Instrument EFA-300

Field analyzer EFA-300 is used for measuring magnetic and electric fields in the workplace and public space. It is used for measuring electromagnetic fields in the frequency range 5 Hz - 32 kHz. For this device I wrote two programs that facilitate and speed up the measurements on the ground. The programs contributed largely to easier measurement of three orthogonal components B and E and are much easier processingof measurement data.

In realization of the first program I tried that the operator has the impression that is working with real instrument. Therefore, measured values of B and F are entered in the fields just like the real instrument does. In addition I used the function keys of the instrument F1, F2, F3 and F4 for the realization of displaying of measurement data in real time. A virtual instrument can display the measurement values in graphical form in real time, while the real device has no this possibility.

Fig.1 Virtual instrument EFA-300

The second version of program I wrote primarily for the transfer of measured data from the instrument to the computer. Over time, I expanded the number of functions and now mainly we use this version in the field.The program contains nine overlapping screens.

In the time interval of one second the program collects data from the instrument EFA-300, performs its processing, displays them in graphical form on multiple screens and measured data are recorded on the disk. When the instrument is used independently, the fastest period of measurement is five seconds. Data files are ASCII compatible files. The columns are separated by a tab character and therefore can be easily read by programs such as Excel and Origin.

Fig.2 Virtual instrument EFA-300 ver. 2

screen. All measurement quantities are displayed in numerical and graphical form. During measurement the user can scale the abscissa and ordinate, change the color and the shape of plotted lines.

The measured magnetic flux density and frequency can be monitored in real time on separate diagrams ( fig. 4). Width of time window, in which the measured signals are monitored, is programmatically defined and the default value is ten minutes. During measurement the operator can monitor all measurement values in real time by activating the desired user screen.

Fig.3 Live data chart

Besides displaying the measurement quantities ​​in real time, it is possible to display the history of measurement quantities from the beginning of the measurement. On the figure 4 are shown the magnetic flux density and the frequency which are measured along the transverse route of the 220 kV transmission line in the village Ledine, Novi Beograd.

Fig.4 Live data graph

By default, the EFA-300 instrument measures the integral value of magnetic induction. The instrument can measure separately the values of magnetic induction along the X, Y and Z axes. Measuring the components of magnetic induction has not been adequately implemented, because the measurement in the same measuring point requires special instrument configuration for each component. It takes about ten seconds to set up measurement along one axis and make the one measurement, which means that this feature is practically useless. However, my program really simplifies the measurement of all three components of magnetic induction and frequency.  Measurement of all quantities is performed in five seconds   and they are displayed on the graph in real time (fig. 5).

Fig.5 Live data chart of Bx, By, Bz

Instrument control commands are listed in tables in the manual and unfortunately they are only briefly explained. There are five types of data that can be transferred from the instrument EFA-300: NORMAL, AUTO, MATRIX, LIST, and VECTOR. Measured data are transferred in ASCII format and can be sent as single measurements or multiple measurements at once (fig. 6).

Fig.6 Transfer data from the instrument EFA-300 to computer

This part of the program provides a graphical presentation of measurement data of multiple measurements on a graph with just one mouse click (fig. 7). If necessary, the displaying of unwanted individual measurements can be removed. There are two cursors that an operator selects a region that wants to process. For the both selected region and signals the program calculates the mean, minimum and maximum value.

Fig.7 Data processing

In spectrum FFT mode, spectrum analysis is performed using Fast Fourier Transformation (FFT). The measured signal is sampled at the maximum rate. The sampling is free running and it does not require any trigger signal derived from the measurement signal or external trigger signal.After completion of the measurement the frequency spectrum is computed and recorded in internal instrument memory. A special part of the program transfers the calculated spectrum and displays it on the screen (fig. 8).

Fig.8 Frequency spectrum

The harmonic analysis is used to automatically measure the entire harmonic spectrum with the

EFA-300 instrument.  The instrument display shows the fundamental frequency and its harmonics (multiples of the fundamental), providing a fast overview of the quality of service. A special part of the program transfers calculated harmonics (up to nine) and displays them on the screen (fig. 9). It can be noticed that odd harmonics are more dominant than even harmonics.

Fig.9 Harmonic analysis

The dependence of reference values ​​for the electric field and magnetic induction from frequency of the measured signals are shown on separate graphics (fig. 10). Each curve can be linked to a cursor and moving the cursor along the curve is performing reading of reference values.

Fig.10 Reference values

Program EFA-300

I wrote the program for the instrument EFA-300 in late 2011. year.

More information about this program you can read in the paper "REMOTE CONTROL OF THE FIELD ANALYZER EFA-300", Radiation & Dosimetry 2012.