| 摘要 |
PURPOSE:To enable the correct performance of the output for detecting a period without any erroneous output even if a noise is mixed by arranging two steps of memories in series to a counter output and without renewing the memory of the 2nd step when the deviation is found large with comparing the both. CONSTITUTION:In case of the difference between the content of the 1st memory 4-1 and the content of the 2nd memory 4-2 being above the set value, a gate circuit 9 prohibits the outputs thereof and so a pulse is not given to the 2nd memory 4-2 and the previous value holding condition comes. If, therefore, a spike like noise comes in, the abnormal value thereof is taken in, due to the pulse for the 1st memory 4-1 being given, in case of the output value of a counter 3 being ''0''. A comparator 8 decides the content of the 1st memory 4-1 as abnormal owing to the difference in the contents of the both memories being above the fixed value and prevents the abnormal count value thereof being memorized in the 2nd memory 4-2 by prohibiting a circuit 9. As the result, the output of erroneous counting signal due to the noise is restricted and a stable period detecting output can be obtd. |
