Effect of bandpass filter on uncertainty of visibility measurement

In the visibility meter, in order to suppress the impact of uncertainty of measurement by the ambient light changes, the probe beam in optical transmitter was modulated, and the bandpass filter was used in photoelectric signal receiver. Since the frequency response function could change,which was induced by the bandpass filter characteristic parameters changing with the temperature in the working environment, the uncertainty was introduced in the measurement of visibility. Taking a second order active bandpass filter as an example, the band pass filter frequency response amplitude variation with temperature was analyzed from the transfer function, and the the frequency response amplitude variation with temperature was measured by experiment. The results show that the bandpass filter provides about 4.5% uncertainty with the environment temperature changing per 1 ℃, at 15 ℃~40 ℃ in high visibility weather conditions, and the effect of bandpass filter on the measurement of visibility is much smaller in low visibility conditions.