| 摘要 |
PURPOSE:To eliminate a large-level noise and to take a distance measurement with high precision, by determining the level of a digital signal by a noise eliminating circuit on the basis of frequencies of appearance of a high and a low level in a preset section. CONSTITUTION:An analog input is compared with a reference voltage ref by a comparator COM1 and converted into a digital signal having binary levels H and L. This signal is shifted by a shift register SR in response to the rise of a pulse phi2. A full-adder FA1 adds the 1st and 2nd bit outputs of the register SR, and a full- adder FA2 adds the 3rd bit output of the register SR, the sum output of the full- adder FA1, and a carry signal. The carry signals of the full-adders FA1 and FA2 are outputted through an OR circuit OR1, but its output signal is an H when >=2 bit outputs of the register SR are Hs. Therefore, when the digital signal has one H level out of three successive levels, it is removed as a noise. Thus, noises are eleminated and a measurement of distance is taken with high precision. |
