The design and analysis of an improved high air flow meter with analog/digital filters

High air flow meters in the range of 0.0 SLM (standard liters per minute) to 200.0 SLM and using a built-in microbridge sensor in flow housing induce a significant amount of turbulence noise in the output signal. The authors analyze the sensor output signal and introduce an analog/digital (A/D) design to reduce the noise and to realize the industrial standard output range of 1.00 VDC to 5.00 VDC. Tests are performed with an A/D data acquisition system and Fourier analyzer for flow data analysis, and the flow data file is used for offline time and frequency domain analysis and digital filter design simulation. The magnitude, the mean and the autocorrelation are calculated and measured. An analog Butterworth filter was implemented on this high flow meter in real time and the signal-to-noise ratio was improved. The digital forward linear predictor was implemented with a digital signal processor, and high- and low-frequency noise was eliminated