PROCESSING OF THE DIGITAL IMAGES OF ANALOGOUS OSCILLOGRAMS AT PULSED MEASUREMENTS

A program for processing the digital images of analog oscillograms at pulsed measurements of the current-voltage characteristics of semiconductor materials and devices in the region of high electric currents is presented. The processing of digital images in this program bases on scanning of coordinates and allows measuring the instantaneous voltages and currents with a relative error of no more than ±1%. The program is created using the languages HTML5, CSS3, JavaScript and Canvas technology. The software environment for program run is the Internet browser.


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field strength EJ, necessary for estimating EJ/EC, can be found from the CVC of varistor ceramic sample in the region of high electric currents.
In [3], it was proposed to use single voltage pulses of exponential form for measuring the current-voltage characteristics. Such pulses allow deploy voltage in a certain range. It makes possible when simultaneously register the voltage and current pulses, to obtain information about CVC in some region of voltage. The simultaneous registration of current and voltage pulses can be realized using a two-beam storage oscillograph. As shown in [4], in the case of analog oscillograph, the accuracy of measuring time intervals and voltages by analog oscillograms one can be led to the accuracy of measuring a digital oscillograph if to use the digital (raster) images of analog oscillograms. Such images can easily be obtained by photographing oscillograms using a digital camera directly from the screen of analog oscillograph. Since the quantization step for raster images is 1 pixel [5], using a digital camera with high resolution, it is possible to ensure high accuracy in determining the parameters of objects in raster image from the scanning data of their coordinates. When performing measurements using digital images, software is required for their processing, which makes it possible to extract the necessary information based on the scan data.
The aim of this work is to create a program for processing digital images of analog oscillograms for pulsed measurements of current-voltage characteristics of materials and devices in the region of high electric currents. In this work, we used HTML 5, CSS 3, JavaScript [6] and elements of the Canvas technology [7] for the software implementation of the described algorithm. As an environment for program created by the above means, any Internet browser can be used.
The program interface in the form of a web page was created using The program interface contains two blocks for control the processing of digital images. In upper right corner of the browser window is block for displaying the coordinates of mouse cursor. This block shows the current coordinates of cursor and it is served by a script that is started by mousemove event.
In the upper left corner of browser window there is a set of buttons. When these buttons click, the scripts are performing for various stages of the processing of oscillograms digital images.
The "Choose File" and "Download" buttons are used to select and download the digital images. Fig. 1 shows the program window after clicking the "Choose File" button. The user, using the standard window, has the ability to select the desired raster image file. In Fig. 1, in accordance with the user's instruction, a digital image of oscillogram is selected with the calibration signal UC of 100 V. This image, after clicking "Download" button, is uploaded on canvas in the program window. The above buttons serve scripts that use properties and methods of the FileReader object to load images, and the drowI-   To determine the voltage scale, a previously loaded image of the calibration voltage oscillogram is used (Fig. 2). As a calibration signal, we used periodic rectangular pulses with amplitude of 100 V and frequency of 1 kHz.
At sweep duration of 10 µs/div, the oscillogram of such pulses is registered as two parallel lines (Fig. 2), the distance between which corresponds to voltage «Системні технології» 1 (126) 2020 «System technologies» where yMU1, yMU2 are the vertical coordinates of two scanned points on the lines of calibration voltage oscillogram. For stages of the digital image processing involving scanning, the user instructions contain "Remove" button. When pressing "Remove" one can delete the instruction if it interferes with scanning (Fig. 3). This block and its supporting scripts are organized as well as for the voltage scale determination. At this stage using the "Choose File" and "Download" buttons, it is necessary to download a digital image of the calibration current oscillogram. As such oscillogram, we used an oscillogram of rectangular voltage pulses with calibrated amplitude UC. Since the value of current resistor is R = 1 Ω (Fig. 2), the UC value is actually equal to the calibra-  Then the script, acting when pressed the "Determine" button, clears the arrays of scan data, removes their visual display, hides the "Determination of zero voltage" block and visualizes the "Determination of zero current" block.
Determination of the coordinate y0I = (y1I + y2I)/2 of electric current zero line is performed in the same way as for coordinate y0U. In this case, after pressing "Determine" button, the "Result" block opens for the last three stages of the algorithm for processing of digital image of analog oscillograms (Fig. 5).
where yiU, yiI are the vertical coordinates in i-scanned point with same coordinate xi on the lines of voltage and current oscillograms, respectively.
In the formula (2), when calculating the voltage drop across the test sample, the voltage drop across the resistor R, connected in series with the sample, was taken into account.
In accordance with (2) Script executed after pressing the "Calculate" button displays the processing results in the hidden form fields (Fig. 5). As can be seen, the relative error in measurement of voltages and currents at using the digital images of analog oscillograms does not exceed ±1%.
After measurement of CVC, the program provides the ability to clean the arrays of scan data xi, yi and delete the visual results of scan. In this case, the initial data, McU, McI scales and the coordinates of zero lines of voltage and current oscillograms y0U, y0I are stored. For this purpose the "Clear" button is used (Fig. 5). After pressing of this button it is possible to measure the cur-SSN 1562-9945 (Print) ISSN 2707-7977 (Online) 64 rent-voltage characteristic, using the same or another part of oscillograms, without overload of the digital image, the scaling and determination of zero.

Conclusions.
A program has been created for processing the digital images of analog oscillograms at pulsed measurements of the current-voltage characteristics of semiconductor materials and devices in the region of high electric currents. The program is created using HTML5, CSS3, JavaScript languages and Canvas technology. The Internet browsers are software environment for program execution. The program allows, using the scan data of digital images of oscillograms, to measure instantaneous values of voltage and current with a relative error of no more than ±1%.