Multi functional circuit board DS200DCFBG1BJB

For analog signals with lower signal-to-noise ratios, significant fluctuations are often caused by on-site instantaneous interference. If only instantaneous sampling values are used for control calculations, significant errors will occur. Therefore, I have adopted digital filtering methods. The on-site signal is converted into a discrete digital signal through A/D conversion, and the resulting data is stored in PLC memory in time series. Then, it is processed using a digital filtering program to filter out noise and obtain a pure signal. There are three practical digital filtering methods: average algorithm filtering, peak rejection filtering, and median filtering. In practical applications, one method can be used alone or multiple methods can be used simultaneously to achieve better results. Its position in the control system is shown in Figure 1.

Taking the coal transportation program control system of a thermal power plant as an example, during on-site debugging, the author used the average filtering method to preprocess analog signals such as equipment working current, belt scale coal quantity, coal crusher temperature and vibration, and coal level in the coal bin. The input signal was replaced with the average of 10 sampling values instead of the current value. However, it was not the usual practice of calculating the average value every 10 sampling times, but rather adding it to the last 9 historical sampling values every sampling time