Understand the importance of the concept of signal filtering
Information sources：本站 | Release date：
2018-03-02
| Browse volume：115
Signal filtering is typically used for eddy current detection to eliminate unwanted frequencies in the receiver signal, although proper filter settings can significantly improve the visibility of the defect signal, but incorrect settings can distort signal performance or even eliminate defects altogether. Signals, therefore, it is important to understand the concept of signal filtering.
Filtering is suitable for receiving signals and is therefore not directly related to the probe drive frequency. This is easy to understand when plotting time and signal amplitude display. In this display mode, the signal filter easily sees that the shape of the signal depends on the time or duration of the probe coil sensing. For example, if a surface probe is placed on the surface of a conductor and oscillated back and forth, a signal-like waveform is produced.
When the probe oscillates quickly, the frequency of the signal will be higher than the frequency at which the probe oscillates back and forth. This signal does not require waveform appearance to have frequency content, and most eddy current signals will consist of a large number of frequencies. Consider a probe that senses a 1/60 second gap. Within one second, the probe may (theoretically) exceed the notch 60 times, resulting in a notch signal having a frequency of 60 Hz. However, imposed on this same signal may be due to probe wobble, electronic noise, conductivity shift, and other factors that produce signals at different frequencies.
