50 Hz Adaptive Filter

One of the main causes of the reduction of accuracy in low frequency signal parameters measurements is the influence of artificial and natural electromagnetic interferences on measuring channels of measuring tools (MT). Under laboratory, production and natural conditions, the main interference is 50 Hz network interference. To eliminate this interference, ZETLAB software package uses a program providing a 50 Hz band-stop filter.

To start the program Adaptive filter 50 Hz, select it in Automation section of ZETLAB panel. You will see the window of the program Adaptive filter 50 Hz. Автоматизация. Адаптивный фильтр 50 Гц

As the program is started, there appears a window with the following parameters: the precise value of 50 Hz interference, interference value in the corresponding measurement units, the diagram of frequency changes depending on time (in seconds). It is necessary to configure two parameters: frequency calculation interval and interference amplitude calculation interval. It is also necessary to assign a number for the channel used for the measured channel integral level display. The program creates an additional virtual channel, where 50 Hz interference and corresponding harmonics are removed.
Адаптивный фильтр 50 Гц

The program “Multichannel oscilloscope” (available in “Display” menu of ZETLAB panel) enables visual representation of this program operation. The top section of “Multichannel oscilloscope” program window shows a signal with 50 Hz interference, below you can see the same signal, that has been filtered.
Многоканальный осциллограф. Сигнал с помехой 50 Гц и отфильтрованный сигнал

Among the advantages of the program “Adaptive filter 50 Hz” one should mention the fact, that it allows to remove 50 Hz interference as well as the accompanying harmonics. This is attributed to the adaptive filter algorithm using Walsh transform, which eliminates the harmonics without distorting the useful signal.

Сигнал с помехой 50 Гц
Signal spectrum prior to filtration

Сигнал, обработанный программой Адаптивный фильтр 50 ГцСигнал, обработанный программой Адаптивный фильтр 50 Гц
Signal spectrum after filtration

Upon activation of the “Adaptive filter 50 Hz” program there appears an additional virtual channel to be used together with the already existing channels. Hence, in the case, if you need to filter 8 channels, you have to start 8 copies of “Adaptive filter 50 Hz” programs simultaneously. In addition to the 8 physical channels, there will be created 8 virtual channels, having similar functional range: display of signal shapes, their spectra, correlational functions, etc.

The program also has an integrated control and automation module from the scope of  ZETLAB STUDIO software package, allowing the user to create software-based measurement system of his own.