The radar level meter is a measurement instrument that converts the distance signal into a linear frequency signal by frequency modulation of the transmitting signal, thus achieving the purpose of distance measurement. So that the signal processing algorithm has an important influence on whether the radar level meter measurement is accurate or reliable. We must understand the signal processing process to better understand the radar level meter, the ultimate goal is to better use it so as to achieve the best measurement results.
The signal processing steps of the radar level meter have four steps, the first step is pre-processing, including sampling and filtering. In the engineering application of radar level meter, the signal received by the antenna is downconverted to zero IF signal after T/R component reception, and then through a low-pass filter to get a relatively flat echo signal, and finally received by AID and stored as a valid sequence of received digits.
In the whole sampling process, in order not to cause too much interference to the later signal processing, the radar level meter usually only samples the measurement range of the actual working condition. The macroscopic representation of this time domain result is the set range.
The data is then subjected to a series of processes, such as noisy data processing and missing data processing.
The second step is the echo signal extraction technique, which can effectively extract the echo signal, wavelet extraction algorithm, using wavelet transform to decompose the feature vector into wavelet pyramid structure, and its normalization threshold algorithm processing.
There are also echo feature extraction algorithms that use the time domain features of the signal and process the signal using adaptive arithmetic averaging. Compared with the traditional threshold extraction algorithm, for the advantages and disadvantages of the single pulse radar echo signal, the polar method is used in engineering to process the signal effectively.
The basic idea of the extreme value method is to extract the extreme value points in the radar level meter echo signal at one time and then separate the effective target reflected electromagnetic wave from the extreme value points.
The third step is the industrial condition screening technique, a kind of comprehensive judgment analysis, mainly based on the time domain reflection characteristics of the basic electromagnetic wave, but in the actual engineering application, there will be a variety of factors combined with results. Data quantification of various industrial conditions. The following are the general steps of comprehensive evaluation analysis: i. The prerequisite for using comprehensive evaluation analysis is to collect, organize, quantify and examine the data of each industrial condition. Then, the various parameters are weighted according to the different operating conditions.
Finally, the entire measurement echo results are weighted and scored according to the operating condition settings. The highest scoring echoes are identified and monitored for subsequent distance calculation. In another kind of dynamic analysis, the main idea is to take the constantly changing level signal as the research object and use the dynamic target tracking technology of radar and the optimized autoregressive data processing algorithm to finally find the actual and industrial echo level.
The last step is the distance calculation technique, if the filtered level signal is to be converted into distance information output, it needs to be processed by the distance calculation algorithm. According to the different methods of distance measurement node selection, the most mainstream methods to calculate the liquid level distance are pulse width median taking style, rising edge taking style, and falling edge taking style, these three.
As I said at the beginning, the signal processing algorithm plays an important role in the accuracy and reliability of the radar level meter. Whether you are a technician or a user in the radar level meter industry, you should be aware of this part of your knowledge.