GB2279523A - Method for the storage and later reconstruction of ultrasonic signals - Google Patents
Method for the storage and later reconstruction of ultrasonic signals Download PDFInfo
- Publication number
- GB2279523A GB2279523A GB9406195A GB9406195A GB2279523A GB 2279523 A GB2279523 A GB 2279523A GB 9406195 A GB9406195 A GB 9406195A GB 9406195 A GB9406195 A GB 9406195A GB 2279523 A GB2279523 A GB 2279523A
- Authority
- GB
- United Kingdom
- Prior art keywords
- interpolation
- maximum
- ultrasonic signals
- signal
- amplitude
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
- H03M1/00—Analogue/digital conversion; Digital/analogue conversion
- H03M1/12—Analogue/digital converters
- H03M1/124—Sampling or signal conditioning arrangements specially adapted for A/D converters
- H03M1/1245—Details of sampling arrangements or methods
- H03M1/1265—Non-uniform sampling
- H03M1/127—Non-uniform sampling at intervals varying with the rate of change of the input signal
- H03M1/1275—Non-uniform sampling at intervals varying with the rate of change of the input signal at extreme values only
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/36—Detecting the response signal, e.g. electronic circuits specially adapted therefor
- G01N29/38—Detecting the response signal, e.g. electronic circuits specially adapted therefor by time filtering, e.g. using time gates
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/36—Detecting the response signal, e.g. electronic circuits specially adapted therefor
- G01N29/40—Detecting the response signal, e.g. electronic circuits specially adapted therefor by amplitude filtering, e.g. by applying a threshold or by gain control
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/44—Processing the detected response signal, e.g. electronic circuits specially adapted therefor
- G01N29/449—Statistical methods not provided for in G01N29/4409, e.g. averaging, smoothing and interpolation
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
- G01S7/52017—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00 particularly adapted to short-range imaging
- G01S7/52023—Details of receivers
- G01S7/52034—Data rate converters
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F1/00—Details not covered by groups G06F3/00 - G06F13/00 and G06F21/00
- G06F1/02—Digital function generators
- G06F1/03—Digital function generators working, at least partly, by table look-up
- G06F1/035—Reduction of table size
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
- G01S7/52017—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00 particularly adapted to short-range imaging
- G01S7/52023—Details of receivers
- G01S7/52025—Details of receivers for pulse systems
- G01S7/52026—Extracting wanted echo signals
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F2101/00—Indexing scheme relating to the type of digital function generated
- G06F2101/04—Trigonometric functions
Abstract
Ultrasonic signals are digitized, the maximum amplitudes and their polarities are determined and only these maximum amplitudes with their corresponding polarities and times are stored in a memory. The ultrasonic signals are reconstructed later from the stored data by connecting a maximum amplitude with the immediately following maximum amplitude by a 180 DEG cosine curve, which has a slope of zero at the positions of the two maximum amplitudes. <IMAGE>
Description
Method for processing digitized ultrasonic
signals originating from an ultrasonic
probe for the storage and later
reconstruction of the ultrasonic signals
from the stored data
The invention relates to a method for processing digitized ultrasonic signals originating from an ultrasonic probe for the storage and later reconstruction of the ultrasonic signals from the stored data.
According to the state of the art the high-frequency signals received by the ultrasonic probes are digitized and can then be further processed by digital computers.
The high-frequency signals are also referred to as ultrasonic signals or as a so-called A-image. In the course of the further processing, a link can be made to the path coordinates of the measuring points, an evaluation and true-to-location representation of the test results (so-called B-, C- or D-images) can be performed, the measured results from several tests carried out in sequence on the same test object can be stored in order to determine changes, an analysis process can be carried out for the purposes of flaw reconstruction using known algorithms.
For most evaluation methods the signal travel time and/or the actual high-frequency signal waveform (the ultrasonic signal) is required in addition to the maximum signal amplitude in each flaw expectation range. For the digital processing the analogue signals must therefore be sampled at a multiple of the probe frequency in order to be able to sample the actual signal waveform with the required accuracy, i.e. in order to achieve the required accuracy for these evaluation methods. The relationship between probe frequency, sampling rate and sampling error is known: the higher the sampling rate selected in relation to the probe frequency, the lower is the sampling error.
If, for example, a probe signal with 15 NHz is to be digitized with a sampling error of 0.1 dB, then the sampling rate must be at 300 MHz. For an evaluation range of e.g. 100 mm (steel, longitudinal) this results for a single test shot in a volume of data of 10,240 digital measured values. If one assumes a testing density of one shot per millimetre of path, then this results in 10,240,000 measured values for a test path of 1 metre.
In practice, however, not only one but several, for example 2 to 16 and more test functions are provided for automatic tests and in addition high test speeds (e.g. 500 mm/s or greater) are necessary. On the basis of these standards up to 81,920,000 measured values per second would result for said example.
These amounts of data cannot be processed in real time with the economically feasible computers in practical use today and also cannot be stored.
In practice digitization is therefore only carried out at 100 MHz, thus a compromise is made between sampling error and the number of measured values arising. In addition the digitized data are reduced to maximum amplitude values per section of the travel path, e.g. 1 value per x mm. A reconstruction of the signal form to the degree of accuracy required for evaluation methods is however no longer possible with these values.
At this point the invention comes in. It has the object of providing a method for the processing of digitized ultrasonic signals originating from a probe, which requires only a small amount of storage space and which nevertheless enables a later reconstruction of the ultrasonic signals from the stored data.
This object is achieved by the method with the characteristics stated in Patent Claim 1.
With this method an ultrasonic signal is digitized with the high digitization rate necessary for the admissible sampling error. For each half-wave from the digitized data only the value of the maximum amplitude, its polarity sign and its location on the time axis are stored. All further digitized values are not considered for storage. It is possible to reconstruct the original ultrasonic signal using only these values because the ultrasonic signals are essentially determined by the probe frequency, and therefore have practically no upper or lower waves.
The reconstruction of the ultrasonic signals, i.e. of the high-frequency signal waveform, from the stored values is now effected in such a way that two neighbouring maximum amplitudes, of which one always has a positive sign and the other a negative sign, are connected by a 1800 cosine curve, which has a slope of zero at the position of the maximum amplitudes. This makes it possible to reconstruct the original signal form with sufficient accuracy for the later evaluation.
The method has the advantage that on the one hand the high digitization frequency required for the digitization (accuracy) can be used, but only two values per complete oscillation must be processed by the digital computers, with which values the signal reconstruction can also be performed.
With this method the amount of data stated above can be reduced by approximately a factor of ten. Such a reduced amount of data can be processed by the computers in practical use today. In particular however, in contrast to reduction processes for data known to date, the signal form can be reconstructed from the reduced data with a accuracy sufficient for the further processing.
The method according to the invention is explained and described in the following on the basis of figures. These figures show in:
Fig. 1 an ultrasonic signal in high-frequency
representation, the amplitude U is plotted
against the time t,
Fig. 2 the ultrasonic signal from Fig. 1,
superimposed in addition on a digitization grid
with sufficiently high digitization frequency,
Fig. 3 the ultrasonic signal from Fig. 1 in
high-frequency representation, shown are the
digital amplitude values,
Fig. 4 in high-frequency representation only the
maximum amplitude values of the representation
from Fig. 3 with their correct polarities,
Fig. 5 in high-frequency representation the
reconstruction of the originally analogue probe
signal (ultrasonic signal) from the reduced data
from Fig. 4,
Fig. 6 a representation to explain the
reconstruction algorithm,
Fig. 7 a block diagram of the circuitry used,
and
Fig. 8 a representation corresponding to Fig. 5
for a different signal waveform, shown is an
evaluation corresponding to Fig. 6.
The processing of the analogue probe signal to a reduced representation can be seen step-by-step from
Figures 1 to 4. The ultrasonic signal according to Fig. 1 is a typical output signal U(t) of a probe. If it is digitized, i.e. superimposed on a digitization grid, as can be seen from Fig. 2, then one receives the representation shown in Fig. 3 of the digital sampling points against the time t, i.e. in high-frequency representation. In other words the continuous curve path from Fig. 1 is now exploded into a point-by-point curve path as in known from the digital representation. One could also represent Fig. 3 with a multitude of individual bars going from the zero line (time line, x-axis) and extending to the relevant indicated point. But then the representation would be practically no longer comprehensible in a real case.
A decisive aspect of the invention is now to be found in the transition from Fig. 4 to Fig. 5. From the multitude of the digital values shown in Fig. 3 only those values continue to be taken into consideration which are the largest values for a half-wave and these are referred to as maximum amplitudes irrespective of their polarity sign. The sign determines whether it is a maximum or minimum value. This simplifies the later description of the reconstruction of the ultrasonic signal from the reduced data.
Following the data reduction there is therefore one maximum amplitude value, its corresponding time value and the sign of the maximum amplitude value present for each half-wave. A considerable reduction has occurred in comparison with the multitude of the digital values shown in Fig. 3, and this can be immediately seen by comparing
Figures 3 and 4. In spite of the high data reduction it is possible to reconstruct the original output signal for the most part, as will be shown on the basis of Fig. 5 and the later figures and description.
Fig. 5 once again shows the maximum values corresponding to Fig. 4 in the same time representation as in Fig. 4. The maximum values, also referred to as nodes of interpolation, have the reference numbers 20, 22, 24, etc. It is now possible with an algorithm to connect these nodes of interpolation 20, 22, 24 with one another in such a way that the ultrasonic signal according to Fig. 1 can be reconstructed for the most part.
For the reconstruction two neighbouring nodes of interpolation, e.g. 20 and 22, are connected to each other by a 1800 cosine curve 26 (a cosine curve from 0 to 180 ). 0) This enters with a slope of zero into the two nodes of interpolation 20 and 22 respectively. The same procedure is carried out with the next nodes of interpolation, i.e. 22 and 24. Here once again a 1800 cosine curve 28 is used to connect the two nodes of interpolation 22, 24, which in turn arrives with a slope of zero in the nodes of interpolation 22, 24. Due to the inverse sign of the nodes of interpolation 22, 24 the branch 1800 to 3600 of the cosine curve is used here. In this way the complete curve shape is reconstructed stepby-step, the procedure always being to move forward from the preceding node of interpolation to the adjacent node of interpolation.
The algorithm described in this way for the reconstruction is again explained in detail on the basis of Fig. 6. Shown in real time are the nodes of interpolation 20, 22, 24, as they can be derived from the reduced representation. U20 is the amplitude value of the node of interpolation 20, U22 is the amplitude value of the node of interpolation 22, which has a negative sign,
U24 is the positive amplitude value of the node of interpolation 24. The time interval between the two nodes of interpolation 22 and 20 is delta t1 and the time interval between the next two nodes of interpolation 24 and 22 is delta t2. The reconstruction between the nodes of interpolation 20 and 22 now results from the formula
iU2(+IU2i ntli}+U2o;Ufl 2 Here i has the value 0 to n and is incremented, whereby n plus 1 points of a 1800 cosine curve result, which extends from the maximum amplitude 20 to the amplitude maximum 22 and enters both maximum amplitudes with a slope of 00. The computation procedure is as if the zero line did not exist and both nodes of interpolation 20, 22 are treated as if they were located on the maximum amplitude values of a cosine curve.
In the same way the connection is achieved between the nodes of interpolation 22 and 24; because reconstruction is from a negative to a positive amplitude value, however, 180 degrees are added to the argument of the "cos" in the formula.
The connection between the two following nodes of interpolation is then again carried out according to the cosine formula stated above.
A connection diagram of the equipment used can be seen in Fig. 7. An analogue probe signal, according to the representation in Fig. 1, is present at an input 30 of a
HF digitizer 32 and is digitized at a frequency of 300
MHz. The result shown in Fig. 3 is present at the output of the digitizer 32. In a downstream processing stage 34 the digitized values are fed on the one hand to a maximum value determination circuit 36 and on the other hand to a measured value counter 38. The maximum value determination circuit 36 determines a maximum value per half-wave and outputs this together with the corresponding polarity sign via a circuit 40. A travel time computing stage 42 is installed downstream of the measured value counter 38, which in turn is connected at its output to a measured value travel time stage 44. This latter stage receives the starting travel time in millimetres from a stage 46 and outputs the travel time value corresponding to the maximum value through a stage 48 "travel time output".
In this way the signals are available at the output of the processing stage 34 as can be seen from Fig. 4.
An on-line storage 52 for the reduced data is located in a downstream computing stage 50. It is connected with a stage 54 for off-line reconstruction, representation and evaluation. The reconstruction in this stage is effected corresponding to the algorithm stated above.
The signal waveform according to Fig. 8 differs from the signal waveforms seen until now according to Figures 1 - 6 in that several maximum amplitudes are passed through, namely true maximum values and intermediate relative minimum and maximum values, both in the positive and in the negative amplitude ranges, without in the meantime the signal waveform reaching the zero amplitude or even changing the polarity sign.
As Fig. 8 shows, the signal initially passes - as previously - through the node of interpolation 20 in the positive amplitude range and subsequently through the node of interpolation 22 in the negative amplitude range, and then again the node of interpolation 24 in the positive amplitude range. Until now there is no difference to the signal waveform discussed so far on the basis of Figures 1 to 6. After the node of interpolation 24 the signal now does not pass through the zero line, but reaches a (relative) minimum at node of interpolation 56, a new maximum at node of interpolation 58, a minimum at node of interpolation 60 and a maximum at node of interpolation 62, and with an amplitude change subsequently passes through two negative maximum amplitudes with an intermediate relative maximum amplitude.
This signal waveform is digitized and processed in the same way as discussed above, but a reference line is inserted as a zero reference, also known as a virtual zero line. Refer to the lines 64, 66 and 68, which have been added to illustrate this.
Therefore a maximum amplitude is to be understood as an area in the course of the signal curve, where an extreme value or extremum is present, where the slope therefore has the value zero, independent of the value of the second derivative, which may be positive or negative.
It is inevitable that the value of the second derivative constantly changes its sign with maximum amplitudes in a time sequence. It is for example negative for the node of interpolation 24, positive for the node of interpolation 56, negative again for the node of interpolation 58, positive for the node of interpolation 60, etc. The invention makes it possible to reconstruct the waveform of the curve between such nodes of interpolation, regardless of whether a zero-crossing occurs between the successive nodes of interpolation. The virtual zero lines 64 - 68 are shown in such a way that they are essentially in the vicinity of the places where the second derivative of the signal has the value zero, i.e. where reversal points are present. Therefore the virtual zero line 64 is drawn through the reversal point in the course of the curve between the nodes of interpolation 24 and 56. The same is true for the virtual zero line 66, which crosses the reversal point in the course of the curve between the nodes of interpolation 56 and 58. It is assumed in a first approximation that the virtual zero line 64 is located in the middle between the two amplitude values of the nodes of interpolation 24 and 56, in other words equidistant from both. This is used in the practical implementation.
The method for the reconstruction corresponding to
Fig. 6 is as described above and using the above-mentioned formula.
Claims (2)
1. Method for processing digitized ultrasonic signals
originating from a probe for the storage and later
reconstruction of the ultrasonic signals from the
stored data, in which the ultrasonic signals are
digitized, the maximum amplitudes and their polarity
signs are determined and only these maximum amplitudes
with their corresponding signs and their corresponding
time values are stored in a memory and then the
ultrasonic signals are reconstructed later from the
stored data by connecting a maximum amplitude with the
immediately following maximum amplitude by a 1800
cosine curve, which has a slope of zero at each of the
positions of the two maximum amplitudes.
2. Method according to Claim 1, characterized in that the
digitization is carried out at a frequency which is at
least ten times, preferably at least twenty times as
high as the probe frequency.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE4310134 | 1993-03-29 | ||
DE4333531 | 1993-09-01 |
Publications (3)
Publication Number | Publication Date |
---|---|
GB9406195D0 GB9406195D0 (en) | 1994-05-18 |
GB2279523A true GB2279523A (en) | 1995-01-04 |
GB2279523B GB2279523B (en) | 1996-04-24 |
Family
ID=25924441
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB9406195A Expired - Fee Related GB2279523B (en) | 1993-03-29 | 1994-03-29 | Method for processing digitized ultrasonic signals originating from an ultrasonic probe for the storage and later reconstruction of the ultrasonic signals |
Country Status (1)
Country | Link |
---|---|
GB (1) | GB2279523B (en) |
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1997011364A1 (en) * | 1995-09-18 | 1997-03-27 | Combustion Engineering, Inc. | Ultrasonic testing (ut) system signal processing |
DE19603574A1 (en) * | 1996-02-01 | 1997-08-07 | Fraunhofer Ges Forschung | Imaging of ultrasonic wave fields using ultrasonic waves cyclically excited in object being tested |
US5837899A (en) * | 1996-09-13 | 1998-11-17 | Combustion Enginineering, Inc. | Ultrasonic testing (UT) system having improved signal processing |
EP1276241A1 (en) * | 2000-04-14 | 2003-01-15 | Sakai, Yasue | Compression method and device, decompression method and device, compression/decompression system, and recorded medium |
WO2007085296A1 (en) * | 2006-01-27 | 2007-08-02 | Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. | Method for the non-destructive examination of a test body having at least one acoustically anisotropic material area |
WO2009053342A1 (en) * | 2007-10-26 | 2009-04-30 | European Aeronautic Defence And Space Company Eads France | Compression and reconstruction of a pseudosinusoidal digital signal |
US8683865B2 (en) | 2011-05-26 | 2014-04-01 | General Electric Company | Ultrasonic scanning with local gain intervals |
-
1994
- 1994-03-29 GB GB9406195A patent/GB2279523B/en not_active Expired - Fee Related
Cited By (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1997011364A1 (en) * | 1995-09-18 | 1997-03-27 | Combustion Engineering, Inc. | Ultrasonic testing (ut) system signal processing |
DE19603574A1 (en) * | 1996-02-01 | 1997-08-07 | Fraunhofer Ges Forschung | Imaging of ultrasonic wave fields using ultrasonic waves cyclically excited in object being tested |
DE19603574C2 (en) * | 1996-02-01 | 2001-09-27 | Fraunhofer Ges Forschung | Method and device for imaging ultrasonic wave springs |
US5837899A (en) * | 1996-09-13 | 1998-11-17 | Combustion Enginineering, Inc. | Ultrasonic testing (UT) system having improved signal processing |
EP1276241A1 (en) * | 2000-04-14 | 2003-01-15 | Sakai, Yasue | Compression method and device, decompression method and device, compression/decompression system, and recorded medium |
EP1276241A4 (en) * | 2000-04-14 | 2006-06-07 | Sakai Yasue | Compression method and device, decompression method and device, compression/decompression system, and recorded medium |
WO2007085296A1 (en) * | 2006-01-27 | 2007-08-02 | Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. | Method for the non-destructive examination of a test body having at least one acoustically anisotropic material area |
WO2009053342A1 (en) * | 2007-10-26 | 2009-04-30 | European Aeronautic Defence And Space Company Eads France | Compression and reconstruction of a pseudosinusoidal digital signal |
FR2923104A1 (en) * | 2007-10-26 | 2009-05-01 | Eads Europ Aeronautic Defence | METHOD AND SYSTEM FOR COMPRESSION AND RECONSTRUCTION OF A PSEUDO-SUSUSOIDAL DIGITAL SIGNAL |
US8683865B2 (en) | 2011-05-26 | 2014-04-01 | General Electric Company | Ultrasonic scanning with local gain intervals |
Also Published As
Publication number | Publication date |
---|---|
GB2279523B (en) | 1996-04-24 |
GB9406195D0 (en) | 1994-05-18 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
EP0928424B1 (en) | Automatic fault location in cabling systems | |
US5159343A (en) | Range information from signal distortions | |
EP1597607B1 (en) | A method and a device for detecting discontinuities in a medium | |
US6208946B1 (en) | High speed fourier transform apparatus | |
US4686457A (en) | Method for measuring a signal's frequency components | |
GB2279523A (en) | Method for the storage and later reconstruction of ultrasonic signals | |
Mahmud | Error analysis of digital phase measurement of distorted waves | |
GB2390167A (en) | Testing an electrical component | |
KR20010051520A (en) | Network analyzer, network analytical method and recording medium | |
US5555180A (en) | Method for processing digitized ultrasonic signals originating from an ultrasonic probe for the storage of and later reconstruction of the ultrasonic signals from the stored data | |
US4192003A (en) | Signal recovery method and apparatus | |
DE3681313D1 (en) | METHOD FOR DEMODULATING AN INPUT SIGNAL PHASED WITH A BINARY BIT SEQUENCE, AND CIRCUIT ARRANGEMENT FOR CARRYING OUT THE METHOD. | |
JP4232937B2 (en) | Processing method of eddy current flaw detection signal | |
KR940017487A (en) | Micro Frequency Shift Detection Method | |
JPS6170473A (en) | Waveform analyzer | |
SU1744502A1 (en) | Method of determining level of substance | |
Shanaurin et al. | Reliability of tests using ferromagnetic transducers | |
RU2143701C1 (en) | Process determining energy consumption in a c circuits and device for its implementation | |
SU1053018A1 (en) | Device for measuring amplitude-frequency response | |
SU1734239A1 (en) | Measurement method of influence of chromaticity signal on brightness signal in television path | |
Hsieh et al. | Source nonlinearity calibration using Volterra adaptive filters | |
EP1061652A2 (en) | Linearization procedure of the transfer characteristic of analog-to-digital converters and relevant circuit | |
Dai et al. | Quasi-synchronous sampling algorithm and its applications-III. High accurate measurement of frequency, frequency deviation and phase angle difference in power systems | |
Lapuh et al. | Autocalibrating phase reference standard | |
JPH1164295A (en) | Automatic phase, sensitivity-adjusting apparatus for eddy corrent inspection signal and, for reference inspecting signal |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19980329 |