Frequency Meter Research Articles

Autonomic cardiac modulation in postmenopausal women with dry eye syndrome: a cross-sectional analytical study.

The aim of this study was to assess cardiac autonomic modulation in postmenopausal women with and without dry eye syndrome (DES) and to identify associations between clinical and socioeconomic factors. A cross-sectional study was carried out at the Institute of Ocular Surgery of the Northeast (ICONE), Brazil. Convenience sample of postmenopausal women, over 40 years old, who were divided into two groups: with and without DES. Clinical, sociodemographic, and ophthalmological characteristics of these women were assessed. Capture of RR intervals was performed using a cardio frequency meter. Differences between the groups were analyzed using the Chi-square test, the Student's t test, and the Mann-Whitney test. Women with DES were present in 60.4% (n=58), highest median age (63.5 years, 95%CI 62.0-67.9; p<0.001), median length of time menopause (19 years old, 95%CI 10.4-24.0; p<0.001). There was a difference in the standard deviation of all normal-to-normal index between the groups. However, when the differences were adjusted to the clinical model, no association was found between DES and heart rate variability (HRV). The analysis of cardiac autonomic modulation in postmenopausal women is similar in the presence or absence of DES. Clinical factors, time of menopause, and intensity of symptoms were not associated with HRV indices.

Effect of dry needling on the variability of cardiac frequency in university members with temporomandibular dysfunction

Introduction: Despite the existence of some theories about the effect of Dry Needling on pain, there is still a lack of research using this technique in the treatment of temporomandibular disorder and its repercussions on the autonomic nervous system. Therefore, the aim was to analyze the effect of Dry Needling on the autonomic modulation of university students with temporomandibular disorders. Methods: This is an interventional, inferential study, carried out with university students with temporomandibular disorders. A frequency meter was used before, during, and after the application of the dry needle to verify its short and medium term effect on the autonomic nervous system. For statistical analysis, the ANOVA test was used. Results: Twenty volunteers with an average age of 21.3 years took part in the study, most of them male (65%). When the rMSSD and pNN50 indexes were analyzed, an increase was observed during dry needling (p = 0.701 and 0.452, respectively). However, after application, these indices fell, remaining above the base values. However, the triangular RR and TINN indices showed a constant increase during collection (p = 0.578 and 0.613, respectively). The high frequency component increased during the technique (p = 0.860), but the same did not happen with the low frequency component (p = 0.693), which suffered a constant increase, even with minor variation. Conclusion: The effect of this technique promotes the improvement of the heart rate variability values, maintaining the balance of the autonomic nervous system without generating cardiovascular risks, and its effects were immediate and lasting.

ВИМІРЮВАННЯ ОПОРНОЇ ЧАСТОТИ ВУЗЬКОСМУГОВОГО РАДІОСИГНАЛУ ОБМЕЖЕНОЇ ТРИВАЛОСТІ

The work concerns analog-digital systems that work with radio signals emitted and received by the antenna, and these signals have a limited duration, ie are pulsed. The propagation conditions of such signals and the processes of formation of echo signals affect their amplitude, frequency and phase characteristics in such a way that they form classical narrowband signals. The operation of the system involves the determination of certain parameters of echo signals, and taking into account their pulse nature for such a definition is given a limited time interval. This means that the procedure for determining the parameters must meet the criterion of high speed, and therefore differ from the traditional, built on the use of phase-locked loop. The article is devoted to solving the problem of measuring the reference frequency of a pulsed narrowband radio signal. By analyzing the results of experimental studies, two types of errors in measuring the reference frequency of a narrowband radio signal were identified and the causes of their occurrence were established. These errors are provoked by the peculiarities of the structure of the narrowband signal. The reason for the error of the 1st type, the absolute value of which correlates with the duration of the half-cycle of the reference frequency, is the so-called phase jumps at the point of change of the sign of the bypass. The frequency of such errors within the duration of the echo signal is generally low, although it increases with increasing signal spectrum width. Type 2 errors occur due to the appearance of zones with almost completely suppressed signal amplitude, which may be the result of intrapulse interference and / or signal attenuation. Such errors also occur more often if the spectrum width is larger. A method for measuring the reference frequency of a narrowband pulsed radio signal is proposed, which is based on counting the number of half-cycles of the reference frequency on a time-limited measurement interval and removing from this procedure areas with completely suppressed signal amplitude. An auxiliary highly stable reference frequency is used to establish the numerical value of the reference frequency. The block diagram of the frequency meter and the algorithm of its operation are given, the implementation of which avoids these errors.

Effect of Transcranial Direct Current Stimulation associated with aerobic exercise on the autonomic modulation of hemiparetic individuals due to stroke: a study protocol for a double-blind randomized controlled trial

Background: Individuals after a stroke have an imbalance in the autonomic nervous system, which increases the risk of death or recurrent episodes of stroke. Transcranial Direct Current Stimulation (tDCS) combined with aerobic exercise has shown an effect on the modulation of this system. Objective: The Heart Rate Variability (HRV) and the distance traveled on the exercise bike will be assessed to verify the additional impact of tDCS combined with aerobic exercise on individuals with chronic stroke sequelae. Methods: The 34 adult individuals with diagnoses of chronic stroke will be randomized into two aerobic exercise intervention groups: G1 (with active tDCS) and G2 (with sham tDCS), three times a week, for 12 weeks. Procedures: tDCS will be implemented during the aerobic exercise with the anodal electrode positioned over the lateral dorsal prefrontal left cortex, and the cathodal electrode over the contralateral supraorbital region, with 2mA, for 20 minutes. Assessments will be carried out pre, immediately after the intervention, and on the 12th, 24th, 36th interventions, and 30 days later. The HRV data that are pulse interval (PI), square root of the mean of the squares of the differences between adjacent normal RR intervals (rMSSD), absolute high frequency (HF), absolute low frequency (LF), high and low frequency ratio (LF / HF) will be collected using a cardio frequency meter. The analysis of the distance traveled on the exercise bike before and after interventions will be analyzed in meters. Discussion: The autonomic control via brain networks after a stroke can be altered and can promote an increase in sympathetic tone, and a higher risk of sudden death or relapse of stroke. It is crucial to demonstrate the effectiveness of available treatments to improve the autonomic function. Trial registration: The study is registered as a BRAZILIAN CLINICAL TEST RECORD (ReBEC): U1111-1222-4588 on the 2018/10/16

Design of the self-oscillating loop of the optically pumped cesium magnetometer

The self-oscillating loop is an important part of the optically pumped cesium magnetometer, and its working characteristics directly determine the accurate measurement of external magnetic field. The design of the self-oscillating loop has been discussed in this paper, including a signal conditioning circuit, a phase shifter and a frequency meter. It can be used to precisely improve the accuracy of resonance signal in a wide range of frequencies from 50 kHz to 350 kHz. The relative error of our system is less than 0.5×10−6 and it has a good prospect in the optically pumped cesium magnetometer.

Design of SOPC digital frequency meter based on MicroBlaze

A method of SOPC implementation of digital frequency meter is presented in this paper. In the method, Encapsulated AXI IP core for frequency measurement and duty cycle measurement are configured with the embedded soft core MicroBlaze processor. The parameter measurement of the digital frequency meter is implemented by FPGA logic resources, and the measured data are transmitted to the soft core processor via AXI bus. The computation, control and display is completed by Microblaze soft core. The system is verified and tested on the Basys3 board card launched by digilent company. The results show that the system has the advantages of accurate measurement, good stability, simple scheme and low cost.

Evaluation of errors of the wattmeter method for determining magnetic losses in transformers

The problem of the influence of the accuracy of dividing magnetic losses into components in transformers on the efficiency of minimizing these losses is considered. Various methods of studying and evaluating the magnetic properties of electrical steels and the power of magnetic losses are described. It is shown that the use of the wattmeter method for determining the components of magnetic losses in a specific transformer, in contrast to the currently used methods for determining the power of specific magnetic losses, does not require special equipment and software. An assessment of two specific errors of the wattmeter method for determining the magnetic losses in the transformer core is carried out. The first error is associated with the errors of the measuring devices (wattmeter and frequency meter), the second – with electrical losses during an idle experiment. The dependences of the errors of these losses on the accuracy class of the devices (wattmeter and cymometer) are obtained. It was found that for a dry single-phase transformer, the error of hysteresis losses is 19 times higher than the accuracy class of devices, and the error of eddy-current losses is 32 times. For low-power transformers (up to 5 kVA), taking into account electrical losses in the no-load experiment underestimates the losses due to hysteresis and overestimates the losses due to eddy currents, the error in determining which can significantly exceed the total error in determining the magnetic losses. It is shown that for transformers with a capacity of over 25 kVA, the error associated with taking into account electrical losses in the no-load test is negligible.

The new state measurement standard of the unit of frequency deviation of frequency-modulated oscillations

The article is devoted to the review of the main results of research and development works performed during the improvement of the state primary measurement standard of the frequency deviation unit. The article analyzes the situation in the field of measuring the parameters of frequency-modulated oscillations in Ukraine that led to the need for improving the unit of frequency deviation created in 1996, namely the need to significantly enhance metrological characteristics and expand the functionality of the measurement standard.Тhe principle of building a modern measurement standard with advanced functionality, improved metrological characteristics was developed. Solutions used the modern hardware level for measuring parameters of oscillations with frequency modulation and expanding modulating frequencies and deviations.In the measurement standard, the role of the reference receiver is performed by the spectrum analyzer, which implements the method of measuring the deviation of the Bessel function “zeros” (NFB). The second method used in the measurement standard is a digital method known as the “electronic counting frequency meter” (ELC) method. One of the comprehensive decisions was the use of digital signal generators, which are based on DDS technology (direct digital synthesis) and its subsequent version – Trueform. The article presents the results of analysis of metrological capabilities of these generators in the FM mode, original methods of their research and new results obtained.During the improvement, the method of receiving the FM signal, based on the use of a spectrum analyzer and an option, analog-digital demodulator, was used and investigated. Automation of control and computational operations on the measurement standard on the basis of the Labview program was carried out.As a result, a reference complex was created, which according to its metrological characteristics and functional capabilities is able to calibrate not only the devices in the FM mode, but also a wide range of radio measuring instruments of both receiving and generating types.

The reproducibility of the 1hz gps in the aciclic displacement with intermittent intensity

Objective: the aim of this study was to verify the reproducibility index of the frequency meter with GPS technology with recording speed of 1Hz in acyclic displacement and intermittent intensity, performed by soccer referees. Materials and methods: it was characterized by a field study with a quantitative trait involving 14 men, aged 20.42 ± 2.78 years, from a barracks in the city of Rio de Janeiro. Polar heart rate monitor with 1Hz GPS model V800 was used. The protocol used was adapted from the FIFA test protocol for soccer referees, so that 10 "shots" of 75m in 15s were accomplished by 25m in 20 of recovery. Testing and retest were applied with 7 days interval and identical protocols: heating, ambiance (4 "shots" following the model of the protocol above) and then the test. Since the circuit covered in the test protocol was 1000 m.Results: a mean of 1002.5 ± 17.12 m was obtained in the test and in the test 1010.83± 32.88 m, the coefficients of variation were respectively 1% and 3%. The difference wasnot significant between the test and the retest (P-value&gt; 0.05), and the intraclasscorrelation coefficient indicated a moderate association between the measures.Conclusion: therefore, it is suggested that it is acceptable to use a frequency gauge with a recording speed of 1Hz to monitor displacements of soccer referees in acyclic displacement and intermittent intensity.

Development of Alternating Current (AC) Line Monitoring Device for Power System Management

This work presents a study of the effect of imbalance between the supply of and demand of power from the National grid on electrical appliances. In the study, an alternating current (ac) line monitoring device was developed using arduino microcontroller to carry out the investigation. The device is a single system capable of measuring both the main frequency and nominal voltage of electricity supply. The device consists of seven major components: 12 V step-down transformer, half-wave rectifier, attenuator, wave-shaping circuit, arduino microcontroller, Liquid crystal display and micro SD card. The heart of the device is the arduino microcontroller that reads the period of the pulses from the shaping circuit and the output voltage from the scale resistor connected to the attenuator circuit in order to measure the levels frequency and voltage of the ac main source. By graphically compared the reading of the voltage obtained by the ac monitoring device with that of the standard Mastech voltmeter, it was shown that the device has a good correlation with the standard voltmeter with a deviation of ±0.21%, and this has proven that the device is capable of measuring ac voltage accurately. From the frequency test level results, it was found that the frequency measured by the device closely related to the frequency measured by the standard frequency meter. This shows that the device satisfied the requirement of the overall design. Hence, it can be used in the laboratory for demonstration and research purposes as well as in power plant industries.&#x0D; Keywords: Mains frequency, nominal voltage, half-wave rectifier, attenuator, wave-shaping circuit, Arduino microcontroller

DESIGN OF DETECTING ACOUSTIC WAVES AT THE EXERCISE SMART MINE USING ACOUSTIC SENSOR

The Indonesian Navy is a unit of defense of the Republic of Indonesia (NKRI). Sea mines are explosive devices placed in waters to destroy ships. Acoustics is a branch of physics that deals with all mechanical waves in liquids, gases and solids, such as vibration, sound and ultrasonic. Arduino has made microcontroller technology more accessible and easier for even novice users. Because of this, there are special functions in audio or acoustic processing techniques aimed at using Arduino. The application of acoustic signals in the military field of the Navy, in the identification of vessels caught by the microphone receiver. The movement of objects that are caught by the microphone will be analyzed to conclude the object. From the results of the sound characteristics raised by the object, it will give a different picture for different variations of the object. Processing acoustic signals using DSP will make it easier to infer the captured acoustic signal. The circuit board used is a microphone signal amplifier and signal conditioner, for processing the audio signal obtained from the microphone and to produce output data which is the result of the process using Arduino. Analog-to-digital converter (ADC) of the microcontroller works in the voltage range from 0.0 V to +3.3 V or +5.0 V. Toachieve good sampling results, that the signal peak is close to the maximum value of the ADC. Additionally, voltage amplitudes above this threshold can damage the controller input port or produce unwanted harmonics. Therefore, a signal pre-amp circuit is needed to guarantee the appropriate audio sample signal as well as to protect the system. The test results obtained from the system analyzer frequency and signal meters can be used to identify acoustic signals.&#x0D; Keyword: Singnal Acoustic/michophone, controller, Arduino Uno, pre-amp frequency analyzer

Classification of the intact carbonate and silicate rocks based on their degree of thermal cracking using discriminant analysis

Discriminant analysis is a multivariate statistical tool that generates a discriminant function to predict about the group membership of sampled experimental data. In this study, discriminant analysis was performed using IBM SPSS software package (version 23) to discriminate between pre-defined groups of measured dynamic properties of thermally treated selected carbonate and silicate rocks. The range of temperature variations was selected from 35 °C (laboratory temperature) to 200 °C to estimate the change in dynamic properties including Q-factor (Q), resonance frequency (Fr), elastic Young’s modulus (Ed), damping ratio (ξ), and specific damping capacity (Ψ) by using the “Erudite Resonance Frequency Meter” apparatus in accordance with ASTM C215 test procedure. The test results revealed significant variations in the values of Q, Fr, Ed, ξ, and Ψ with the rise in temperature. The measured dynamic properties of selected sedimentary rocks were classified into 2 discrete groups based on their extent of thermal treatment (i.e., 35–100 °C and 100–200 °C). Discriminant analysis–based classification results showed the sensitivity level of 86.70% and specificity level of 100.00% between predicted and original group membership. The estimated model hit ratio of 92.00% found better than maximum chance criterion and proportional chance criterion that indicates the high level of significance of classification results. Q-statistic results also satisfied the high prediction accuracy of discriminant function. The outcomes of this study could provide useful references in the classification and characterization of experimental data related to geotechnical and geomechanical studies.

Особенности модернизации частотомера UA Ч3-101

JSC «Meridian» n. a. S. P. Korolyov at one point developed and mass-produced a wide-range microwave frequency meter of the 8-mm wavelength range UA Ч3-101. Over time, however, the device has become obsolete for a number of reasons, and the question arose of the need to replace it. Since the cost of foreign models of frequency meters with similar parameters available on the market is quite high, the enterprise’s capabilities in solving this issue were considered. The analysis showed that the development of a new similar frequency meter will also be quite expensive, but the modernization of the existing one might be much cheaper, since the enterprise has all the infrastructure for serial production of the upgraded frequency meter. This article describes technical solutions for the replacement of labor-consuming microwave components of the UA Ч3-101 frequency meter, such as microstrip and waveguide input microwave converters, as well as optimization of the frequency measuring process of the input signal, which allowed us to upgrade the device according to the requirements. The use of the developed broadband small-sized frequency converter in the modernized UA Ч3-101A frequency meter made it possible to simplify the circuit and the frequency measurement process as much as possible, to use only one input microwave converter, to significantly reduce the weight and size of the device, to abandon the labor-consuming and expensive waveguide components of the device, and to double the sensitivity upgraded frequency meter. The proposed technical solution allowed simplifying the production process of the frequency meter, making the device more convenient to use. In addition, due to the optimization of circuit and design solutions in the upgraded frequency meter, it was possible to combine the counter and the gate driver on the same board, combine the reference frequency block with a 100 MHz tunable generator, abandon the switch, which allowed reducing power consumption and increasing the reliability of the device.

Частотомір електричних імпульсів на базі програмованого мікроконтролера

Частотомір електричних імпульсів на базі програмованого мікроконтролера

Исследование диэлектрических свойств сополимеров на основе 2,3,4,5,6-пентафторстирола, стирола, 4-фтор-α-метилстирола и α-метилстирола

Three new copolymers based on fluorine-containing derivatives of styrene and α-methylstyrene were obtained. According to the results of the previous stages of the study, copolymers based on styrene derivatives have improved dielectric properties compared to polystyrene and a copolymer of styrene and α-methyl styrene. The dielectric constant ε and dielectric loss tangent tanδ were measured for the initial and synthesized samples of styrene – α-methyl styrene copolymer at Samara Electromechanical Plant OJ-SC (Samara city, Russia). All measurements of dielectric characteristics were carried out at an alternating current frequency of 10 GHz on a pressed copolymer tablet with a diameter of 10 and a thickness of 3 mm. During the experiment, a measuring stand was used, consisting of a high-frequency signal generator G4-83, an electronically counting frequency meter Ch3-54 with a frequency converter YaZCh-43, a measuring amplifier U2-4; low-frequency signal generator G3-109; measuring unit FKDG 418151.002. The results obtained indicate high values of the dielectric constant. For samples of copolymers of α-methylstyrene – 4-fluoro-α-methylstyrene and styrene – 4-fluoro-α-methylstyrene, values of 4.63 and 4.21, respectively, were obtained. These dielectric permittivity values are superior not only to samples previously obtained during the experiment, but also to some other compounds that are widely used in industry. In particular, the dielectric constant of lavsan, which is used in the manufacture of capacitors, is 3.1-3.3. The improved dielectric constant values are probably related to the high-quality composition of the copolymer. Samples of the copolymer containing 4-fluoro-α-methylstyrene are significantly superior to the copolymer with 2,3,4,5,6-pentafluorostyrene for this characteristic. The values of the dielectric loss tangent are in the range from 8.74∙10−4 to 37.4∙10−4. Given the dielectric characteristics of the synthesized copolymers, we can conclude that there are good prospects for the use of fluorine-containing styrene copolymers. The obtained values of permittivity and dielectric loss tangent indicate a good possible competitiveness of new materials based on new copolymers. In the future, it is planned to study a number of other physicochemical properties of these materials in order to obtain the most complete spectrum of their characteristics.

Measurement of low frequency mechanical vibrations based on an inverted magnetic pendulum

&lt;span&gt;In this paper is presented the mathematical model, design and construction of a prototype of a vibration frequency meter in an adjustable range of 2 Hz to 30 Hz; The experimental results and their analysis are also presented, making a comparative evaluation with the theoretical model. The device is based on the principle of resonance applied in an inverted magnetic pendulum whose natural frequency can be modified by variations of physical parameters. The oscillation of the pendulum is recorded detecting variations in the magnetic field using hall effect sensors; the data recorded with a microprocessor is analyzed and the results are simultaneously plotted in a computer interface. The data obtained were processed to be plotted in the frequency domain, facilitating its analysis. It was proved that the prototype can be used as a frequency meter and that the adjustable character of the device works according to the mathematical model. Finally, The effect of the friction force was studied, it was concluded that the friction force affects the measurement after a considerable period of time of oscillation, but not in the first moments.&lt;/span&gt;

Device for Generating and Measuring Time Intervals

The article suggests a device that extends the functionality of the measuring devices such as generators and frequency meters. So these devices can be used as part of working standards in a complex for verification and calibrating stopwatches. The device consists of an electronic commutator and a component controlled by a microcontroller, which forms the required intervals of time and provides a necessary connection from the generator output to the frequency counter input, turned on in the pulse counting mode. The control signal simultaneously arrives at the commutator and the device for automatic start/stop of stopwatches. The circuit design of the device allows minimizing the device’s influence on the overall metrological characteristics of the complex through the use of a high-speed controlled M74HC125 buffer (high-speed CMOS QUAD BUFFER (3-STATE)) as a switch. The M74HC125 buffer in this device is the only metrologically significant node; the state switching time of which in the aspect of this task can be ignored (Fig. 3). A computer and standard software, such as HyperTerminal from the Windows XP or PuTTY distribution, are used to control and communicate with the device. The device can be connected to the computer via USB. For laboratories that have these instruments in operation, this approach can help to avoid acquisitions of the additional reference equipment, which helps to reduce the maintenance and calibration costs of reference equipment.

Relationship of the Aggregation of Cardiovascular Risk Factors in the Parasympathetic Modulation of Young People with Type 1 Diabetes.

Background and objectives: In healthy individuals, autonomic alterations are associated with the aggregation of cardiovascular risk factors. However, in individuals with type 1 diabetes, who are known to present autonomic alterations, mainly characterized by a reduction in parasympathetic modulation, these associations have not yet been investigated. We assess whether the aggregation of cardiovascular risk factors influences parasympathetic indices of heart rate variability in young people with type 1 diabetes. Materials and methods: This cross-sectional study included 39 individuals with type 1 diabetes (22.54 ± 4.31), evaluated in relation to the risk factors: blood pressure, fat percentage, and resting heart rate. For heart rate variability analysis, heart rate was recorded beat-to-beat using a cardio frequency meter (PolarS810i) for 30 min with the volunteers in dorsal decubitus. The parasympathetic heart rate variability indices were calculated: rMSSD, pNN50, high frequency (HF) n.u (normalized units), SD1, 2LV, and 2ULV. Data collection was carried out in 2014 and analyzed in 2017. Results: Individuals with two aggregate risk factors present a reduction in the values of the indices that reflect parasympathetic autonomic modulation compared to individuals without the risk factors analyzed, regardless of sex and age. Conclusion: In young people with type 1 diabetes, the aggregation of cardiovascular risk factors is associated with parasympathetic autonomic impairment.

Length Effect on the Stress Detection of Prestressed Steel Strands Based on Electromagnetic Oscillation Method.

Prestress detection of structures has been puzzling structural engineers for a long time. The inductance–capacitance (LC) electromagnetic oscillation method has shown a potential solution to this problem. It connects the two ends of a steel strand, which is simulated as an inductor, to the oscillation circuit, and the stress of the steel strand can be calculated by measuring the oscillation frequency of the circuit through a frequency meter. In the previous studies, the authors found that stress-frequency relation of 1.2 m steel strand was negatively correlated, while the stress-frequency of 10 m steel strand was positively correlated. To verify this conflict, two kinds of electrical inductance models of steel strands were established to fit the lengths. With the models, the stress-frequency relations of steel strands with different lengths were analyzed. After that, two kinds of experimental platforms were set up, and a series of stress-frequency relationship tests were carried out with 1.2 m, 5 m, 10 m and 15 m steel strands. Theoretical analysis and experimental results show that when the length is less than 2.013 m, the stress and oscillation frequencies are negatively correlated; when length is more than 2.199 m, the stress and oscillation frequencies are positively correlated; while when length is between 2.013 m and 2.199 m, the stress-frequency relationship is in transit from negative correlation to positive correlation.

Study on Gate Circuit Multivibrator Based on FPGA

Gate circuit multivibrator is composed of logic gates and RC circuit. When the vibrator is designed based on FPGA, the pulse frequency measured using frequency meter in FPGA is much higher than theoretic analysis value. If this circuit is used as a pulse signal generator, mistakes will be made easily. In this paper, a gate circuit multivibrator based on FPGA is designed, and its vibrating frequency is measured using the FPGA itself. A frequency error is measured. The reason that causes this error is analyzed, and it is testified through simulation and real signal test. Pulse shaping through Schmitt trigger is an effective solution method. This study shows that clock pulse is very important to FPGA system.