A time sequence control circuit that can control time sequence of a computer. The signal generating device includes an analog peak value detector for detecting a peak value of the reflected write pulse from the optical detector, at least one sample-hold circuit for sampling the reflected write pulse to obtain at least one amplitude value, and a processor for generating the mark formation effectiveness signal according to the peak value and the amplitude value. In this manner, accurate and consistent flow division can be accomplished, which is particularly useful for multi-dimensional liquid analysis.