EMI Measurement Research Articles

Alternative Approach Leading to Reduction in Measurement Instrument Uncertainty of EMI Measurement

Abstract Even in the field of electromagnetic compatibility, low measurement uncertainty means high measurement quality. Although there are standardized procedures for obtaining the uncertainty of such a measurement, which facilitate uncertainty estimation, modern approaches show further reduction possibilities. The paper presents an alternative approach to reducing measurement instrument uncertainty in the case of electromagnetic interference measurement based on many years of our experience and a large number of measurements in this field. In the paper, two different methods of uncertainty reduction are described. The first method is based on a detailed analysis of the sources of uncertainty and the subsequent division of the analyzed frequency band into more subranges. Another method uses the choice of the antenna factor, which also contains information about the test site where the measurement is carried out. In this way, despite a lengthy analysis, it is relatively easy to achieve a measurement instrument uncertainty that is below the maximum measurement uncertainty given by the CISPR standard.

Synchronous Multipoint Low-Frequency EMI Measurement and Applications

Increased implementation of power electronics devices as well as high penetration of micro grids and embedded generation with low-supply inertia is resulting in grid stability problems, especially in transient or startup situations. The electromagnetic compatibility of these systems with regards to transients can be difficult to diagnose due to the short time duration and often intermittent nature of events. This letter proposes a multichannel measurement system which is able to measure voltage and current waveforms in multiple locations with synchronization and sample rates in the megahertz range. The overall design, characteristics, as well as applications are showcased in this letter.

Effects of feed gap arrangements of loop antennas on site validation for EMI measurements below 30 MHz

Effects of feed gap arrangements of loop antennas on site validation for EMI measurements below 30 MHz

Basic characteristics of magnetic field antenna factor of loop antennas for EMI measurements

Basic characteristics of magnetic field antenna factor of loop antennas for EMI measurements

Analysis of Low-Frequency Drone-Borne GPR for Root-Zone Soil Electrical Conductivity Characterization

In this study, we analysed low-frequency drone-borne ground-penetrating radar (GPR) and full-wave inversion for soil electrical conductivity mapping. Indeed, in the lowest GPR frequency ranges, the soil surface reflexion coefficient depends more on the soil electrical conductivity than on its permittivity. Numerical experiments were conducted within the frequency range 15-45 MHz to analyse parameter sensitivities, the well-posedness of the inverse problem as well as the depth of sensitivity. The results show that the soil surface reflexion is significantly more sensitive to the soil electrical conductivity than the soil permittivity. Therefore, the conductivity can be retrieved using full-wave inversion within this frequency range, with a characterization depth varying from 0.5 to 1 m, depending on the soil properties. Yet, the permittivity also affects the results and should be accounted for in the inversion strategy. Field measurements were performed using low-frequency drone-borne radar with a 5-metre half-wave dipole antenna, and EMI measurements with different depth sensitivities were conducted for comparison. Kriging interpolation was used to get maps from measurement points. The soil conductivity maps obtained by the proposed GPR and EMI are compliant in terms of absolute values and spatial patterns. This study demonstrated the capacity of low-frequency drone-borne GPR for fast, field-scale soil electrical conductivity mapping.

A novel approach for non-destructive EMI-based corrosion monitoring of concrete-embedded reinforcements using multi-orientation piezoelectric sensors

One of the major problems with the durability of concrete structures is the corrosion of embedded rebar in concrete. Early detection of corrosion can prevent catastrophic failures in structures. In this paper, the electromechanical impedance method (EMI) is used for structural health monitoring (SHM) and non-destructive corrosion diagnostics. Compared to previous methods, a new method with the highest accuracy is proposed to evaluate the electromechanical impedance curves. By using piezoelectric (PZT) sensors in concrete, the sensitivity of these sensors to compressive force is investigated through a series of experiments. Also, by bonding two PZT sensors on reinforcing bars in two different orientations, the behavior of specimens, are consistently compared with the EMI measurements. According to the results, a solution for the detection of the corrosion rate and its direction as well as the period of corrosion initiation is proposed based on the variations of the impedance curve during the corrosion.

A semi‐empirical model to predict the EM38 electromagnetic induction measurements of soils from basic ground properties

AbstractElectromagnetic induction (EMI) measurements (σb*) are widely used for the survey of several soil attributes, among which basic properties such as salinity (σe), water content (θw), clay (wc), organic matter (wom) and bulk density (ρb) stand out. In usual practice, purely empirical models relating one of these properties to σb* are calibrated at selected sites. However, this calibration is site and time specific and has to be repeated time and again. In order to understand where the variability of the EMI empirical models comes from, it is necessary to know how the different soil properties contribute to them and, with this aim, a more physically based relationship between σb* and, at least, σe, θw, wc, wom and ρb was developed in this work, additionally including soil temperature (t). It was calibrated and cross‐validated with the data from one survey carried out in a wide agricultural irrigation area in SE Spain, taking σb* measurements with the Geonics EM38 in the horizontal and vertical dipole modes and at various heights over the ground. Then, it was externally validated with the data from a second survey carried out 4 years later in the same area but in a different season. In the calibration, R2 and root mean square error (RMSE) were 0.84 and 0.18 dS m−1 (41%), respectively, for the vertical dipole orientation and 0.90 and 0.11 dS m−1 (39%) for the horizontal one. In the external validation, R2 and RMSE were 0.80 and 0.24 dS m−1 (44%), respectively, for the vertical dipole orientation and 0.90 and 0.13 dS m−1 (38%) for the horizontal one. Therefore, because the performance of the model barely worsened as time passed by, it can be considered to represent the underlying physical process and, therefore, to increase our understanding of how the soil EMI signals are generated, with potential benefits for the planning and comparability of EMI soil measurements, specifically with the EM38, among different areas.Highlights A semi‐empirical model was developed to predict soil EMI measurements from basic ground properties. Salinity, water content, clay, organic matter, bulk density and temperature were used as predictors. The model was able to explain between 80 and 90% of the variance in EMI measurements in the validation. This model helps us understand how the basic soil properties contribute to the EMI measurements.

Novel Test Set Up for GTEM Cell Characterization

The GTEM cell is a new version of the modified transmission line, operated at very high-frequency test equipment for EMI or EMC measurement. The equipment is designed for an electromagnetic compatibility, immunity and radiated emissions test. In this paper, GTEM is designed using ANSYS HFSS 13.0 and fabricated for 1 to 3.9 GHz frequency. This paper focuses mainly on the novel validation test for the manufactured GTEM cell characterization without using costly Vector Network Analyzer. The novel test set up comprises of GTEM cell, transmitter and the receiver is designed and tuned at 2.4 GHz. Using this set up field uniformity is checked for fabricated GTEM ranges within +/− 6dB. This makes a compact and cost-effective novel test validation set up for the designed, developed and manufactured GTEM for 1 to 3.9 GHz.

The Essence of the Little Box Challenge-Part B: Hardware Demonstrators & Comparative Evaluations

In order to expedite the development of power electronic systems towards higher power density and efficiency at a lower cost of implementation, Google and IEEE initiated the Google Little Box Challenge (GLBC) aiming for the worldwide smallest 2 kVA/450 VDC/230 VAC single-phase PV inverter with η > 95% CEC weighted efficiency and an air-cooled case temperature of less than 60 °C by using latest power semiconductor technology and innovative topological concepts. This paper, i.e. Part B of a discussion of The Essence of the Little Box Challenge, presents the hardware implementations and novel control concepts of two GaN-based inverter systems selected by the authors to counter the challenge: (i) Little Box 1.0 (LB 1.0), a H-bridge inverter with two interleaved bridge-legs both operated with Triangular Current Mode (TCM) modulation which features a power density of 8.18 kW/dm 3 (134 W/in 3 ) and a nominal efficiency of 96.4% and (ii) Little Box 2.0 (LB 2.0), an inverter topology with single bridgeleg DC/|AC| buck-stage operated with constant frequency PWM and a subsequent |AC|/AC H-bridge unfolder, which features a remarkable power density of 14.8 kW/dm 3 (243 W/in 3 ) and a nominal efficiency of 97.4% Implemented using latest GaN power semiconductor technology, Zero Voltage Switching (ZVS) throughout the AC period and a variable switching frequency in the range of 200 kHz-1 MHz in order to shrink the size of filter passives, the LB 1.0 was ranked among the top 10 out of 100+ teams actively participating in the GLBC. The LB 2.0 is the result of further research and considers lessons learned from the GLBC and achieves despite moderate 140 kHz constant frequency PWM and hard-switching around the peak of the AC output current a higher power density ρ and a higher efficiency η. For both implemented prototypes experimental results are provided to confirm that all GLBC technical requirements are met. The experimental results include steady-state and step-response waveforms, EMI and ground current measurements, as well as efficiency and operating temperature measurements. The reason for the ηρ-performance improvement of LB 2.0 over LB 1.0 are then discussed in detail. Furthermore, the solutions of other GLBC finalists are described and then compared to the performance achieved with the hardware prototypes presented in this paper. This leads to findings of general importance and provides key guideline for the future development of ultracompact power electronic converters.

Verification of pressure sensing sensitivity via EMI measurement of an external pipe for a membrane integrity test

Verification of pressure sensing sensitivity via EMI measurement of an external pipe for a membrane integrity test

Effect of fertilizers and irrigation on multi‐configuration electromagnetic induction measurements

AbstractElectromagnetic induction (EMI) data are often used to investigate spatial and temporal patterns of soil texture, soil water content and soil salinity. We hypothesized that the EMI methodology might thus also offer potential to detect agricultural legacy effects originating from fertilizer application and irrigation of different fields. Therefore, we performed EMI measurements on two long‐term field experiments (LTFE) at Thyrow near Berlin (Germany) that differed in agricultural management with regard to long‐term irrigation in combination with mineral (NPK and lime) and organic amendments (straw and farmyard manure). Two different rigid‐boom multi‐coil EMI instruments were used to measure simultaneously the apparent electrical conductivity (ECa) over nine different depth ranges to study the entire soil profile from topsoil to deep subsoil. Additionally, soil samples were taken from the different treatments to ground‐truth the measurements and disentangle the nutrient application or irrigation effects from natural soil heterogeneity. The soil samples indicated a rather homogenous soil and the correlation between soil parameters or states were not significant. However, the treatments showed significant differences in measured ECa values. In general, ECa values were largest on regularly irrigated as well as on mineral and organic fertilized plots, with regular irrigation exhibiting the largest impact on EMI records even though the last application was months before the EMI measurement. Overall, this study reveals that EMI data can support the classical in situ assessment of agricultural management effects within LTFE, while offering new potentials in detecting and understanding legacy effects of agricultural management on spatial soil properties at farm level.

Improved Geoarchaeological Mapping with Electromagnetic Induction Instruments from Dedicated Processing and Inversion

Increasingly, electromagnetic induction methods (EMI) are being used within the area of archaeological prospecting for mapping soil structures or for studying paleo-landscapes. Recent hardware developments have made fast data acquisition, combined with precise positioning, possible, thus providing interesting possibilities for archaeological prospecting. However, it is commonly assumed that the instrument operates in what is referred to as Low Induction Number, or LIN. Here, we detail the problems of the approximations while discussing a best practice for EMI measurements, data processing, and inversion for understanding a paleo-landscape at an Iron Age human bone depositional site (Alken Enge) in Denmark. On synthetic as well as field data we show that soil mapping based on EMI instruments can be improved by applying data processing methodologies from adjacent scientific fields. Data from a 10 hectare study site was collected with a line spacing of 1–4 m, resulting in roughly 13,000 processed soundings, which were inverted with a full non-linear algorithm. The models had higher dynamic range in the retrieved resistivity values, as well as sharper contrasts between structural elements than we could obtain by looking at data alone. We show that the pre-excavation EMI mapping facilitated an archaeological prospecting where traditional trenching could be replaced by a few test pits at selected sites, hereby increasing the chance of finding human bones. In a general context we show that (1) dedicated processing of EMI data is necessary to remove coupling from anthropogenic structures (fences, phone cables, paved roads, etc.), and (2) that carrying out a dedicated full non-linear inversion with spatial coherency constraints improves the accuracy of resistivities and structures over using the data as they are or using the Low Induction Number (LIN) approximation.

Integrating auxiliary data and geophysical techniques for the estimation of soil clay content using CHAID algorithm

This study was conducted to estimate soil clay content in two depths using geophysical techniques (Ground Penetration Radar—GPR and Electromagnetic Induction—EMI) and ancillary variables (remote sensing and topographic data) in an arid region of the southeastern Iran. GPR measurements were performed throughout ten transects of 100m length with the line spacing of 10m, and the EMI measurements were done every 10m on the same transect in six sites. Ten soil cores were sampled randomly in each site and soil samples were taken from the depth of 0–20 and 20–40cm, and then the clay fraction of each of sixty soil samples was measured in the laboratory. Clay content was predicted using three different sets of properties including geophysical data, ancillary data, and a combination of both as inputs to multiple linear regressions (MLR) and decision tree-based algorithm of Chi-Squared Automatic Interaction Detection (CHAID) models. The results of the CHAID and MLR models with all combined data showed that geophysical data were the most important variables for the prediction of clay content in two depths in the study area. The proposed MLR model, using the combined data, could explain only 0.44 and 0.31% of the total variability of clay content in 0–20 and 20–40cm depths, respectively. Also, the coefficient of determination (R2) values for the clay content prediction, using the constructed CHAID model with the combined data, was 0.82 and 0.76 in 0–20 and 20–40cm depths, respectively. CHAID models, therefore, showed a greater potential in predicting soil clay content from geophysical and ancillary data, while traditional regression methods (i.e. the MLR models) did not perform as well. Overall, the results may encourage researchers in using georeferenced GPR and EMI data as ancillary variables and CHAID algorithm to improve the estimation of soil clay content.

EMI Issues in Pseudo-Differential Signaling for SDRAM Interface

H-field EMI measurements have been performed for the single-ended, the differential, and the pseudo-differential signaling on a 11” FR4 microstrip line. The pseudo-differential signaling reduces EMI by more than 10 ㏈ compared to the single-ended signaling if the delay mismatch is lower than 5% of a period for a 3 ㎓ clock signal. Empirical H-field equations for both differential and single-ended signaling showed fair agreements with measurements.

On the Statistical Properties of the Peak Detection for Time-Domain EMI Measurements

This paper presents a discussion on the inherent characteristics of the measurements performed with time-domain electromagnetic interference measurement systems in regards of the detection of the maximum emissions levels. In that sense, some relevant statistical properties of the frequency components of the maximum emissions levels in the amplitude spectrum are investigated using the extreme value theory to provide a model based on the Gumbel probability distribution and estimates for its parameters, expected value, variance, and Cramer-Rao bounds. The results suggest that using the expected maximum value of the emissions levels instead of the just the observed maximum value improves the measurement repeatability and also reduces the uncertainty in the results. This paper presents an additional insight measure that enhances our understanding of the statistical behavior of the measured EMI and of the time-domain measurement process itself.

Improving time-domain EMI measurements through digital signal processing

This article is intended to provide a set of recommended practices for improving of the Time-Domain EMI measurement systems by means of digital signal processing. We have focused on two major aspects: the optimal configuration settings of the direct measurement equipment and the deployment of algorithms to process the measurement result. In that sense, we believe that general purpose time-domain instruments, as oscilloscopes, can be successfully used as an alternative hardware to measure EMI, since they provide accurate and reliable results, surpassing the conventional frequency-domain approach when transient disturbances are present.

Three‐dimensional imaging of subsurface structural patterns using quantitative large‐scale multiconfiguration electromagnetic induction data

AbstractElectromagnetic induction (EMI) systems measure the soil apparent electrical conductivity (ECa), which is related to the soil water content, texture, and salinity changes. Large‐scale EMI measurements often show relevant areal ECa patterns, but only few researchers have attempted to resolve vertical changes in electrical conductivity that in principle can be obtained using multiconfiguration EMI devices. In this work, we show that EMI measurements can be used to determine the lateral and vertical distribution of the electrical conductivity at the field scale and beyond. Processed ECa data for six coil configurations measured at the Selhausen (Germany) test site were calibrated using inverted electrical resistivity tomography (ERT) data from a short transect with a high ECa range, and regridded using a nearest neighbor interpolation. The quantitative ECa data at each grid node were inverted using a novel three‐layer inversion that uses the shuffled complex evolution (SCE) optimization and a Maxwell‐based electromagnetic forward model. The obtained 1‐D results were stitched together to form a 3‐D subsurface electrical conductivity model that showed smoothly varying electrical conductivities and layer thicknesses, indicating the stability of the inversion. The obtained electrical conductivity distributions were validated with low‐resolution grain size distribution maps and two 120 m long ERT transects that confirmed the obtained lateral and vertical large‐scale electrical conductivity patterns. Observed differences in the EMI and ERT inversion results were attributed to differences in soil water content between acquisition days. These findings indicate that EMI inversions can be used to infer hydrologically active layers.

Common-Mode Filter Design for PWM Rectifier-Based Motor Drives

A common-mode (CM) filter based on the LCL filter topology is proposed in this paper, which provides a parallel path for ground currents and which also restricts the magnitude of the EMI noise injected into the grid. The CM filter makes use of the components of a line to line LCL filter, which is modified to address the CM voltage with minimal additional components. This leads to a compact filtering solution. The CM voltage of an adjustable speed drive using a PWM rectifier is analyzed for this purpose. The filter design is based on the CM equivalent circuit of the drive system. The filter addresses the adverse effects of the PWM rectifier in an adjustable speed drive. Guidelines are provided on the selection of the filter components. Different variants of the filter topology are evaluated to establish the effectiveness of the proposed circuit. Experimental results based on EMI measurement on the grid side and the CM current measurement on the motor side are presented. These results validate the effectiveness of the filter.

Conversion Factors Between Common Detectors in EMI Measurement for Impulse and Gaussian Noises

Based on the operating principle of a typical electromagnetic interference test receiver and the circuits of various commonly used detectors, a simulation model is developed. With the model, the response of each detector to broadband emission can be simulated and analyzed. The conversion factors between different types of detectors for the same type of broadband emission are determined and verified with those reported in well establish standards. The systematic analysis provides both insight and rationale behind how these conversion factors are derived.

MODELING RADIATED ELECTROMAGNETIC EMISSIONS OF ELECTRIC MOTORCYCLES IN TERMS OF DRIVING PROFILE USING MLP NEURAL NETWORKS

Current automotive electromagnetic compatibility (EMC) standards do not discuss the efiect of the driving proflle on real tra-c vehicular radiated emissions. This paper describes a modeling methodology to evaluate the radiated electromagnetic emissions of electric motorcycles in terms of the driving proflle signals such as the vehicle velocity remotely controlled by means of a CAN bus. A time domain EMI measurement system has been used to measure the temporal evolution of the radiated emissions in a semi-anechoic chamber. The CAN bus noise has been reduced by means of adaptive frequency domain cancellation techniques. Experimental results demonstrate that there is a temporal relationship between the motorcycle velocity and the radiated emission power in some speciflc frequency ranges. A Multilayer Perceptron (MLP) neural model has been developed to estimate the radiated emissions power in terms of the motorcycle velocity. Details of the training and testing of the developed neural estimator are described.