9 connections of the equivalent of the patient are connected to each other and closed to analog ground.

Each channel of the 8-channel 9 and 2-channel 12 patient equivalent connection blocks is made in the form of parallel-connected resistor R and capacitor C, to which the circuit breaker 11 is connected, while the input and output of the specified channel are the connection points of the specified circuit breaker 11. Automatic control the switch is carried out by microcontroller 3.

At the same time, each channel of the 8-channel 10 and 2-channel 13 circuit break simulation blocks is made in the form of a circuit breaker 11, one contact of which is the connection point to the output of the corresponding channel of the 8-channel circuit break simulator 9, and the other contact connects the corresponding signal electrode. The circuit breaker is controlled by microcontroller 3.

In a possible embodiment of the simulator construction, the stabilized voltage generation unit 7 contains series-connected power control unit 15, the voltage converters unit 16, the voltage stabilizer unit 18 and the reference voltage driver 19, the output of which is the output of the stabilized voltage generation unit 7, and also connected to the control unit 15 a galvanic cell 14, for example, a battery, and a voltage inverter 17 connected between the second output of the second voltage converter unit 16 an input unit 18, voltage stabilizers.

Currently, design documentation and a prototype of the proposed simulator for metrological verification and testing of electrocardiographs have been developed. Preliminary tests of this sample were carried out in stand-alone (without a PC) operating mode, which showed its high ergonomic advantages over existing analogues and compliance with the requirements of the aforementioned GOST R IEC 60601-2-51-2011. Photographs of the placement of the electronic components of the device on a printed circuit board and the general appearance of the product are shown in FIG. 4 and FIG. 5, respectively.

The key structural unit of the simulator - microcontroller 3 is made on the STM32F407 chip. The eight-channel DAC 5 is implemented on the AD1934 chip. To implement an 8-channel low-pass filter, the OPA320 operational amplifier was used. In the eight- and two-channel connection blocks of the patient equivalent 9 and 12, respectively, and in the eight- and two-channel blocks for simulating open circuits 10 and 13, respectively, the TS 5A22362 electronic switch chip was used. All of these components are purchased products that are generally available on the electronic component market. Therefore, the industrial feasibility of the proposed technical solution is not in doubt.

The proposed simulator for metrological verification and testing of electrocardiographs works as follows.

In preparation for a metrological verification session or tests of the electrocardiograph from a PC via a USB 2.0 serial port 1 to a memory block 2, which is a Micro SD memory card, using microcontroller 3 or directly using a PC, test ECG signals are pumped in a digital format, selected to simulate the ECG of the patient’s biosignals in this test run.

The microcontroller 3 is controlled using the touch screen of the display 4. When you press the "On" button the simulator enable signal is sent to microcontroller 3, which initializes the 8-channel DAC 5. All actions of the operator to control the simulator are accompanied by sound signals, for which the sound indication unit 6 connected to the fourth (audio) output of microcontroller 3 is used. The minimum bit depth of microcontroller 3 is determined the capacity of the 8-channel DAC 5. The speed of the microcontroller 3 should be sufficient to work with the LCD display and the DAC of the required capacity. The amount of built-in microcontroller 3 FLASH memory should be sufficient to store all the information used on the forms of test signals.

In the mode of generating test ECG signals, the data from the memory unit 2, necessary for reproducing signals of a given shape, is processed by the microcontroller 3 and fed to the inputs of the channels of the 8-channel DAC 5. The DAC channels interact with the microcontroller 3 using the interface of the electrical serial bus of peripheral devices (I2S) . This interface, unlike most other serial interfaces, allows you to organize fast DAC switching with a high sampling rate of the signal at the outputs of its channels.

The use of this interface can also significantly reduce the number of connections without a significant loss in speed compared to the parallel interface. As the source of the reference voltage of the 8-channel DAC 5, the stabilized voltage generating unit 7 is used, which forms with high accuracy a stable constant voltage of the required amplitude. After digital-to-analog conversion in each channel of the 8-channel DAC 5, the signal from the output of this channel goes to the input of the corresponding channel of the 8-channel low-pass filter 8. The cutoff frequency is determined by the required maximum frequency of the output signals of the 8-channel DAC 5. In order to reduce the number of circuit elements, reduce the cost of the device and simplify its configuration, specialized integrated circuits are used as filters, which allow realizing high-order analog filters and reducing noise at the outputs 8- channel DAC 5.

Smooth signals from the outputs of the 8-channel low-pass filter 8 are further converted to test ECG signals. These transformations are carried out in series-connected channels of the 8-channel block 9 connecting the patient’s equivalent and the 8-channel block 10 of the open circuit, the eight outputs of which result in the formation of predetermined analogs of the patient's ECG signals at the electrodes L, F, C1 - C6, respectively.

The patient equivalent in each channel of the 8-channel unit 9 of the patient equivalent connections is a resistor R and a capacitor C connected in parallel (Fig. 2). In parallel with these elements, the circuit breaker 11 is connected. The closed state of the circuit breaker 11 means that the equivalent of the patient is turned off, and open - its connection. All the indicated connections / disconnections of the patient equivalent can be carried out independently via separate channels in the program mode - in accordance with the previously generated file for simulating the ECG signal. Moreover, as options, both manual mode of switching the patient’s equivalent and real-time interaction of the simulator with the PC are possible, in which the computer sends control commands to switch the patient’s equivalent with the simultaneous sending of data to simulate ECG signals. These innovations allow not only to implement an automatic test report in accordance with the standard R 50.2.009-2011, but also do not require the connection of a calibration switching device used for verification in accordance with R 50.2.009-2011.

In accordance with the standard GOST R 55952-2014, one of the requirements for ECT is an indication of open circuit (leads). Manually, this check would be performed by disconnecting one of the lead cables from the electrocardiograph by the operator. In the proposed device, this is done automatically - by installing at the output of the 8-channel block 9 connections the patient’s equivalent of the 8-channel block 10 simulating an open circuit, each channel of which is a circuit breaker 11. This innovation allows you to automate the process of verification and identification of these defects, as in production and in tests of ECT in laboratories "in the field".

To test the circuits of the electrode N and the reference R electrode, the proposed simulator uses a 2-channel block of 12 patient equivalent connections and a 2-channel block of simulated open circuit. The construction scheme of each of the channels of the first of these blocks is identical to the construction scheme described above (Fig. 3) of the channel of the 8-channel unit 9 for connecting the patient’s equivalent. Each channel of the second of these blocks, as well as the channel of the 8-channel block circuit simulation, contains a single element - circuit breaker 11.

The difference in the construction of the switching circuits for testing the N electrode and the reference R electrode from the switching circuits for testing the signal electrodes L, F, C1 - C6 is that the inputs of the first and second channels of the 2-channel unit 12 of the patient equivalent connections are connected to each other and closed to analog ground. Accordingly, the operation of the circuit breakers 11 in these channels is controlled by analog ground.

To ensure the required accuracy of generating test ECG signals, the simulator should have its own autonomous source of stabilized voltage. A possible scheme for constructing such a source — a stabilized voltage generating unit 7 (FIG. 3) includes a galvanic cell 14 to which a power control unit 15 is connected. Unlike the power supply unit of the closest analogue, the power control unit 15 in the proposed simulator allows not only to receive power from the galvanic cell 14, which is a Li-Ion battery, but also to charge it. Charging can be carried out from an external power supply device, for example, from a PC or some regular power supply unit that has a USB connector. From the power control unit 15, the supply voltage is supplied to the voltage converter unit 16, which raises the voltage to the required levels necessary for the normal operation of all simulator units. To provide bipolar power, a voltage inverter 17 is used, which converts a positive voltage to a negative one. The bipolar voltage is supplied to the inputs of the voltage stabilizer block 18, in which the possible surges of supply voltages are smoothed out due to interference and instabilities of external supply devices, which makes it possible to obtain a supply voltage with a low noise level and the possibility of recharging from power supplies at the output of the reference voltage shaper 19 Computing devices containing USB ports.

Thus, the combination of essential features of the proposed device, common with the closest analogue, and distinctive features allows you to get the expected technical result, which consists in reducing the complexity of metrological verification procedures, certification and production tests of electrocardiographs with a minimum error probability of the personnel conducting these tests, that is, to achieve more high level of ergonomics. The creation and successful production testing of prototypes of this device confirmed the possibility of its mass production on the existing element base and installation technologies.

Claims (4)

1. A simulator for metrological verification and testing of electrocardiographs, containing a universal serial bus interface USB 2.0 port for communication with a personal computer, a memory unit and a display connected to a microcontroller, the fourth output of which is connected to the sound indication unit, and the fifth to the first input 8- channel digital-to-analog converter, to the second input of which the output of the stabilized voltage generating unit is connected, made with the possibility of connection to external power devices, at m each of the eight outputs of the 8-channel digital-to-analog converter is connected to the input of the corresponding channel of the 8-channel low-pass filter, characterized in that an 8-channel patient equivalent connection block and an 8-channel open circuit simulation block are connected in series, the outputs of which are simulator outputs intended for parallel connection of eight signal electrodes L, F, C1-C6, respectively, as well as 2-channel patient equivalent equivalent connection block connected in series and 2-channel unit simulate an open circuit, whose outputs are the outputs of the simulator intended for parallel connection electrode N and the reference R electrode, respectively, the two input 2-channel unit patient equivalent connections are connected to analog ground. 2. The simulator according to claim 1, characterized in that each channel of the 8-channel and 2-channel patient equivalent connection blocks is made in the form of parallel-connected resistor R and capacitor C, in parallel with which a circuit breaker is turned on, while the input and output of the specified channel are the connection points, respectively, of the output of the corresponding channel of the 8-channel low-pass filter and the input of the corresponding channel of the 8-channel circuit break simulator. 3. The simulator according to claim 1, characterized in that each channel of the 8-channel and 2-channel simulation circuit breakers is made in the form of a circuit breaker, one contact of which is the connection point to the output of the corresponding channel of the 8-channel circuit break simulation simulator, and another pin is used to connect the corresponding signal electrode. 4. The simulator according to claim 1, characterized in that the stabilized voltage generating unit comprises power supply control unit, voltage converters unit, voltage stabilizer unit and reference voltage driver, the output of which is the output of the stabilized voltage generating unit, and also connected to the control unit a galvanic cell, such as a battery, and a voltage inverter connected between the second output of the voltage converter unit and the second input of the stub unit recuperators stresses.

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