Study on Denoising Method of Photoionization Detector Based on Wavelet Packet Transform

Aiming at the task of noise suppression caused by the photoionization detector (PID) monitoring signal of volatile organic compounds (VOCs) due to local non-uniformity of the photocathode surface of PID in the ionization chamber, this paper proposes an analytical method of a PID signal with the adaptive weight of the small wave package decomposition node. The PID signal is transmitted to the upper machine software through the single-chip microcontroller. The appropriate wavelet packet decomposition level is determined according to the time frequency characteristics of the original signal of the PID, and the optimal wavelet packet base is selected through the polynomial fitting of the signal quality evaluation index. By comparing the quality of signals processed by the traditional wavelet packet denoising method and the denoising method presented in this paper, the superiority of the proposed method in the denoising signals of PID was verified. This method can eliminate the noise generated by local non-uniformity on the photocathode surface of the PID ionization chamber in a high humidity environment, which lays a foundation for the accurate monitoring of VOCs in a high humidity environment.

Automated summary

This paper proposes an analytical method of PID signal with the adaptive weight of small wave packet decomposition node to suppress noise caused by the photoionization detector monitoring signal of VOCs. The PID signal is transmitted to the upper machine software through a single-chip microcontroller. By comparing with traditional wavelet packet denoising method, the superiority of the proposed method in denoising signals of PID is verified. This method lays a foundation for accurate VOCs monitoring in a high humidity environment by eliminating noise generated by local non-uniformity on the photocathode surface of PID ionization chamber.